Best Way for Homeowner to Air Seal?
After getting some really helpful advice on here (will link below) for our new construction, we’ve decided to insulate with Roxul batts that we’ll install ourselves. Now that we’re looking in to how to properly air seal, it seems like to do it right takes a professional and proper equipment. Is that the case? Should we just be hiring a contractor to do it all (air seal and insulate)? None of the quotes we received for insulation included air-sealing, except for one, which added over 2k to the price. Is this a high, hidden cost of insulation that we’re just discovering now? Any tips on how to air seal as a non-pro? Which products should we use that are compatible with Roxul batts?
Links to prior questions:
https://www.greenbuildingadvisor.com/community/forum/gba-pro-help/26868/interior-insulation-stud-bays-when-we-have-exterior-insulation
https://www.greenbuildingadvisor.com/community/forum/gba-pro-help/26143/vapor-retarder-interior-if-exterior-has-vapor-barrier
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Replies
Cathy,
The work required for air sealing isn't particularly complicated. However, it isn't intuitive, either. Even experienced contractors usually misunderstand which areas need to be air sealed until they watch a blower-door test or the use of a fog machine.
Air sealing isn't done at the end of the job. It's done at every stage of construction: by framers, drywallers, plumbers, electricians, and insulation contractors. If you start air sealing at the end of the job, it's often too late to do a good job.
If you are an experienced builder, you can do it. Study up on this topic by reading articles on this website and in Home Energy magazine. To verify that you (or your crew) has done a good job, be sure to perform a blower-door test on your home. Without a blower-door test, you're just guessing.
Critical seams often missed in studwalls are those between doubled top plates, between bottom plate and subfloor, and between subfloor and band joist. While it's possible to hit them after the framing is all up, it's better and easier to lay your bead of goop (acoustic sealant caulk or construction adhesive) as the framing is assembled and installed rather than a retrofit-bead at the edge after it's already up. Caulking the sheathing to the studs in each stud bay after the fact can sometimes be easier than during assembly though- it depends. Don't forget to foam-seal all wiring & plumbing penetrations of the studs & plates too. (What? Air can move sideways? Who knew! :-) )
If it's already up and sheathed, do the best you can- it'll all help. But it's probably worth blower-door testing BEFORE you start hanging batts.
When using batts be sure to trim carefully, splitting rather than compressing over wiring runs etc, and tuck the edges & corners to guarantee that it fills all the way to the back, then tug it out a bit so that it's just proud of the stud edge to guarantee it fills the entire cavity. even small gaps at the corners of the cavities running the full length become easy paths for convection loops. With a lot of detailing you can get the performance out of high density batts, but it's a lot easier to get the near-perfect fill with blown or sprayed insulation.
Thanks everyone who answered so far! My husband has been air sealing throughout the building process (framing, exterior insulation, etc), but now that we're going to air seal prior to installing the insulation ourselves I started research doing it right (mostly on this website) and that's where I felt I hit a wall. One post says that caulk doesn't do the trick, another says that there are these two new great products for air sealing, but they're only for pros and only work with certain insulation products. So I'm wondering what products are best for sealing the interior and wiring/plumbing penetrations, and whether those products work with the Roxul batts. Am I overthinking this? One insulation company I spoke with told me if we were going to air seal ourselves we needed to buy this closed cell foam kit for $500+ plus that sounds like a nightmare to operate. Does anyone have any different recommendations?
I would hire an experienced contractor to air-seal and insulate if you can. They should own a blower door and use it while air-sealing--if they don't, they're not even in the game IMO. I don't see the appeal of batts if you can get dense-packed cellulose. Is anyone offering these options? How big is the house, and what are the details (wall heights, # stories, basement/crawl, attic/cathedral, etc.)?
$2000 extra sounds like a lot to me to air-seal the average house, so maybe there is something else about their proposal that has value... or maybe not. I think as a homeowner you are at a disadvantage when it comes to evaluating proposals from subs. If you want to cross out the identifying information and post them here, we could see what they are offering and what they charge for it.
I am working on my house and have bought a variety of books and then use the website to get the most current information.
A great book is Insulate and Weatherize, a Taunton publication, which I think also owns this website.
I think I wasn't clear with my question because air sealing happens at so many different steps. Here is my question:
What is the best way for a homeowner to air seal the interior of framing and wiring/plumbing penetrations when they are going to use Roxul batts as insulation?
Thanks everyone!
Answer, buy a foam gun and canned foam for it. A good way to do that is by calling Small Planet Workshop, they will send you what you need. I like Tremco LEF foam. There are places where you may also want to use caulk, sheet metal, or rigid foam. http://www.smallplanetworkshop.com/
David, I don't think Cape Cod is punching the same weight as wherever you are. i've talked to every one of the large insulation companies and most of the small ones, and no one has mentioned air sealing, but one, and no one has mentioned doing their own blower door test. (Our town's code requires it, but from what I can tell you get a different company to do it). The proposals don't tell you much, I don't think it worth posting.
The house is 24 x 24, 2 floors, dormered gambrel roof, but no cathedral ceilings. 2x6 framing. My husband has done every step up until now except electric and plumbing, including air sealing at the other steps (exterior insulation, sheathing, etc). He can install Roxul batts if its as easy as everyone says. I just want to do our homework about how to air seal properly on the interior before we insulate. I could be overthinking this. I'm not the construction professional, I'm just the one that uses the computer :)
Thanks!
Cathy,
It is tough to know how and where to air seal, but keep the faith. After all, in the end, it's just plugging holes. You're probably up to it.
We just did it at our offices and got a really leaky existing building (9.5ACH50) down to one that was really tight (1.98 ACH50). Before we started, we had a blower door test done. That's how we knew where to seal.
Perhaps plan on doing what you can until you're at a point where you can ask someone to put a blower door on your house. The best time is after the windows are in and before the insulation. Or perhaps after drywall if your house uses a truss roof. Just try and plan on a time when the house has some kind of air barrier but you still have access to the guts. It's an imperfect choice of timing, just do your best. Hire a pro for a day, get some tape, gun foam, caulk, goo and... Lots of friends. Depressurize the building and go to town!
Martin had an excellent piece in Fine Homebuilding on air sealing:
http://www.finehomebuilding.com/how-to/departments/energy-smart-details/airtight-drywall.aspx
You can do a lot of seam sealing with acoustic sealant caulk (buy a case of the fat tubes and a powered caulking gun if you have a lot to do- your carpal tunnels will thank you.) For bigger gaps like wiring & plumbing penetrations you can get a lot out of a single 12 board foot FrothPak (available at box stores, eg: http://www.lowes.com/pd_144279-236-157802_0__ ), which is a low expansion 1.75lb density closed cell polyurethane foam, or a $50 pro-style foam gun for 1-part foam that takes the screw-on cans (try Graingers, or internet sources.) The notion that you need a $500 2-part foam kit to air-seal a smaller house is just silly, unless you're planning on using it to flash-foam over the entire band joist & foundation sill rather than seam-seal.
You should consider performing your own "blower door" guided air sealing to compliment a calibrated blower door test. Get one or two heavy duty fans, use plywood/plastic or whatever you need to, secure and seal the fan(s) in an exterior door opening. Fire them up and start looking for drafts! Congratulations on your new, efficient home.