Underfloor air barrier - Client's bedroom is super cold

[rselvig]

My clients' home has two bedrooms on the lower floor. The house is built on a hill with a raised perimeter foundation that exposes both the walls and floor systems to the vented crawl space. My plan is to spray can foam the major penetrations and then install a layer of thermo-ply with a bead of caulk at each joist and tape all of the seams.

Has anyone used this approach or does anyone have any other ideas/concerns?
Thanks,
Rolf

[calvert]

I am not sure if you are trying to address heat loss or air infiltration. Why not, at the very least, install some form of insulation in the floor cavities prior to installing the exterior air barrier. I would also make sure you review the rim joists for sources of air leakage and deal with that with an appropriate application of sealants and insulation as well.

[rselvig]

Calvert,
Thanks for the response. I should have mentioned that the floor and walls are already insualted with fiberglass batts. That said, I'll pull them away to inspect and air seal...good point on the rim joist. Right now, air is whipping through the walls (opened a j-box and it was super breezy) and they can't keep any heat in the downstairs (stack effect my be contributing as well).

My goal is to air seal as best as possible while reducing any chance of moisture build-up that might cause other problems. I am probably being paranoid as the earth is very dry with no visible moisture even with the heavy rains we have had this winter.

[ThingOfBeauty]

I would think about iso foam board (Rmax or similar) instead of thermoply, easier to work with and better at insulation.

This is not the worst way to air seal a crawl floor, but it sounds like more is probably going on. Can you ring up a good energy auditor with a blower door and a thermal camera, and hopefully a decade or more experience in construction? You'd hate to put in a lot of effort on one possibility and later realize that wasn't even the real problem.

[Lavrans]

OK, not adding anything but a good quote I heard the other day:

"The floor was plank, and the cold came through the cracks like razor blades"

[rselvig]

Doug,
We ruled out the polyiso board due to cost. I think the best way would be to spray foam the entire rim, floor and wall assemblies, but here again the cost is an issue. Even without spending the $1500 plus on the blower door it is very clear the building is sucking (stack effect) from the lower floor to to the upstairs.
I think Lavrans' quote pretty much nails it.
R

[Mark Parlee]

Rolf
Sometimes, actually most times the clients are so cheap that they will not do the best recommended method of repair. They want the best but when they find out how much the best costs they settle for less.
your comments on the polyiso being too much but you will spray foam the entire assembly but cost is an issue make no sense.
i am not trying to pick you apart but we as contractors get into a pickle as we "feel our clients pain"
If they want this corrected there are a couple, maybe three ways to do it; one being better than the other and also being more expensive.
give them the options, the prices, and the benefits of each over their current problem. Let them know the less you put into it the less they can expect and let them make the choice. Then let them live with their decision.

can you tell sometimes I get a little pissed that clients expect us to figure out their problems then want to whine about costs as they choose the less of the best then expect superior performance. It's like buying an old gas guzzler, tuning it up, adding some cheap part to the air filter and expecting it to get the mileage of a hybrid.

[rselvig]

Mark,
Thank you for your well made points. I am trying to parse out a fixed budget while the "want list" continues to grow. That rarely leads to optimal solutions, especially when it involves items a client doesn't see nor understand the value of. But your point on letting them live with their decisions is, again, well made.

I certainly share your frustration when people want the best but are unwilling to pay for it. It is very frustrating because no matter what you say, we are to "blame" if something isn't just right in the client's mind even if they went for the cheaper option. Fortunately I have a very reasonable client who is happy to pay for good work, but the budget is fixed and I am trying to "help" when I should just present the options.

[ThingOfBeauty]

We ruled out the polyiso board due to cost.

Isn't polyiso maybe $50-100 more than therm-a-cardboard, maybe $3-5 per sheet? and much easier to cut & tape? in the bay area you don't need to use a thick board, even half an inch would be helpful.

Even without spending the $1500 plus on the blower door it is very clear the building is sucking (stack effect) from the lower floor to to the upstairs.

$1500!!!!!! that would make a big difference. Around here you can get a full house audit with CAZ testing for $500, and a site consult with blower door for half that.

Stack effect leakage is plausible, but there are several other mechanism which could easily have the same effect. Have you done any smoke testing? Even walking around with an incense stick looking for air movement might be helpful if it's really $1500 for a blower door test. (If that's what they cost you could buy one and pay it back on two jobs!)

I think Lavrans' quote pretty much nails it.

That's how it usually works!

[rselvig]

Doug,
Just back to my email. Thanks for your comments. In order are responses:
Polyiso, obviously depending on thickness chosen, would cost a bit more, but my insulation sub said not to go that route as the joist bays are not super filled with insualtion (R19) and per his thinking wouldn't be worth doing...I am all ears on this one.
Yup $1200-1500 is goig rate that I have been told from the guys doing it. I have not paid it as I think it is a really steep cost for a relatively simple bit of work. Maybe nicking my nose despite my face, but it seems like a steep charge.
No smoke sticks, but I am going there next. Really all you have to do is open up a cover plate on any outlet in that house and hang on to whatever hair you have left on your head cause it is blowing a strong wind!
Thanks,
Rolf

[ThingOfBeauty]

Thanks for your considerate reply. It occurred to me later I could have tried to be more clear, i am just curious how things add up for different people, I always learn when I get into the tiny details, like which sheet good to apply on a crawl ceiling!
For me there isn't a huge benefit for using polyiso, but there's some because it's so easy to work with and tape sticks so well.
I just wonder if you may be having more wall & attic leakage than crawl leakage is all. There could be a big bypass or two, or something that would be easy to fix.
Are there any subsidy or utility programs where you can get an audit at a more reasonable price? In Maryland you can get a full audit for $100 right now.
Good luck with your project!

[rselvig]

Doug,
I think this first problem is related to the crawl space and maybe the rim and I am looking to start sealing from the largest hole in the immediate location (ie: the cross planked sub floor) But you are certainly correct that I am making this assumption (walls certainly are a problem)and you raise an excellent point that the utility cos may have a subsidized service which I will check out today. Thanks for your considered inputs and keep up the good work.
All the Best,
Rolf