Insulating Floor Truss In Crawl Space

72chevy4x4

I'm looking at a job which will require removing all of the insulation in a crawl space and vapor barrier (plastic), airing it out and reinstalling. The floor trusses are 24" OC and about 16" deep (didn't measure). The R19 which was installed was installed vapor barrier down at the bottom of the truss-leaving an air gap between the insulation and the floor. Again, vapor barrier was facing down. The high levels of humidity in this space beaded on the kraft paper and the insulation fell down.

question-what is the proper insulation method in this case? my guess is non-faced against the floor held up by insulation rods. Is it improper to install kraft paper on the side not facing the conditioned space?

Any tricks for installing insulation in a situation as this where it will have to be tucked up into each truss.

Is there any merrit to the original installation where the insualtion was installed at the bottom of the truss leaving a ~9" air space between it and the subfloor?

72chevy4x4

I found this: http://www.southface.org/web/resourc...floors4PDF.pdf which answered most of my questions. One thing that looks challenging is filling the webs of the 4" floor trusses since the insulation won't 'stretch' into those voids. Would the most cost effective solution be to cut R13 into strips to fill the void? Is it possible to order insulation in 28" widths?

We Fix Houses

Try chicken wire or a similar hardware cloth cut 1 1/2" wider than the opening. Place continuously or in 2' lengths.

thom

It seems you left some important questions unanswered.

Is there water piping in that truss space?
Is there DWV piping in that truss space?
Is there HVAC ducting in that truss space?

Generally the vapor barrier belongs on the moist side. Insulating at the bottom of the truss leaves the web space heated. That space may need to be heated.

I don't think the original installation was a problem, excessive moisture in the crawl space may be a problem. The space may require mechanical ventilation or mechanical de-humidification.

dlcj

Im glad its you and not me
Floor insulation is not common in
the south (cost vs savings thing)
and we dont offer it. In the last 15
years only one h o wanted it done
and did it him self.
As for the question- i agree with thom
and you may need to add more foundation
vents or some if there are none.
Allso you may need to take a good look at
the lanscaping and or gutter drainage. We've had
problems like that before.

72chevy4x4

I all ready identified the origin of the problem as being the downspouts and landscaping backflowing into the foundation entrance and vents and recommended not to have the insulation problem fixed unless the water drainage problem is fixed.

the link I posted addresses use of crawl space vents. It actually makes a case against vents IF there is air leakage into the structure (negative) whcih would draw outside air into the crawl space which would create moisture b/c of difference in dew point between outside/inside air.

Regarding Thom's comment, there is no need to heat the crawl space in our area as the temperature doesn't drop enough. Water and sewer connections are in the crawl space, but all grouped tightly (kitchen and baths are next to one another).

JPC2

Hey Chevy, where in DE are you? Conditioned crawl spaces are becoming way more popular these days. Over the last few years, we've seen alot of mold problems in conventional crawls.

neolitic

Page two of the link you posted has
everything you need to do.

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(Sorry....it seems there really are dumb questions)

72chevy4x4

Thanks-I read it before posting Based on what research I've done so far, the recommendations in the link seem appropriate for this job.

Our area (central DE) has a high water table which lends to higher moisture levels in the soil which comes through in the crawl space. This particular complex has wetlands nearby (>500ft).

I was also interested to know if others have been moving to conditioned crawl spaces, especially in an area which may have wet soil (parts of Florida may be similar).