Crawl space insulation recommendation
There have been a few posts here recently on insulation questions. I just had my crawl space insulated by Federal Conservation (631-264-7271) and I highly recommend them. They called right back after I left a message and called me practically every day updating me as to when they could come because the weather has been…
There have been a few posts here recently on insulation questions. I just had my crawl space insulated by Federal Conservation (631-264-7271) and I highly recommend them. They called right back after I left a message and called me practically every day updating me as to when they could come because the weather has been so bad.
I’ve got a pretty standard 20′ X 50′ brownstone with three skylights. They cut two holes in the roof and go in from there and blow in about 12″ of insulation. The roof holes are then covered and vented. Vents are necessary for moisture and heat removal from the remaining space above the insulation. It was $2000 ($2 per sq. ft.) plus $200 for the two vents. They were great and cleaned up nicely afterwards including any stray bits that blew onto my neighbors property.
They told me that the side walls of attached brownstones really can’t be insulated but that the front and rear walls are deep enough and that they typically drill a few holes in the plaster and fill them with expanding foam if I wanted to do that in the future.
Highly Recommended, very professional.
I can confirm Smokychimp’s scenario. My Home Depot wind turbines rusted out after 20 years (I’m not complaining). One stopped spinning and the other squeaked annoyingly. When the big blowing snow came I had snow in my crawlspace under the frozen one.
I tossed both and replaced them with better quality products I picked up in LIC ($60 per). In addition, I got extenders to position them higher off the surface.
The argument for venting a flat roof is not as simple as described above.
Vents have advantages, as already pointed out exhausting moisture vapor is their primary purpose.
However, this has to be weighed against two negatives. Vents are only feasible if there is sufficient space between the insulation and roof for air to circulate. On a sloped roof, this can be a very narrow gap since the natural weight of the air at different temperatures will insure circulation (this is why venting a sloped roof is standard practice). A flat roof condition has very little natural circulation so needs more of a gap between the insulation and roofing. If there is very little distance between roofing and insulation, or if mounded insulation will come in contact with the roofing every once in a while, the vents could be counterproductive.
The second issue is that creating a “cold” roof condition on a flat roof has its own problems to attend — since snow will not melt off quickly from building heat, the vents, openings, skylight bulkheads, etc. should be located higher up above the roof than usual in order to avoid backing in snow melt.
As you know there are a lot of uninformed opinions on this site…some comments above as well. Don’t take my word for it…search the web. The difference in safe vs. unsafe is in what chemicals are used as fire retardants. You have to look for the ones that don’t use penta-BDEs. Urethane is not safe longer term but really only if it is exposed. Icynene is the safe one. Airkrete is a natural cementitious sprayed insulation but not as easy to find and much more expensive.
I did a country house with rubble filled walls and 200 year old clapboards and its as tight as a drum. You can aslo waterproof a whole leaky basement with it (and then lay down gravel and cement to make a flat floor surface). The attic is tight and you could live up there without heat in the winter. Its been on the market for about 12-15 years.
daveinbedstuy,Do you know if expandable foam is safe? Is there any problem with outgassing toxic fumes?
YOU NEED VENTS IF YOU INSULATE THE CRAWL SPACE. They should be sealed with a mesh type webbing, NOT TARPAPER, and then gone over with roof cement (tar). Federal Conservation guarantees their work. When expandable foam is used on walls it is essentially its own moisture barrier as it is waterproof…you can actually waterproof a whole leaky stone basement with it. It won’t let moiusture through either side.
You need to vent a rafter style roof (gabled or hip) if you use batts to insulate or if you blow in the insulation. The only time you do not need vents is if you blow expandable foam insulation on the inside roof surface.
1:12,
When I had insulation blown into my roof the installers planned to blow it in through the holes they cut for the vents. Howevera previous owner had cut an opening into the wall of the closet holding the roof access ladder and covered it with sheet metal. The installers removed the sheet metal and crawled inside the cock loft to blow in the insulation. They said that allowed them to distribute the stuff more evenly.
2:58,
I had an experience similar to ypur neighbors’s, although in my case it was more an annoyance than a disaster. My vents leaked because the installers neglected to seal a seam in the side of each one. They came back and sealed the seams. It’s been over 30 years and no more leaks to date. I DID learn a lession though. Last week I had a roofer install another vent for a vent fan in my top floor bathroom. He insisted that the seam didn’t need sealing [and it DID look watertight]. I didn’t argue, but after he left I ran a bead of silicone caulking along the seam-possibly redundant, but it only took a few minutes and I felt better.
Oh and you really DO need vents–condensation would cause more damage than a leaking vent, although it could take years to show up.Just make sure they seal the vents properly INCLUDING any seams in the side of the sheet metal.
Most of the time, the crawl space can be vented from the front and back. Small vents can be installed below the cornice or throught the rear wall. I would generally be opposed to anyone cutting holes in my roof unless absolutely necessary.
And yes, your crawl space should be vented. With front and back vents you will get cross ventillation which is more effective than a single roof vent.
My neighbor had a nightmare experience, however, when the roof vents leaked, and during one recent heavy downpour, had water running into the roof space from the vents where the insulation was blown in. Now he has to deal with mold, mildew, new roof, etc. He said never allow anyone to cut into the roof and blow it in from above.
So if you need it vented – who is correct?
Yes, there often is space to insulate the front and rear walls, BUT, since AFAIK they can’t be vented, having insulation blown in might cause serious problems with water condensation.