funny smell after crawlspace encapsulation

[RustyShackleford]

My house has developed a strange smell. I think it has to do with the encapsulation of the crawlspace, which I had done about a year ago, because I first noticed the odor IN the crawlspace, and assumed it was just a residual odor from the materials they used (rigid foam insulation board, spray foam to seal edges and gaps, and plastic sheeting on the floor). But now the smell seems to have permeated the entire living space of the house; it's very noticeable when coming home to a closed-up house.

I guess mold would be the obvious suspect, but the crawlspace wasn't that humid beforehand, and the encapsulation has only improved it (it's 70% or less) and I don't see any obvious signs, and I don't really think it smells like mold anyhow. If it IS residual chemical smells, I guess they have nowhere to go since the crawlspace is sealed (that's the whole point, after all), and you think they'd have dissipated after a year, but they really have nowhere to go except up into the house. So maybe the solution is to somehow air out the crawlspace during some of the forthcoming cool/dry autumn weather.

I have no idea what sort of person you'd call to come check out an odor and tell you what it is. At least without a pre-prejudiced person (when you have a hammer everything looks like a nail), like a mold person who wants to think everyhting is mold and has a big financial incentive to make you think that too.

 

[woodgeek]

What kind of rigid foam board? Could be the blowing agent in the foam. is there are LOT of sprayfoam (or just a few cans for sealing cracks)...b/c sprayfoam can def stink if its not done right. Often 'fishy'.

What does it smell like?

 

[RustyShackleford]

What kind of rigid foam board? Could be the blowing agent in the foam. is there are LOT of sprayfoam (or just a few cans for sealing cracks)...b/c sprayfoam can def stink if its not done right. Often 'fishy'.

What does it smell like?

I think I've decided it's mold from excess humidity. I'd hoped I could get by without active dehumidification, but I think that was wishful thinking. RH has been about 70% and I am told that is too high. So I rigged a regular stand-alone room dehumidifier down there, and coupled with drier autumn outside air, the RH has dropped to the mid 50s. Smell seems like it might be abating. I'm advised, though to invest $1000+ for a "whole house" unit like:

http://www.supplyhouse.com/Honeywell-DR90A2000-TrueDRY-DR90-90-pint-Whole-House-Dehumidifier

... on the basis that the cheap one (i'm using now) has to work very hard to get below 60% (it's probably only in the 50s now because of how dry the outside air has become), and also, supposedly, the new one will keep a given low RH for far less electrical usage.

I don't know anything about the rigid foam they used, except it's about 1.5" thick and foil faced. Yes. there's quite a bit of sprayfoam, all along the edges of the rigid foam-board, along the sill plate to cinderblock seam, and all the various penetrations of the foam and of the ground plastic.

 

[wildwildwest]

turn on some fans down there to ventilate, open up doors and windows upstairs and put heating stove on high. Wait till wife is not there...

 

[woodgeek]

Aah. this all makes sense. I assume they insulated the sides, put a membrane over the dirt floor of the crawl, and left the floor above unsealed/insulated. And that you have no powered air exchange with the house above.

If so, that framing might have molded from earlier (pre sealing) episodes, and mignt've been quite wet at the time of sealing. Not clear why it can't dry out to the house if its well sealed.

Your solution seems a good one....when you get it dry and deodorized (big trays or dropcloths covered in baking soda?) you might consider an AC brach dumping air down there as a more efficient permanent soln.

I would def ventilate the upstairs, although at this time of year it can be hard...air outside can still very humid, might not be hot enough to run the AC. This is my hardest time of year for indoor hum control.

 

[semipro]

I don't know anything about the rigid foam they used, except it's about 1.5" thick and foil faced.

Hmm. Most foil-faced foam I've seen is polyiso. One nasty habit polyiso has it that it will absorb water...
Some EPS is foil faced though.

 

[brian89gp]

Playing devils advocate, how much energy you saving by having it super sealed vs now needing to run a dehumidifier all the time? Unless it is a desert climate moisture is constant battle in well sealed houses.

 

[woodgeek]

Once its dried out it is unlikely to need a dehumidifier (if the house is ACed). If it doesn't dry out permanently, he should call back the excapsulators...another possibility is they left an air bypass to the outside somewhere....and new moisture is now coming into an even cooler crawl.

 

[RustyShackleford]

Aah. this all makes sense. I assume they insulated the sides, put a membrane over the dirt floor of the crawl, and left the floor above unsealed/insulated. And that you have no powered air exchange with the house above.

Yes.

If so, that framing might have molded from earlier (pre sealing) episodes, and mignt've been quite wet at the time of sealing. Not clear why it can't dry out to the house if its well sealed.

I believe that's likely, that the framing was wet and had some mold - especially given the encapsulation was done a little over a year ago, in late summer. Probably can't dry out to the house because the house just ain't that dry. We're talking North Carolina summers !

I'm really pretty convinced that I need active dehumidification down there, which will also help keep the house itself drier.

Playing devils advocate, how much energy you saving by having it super sealed vs now needing to run a dehumidifier all the time?

The option wasn't super-sealed versus what it is now; it's now more or less super-sealed. But I take your point. I didn't think I had a major problem before I did the encapsulation, just thought things would be better now. In some ways they are, in particular, house seems to stay warm a lot more easily. But now, given it appears I'm going to need to run a dehumidifier, I do wonder "what is THAT going to cost me ?"; I take some solace in the fact that I'll probably only have to run it much in the summertime, and that I can set a timer to run it only during off-peak hours, when I only pay about half the usual KWH rate.

Unless it is a desert climate moisture is constant battle in well sealed houses.

Actually, as far as the crawlspace, in this climate being well-sealed makes moisture less of a battle.

If it doesn't dry out permanently, he should call back the excapsulators...another possibility is they left an air bypass to the outside somewhere...

No, I've checked for that. However, they did do one fairly half-assed thing, insulating the perimeter of the joist system with little chunks of fiberglass batts; apparently the better thing would have been to use chunks of the rigid foam they used on the cinderblock walls, caulked around the edges with spray foam. I'm told, next summer when it's humid again, pull back some of those batts to see if there's evidence of moisture infiltration there (mildew and such).

 

[woodgeek]

No, I've checked for that. However, they did do one fairly half-assed thing, insulating the perimeter of the joist system with little chunks of fiberglass batts; apparently the better thing would have been to use chunks of the rigid foam they used on the cinderblock walls, caulked around the edges with spray foam. I'm told, next summer when it's humid again, pull back some of those batts to see if there's evidence of moisture infiltration there (mildew and such).

That's really not good. If I follow....they might NOT have sealed under the sill/rim joist with spray foam. Up north, the FG in there is a no-no because the joists will mold in the winter, but I think you might be ok with that in your winter climate.

BUT, the major source of air infiltration in the bottom of houses is the gap between the wood sill and the concrete or block foundation. Modern houses put an EPDM or foam gasket there, older house leave a gap, up to 1/8" (irregular). Times the perimeter of your foundation, that is a huge opening area. Most pros would do a thin layer of sprayfoam over the sill/rim to provide airsealing (primary) and insulation (secondary). If that was not done, you have an insulated crawl, but not an airsealed one. If their contract said they would airseal, they are in violation, if not, you will need to get it done, or run a dehumidifier forever.

 

[shoot-straight]

i had mine done about 5 years ago. insulated floor vapor barrier, sprayfoamed block walls, peirs, band joist and sill plates.

i put a small dehumidifier set on 50% down there and a small fan on a cheap timer just to move air around sometimes and make it more uniform. i also put a remote wx station thing down there (10$) with the readout in the kitchen. all it takes is a glance to see that all is well, or something is wrong down there (like a pipe leak). in 5 years i am on my second dehumidifier. oh, almost forgot- i put a condensate pump with a line outside the crawl for the water to go to, no dumping. i do go down every few months just to check on things. went down last night in fact.

 

[TradEddie]

I'm told, next summer when it's humid again, pull back some of those batts to see if there's evidence of moisture infiltration there (mildew and such).

Don't wait. If all they did was fiberglass and never caulked, you'll have a moisture problem, better find it sooner than later. As woodgeek said, the gap between the wood sill and the foundation is a huge air leak, and so too is all around the rim joist. 70% RH isn't necessarily extreme for a non-occupied space but if you've got warm moist air from outside getting in condensing on the cool walls, or behind the FG, that's a problem.

TE

 

[RustyShackleford]

They caulked the gap between the wood sill and the foundation properly (but only after I called 'em back to do it), but claim the fiberglass in the joist spaces is good enough. I think I bombed out on these guys. Did give 'em a bad review at Angieslist, but don't subscribe there anymore, so can't see if there was any response (or if they removed it, which I suspect they do, given the almost uniformly positive reviews that one sees there).

The friend who consults on this stuff, and who I've talked to, says 70% is way too high and almost certainly the cause of my odor problem. He also says not to get bent out of shape about the fiberglass and to wait 'til next summer and try to evaluate how much moisture is getting in there.

 

[woodgeek]

I agree that 70% is too high and will grow mold in a dusty space.

 

[Hogwildz]

70% is way too high. Anything over 50% can cause issues in the research I been doing. 70%... how could you not have mold.
If the space was air sealed correctly and floor and walls done properly, there should be little to no moisture issue in there. And also if done properly, you should not need or want insulation under the floor above.

 

[TradEddie]

70% is way too high. Anything over 50% can cause issues in the research I been doing.

I have to slightly disagree, depending on what "issues" you mean. Mold is everywhere and most species are harmless, the "toxic mold" that scares everyone requires a lot of moisture, either water leaks, or condensation. The recommendations you see for RH are generally related to living spaces, or for conservation of valuable art/furniture/artifacts. If an area was well insulated, and well air sealed then 70% RH would be unlikely to cause mold problems because there shouldn't be cooler areas where moisture would condense. OTOH, if the area was well insulated and well air sealed, he probably wouldn't have high humidity either. My basement has remained at or just below 70% for the last two years since I completed my air sealing, and I store old magazines, paperwork etc. there without a problem (although raised from the floor, not near the walls and with plenty of air space).
Mold will grow below 70% if the substrate (wood, paper, drywall backing, etc.) already has a high internal moisture content and is unable to dry out due to the high humidity.

Back on point, if they have properly caulked the sill and rim/band joist, I think that FG should be okay in the bays, but would a proper vapor barrier be better?

TE

 

[Highbeam]

We always target 50% RH because above that DUST MITES will thrive. Yuk!

 

[RustyShackleford]

I have to slightly disagree, depending on what "issues" you mean. Mold is everywhere and most species are harmless, the "toxic mold" that scares everyone requires a lot of moisture, either water leaks, or condensation.

Maybe, but I am in fact having a problem, that being the odd smell that prompted my original post in this thread. The 70% humidity seems a likely culprit, and in fact the odor has subsided since I put in the stand-alone room dehumidifier and got it down in the 50+% range.

I imagine I'll replace it with the $1000+ whole-house unit next spring, for 4 reasons:
1. I doubt the current unit can keep up (with the dehumidification) when high summer humidity returns.
2. I believe the whole-house unit is supposed to be far more efficient (pints of water per kwh).
3. I'm told the small unit will probably die from working so hard.
4. I have a separate smaller crawlspace, and I can use the ducting of the whole house unit to force air through there.

I also need to look at sealing around the perimeter of the joist system. Probably do it myself or pay someone, which pisses me off, the original guys should have done it. Even so, from talking to consultant friend, he believes active dehumidification will still be required, and he's supervised lots of these projects in this area.

 

[woodgeek]

Ok. Do you run a central AC upstairs all summer? If you did, an airsealed crawl would likely be ok w/o a dehum. Of you don't some active dehum would likely be required.

 

[semipro]

If the humidity bounces back up in the crawlspace after you dry it out you gotta wonder where the moisture is coming from.
I agree with woodgeek that if the house has AC and you use it that just ventilating the crawlspace to the house should keep RH levels down.
Of course if more water is entering through the crawlspace area. then maybe not.

 

[RustyShackleford]

I run AC some, but not all the time.

 

[TradEddie]

The 70% humidity seems a likely culprit, and in fact the odor has subsided since I put in the stand-alone room dehumidifier and got it down in the 50+% range.

70% humidity isn't really the culprit, it's just a symptom of poor air sealing. If you need to run that dehumidifier hard, you may even have ground moisture problem.

TE

 

[RustyShackleford]

70% humidity isn't really the culprit, it's just a symptom of poor air sealing. If you need to run that dehumidifier hard, you may even have ground moisture problem.

Update: I put a room dehumdiifer down there and the RH is below 50% and the smell is subsiding. I will likely have to replace it with an expensive whole-house unit ($1000+) next summer.

Agreed that the air sealing job was substandard, but I am also told by experts around here (and NC is where this whole notion was first demonstrated, I believe) that you really cannot get by without some sort of active dehumidification. The poor air sealing just means the dehumidifier will probably burn more electrons.

 

[TradEddie]

How would running a/c keep crawlspace humidity down (unless the a/c or its ducts were leaking into the crawlspace)? Would the denser cool air be enough to overcome the stack effect?

TE

 

[RustyShackleford]

How would running a/c keep crawlspace humidity down (unless the a/c or its ducts were leaking into the crawlspace)?

I'm not talking about running AC (not sure what you're talking about, maybe my answer in post #21 ?) I'm talking about a separate dehumidifier in the crawlspace. Though in fact the code requires (and there is) a small outlet from the HVAC supply into the crawlspace; but it obviously ain't enough to do the job for me.