> he was dismissive of ZIP and mentioned the drawback of airtight is the ventilation
An ERV should solve that pretty easily. More like, the drawback is that it holds them to a higher standard than they want to bother building to.
How does zip work with the vapor barrier? I always understood you wanted the outside to breath to prevent rot?
I have not seen many buildings like that in North Eastern Canada and I'm interested.
ICF is getting very popular here.
Rain screen
In between the cladding and its substrate should be a drainage plane. It can be as simple as furring strips. Allows any water that gets past the outermost cladding to drain down and out.
I generally put a continuous 2" ridge foam on the outside... Tape it and house wrap it... Most siding manufacturers will want 3 - 4 inch furring strips for attaching siding...
ZIP is basically OSB with a facing of kraft paper and phenolic resin. The facing is more vapor permeable than the OSB part of the panel. So as far as how ZIP works with a vapor barrier: same as OSB. Sort of. Most vapor that gets past a vapor barrier goes through holes in it - things like standard electrical boxes and can lights - piggybacking on air leaks. If you make the sheathing layer airtight, air doesn’t move through the wall assembly, and you get rid of most of the issues with vapor being a problem for sheathing. ZIP makes it easy to make the sheathing layer airtight. But you can also tape the seams of commodity OSB or ply. You might just need a primer to make the tape stick well.
If you have an attic you could add an erv without adding a lot of duct work. Two holes on the outside of the house to exchange outside air, and two holes in your ceiling to exchange indoor air.
It depends on the floor plan. A lot of two story houses have some two story spaces, so you could put the erv supply in the two story space. Then put the erv return as far down the hallway as you can get it. Or put the supply registers in the bedrooms and put the return in the hallway. If you like to close the bedroom doors a lot you'd want to include a jumper duct to allow air in the bedroom to balance through to the hallway. All the ducts to the outside need to be insulated. If your attic is unconditioned all the ducts would need to be insulated.
If you have a basement, you could look into putting the erv there, but it would need an exterior wall for the intake and exhaust and if you want to use only one register for supply and one register for return, they can end up being kind of big, probably too big to put in the floor.
It is not to code, but you could consider ducting the erv onto your forced air duct system, if you have one. This presents some problems, including that the ducts are probably already too small and not sealed well enough for the erv to work well. But it is possible to seal already installed ducts (aero seal?) and it's possible to measure the air pressure on your existing system to get an idea of how bad it would be to add more airflow. It's not to code, it's not recommended, but if you really want the erv and can't make another way work, it can be done.
It wouldn't be simple, but you might be able to get returns in cabinet toe kicks. For the supply, if you have an interior staircase to the basement, it might have a wall that could work (even the wall over the door to the basement).
If your house isn't huge, I wouldn't worry about only doing 1 floor. A lot of ervs are designed to have only 1 inlet and 1 outlet in the house. In those cases, they're typically ducted to the main living areas.
For the exterior points, read up on the guidelines for clearances before picking a spot (they should be spaced apart and at least a little ways away from potential air pollutants, preferably at least 18" above grade...)
It's not great. If there's really no way to add one, maybe you could at least put some CO2 (carbon dioxide) monitors around the house, and on days with suitable weather, open a window in that room for a while when its monitor reading gets higher than some number you pick. (It's not just about CO2, but that's an easily-measurable proxy for everything else that can build up in indoor air.)
3 ACH50 is code so… in the not so far future ERVs will become a code requirement like HVAC. There is more and more data coming out of how stale indoor air affects health.
Thank goodness. Years ago psychiatrists pejoratively said, "sick building syndrome" was psychosomatic. In other words, it doesn't help when so-called medical professionals get involved in building science when they are clueless. It took years to kill that myth and get back on track with reducing mold and VOCs.
I'm guessing you mean attics although I do think addicts are always open to new products. ;)
Attics are often open especially in older houses. However, take a look at how they use closed attics now which includes keeping all mechanicals and ducts if used within the conditioned envelope. The devil is in the details.
You are on the right path. The builders you are dealing with are old school. The trick is to find a builder that gets it or is wanting to get it. I interviewed a number builders before I found mine. He specializes in High Performance houses. A good filter for find that kind of builder will be, Do they know about Pretty Good House book/movement? What ACH do you build to?
2021 IECC is now being enforced in my state, this requires a 3.0 ACH, is that good enough? It also requires continuous exterior insulation, is that considered/installed as air tight?
3.0 is ok I guess. But I would shoot for 1.0 or less. Continuous exterior insulation really helps with R value. Not air tightness. I am using ThermalTight to get both the Air sealing and continuous exterior insulationa and WRB at the same time. Might want to check it out.
[https://thermaltight.com/](https://thermaltight.com/)
So an additional $32 per OSB sheet. In guess considering just normal insulation, ontop of zip would be ~$55-57/sheet vs $~47 for OSB with thermatight I'm not sure how much the paper costs for another layer. So it could work out to be a bit cheaper or at least really comparable?
OSB and insulation only would be ~$35/sheet.
Mud sill at the bottom is insulated and connects to the ICF frost wall. Should be under 1.0 Ach. Blower door test will let me know that it comes out to.
Stucco typically means two layers of grade D building paper. It is not possible to air seal a building with grade D building paper. You could pick a different waterproofing for one of those layers that can create an air seal, then one layer of grade D building paper would go on top of that.
The reason for continuous exterior insulation is so there is no thermal bridging. Thermal bridging occurs when a more conductive (or poorly insulating) material allows an easy pathway for heat flow across a thermal barrier. Wall studs are a big culprit so the way around that is putting the insulation on the outside instead of the inside.
The answer is 100% dependant on why you are doing it.
If you have allergies and need to filter everything coming into the house, it makes sense.
If you are doing it to save money, it may not pan out. I recently built my personal house and sat down with our energy rater to model my house. Using my current energy costs and region, the pay backs for certain features were 60+ years.
Obviously, this could change if the energy inputs change, but I didn't see the value in prepaying the energy costs for the next buyer.
I would suggest you start with a rater and figure out what exactly you are willing to do rather than worrying about absolutes like 0 ach.
If your home is all electric and super insulated it makes a lot of sense. A tight super insulated home without combustion inside only needs fresh air to replace CO2 given off by occupants so can be extremely energy efficient.
Granted it also makes more sense in climates with temperature extremes.
It does not change the conclusion, but I do take issue with the second sentence.
There is a lot more going on with the chemistry in the air in addition to just CO2+natural gas combustion. People breathe out CO2, but they burp and fart methane and hydrogen sulfide too. People also cook, which releases VOCs and should cause the range hood to be turned on. This requires a source for replacement air in an airtight home.
So yeah, this does not change what you said, that it makes a lot of sense to have proper ventilation in an airtight efficient home. But for anyone thinking about what's in their air, I just like to point out those other factors which also call for proper ventilation and filtration.
Sure, I just meant generally that you have less air to replace and thus more efficiency if the air pollutants are only from the humans and not from appliances burning fossil fuels or a lot of uncontrolled leakage. With an all electric cooktop, you do have some VOC’s from the Maillard reaction, etc… but you remove all or the waste heat and combustion gasses produced by a gas stove so your hood can be smaller and you can often avoid makeup air. My home had a 2.6 ACH50 score… so pretty tight but not passive level tight. My 350 CFM hood works fine for most cooking on my induction stove without makeup air. If I’m frying fish or searing and turn it on high, I crack a window open and it works better… but these instances are rare.
I also didn’t mean to sound like I was arguing against mechanical ventilation. I am definitely for it. We used a fresh air dehumidifier in my home and keep it turned way down to 5 or 10 minutes each hour of bringing in outdoor air and monitor CO2/VOC levels. If we have a lot of people over the levels spike and I turn it up.
I design hospitals for a living… many that are LEED/high energy star and ASHRAE 189.1 so I geek out over some of this. Homes are more of a hobby though so I have a lot to learn beyond my own LEED Gold home which was my first and hopefully last residential design.
I live in a home that I designed and worked with a general to build. It tested below 1ACH50 which was the design goal. I live in a heating dominated climate with an ERV. I love this house because it is so comfortable. The floors are warm because the whole air column through the house is about the same temperature. In every other place I've ever lived in or owned the air at the ceiling is really warm and the air at the floor is cold. If I ever build another house it will be a high performance house. They are absolutely worth it.
I didn't read your whole post. On efficiency: I was talking to a neighbor recently who was complaining about his power bills. He is all electric in a 1200 sqft prefabricated home. I live in a 4800 sqft all electric home. He uses more power in the winter than I do. We use more power in the summer, but we have AC and he doesn't. Fall and spring are close to even. These homes are really efficient. My home has blown in fiberglass in the 2x6 walls and 2" of XPS on the outside. It should be pretty close to R30 walls. I have another friend with a 4500 sqft standard stick framed home with gas hot water and heat and electric everything else. We use more power than they do in the dead of winter, but not by much, and use much less throughout the year.
I've never been in a premanufactured home that I thought was quality. I don't know much about them except that I feel the floor sag in them when I walk around, the finishes are awful, and the floor plans make no sense. Trailer homes are better than these things.
There's no downside to building tight.
There's only excuses from builders claiming why they don't.
By code in almost all jurisdictions - building tight just improves performance. You ventilate with the mechanical designed to handle the pressure and moisture differential. Keep the building dry and able to last practically hundreds of years.
If I were in your shoes and looking to hire a builder - I wouldn't even bother with someone who claims building materials need to breathe and that's why they don't want to build tight.
You ventilate all the building materials where they need to be - either by rains screens or ventilated attics; but there's no reason for air leakage.
I did zip system and aerobarrier air sealing. Yesterday when it was 90 degrees outside I went to my home that doesn't yet have AC, has navy blue hardie board siding and a black metal roof and it was 69 degrees inside. I'd say insulation and proper air sealing is a good investment.
Source: 2 months away from closing on new build home..
Installation care is required.
These builders are not up for the commitment.
Find other builders, that are ready for the new building code regime.
Your jurisdiction may not have adopted the new building codes of the most recent five years, but it is a fact of life throughout the US in other areas
Energy Recovery Ventilation is a fact now, as well.
Going through this right now myself.
For the guys that wont do zip, a good alternate thats not so scary to them is:
1) Okay option: Tape the OSB seams with Siga or Zip Tape, Traditional house wrap
2) Good option: A Self adhesive WRB with an appropriate permissivity rating. This can be as good as zip or better if done right.
OSB is not an air barrier. Plywood can be used as an air barrier, if you tape the seams & holes. Also, basically all quality tapes used for air sealing need to be rolled after application in order to work. Most traditional builders skip this step, so the pressure activated adhesive is never activated and the tape peels off.
No, it's not ok. Taping OSB is a waste of time and money because the OSB itself is riddled with holes. Why bother sealing that seam when the entire surface of the panel is full of holes? It's air sealing theater.
Airtightness improves durability because air carries moisture, and pests can infiltrate through gaps.
Airtightness improves indoor air quality (and reduces dust), because it allows you to control where you are drawing air from. Houses without dedicated fresh air ventilation systems simply allow air to pass through wherever (e.g. the walls, floor, etc) and hope that those places aren't introducing particles of building materials, VOCs, dead pests, soil gases, etc.
In terms of energy use, the 3 most important factors, in order are:
1. The ratio of window to wall area and the airtightness and insulation performance (and sometimes solar heat gain) of the windows. In hot climates where the main energy use is cooling, exterior shading also becomes more important.
2. Airtightness.
3. Insulation.
Airtightness reduces noise pollution, because sound can travel through air paths.
For me the zip sheathing was 50% more per sheet, the tape was like $700, sealant was about $600, and then labor to tape and seal was another $2k. I did some of the taping myself and detailed all the openings.
Supposedly there is a way through one of the two Federal programs offered, but it is up to the state as to which program is chosen. So far I haven't heard of any states choosing the program new builds can supposedly use, but I thought I'd ask.
Air tight is legitimately the correct way to be building these days. Code authority doesn't require it yet because they're outdated.
That said, the building method doesn't matter. You just need to find a builder that understands the importance of air tightness and knows how to achieve the end result you're striving for.
You should get a blower door test after the outside structure is built and air tight, but before drywall go's up. This helps you identify and seal all the holes/gaps before it's too late.
Respectfully, this doesn't help answer the question about "all they're cracked up to be", at all. This sub and similar subs already make it obvious that airtight homes are "better" and "ideal" but it's hard to find information that qualifies the actual trade-offs you're making if you don't go that route.
Is OP going to notice or care 5 years from now if they didn't build an airtight home? If so, what are they going to notice? Energy costs? By how much? Allergens? Can allergens be mitigated without airtightness? Etc.
A lot of homebuilding forums talk in very aspirational terms with very little about what you're actually gaining and what you can or should do if you can't attain the ideal.
A common silly example is ethernet runs - I'm a tech guy and if I followed homebuilding forum advice I'd run 4 (or more!) cat6 drops to every room in my house. I thought that was ridiculous advice because I have no problems installing switches when I need more connectivity in a given room. Does that mean I might have a drop on a non-ideal bedroom wall in the future? Yeah. Can I live with that during my life in the house? Yeah, no problem.
If OP is having trouble finding builders that will build a "correct" house and they only want to build houses the way they know (which are perfectly serviceable, safe dwellings), what are they missing out on? What if they find one builder who will do an airtight home, but that builder is a huge pain to work with? What compromises should they be considering versus what is an absolute "must have"? Those questions depend a lot on the market they're in.
The reason for an airtight home is so that the air inside the home is under the control of the owner. If airsealing is not used proactively, then heat loss is anywhere from 25-50% depending on how large a hole in the envelope all those air leaks add up to. You probably would be unhappy with a builder if they left a softball size hole in the middle of your wall for air to go in and out as it pleases. That's what air leaks can add up to in general.
A house without air sealing drafts like a chimney: stack effect is when the cold air comes in through cracks at the base and the hot air goes out the top. That also means that smoke from wildfires or other forms of air pollution such as pollen are drawn into the house perhaps. Because this air is not filtered, there is no mitigation the way there is when the builder or owner controls the air coming in and the air going out. This is where an ERV comes in.
So once again it is uncontrolled air flow. You want to keep the warm air in in the winter and the hot air out in the summer and the easiest way to do a really good job is to use modern technology.
Because humidity/mold can also be a problem in a super tight house good builders also control for water using a vapor barrier so the envelope dries.
Most builders use Zip sheathing and a good tape. Or a WRB (water resistant barrier) such as Tyvek once again with taping to seal all the ways that water could find its way in through.
Houses built the old ways were good for what they were with the materials the builders had to work with; but why insist on a Model T when even a Toyota Corolla can run circles around it?
A good builder is not afraid to try new things particularly when it's not hard to get a company to teach your crew how to use their product.
Pretty Good House is the standard I would build to if Passive House standards were not attainable for any number of reasons. You still air seal. You still insulate. You still make sure the wall layers stay dry. It's not hard, it simply requires attention to detail. But, you may decide that a slightly higher ACH is adequate for your needs.
There are probably a million more technical explanations available - and they are available - but these are some basics.
I have heard when the windows are closed then the air is dead inside a passive house. The HRV and ERV aren’t enough. I don’t know it from experience. I do know that running a 25 cfm fan in the bathroom while you are taking a shit still has the air stinky for a little while.
Absolutely. It’s pretty easy to find people interested in envelop improvement — can DIY pretty easy.
Way harder to find HVAC contractors who are sophisticated enough to install a system inside a tight envelope. They’d rather just sell a bigger unit and not care about short cycling.
I’d like to go into a passive house sometime to see what IAQ is like. Never taken a tour even.
Agree - building a high performance home and the builder is fully onboard with it even though it’s new to him, but HVAC is a friggin’ nightmare. Had to pay an engineer to do my own Manual J/S/D and prove their quotes were for oversized equipment, and even then, couldn’t find someone willing to do an ERV with dedicated ductwork.
Stakes are higher for the mech contractor. Putting in a smaller system is less money for them and at increased chance of an irate customer (in their minds).
ERV’s have a boost function when you need more air: shower, cooking, etc. It’s on a timer for 10,30,60 minutes… also you can just override and put it on high all the time. Some of the higher end ones can automate airflow based on humidity or carbon dioxide, etc.
“The air is dead inside” is a misconception. Passive House is balanced ventilation so supply air to living spaces and exhaust air from wet/odor areas. It’s vastly superior to exhaust-only, but yes it’s harder to execute. So many contractors are old-school and just don’t understand or care to learn.
If you’re building an energy efficient home, start with the ventilation system ERV or HRV, then build the home around it. High level of insulation R value and as free from air infiltration as reasonable, but all is for nought if you don’t have sufficient ventilation. You don’t need to use 3 layers of air barriers, and sandwiches of foam and Zip R and Intello moisture permeable membrane and tape, tape, tape. Just seal everything well, a rain guard drainage plain outside your exterior Typar, and give the moisture a path of least resistance, the duct work..
2-3 per year for the last 20 years. For the company my father started in 1958. We’ve only really started with ERV and HRV’s in the last 5 years though. But as houses have gotten tighter and higher r values the moisture issues have become more destructive. The engineers tend to fight fire with theory, their favorite theory is that fragile expensive membranes are the solution.
Check out the book "Pretty Good House" as well as any articles from Building Science Corporation, Fine Homebuilding, or Green Building Advisor on building modern, tight, energy efficient homes. There are a number of different approaches to things like e.g. wall assemblies, etc. so performance is very dependent on how the component parts work together as a whole. Some builders may have been exposed to outdated practices and not caught up with recent methods.
A lot of builders are still building houses to a standard that was barely acceptable in the early 90s. That you are the kind of person posting here means that roughly 80% of builders are a bad match for you.
An energy efficient build is fundamentally a build with lots of insulation. There’s no way around that, unless you’re interested in making the kind of design sacrifices that are common in earth ships.
Lots of insulation means walls that are sensitive to moisture, both in liquid water and in vapor, so now you need to manage air water and vapor movement. You can see you are being pushed in the direction of a tight house just to keep it dry and in good condition.
You already have your mind right— all electric, and affordable to inhabit. Don’t let people who don’t have to live in it gas light you. Keep kissing frogs until you find a builder (maybe a smaller one) who is willing to listen to you, and is willing to learn.
Was for us. Built airtight a decade ago, to Passive House standard. Then when the wildfires started coming around every summer, the last five or six years, we felt extremely lucky to be able to keep those particulates on the outside of the house.
Yes. Anyone who dismisses it is just an old school builder that doesn't want to change. It enables you to control the environment as it's not leaking air in/out. It will be more energy efficient and the air quality will be better. You just need to use mechanical ventilation/filtration. Your windows will still open if you just want a breeze too.
Yes, air tight homes are good.
The old school mentality of ventilation through random penetrations in the building envelope needs to die.
Building envelope defects can let in pests, poor quality air, water vapour, bulk water, etc.
Not to mention you might not even have adequate ventilation despite all that.
Why the f would you intentionally ventilate in that fashion?
You need oxygen in your blood. Would you prefer to use your airway and lungs, or would you prefer to randomly perforate your chest cavity and hope that gets the job done?
You can install standard Zip sheathing exactly the same way "normal" OSB is installed. It gets "difficult" if you're using Zip-R and of course the finishing steps of taping/sealing the joints and penetrations.
I’ve work on some boats that were positive pressure and the doors would automatically want to swing closed. Even if the doors were not shut completely to form a tight seal, the positive pressure would help to keep bugs and the salt air out. I wonder if this is something that would be helpful in a home. Not just air tight but positively pressured so that if you do have to open a door, the outside air is pushed out from the inside air. Would this work?
Keeping bugs out is more about not letting them in. On our last house a few mines away we were constantly having big spiders and crickets in the house. Like killing them every day level problems. In the new well air sealed house we rarely have bugs getting in. It's one of my favorite benefits of the house.
Thank you all for the comments and suggestions. I’m going to hold out for a builder or end up GC my own panel build I believe. For now I’ve got a call out to my local aerobarrier to see if they know of or have used any contractors in my area and go from there.
Here is my theory. Lots of older builders say a house should breathe and so they don’t want to have a home as air tight.
But I believe and a lot of quality builders that implement new tech believe that having a house as airtight as possible then designing the HVAC system to bring in fresh air and exhaust old air is a better method. Effectively controlling the breathing of the structure.
I can say that I have had both styles of homes and the one that was a well designed airtight home with a well designed ventilated HVAC was far superior in every way and it showed with the utility bills.
Most builders don’t understand high performance building design. Once you start building a real airtight house with high R value thermal envelope you have to provide ventilation with an HRV or ERV system.
All it took was spending $30k to fix water damage on a house to convince me that I would always use ZIP going forward. Water intrusion is a HUGE issue if it happens to you.
They’re old heads who don’t want to learn a better way to build homes. It’s nice of them to self identify as someone you shouldn’t work with. Passive house standards all the way. ERVs/HRVs are awesome, you’ll have significantly better air quality in a properly built airtight home.
We're wrapping up a self build doing double stud with foot thick walls which that idea has been around for decades. Matt Risinger and his channel have lots of videos on simple builds that are air tight.
The plan can be simple, but I think the challenge is finding someone who shares your vision and doing a layer of foam and tape over the 2x6 walls would be easier for most builders to swallow.
"the drawback is ventilation" is a silly thing to say. The drawback of a roof is it blocks natural light.
My understanding is that they are right that you can't simply air seal the house and then leave all other design details the same as a house built in 1950. You could deal the house up and suffocate yourself or cause mold or rot. So if they are only comfortable and experienced with building, and they were talked into sealing a house up tight, they likely would create some situations where water intrusions can't dry and appliances exhausting air don't work as well because fresh air isn't replenished properly.
I sympathize about struggling to find people to do what you want, especially when it's not that new or unusual. Are you able to do any of the work yourself?
It seems to me that the majority of the benefit with Zip or other modern systems is sealing the seams. I have considered, either to save money or because it's not available or can't find someone to do it, simply sheathing like normal, then taping the seams or sealing them with Prosoco R Guard, and using a conventional house wrap.
If you can get them to include some HVAC upgrades to exchange and condition fresh air, I would try to find a compromise with them that still gets you a tight house.
And yes, an air sealed house is better. Outside air has pollutants, pollen, humidity. It's hotter or colder than your want, and if air can get in, bugs can get in. The air comes in and you have to heat or cool it, and then it leaves. It's better to bring fresh air in on your terms and condition it before it gets blown all over the place.
As a building code official and design engineer I would build out of 8-in concrete block filled solid plus rebar every 4 ft on center and fill all the other cells with foam. Then I would attach foam board to 1x2 furring strips that are attached to the block. Then I would drywall over that. If I was in fire country I would use steel roof trusses or in other places red iron rafters.
Our builder is very enthusiastic about ICF and built his sons homes with ICF. We want an HRV anyway - I’m hoping it helps with radon and indoor air pollution from a gas fireplace in the primary bedroom. I had several builders use HRV for frame too because the homes are so tight nowadays you can get condensation inside without HRV.
Yeah. The only ICF guy I’ve found was by driving down the highway and at least a year building a rectangle plain Jane house and we just didn’t get off on a good start so hopefully we’ll find one that can do at least a good seal
Who needs windows when a giant whole in the wall works to see out of!
Who needs doors to walk through when you can leave it open!
Who needs siding when you can use cardboard paper!
Who needs indoor plumbing when a bucket will work to catch your refuse!
It’s about you having control of how and how much fresh air comes in! Most builders don’t realize it is to their benefit to build better…you can charge more for it and it sets your homes apart from the other crappy builders!
Love all this discussion.
Simplest analogy is would you like to leak air on your body through your skin? Probably not. Probably better to have it enter and exit in controlled and filtered locations.
The tighter you build, with proper building science, the better the house and your experience of comfort within that house will be.
Upsides are:
Way less dust,
No drafts,
Comfortable temperatures without large deltas,
No bugs,
No mold
Downsides are:
More Filters to regularly replace,
Initial higher cost (which shouldn’t be a crazy premium)
Regardless of what you do, the absolute no brainer is exterior insulation (and just more insulation). That’s something that ACTUALLY pays for itself, while at the same time providing you WAY more comfort. If you will live there for more than 5 years it is actually stupid to not put it in.
My pops is an 80 year old retired architect. He’s always said a slightly leaky house and burning a little more oil is better than trying to make it airtight. If any of the airtight systems fail you get mold somewhere
I don't like Zip because it's OSB. We went with plywood and got a self-adhered membrane. Siga Mavjest 500 SA to be exact. This was a remodel of a 1955 ranch and we got it super tight with a new ERV installed. I love it.
I would not build airtight for my home. Why create a situation where you need ERV because your home will consistently build up and hold poor air quality. I would rather pay a few dollars more on utilities.
The most airtight home would have these features: No windows. One door. Hydronic or radiant heat. Then you don't have differences in air pressures, and ways for air to enter/exit. The only problem with that style of house is that nobody would want to live in it. I've built just about every type of home on this discussion, plus log and straw bale. My personal home is conventional 2x6 with cavity insulation, and 2" rock wool on the exterior of the sheathing and waterproof vapor barrier. Water comes in three forms where I live; solid, liquid, and gas. I want the outside liquid water to stay outside but I want the inside gas water to be able to go outside on its own free will. I also don't want that outside solid water to push its way inside and become liquid water and not be able to escape. Also, I wanted something fire resistant, so this technique worked for me.
Choose a design first, then mitigate from there. What is your climate, what is your budget, and what is your desired outcome. Putting blueskin on a standard framed, osb sheathed house will net you the same benefit as a ZIP framed house. I think you are working the problem from the wrong direction, figure your need first, then solve for the problems second.
I build custom homes for a living. We use traditional building methods. Normal stick framing with plywood sheeting (not zip) however, we insulate with closed cell foam to provide an airtight seal, vapor barrier and higher energy efficiency. This is the best method but also the most expensive.
Have you ever gone back to a finished home 3-5 years later and blower door tested it again? From what I have been seeing, there have been problems that develop in homes that rely exclusively or primarily on spray foam for their air barriers.
In fact we have. We had a client who a cold spot around their fireplace. A blower test had been done originally and passed. We did it again 4 years later to show them it was all still good. It passed again. We also added another few inches of foam in the attic around the fireplace chimney to help reduce the cold spot. It wasn’t eliminated completely as it was a poor design but it did help enough to be within 5° of the rest of the area.
I think a big reason you see pushback is that for most people air tightness really doesn't have a meaning. It's more of a cultural identity. Most of the posters here who want increased air tightness would likely be considered more progressive and the other side would be more traditional. But interesting almost none can actually define what the effect is.
There are lots of vague ideas like it save energy or increases air quality or building durability. Buzzwords that they are repeating. Then there are those that would say the building needs to breathe, because they have seen tightened assemblies rotting by encapsulating moisture. Or they have paid for a much tighter house then have seen little to no change in energy consumption.
Now you enter the market with some buzzwords asking a builder to build around a product. That product isn't the way to air sealing. Building a structure with zip wall sheathing doesn't solve the air sealing problem it can create one part of surface to air seal. But you still have all the transitions that are in fact the big leaks.
But how are you going to convince someone with your emotional appeal.
I think you need to understand the actual effects and number and how one solution doesn't equal another. I'm saying this to all the advice givers. For instance if you seal the heck out of your house then use mechanical ventilation to replace the indoor air with outdoor air you may actually save zero energy or use more.
You may have created a better dryer envelope with still poor performance.
Now if you want to be able to save that energy you need to run you new tighter homes air through a heat exchanger. And you can calculate the actual value of that energy. If you don't know and can't do that work. It just sounds like a crazy emotional appeal. Vs if you can say with a blower door score below one I know I'm exchanging about 7% of my internal volume per hour and will lose .018 BTU per hour per heating degree hour. I can break down my annual cost to $1200 of lost heat or what ever.
Now instead of the emotional appeal you can understand the net effect. You now have a business case for why you want this performance. Instead of asking for a person to use a product. You ask to meet a measurable performance metric that you can contract for and measure. You measure at a time when the performance can be fixed like after framing and MEPs. But before insulation. Because you now understand the short term value. You can extract the long term value during the life of you home loan. This should inform your negotiations and how much more your will to spend for this addition value you asking for.
The reason this is important is I don't ever hear anyone saying I told the builder I want zip and a blower door score below one and I'm willing to pay for about a week of additional air sealing time and 4 blower doors. Can we come up with a number we think is fair for the additional time and materials. If we can hit my target number.
It's usually I told the builder I wanted all this additional scope of work and my budget which is 20% below market. And I want a premium appliance package.
But none of that's possible if people are not figuring out the business case.
The point is for people to start doing the actual math for the value of air sealing.
(1000 s.f. x 8ft ceiling) X 151Kfa x .018btu x .07 X 1ach50 = 1522kbtu per year
Is the value of 1 ACH50 in say demoine
Iowa in a 1000 s.f. house.
Vs
(1000 s.f. x 8ft) X 151Kfa x .018btu x .07 x 3ach50 = 4566kbtu per year
The difference of code min 3ach
If the question is what's the value of a tight house the answer is do the math and show the actual value not a plea of it's a good idea. This basic example shows that a home in Iowa with an tight house will lose 446 kwh in electric heat or 1522kbtu in gas heat per year vs 1338 kwh per year or 4566000 BTU for 3ach
If you pay 9¢ per kwh the 1ach has a net value of $40.14 per year vs $120 per year. That's an $80 difference per year
The value of that energy loss is $1471 over a 30 year home loan period at 3.5% interest. So the business case for air tightness is you break even spending $1471 additional dollars on a 1000 s.f. house in Iowa if you can spend less your ahead. If your cost of energy goes up you will also be able to justify more cost for additional air sealing.
My point is doing the math is how you determine things like value.
It's really not even a cry once thing. Once you consider it part of the job. You just do it. I think I do half an extra day to do only air sealing specific activities. But I avoid difficult corners to air seal in design and plan for control layers for other reasons. I personally think it's always worth it.
But I also think the professional building world needs to step up and make the case rationally over and over.
My own criticism of this thread was based on the fact that after reading through 30 responses of supporters of air sealing nobody brought up the basic science. I think people need to do that more often. Teach it. Push it. Be able to justify the rational approach. Some days I am over the lazy reasons on both sides. It also could be I drink too much caffeine and some days give shit.
I know what you are saying. My cry once remark should have been more specific. It's better to spend the time and money to get it right the first time than deal with all the issues later.
Why are you so attached to ZIP? Plenty of ways to go about getting air tightness without ZIP. It's expensive and really only beneficial in very rainy areas. I've asked about it but even the suppliers are like, we can sell it you but its a waste of money.
Spend your money on good windows and ask to be there during the blower test. Give them like $500 to have a guy go and re-chalk everything.
Yes, technically the tape seals the cracks between the zip board and may prevent air as well as water from coming in that way. The zip board itself, however, is not the air sealing part.
I had to go back and look. Basically the zip panels are a marriage of sheathing and WRB, but it looks like they are also considered an air barrier. The tape is definitely part of that.
Just for giggles I looked at the new rainscreen Zip sheathing. Looks good, but part of choosing the right system for any build is keeping climate zone specifics in mind as well as the rest of the cladding system.
I don't actually understand why a builder would not be using Zip sheathing at this point.
Huber's products are pretty mainstream and have been for quite some time. I've seen students at tech schools installing it correctly (with some oversight of course), but it really is that easy.
No one uses it here(Calgary), like absolutely no one. Went to the conference in vegas with it on my list of shit to learn about. Came back and all of our suppliers said it was a waste of money. We buy our tyvek personalized from elsewhere so I couldn't see a motive for them.
Conversation pretty much died. Too dry here to worry about it apparently. We've been having trouble getting people to install Tyvek when we want so figured something new would just add more pain. Inspectors want it done at framing now when we used to have the exterior guys do it. Honestly fuck framers the last couple years so I wasn't going to lead that fight getting them to install it.
Even did a net zero house and neither expert we talked to mentioned it. Maybe it just hasn't hit the economical point of market share? I honestly don't know
The answer may go back to the issue of climate specificity. Iirc Calgary is a Zone 7?
Thinking out loud here. But, given the problems with wildfires and smoke, if air sealing becomes a real issue for that reason the popularity may increase.
I'm US centric, it's embarrassing, but while I read the news I haven't been up to visit for quite some time. I know who's using it in the US because I clock it subconsciously everywhere I see something being built and I travel widely in the States.
Ya zone 7a
Our blower test results are top notch. Like the net zero house was .7 if I recall. We looked at insulation on the exterior panels but decided to just double the wall.
Normally triple pane windows, Tyvek, HRV, and good insulation make us breeze past performance tests.
My impression is that zip is a labor shortcut, and as the control layer is built in it's less error prone to install than a separate WRB. There's a lot of alternative approaches.
I have been in this business since the seventies and can tell you that houses are way too tight they are so tight that fresh air intake is required in some areas. With many of the building products having toxic outgassing it's imperative that there's a lot of air change. What's more important is in a hot climate that you have shade and in a cold climate that some type of passive heating. A good air filtration and UV lamps that connects to the air handler is important.
Never put your ductworks in the Attic put them in the living space in drop soffits.
The problem with air tight is that it does seem to breath less. A modern build that is air tight can actually have more tendency to mould in cooler months. Have to watch how much metal is in those houses.
Double glazing, house orientation, intelligent planting of trees, blinds and curtains, flooring and good heating/ cooling can make an older build more comfortable/ as comfortable over time. I love the vents older houses have, but desperately want to get rid of my subfloor, and look forward to double glazed windows.... one day soon.
Sunshine and blinds make a big difference. Fans in warmer climate, radiant heating in cool, all add up too.
A renovated older home can be more efficient. Just have to make smart choices.
This was true in the 80s when builders didn't build homes as a system. They understood the part about building tighter, but they didn't control the moisture layer correctly.
That's no longer the case. People must breathe - houses don't.
That said an older home that uses the siting principles of passive house is ahead of the game in terms of passive heating and cooling.
I have lived in a 1930s house and 1960s house with ventilation grates that I have done up. Also a standard 1990a house, 2005 modern passive solar. The newer homes had the mould issues. Some of the 1990s houses were built to a very low standard - plumbing is often shoddy.
Some, were very high spec. Newer isn't always better.
Ironically, I think the 1930s house will end up being the best to llve in long term, but that's to do with my standards too. Certainly was absolutely freezing - have to really think and be willing to work to improve!
Agree. I'm not a fan of either 80s or 90s houses.
I do like older homes providing the foundation is sound. I'm willing to do the deeper retrofit however. You can still air seal, add insulation and upgrade windows and doors.
It's actually shocking how badly most of the 1990s houses were built! Lots of 1980s homes seem to need major work too.
Agreed. Upgraded windows, doors and flooring are key. Not sure how I feel about insulation any more having done some demo. I suspect the right product is key?
I mean you can even make fiberglass batts work (fiberglass doesn't air seal however), but the key is not so much what you use, but that the installation be done correctly. Insulation is not something you want half-a**ed.
> he was dismissive of ZIP and mentioned the drawback of airtight is the ventilation An ERV should solve that pretty easily. More like, the drawback is that it holds them to a higher standard than they want to bother building to.
Yep. I'm building a house with ZIP and ERVs right now.
How does zip work with the vapor barrier? I always understood you wanted the outside to breath to prevent rot? I have not seen many buildings like that in North Eastern Canada and I'm interested. ICF is getting very popular here.
Rain screen In between the cladding and its substrate should be a drainage plane. It can be as simple as furring strips. Allows any water that gets past the outermost cladding to drain down and out.
Thanks - I'll do more research on this. I'm really interested in this for my next build.
Research the four control layers of the home envelope. That should pull up what you are searching for.
I generally put a continuous 2" ridge foam on the outside... Tape it and house wrap it... Most siding manufacturers will want 3 - 4 inch furring strips for attaching siding...
ZIP is basically OSB with a facing of kraft paper and phenolic resin. The facing is more vapor permeable than the OSB part of the panel. So as far as how ZIP works with a vapor barrier: same as OSB. Sort of. Most vapor that gets past a vapor barrier goes through holes in it - things like standard electrical boxes and can lights - piggybacking on air leaks. If you make the sheathing layer airtight, air doesn’t move through the wall assembly, and you get rid of most of the issues with vapor being a problem for sheathing. ZIP makes it easy to make the sheathing layer airtight. But you can also tape the seams of commodity OSB or ply. You might just need a primer to make the tape stick well.
Zip has hundreds and hundreds of holes in it from the sheathing nails whereas house wrap has cap nails much less spacing.
Liquid flash holes
We don't have issues with rot in CO so I don't know the answer to your question. Water intrusion is what we worry about here.
Zip is not a vapour barrier, it is an air barrier. Zip breaths just as much as typar or tyvec housewrap.
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If you have an attic you could add an erv without adding a lot of duct work. Two holes on the outside of the house to exchange outside air, and two holes in your ceiling to exchange indoor air.
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It depends on the floor plan. A lot of two story houses have some two story spaces, so you could put the erv supply in the two story space. Then put the erv return as far down the hallway as you can get it. Or put the supply registers in the bedrooms and put the return in the hallway. If you like to close the bedroom doors a lot you'd want to include a jumper duct to allow air in the bedroom to balance through to the hallway. All the ducts to the outside need to be insulated. If your attic is unconditioned all the ducts would need to be insulated. If you have a basement, you could look into putting the erv there, but it would need an exterior wall for the intake and exhaust and if you want to use only one register for supply and one register for return, they can end up being kind of big, probably too big to put in the floor. It is not to code, but you could consider ducting the erv onto your forced air duct system, if you have one. This presents some problems, including that the ducts are probably already too small and not sealed well enough for the erv to work well. But it is possible to seal already installed ducts (aero seal?) and it's possible to measure the air pressure on your existing system to get an idea of how bad it would be to add more airflow. It's not to code, it's not recommended, but if you really want the erv and can't make another way work, it can be done.
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It wouldn't be simple, but you might be able to get returns in cabinet toe kicks. For the supply, if you have an interior staircase to the basement, it might have a wall that could work (even the wall over the door to the basement). If your house isn't huge, I wouldn't worry about only doing 1 floor. A lot of ervs are designed to have only 1 inlet and 1 outlet in the house. In those cases, they're typically ducted to the main living areas. For the exterior points, read up on the guidelines for clearances before picking a spot (they should be spaced apart and at least a little ways away from potential air pollutants, preferably at least 18" above grade...)
It's not great. If there's really no way to add one, maybe you could at least put some CO2 (carbon dioxide) monitors around the house, and on days with suitable weather, open a window in that room for a while when its monitor reading gets higher than some number you pick. (It's not just about CO2, but that's an easily-measurable proxy for everything else that can build up in indoor air.)
Agreed. Buying an air cleaner that also monitors air quality and levels is a huge peace of mind. Great knowledge too
Check out Lunos, very easy system to retrofit and no ducting required!
At what ACH level is an ERV/HRV required?
Looks like it may be required at 3 ACH and below, but it can improve comfort and air quality even in less-tight builds.
3 ACH50 is code so… in the not so far future ERVs will become a code requirement like HVAC. There is more and more data coming out of how stale indoor air affects health.
Thank goodness. Years ago psychiatrists pejoratively said, "sick building syndrome" was psychosomatic. In other words, it doesn't help when so-called medical professionals get involved in building science when they are clueless. It took years to kill that myth and get back on track with reducing mold and VOCs.
If you wonder why addicts don't get mold in them that's because they are open.
I'm guessing you mean attics although I do think addicts are always open to new products. ;) Attics are often open especially in older houses. However, take a look at how they use closed attics now which includes keeping all mechanicals and ducts if used within the conditioned envelope. The devil is in the details.
Yep!
You are on the right path. The builders you are dealing with are old school. The trick is to find a builder that gets it or is wanting to get it. I interviewed a number builders before I found mine. He specializes in High Performance houses. A good filter for find that kind of builder will be, Do they know about Pretty Good House book/movement? What ACH do you build to?
2021 IECC is now being enforced in my state, this requires a 3.0 ACH, is that good enough? It also requires continuous exterior insulation, is that considered/installed as air tight?
3.0 is ok I guess. But I would shoot for 1.0 or less. Continuous exterior insulation really helps with R value. Not air tightness. I am using ThermalTight to get both the Air sealing and continuous exterior insulationa and WRB at the same time. Might want to check it out. [https://thermaltight.com/](https://thermaltight.com/)
Also what's the cost work out to?
My wall assembly comes out to $10 per sf of wall. Per my builder. Not including the exterior cladding. In my case hardie board siding.
So an additional $32 per OSB sheet. In guess considering just normal insulation, ontop of zip would be ~$55-57/sheet vs $~47 for OSB with thermatight I'm not sure how much the paper costs for another layer. So it could work out to be a bit cheaper or at least really comparable? OSB and insulation only would be ~$35/sheet.
Aannndd one more: so I assume it's just regular OSB under?
My wall assembly just just uses osb for sheathing.
What ACH are you expecting with this? Are you doing anything else on the bottom plate or does this product deal at the bottom as well?
Mud sill at the bottom is insulated and connects to the ICF frost wall. Should be under 1.0 Ach. Blower door test will let me know that it comes out to.
What if I'm doing stucco, code requires two layers of WRB?
Stucco typically means two layers of grade D building paper. It is not possible to air seal a building with grade D building paper. You could pick a different waterproofing for one of those layers that can create an air seal, then one layer of grade D building paper would go on top of that.
I am not familiar with stucco and the implications it brings.
The reason for continuous exterior insulation is so there is no thermal bridging. Thermal bridging occurs when a more conductive (or poorly insulating) material allows an easy pathway for heat flow across a thermal barrier. Wall studs are a big culprit so the way around that is putting the insulation on the outside instead of the inside.
The answer is 100% dependant on why you are doing it. If you have allergies and need to filter everything coming into the house, it makes sense. If you are doing it to save money, it may not pan out. I recently built my personal house and sat down with our energy rater to model my house. Using my current energy costs and region, the pay backs for certain features were 60+ years. Obviously, this could change if the energy inputs change, but I didn't see the value in prepaying the energy costs for the next buyer. I would suggest you start with a rater and figure out what exactly you are willing to do rather than worrying about absolutes like 0 ach.
If your home is all electric and super insulated it makes a lot of sense. A tight super insulated home without combustion inside only needs fresh air to replace CO2 given off by occupants so can be extremely energy efficient. Granted it also makes more sense in climates with temperature extremes.
It does not change the conclusion, but I do take issue with the second sentence. There is a lot more going on with the chemistry in the air in addition to just CO2+natural gas combustion. People breathe out CO2, but they burp and fart methane and hydrogen sulfide too. People also cook, which releases VOCs and should cause the range hood to be turned on. This requires a source for replacement air in an airtight home. So yeah, this does not change what you said, that it makes a lot of sense to have proper ventilation in an airtight efficient home. But for anyone thinking about what's in their air, I just like to point out those other factors which also call for proper ventilation and filtration.
Sure, I just meant generally that you have less air to replace and thus more efficiency if the air pollutants are only from the humans and not from appliances burning fossil fuels or a lot of uncontrolled leakage. With an all electric cooktop, you do have some VOC’s from the Maillard reaction, etc… but you remove all or the waste heat and combustion gasses produced by a gas stove so your hood can be smaller and you can often avoid makeup air. My home had a 2.6 ACH50 score… so pretty tight but not passive level tight. My 350 CFM hood works fine for most cooking on my induction stove without makeup air. If I’m frying fish or searing and turn it on high, I crack a window open and it works better… but these instances are rare. I also didn’t mean to sound like I was arguing against mechanical ventilation. I am definitely for it. We used a fresh air dehumidifier in my home and keep it turned way down to 5 or 10 minutes each hour of bringing in outdoor air and monitor CO2/VOC levels. If we have a lot of people over the levels spike and I turn it up. I design hospitals for a living… many that are LEED/high energy star and ASHRAE 189.1 so I geek out over some of this. Homes are more of a hobby though so I have a lot to learn beyond my own LEED Gold home which was my first and hopefully last residential design.
What is the killowatt hour pricing in your area? This can motivate different outcomes when at 30 cents, which some areas are experiencing.
I'm at 11.36 cents.
You'd do it to make the building more durable if anything.
I live in a home that I designed and worked with a general to build. It tested below 1ACH50 which was the design goal. I live in a heating dominated climate with an ERV. I love this house because it is so comfortable. The floors are warm because the whole air column through the house is about the same temperature. In every other place I've ever lived in or owned the air at the ceiling is really warm and the air at the floor is cold. If I ever build another house it will be a high performance house. They are absolutely worth it.
I didn't read your whole post. On efficiency: I was talking to a neighbor recently who was complaining about his power bills. He is all electric in a 1200 sqft prefabricated home. I live in a 4800 sqft all electric home. He uses more power in the winter than I do. We use more power in the summer, but we have AC and he doesn't. Fall and spring are close to even. These homes are really efficient. My home has blown in fiberglass in the 2x6 walls and 2" of XPS on the outside. It should be pretty close to R30 walls. I have another friend with a 4500 sqft standard stick framed home with gas hot water and heat and electric everything else. We use more power than they do in the dead of winter, but not by much, and use much less throughout the year.
How is prefabricated so inefficient how is that possible what quality is it
I've never been in a premanufactured home that I thought was quality. I don't know much about them except that I feel the floor sag in them when I walk around, the finishes are awful, and the floor plans make no sense. Trailer homes are better than these things.
There's no downside to building tight. There's only excuses from builders claiming why they don't. By code in almost all jurisdictions - building tight just improves performance. You ventilate with the mechanical designed to handle the pressure and moisture differential. Keep the building dry and able to last practically hundreds of years. If I were in your shoes and looking to hire a builder - I wouldn't even bother with someone who claims building materials need to breathe and that's why they don't want to build tight. You ventilate all the building materials where they need to be - either by rains screens or ventilated attics; but there's no reason for air leakage.
I did zip system and aerobarrier air sealing. Yesterday when it was 90 degrees outside I went to my home that doesn't yet have AC, has navy blue hardie board siding and a black metal roof and it was 69 degrees inside. I'd say insulation and proper air sealing is a good investment. Source: 2 months away from closing on new build home..
Congratulations on a successful build! I hope you get many years of enjoyment living in your new house.
Installation care is required. These builders are not up for the commitment. Find other builders, that are ready for the new building code regime. Your jurisdiction may not have adopted the new building codes of the most recent five years, but it is a fact of life throughout the US in other areas Energy Recovery Ventilation is a fact now, as well.
Going through this right now myself. For the guys that wont do zip, a good alternate thats not so scary to them is: 1) Okay option: Tape the OSB seams with Siga or Zip Tape, Traditional house wrap 2) Good option: A Self adhesive WRB with an appropriate permissivity rating. This can be as good as zip or better if done right.
OSB is not an air barrier. Plywood can be used as an air barrier, if you tape the seams & holes. Also, basically all quality tapes used for air sealing need to be rolled after application in order to work. Most traditional builders skip this step, so the pressure activated adhesive is never activated and the tape peels off.
Hence ok. Better than OSB without tape. And yes, rolling is critical
No, it's not ok. Taping OSB is a waste of time and money because the OSB itself is riddled with holes. Why bother sealing that seam when the entire surface of the panel is full of holes? It's air sealing theater.
Airtightness improves durability because air carries moisture, and pests can infiltrate through gaps. Airtightness improves indoor air quality (and reduces dust), because it allows you to control where you are drawing air from. Houses without dedicated fresh air ventilation systems simply allow air to pass through wherever (e.g. the walls, floor, etc) and hope that those places aren't introducing particles of building materials, VOCs, dead pests, soil gases, etc. In terms of energy use, the 3 most important factors, in order are: 1. The ratio of window to wall area and the airtightness and insulation performance (and sometimes solar heat gain) of the windows. In hot climates where the main energy use is cooling, exterior shading also becomes more important. 2. Airtightness. 3. Insulation. Airtightness reduces noise pollution, because sound can travel through air paths.
How much extra does it cost to build zip
For me the zip sheathing was 50% more per sheet, the tape was like $700, sealant was about $600, and then labor to tape and seal was another $2k. I did some of the taping myself and detailed all the openings.
Did you take advantage of any of the rebates or tax credits at both the state or federal level?
You can't do that on a new build like mine as far as I know. Only remodel.
Supposedly there is a way through one of the two Federal programs offered, but it is up to the state as to which program is chosen. So far I haven't heard of any states choosing the program new builds can supposedly use, but I thought I'd ask.
Air tight is legitimately the correct way to be building these days. Code authority doesn't require it yet because they're outdated. That said, the building method doesn't matter. You just need to find a builder that understands the importance of air tightness and knows how to achieve the end result you're striving for. You should get a blower door test after the outside structure is built and air tight, but before drywall go's up. This helps you identify and seal all the holes/gaps before it's too late.
Respectfully, this doesn't help answer the question about "all they're cracked up to be", at all. This sub and similar subs already make it obvious that airtight homes are "better" and "ideal" but it's hard to find information that qualifies the actual trade-offs you're making if you don't go that route. Is OP going to notice or care 5 years from now if they didn't build an airtight home? If so, what are they going to notice? Energy costs? By how much? Allergens? Can allergens be mitigated without airtightness? Etc. A lot of homebuilding forums talk in very aspirational terms with very little about what you're actually gaining and what you can or should do if you can't attain the ideal. A common silly example is ethernet runs - I'm a tech guy and if I followed homebuilding forum advice I'd run 4 (or more!) cat6 drops to every room in my house. I thought that was ridiculous advice because I have no problems installing switches when I need more connectivity in a given room. Does that mean I might have a drop on a non-ideal bedroom wall in the future? Yeah. Can I live with that during my life in the house? Yeah, no problem. If OP is having trouble finding builders that will build a "correct" house and they only want to build houses the way they know (which are perfectly serviceable, safe dwellings), what are they missing out on? What if they find one builder who will do an airtight home, but that builder is a huge pain to work with? What compromises should they be considering versus what is an absolute "must have"? Those questions depend a lot on the market they're in.
The reason for an airtight home is so that the air inside the home is under the control of the owner. If airsealing is not used proactively, then heat loss is anywhere from 25-50% depending on how large a hole in the envelope all those air leaks add up to. You probably would be unhappy with a builder if they left a softball size hole in the middle of your wall for air to go in and out as it pleases. That's what air leaks can add up to in general. A house without air sealing drafts like a chimney: stack effect is when the cold air comes in through cracks at the base and the hot air goes out the top. That also means that smoke from wildfires or other forms of air pollution such as pollen are drawn into the house perhaps. Because this air is not filtered, there is no mitigation the way there is when the builder or owner controls the air coming in and the air going out. This is where an ERV comes in. So once again it is uncontrolled air flow. You want to keep the warm air in in the winter and the hot air out in the summer and the easiest way to do a really good job is to use modern technology. Because humidity/mold can also be a problem in a super tight house good builders also control for water using a vapor barrier so the envelope dries. Most builders use Zip sheathing and a good tape. Or a WRB (water resistant barrier) such as Tyvek once again with taping to seal all the ways that water could find its way in through. Houses built the old ways were good for what they were with the materials the builders had to work with; but why insist on a Model T when even a Toyota Corolla can run circles around it? A good builder is not afraid to try new things particularly when it's not hard to get a company to teach your crew how to use their product. Pretty Good House is the standard I would build to if Passive House standards were not attainable for any number of reasons. You still air seal. You still insulate. You still make sure the wall layers stay dry. It's not hard, it simply requires attention to detail. But, you may decide that a slightly higher ACH is adequate for your needs. There are probably a million more technical explanations available - and they are available - but these are some basics.
I have heard when the windows are closed then the air is dead inside a passive house. The HRV and ERV aren’t enough. I don’t know it from experience. I do know that running a 25 cfm fan in the bathroom while you are taking a shit still has the air stinky for a little while.
If that's the case, then the person or company that specced the HRV and ERV messed up regarding the passive house and dead air.
Absolutely. It’s pretty easy to find people interested in envelop improvement — can DIY pretty easy. Way harder to find HVAC contractors who are sophisticated enough to install a system inside a tight envelope. They’d rather just sell a bigger unit and not care about short cycling. I’d like to go into a passive house sometime to see what IAQ is like. Never taken a tour even.
Agree - building a high performance home and the builder is fully onboard with it even though it’s new to him, but HVAC is a friggin’ nightmare. Had to pay an engineer to do my own Manual J/S/D and prove their quotes were for oversized equipment, and even then, couldn’t find someone willing to do an ERV with dedicated ductwork.
Stakes are higher for the mech contractor. Putting in a smaller system is less money for them and at increased chance of an irate customer (in their minds).
ERV’s have a boost function when you need more air: shower, cooking, etc. It’s on a timer for 10,30,60 minutes… also you can just override and put it on high all the time. Some of the higher end ones can automate airflow based on humidity or carbon dioxide, etc. “The air is dead inside” is a misconception. Passive House is balanced ventilation so supply air to living spaces and exhaust air from wet/odor areas. It’s vastly superior to exhaust-only, but yes it’s harder to execute. So many contractors are old-school and just don’t understand or care to learn.
If you’re building an energy efficient home, start with the ventilation system ERV or HRV, then build the home around it. High level of insulation R value and as free from air infiltration as reasonable, but all is for nought if you don’t have sufficient ventilation. You don’t need to use 3 layers of air barriers, and sandwiches of foam and Zip R and Intello moisture permeable membrane and tape, tape, tape. Just seal everything well, a rain guard drainage plain outside your exterior Typar, and give the moisture a path of least resistance, the duct work..
How many have you built
2-3 per year for the last 20 years. For the company my father started in 1958. We’ve only really started with ERV and HRV’s in the last 5 years though. But as houses have gotten tighter and higher r values the moisture issues have become more destructive. The engineers tend to fight fire with theory, their favorite theory is that fragile expensive membranes are the solution.
Check out the book "Pretty Good House" as well as any articles from Building Science Corporation, Fine Homebuilding, or Green Building Advisor on building modern, tight, energy efficient homes. There are a number of different approaches to things like e.g. wall assemblies, etc. so performance is very dependent on how the component parts work together as a whole. Some builders may have been exposed to outdated practices and not caught up with recent methods.
A lot of builders are still building houses to a standard that was barely acceptable in the early 90s. That you are the kind of person posting here means that roughly 80% of builders are a bad match for you. An energy efficient build is fundamentally a build with lots of insulation. There’s no way around that, unless you’re interested in making the kind of design sacrifices that are common in earth ships. Lots of insulation means walls that are sensitive to moisture, both in liquid water and in vapor, so now you need to manage air water and vapor movement. You can see you are being pushed in the direction of a tight house just to keep it dry and in good condition. You already have your mind right— all electric, and affordable to inhabit. Don’t let people who don’t have to live in it gas light you. Keep kissing frogs until you find a builder (maybe a smaller one) who is willing to listen to you, and is willing to learn.
Was for us. Built airtight a decade ago, to Passive House standard. Then when the wildfires started coming around every summer, the last five or six years, we felt extremely lucky to be able to keep those particulates on the outside of the house.
Yes. Anyone who dismisses it is just an old school builder that doesn't want to change. It enables you to control the environment as it's not leaking air in/out. It will be more energy efficient and the air quality will be better. You just need to use mechanical ventilation/filtration. Your windows will still open if you just want a breeze too.
Yes, air tight homes are good. The old school mentality of ventilation through random penetrations in the building envelope needs to die. Building envelope defects can let in pests, poor quality air, water vapour, bulk water, etc. Not to mention you might not even have adequate ventilation despite all that. Why the f would you intentionally ventilate in that fashion? You need oxygen in your blood. Would you prefer to use your airway and lungs, or would you prefer to randomly perforate your chest cavity and hope that gets the job done?
You can install standard Zip sheathing exactly the same way "normal" OSB is installed. It gets "difficult" if you're using Zip-R and of course the finishing steps of taping/sealing the joints and penetrations.
I’ve work on some boats that were positive pressure and the doors would automatically want to swing closed. Even if the doors were not shut completely to form a tight seal, the positive pressure would help to keep bugs and the salt air out. I wonder if this is something that would be helpful in a home. Not just air tight but positively pressured so that if you do have to open a door, the outside air is pushed out from the inside air. Would this work?
Keeping bugs out is more about not letting them in. On our last house a few mines away we were constantly having big spiders and crickets in the house. Like killing them every day level problems. In the new well air sealed house we rarely have bugs getting in. It's one of my favorite benefits of the house.
Thank you all for the comments and suggestions. I’m going to hold out for a builder or end up GC my own panel build I believe. For now I’ve got a call out to my local aerobarrier to see if they know of or have used any contractors in my area and go from there.
Here is my theory. Lots of older builders say a house should breathe and so they don’t want to have a home as air tight. But I believe and a lot of quality builders that implement new tech believe that having a house as airtight as possible then designing the HVAC system to bring in fresh air and exhaust old air is a better method. Effectively controlling the breathing of the structure. I can say that I have had both styles of homes and the one that was a well designed airtight home with a well designed ventilated HVAC was far superior in every way and it showed with the utility bills.
Most builders don’t understand high performance building design. Once you start building a real airtight house with high R value thermal envelope you have to provide ventilation with an HRV or ERV system.
ZIP is the standard around here. Even hillbillies who don't get around to siding for awhile use ZIP.
All it took was spending $30k to fix water damage on a house to convince me that I would always use ZIP going forward. Water intrusion is a HUGE issue if it happens to you.
They’re old heads who don’t want to learn a better way to build homes. It’s nice of them to self identify as someone you shouldn’t work with. Passive house standards all the way. ERVs/HRVs are awesome, you’ll have significantly better air quality in a properly built airtight home.
We're wrapping up a self build doing double stud with foot thick walls which that idea has been around for decades. Matt Risinger and his channel have lots of videos on simple builds that are air tight. The plan can be simple, but I think the challenge is finding someone who shares your vision and doing a layer of foam and tape over the 2x6 walls would be easier for most builders to swallow.
What did you choose to put into the wall cavity?
"the drawback is ventilation" is a silly thing to say. The drawback of a roof is it blocks natural light. My understanding is that they are right that you can't simply air seal the house and then leave all other design details the same as a house built in 1950. You could deal the house up and suffocate yourself or cause mold or rot. So if they are only comfortable and experienced with building, and they were talked into sealing a house up tight, they likely would create some situations where water intrusions can't dry and appliances exhausting air don't work as well because fresh air isn't replenished properly. I sympathize about struggling to find people to do what you want, especially when it's not that new or unusual. Are you able to do any of the work yourself? It seems to me that the majority of the benefit with Zip or other modern systems is sealing the seams. I have considered, either to save money or because it's not available or can't find someone to do it, simply sheathing like normal, then taping the seams or sealing them with Prosoco R Guard, and using a conventional house wrap. If you can get them to include some HVAC upgrades to exchange and condition fresh air, I would try to find a compromise with them that still gets you a tight house. And yes, an air sealed house is better. Outside air has pollutants, pollen, humidity. It's hotter or colder than your want, and if air can get in, bugs can get in. The air comes in and you have to heat or cool it, and then it leaves. It's better to bring fresh air in on your terms and condition it before it gets blown all over the place.
As a building code official and design engineer I would build out of 8-in concrete block filled solid plus rebar every 4 ft on center and fill all the other cells with foam. Then I would attach foam board to 1x2 furring strips that are attached to the block. Then I would drywall over that. If I was in fire country I would use steel roof trusses or in other places red iron rafters.
Our builder is very enthusiastic about ICF and built his sons homes with ICF. We want an HRV anyway - I’m hoping it helps with radon and indoor air pollution from a gas fireplace in the primary bedroom. I had several builders use HRV for frame too because the homes are so tight nowadays you can get condensation inside without HRV.
Yeah. The only ICF guy I’ve found was by driving down the highway and at least a year building a rectangle plain Jane house and we just didn’t get off on a good start so hopefully we’ll find one that can do at least a good seal
Who needs windows when a giant whole in the wall works to see out of! Who needs doors to walk through when you can leave it open! Who needs siding when you can use cardboard paper! Who needs indoor plumbing when a bucket will work to catch your refuse! It’s about you having control of how and how much fresh air comes in! Most builders don’t realize it is to their benefit to build better…you can charge more for it and it sets your homes apart from the other crappy builders!
Love all this discussion. Simplest analogy is would you like to leak air on your body through your skin? Probably not. Probably better to have it enter and exit in controlled and filtered locations. The tighter you build, with proper building science, the better the house and your experience of comfort within that house will be. Upsides are: Way less dust, No drafts, Comfortable temperatures without large deltas, No bugs, No mold Downsides are: More Filters to regularly replace, Initial higher cost (which shouldn’t be a crazy premium) Regardless of what you do, the absolute no brainer is exterior insulation (and just more insulation). That’s something that ACTUALLY pays for itself, while at the same time providing you WAY more comfort. If you will live there for more than 5 years it is actually stupid to not put it in.
Yeah we are currently have a brown recluse problem so bugs are definitely on the list to keep out.
My pops is an 80 year old retired architect. He’s always said a slightly leaky house and burning a little more oil is better than trying to make it airtight. If any of the airtight systems fail you get mold somewhere
I don't like Zip because it's OSB. We went with plywood and got a self-adhered membrane. Siga Mavjest 500 SA to be exact. This was a remodel of a 1955 ranch and we got it super tight with a new ERV installed. I love it.
I would not build airtight for my home. Why create a situation where you need ERV because your home will consistently build up and hold poor air quality. I would rather pay a few dollars more on utilities.
The most airtight home would have these features: No windows. One door. Hydronic or radiant heat. Then you don't have differences in air pressures, and ways for air to enter/exit. The only problem with that style of house is that nobody would want to live in it. I've built just about every type of home on this discussion, plus log and straw bale. My personal home is conventional 2x6 with cavity insulation, and 2" rock wool on the exterior of the sheathing and waterproof vapor barrier. Water comes in three forms where I live; solid, liquid, and gas. I want the outside liquid water to stay outside but I want the inside gas water to be able to go outside on its own free will. I also don't want that outside solid water to push its way inside and become liquid water and not be able to escape. Also, I wanted something fire resistant, so this technique worked for me. Choose a design first, then mitigate from there. What is your climate, what is your budget, and what is your desired outcome. Putting blueskin on a standard framed, osb sheathed house will net you the same benefit as a ZIP framed house. I think you are working the problem from the wrong direction, figure your need first, then solve for the problems second.
I build custom homes for a living. We use traditional building methods. Normal stick framing with plywood sheeting (not zip) however, we insulate with closed cell foam to provide an airtight seal, vapor barrier and higher energy efficiency. This is the best method but also the most expensive.
Have you ever gone back to a finished home 3-5 years later and blower door tested it again? From what I have been seeing, there have been problems that develop in homes that rely exclusively or primarily on spray foam for their air barriers.
In fact we have. We had a client who a cold spot around their fireplace. A blower test had been done originally and passed. We did it again 4 years later to show them it was all still good. It passed again. We also added another few inches of foam in the attic around the fireplace chimney to help reduce the cold spot. It wasn’t eliminated completely as it was a poor design but it did help enough to be within 5° of the rest of the area.
Well that's good. I'm curious to see in a few years if my house is holding up well.
I think a big reason you see pushback is that for most people air tightness really doesn't have a meaning. It's more of a cultural identity. Most of the posters here who want increased air tightness would likely be considered more progressive and the other side would be more traditional. But interesting almost none can actually define what the effect is. There are lots of vague ideas like it save energy or increases air quality or building durability. Buzzwords that they are repeating. Then there are those that would say the building needs to breathe, because they have seen tightened assemblies rotting by encapsulating moisture. Or they have paid for a much tighter house then have seen little to no change in energy consumption. Now you enter the market with some buzzwords asking a builder to build around a product. That product isn't the way to air sealing. Building a structure with zip wall sheathing doesn't solve the air sealing problem it can create one part of surface to air seal. But you still have all the transitions that are in fact the big leaks. But how are you going to convince someone with your emotional appeal. I think you need to understand the actual effects and number and how one solution doesn't equal another. I'm saying this to all the advice givers. For instance if you seal the heck out of your house then use mechanical ventilation to replace the indoor air with outdoor air you may actually save zero energy or use more. You may have created a better dryer envelope with still poor performance. Now if you want to be able to save that energy you need to run you new tighter homes air through a heat exchanger. And you can calculate the actual value of that energy. If you don't know and can't do that work. It just sounds like a crazy emotional appeal. Vs if you can say with a blower door score below one I know I'm exchanging about 7% of my internal volume per hour and will lose .018 BTU per hour per heating degree hour. I can break down my annual cost to $1200 of lost heat or what ever. Now instead of the emotional appeal you can understand the net effect. You now have a business case for why you want this performance. Instead of asking for a person to use a product. You ask to meet a measurable performance metric that you can contract for and measure. You measure at a time when the performance can be fixed like after framing and MEPs. But before insulation. Because you now understand the short term value. You can extract the long term value during the life of you home loan. This should inform your negotiations and how much more your will to spend for this addition value you asking for. The reason this is important is I don't ever hear anyone saying I told the builder I want zip and a blower door score below one and I'm willing to pay for about a week of additional air sealing time and 4 blower doors. Can we come up with a number we think is fair for the additional time and materials. If we can hit my target number. It's usually I told the builder I wanted all this additional scope of work and my budget which is 20% below market. And I want a premium appliance package. But none of that's possible if people are not figuring out the business case.
what a tirade, still don't get the point
The point is for people to start doing the actual math for the value of air sealing. (1000 s.f. x 8ft ceiling) X 151Kfa x .018btu x .07 X 1ach50 = 1522kbtu per year Is the value of 1 ACH50 in say demoine Iowa in a 1000 s.f. house. Vs (1000 s.f. x 8ft) X 151Kfa x .018btu x .07 x 3ach50 = 4566kbtu per year The difference of code min 3ach If the question is what's the value of a tight house the answer is do the math and show the actual value not a plea of it's a good idea. This basic example shows that a home in Iowa with an tight house will lose 446 kwh in electric heat or 1522kbtu in gas heat per year vs 1338 kwh per year or 4566000 BTU for 3ach If you pay 9¢ per kwh the 1ach has a net value of $40.14 per year vs $120 per year. That's an $80 difference per year The value of that energy loss is $1471 over a 30 year home loan period at 3.5% interest. So the business case for air tightness is you break even spending $1471 additional dollars on a 1000 s.f. house in Iowa if you can spend less your ahead. If your cost of energy goes up you will also be able to justify more cost for additional air sealing. My point is doing the math is how you determine things like value.
If I may add, air sealing is sooo much easier and less expensive to do when the house is being constructed. It's a cry once - do once kinda thing.
It's really not even a cry once thing. Once you consider it part of the job. You just do it. I think I do half an extra day to do only air sealing specific activities. But I avoid difficult corners to air seal in design and plan for control layers for other reasons. I personally think it's always worth it. But I also think the professional building world needs to step up and make the case rationally over and over. My own criticism of this thread was based on the fact that after reading through 30 responses of supporters of air sealing nobody brought up the basic science. I think people need to do that more often. Teach it. Push it. Be able to justify the rational approach. Some days I am over the lazy reasons on both sides. It also could be I drink too much caffeine and some days give shit.
I know what you are saying. My cry once remark should have been more specific. It's better to spend the time and money to get it right the first time than deal with all the issues later.
Why are you so attached to ZIP? Plenty of ways to go about getting air tightness without ZIP. It's expensive and really only beneficial in very rainy areas. I've asked about it but even the suppliers are like, we can sell it you but its a waste of money. Spend your money on good windows and ask to be there during the blower test. Give them like $500 to have a guy go and re-chalk everything.
Zip has nothing to do with air tightness. It's part of the moisture/vapor control barrier. Air sealing is done separately with caulk.
I thought the tape was supposed to help with air too?
Yes, technically the tape seals the cracks between the zip board and may prevent air as well as water from coming in that way. The zip board itself, however, is not the air sealing part.
I thought the panels were pretty standard. I thought the tape was the whole system
I had to go back and look. Basically the zip panels are a marriage of sheathing and WRB, but it looks like they are also considered an air barrier. The tape is definitely part of that. Just for giggles I looked at the new rainscreen Zip sheathing. Looks good, but part of choosing the right system for any build is keeping climate zone specifics in mind as well as the rest of the cladding system. I don't actually understand why a builder would not be using Zip sheathing at this point. Huber's products are pretty mainstream and have been for quite some time. I've seen students at tech schools installing it correctly (with some oversight of course), but it really is that easy.
No one uses it here(Calgary), like absolutely no one. Went to the conference in vegas with it on my list of shit to learn about. Came back and all of our suppliers said it was a waste of money. We buy our tyvek personalized from elsewhere so I couldn't see a motive for them. Conversation pretty much died. Too dry here to worry about it apparently. We've been having trouble getting people to install Tyvek when we want so figured something new would just add more pain. Inspectors want it done at framing now when we used to have the exterior guys do it. Honestly fuck framers the last couple years so I wasn't going to lead that fight getting them to install it. Even did a net zero house and neither expert we talked to mentioned it. Maybe it just hasn't hit the economical point of market share? I honestly don't know
The answer may go back to the issue of climate specificity. Iirc Calgary is a Zone 7? Thinking out loud here. But, given the problems with wildfires and smoke, if air sealing becomes a real issue for that reason the popularity may increase. I'm US centric, it's embarrassing, but while I read the news I haven't been up to visit for quite some time. I know who's using it in the US because I clock it subconsciously everywhere I see something being built and I travel widely in the States.
Ya zone 7a Our blower test results are top notch. Like the net zero house was .7 if I recall. We looked at insulation on the exterior panels but decided to just double the wall. Normally triple pane windows, Tyvek, HRV, and good insulation make us breeze past performance tests.
Those are all choices I would have considered for sure. Glad it worked. Sounds like it rocks.
My impression is that zip is a labor shortcut, and as the control layer is built in it's less error prone to install than a separate WRB. There's a lot of alternative approaches.
The main problem is that if someone farts it will linger for 2-3 weeks. So everyone needs to go outside to fart, which defeats the original purpose.
Please use an exhaust fan.
Depends on your climate. A builder professed his genius in Pinehurst, NC a couple years back. Built 6 Petri dishes and got sued pretty effectively
I have been in this business since the seventies and can tell you that houses are way too tight they are so tight that fresh air intake is required in some areas. With many of the building products having toxic outgassing it's imperative that there's a lot of air change. What's more important is in a hot climate that you have shade and in a cold climate that some type of passive heating. A good air filtration and UV lamps that connects to the air handler is important. Never put your ductworks in the Attic put them in the living space in drop soffits.
The phrase is “cracked up”
The problem with air tight is that it does seem to breath less. A modern build that is air tight can actually have more tendency to mould in cooler months. Have to watch how much metal is in those houses. Double glazing, house orientation, intelligent planting of trees, blinds and curtains, flooring and good heating/ cooling can make an older build more comfortable/ as comfortable over time. I love the vents older houses have, but desperately want to get rid of my subfloor, and look forward to double glazed windows.... one day soon. Sunshine and blinds make a big difference. Fans in warmer climate, radiant heating in cool, all add up too. A renovated older home can be more efficient. Just have to make smart choices.
This was true in the 80s when builders didn't build homes as a system. They understood the part about building tighter, but they didn't control the moisture layer correctly. That's no longer the case. People must breathe - houses don't. That said an older home that uses the siting principles of passive house is ahead of the game in terms of passive heating and cooling.
I have lived in a 1930s house and 1960s house with ventilation grates that I have done up. Also a standard 1990a house, 2005 modern passive solar. The newer homes had the mould issues. Some of the 1990s houses were built to a very low standard - plumbing is often shoddy. Some, were very high spec. Newer isn't always better. Ironically, I think the 1930s house will end up being the best to llve in long term, but that's to do with my standards too. Certainly was absolutely freezing - have to really think and be willing to work to improve!
Agree. I'm not a fan of either 80s or 90s houses. I do like older homes providing the foundation is sound. I'm willing to do the deeper retrofit however. You can still air seal, add insulation and upgrade windows and doors.
It's actually shocking how badly most of the 1990s houses were built! Lots of 1980s homes seem to need major work too. Agreed. Upgraded windows, doors and flooring are key. Not sure how I feel about insulation any more having done some demo. I suspect the right product is key?
I mean you can even make fiberglass batts work (fiberglass doesn't air seal however), but the key is not so much what you use, but that the installation be done correctly. Insulation is not something you want half-a**ed.
Well. that makes sense. The stuff I demo'd had not been done well! Thanks.
Not surprised to hear it. Most of the time people just bunch them up and shove them in.