Loose FG insulation under floor
PenobscotMan
| Posted in Energy, Heating & Insulation on
We stuck FG insulation under he floor our our house in coastal Maine. The house is built on piers. Last winter it started coming down in big chewed-over hunks (pictures below). I had it held up with furring strips. The culprit must be a combination of gravity and forest mammals. What to do? If I keep the FG, my idea is to staple up chicken wire or hardware cloth. There must be other more modern options.
I’d appreciate any advice.
Replies
this is not a very good application for fiberglass. I would consider this a stellar time to investigate a closed cell spray foam. You can encapsulate the joists themselves as well. As mr. Lstiburek likes to say, warm wood is happy wood.
Of course, furrry little critters like to gnaw through foam too.
unless they know how to fly, that's unlikely to be much of an issue in this case.
Can you spray up into a cavity? Is this a DIY job or one for a specialist contractor?
fiberglass invented to be an industrial filter air moves right
Howdy consider installing a breathible house wrap once you have resecurred the fiberglass into the cavities. I prefer Typar putting the face out towrds the ground. To increase its effectiveness consider caulking the edges to again reduce air infiltration. If you wnat to upgrade consider installing rock wool batts they are rigid and will not sag like the fiberglass did and rodents do not like it.
Spray foam?
There are a great many horror stories on the net of spray foam that has gone wrong due to opperator error.
Unless the surface temperature is right, the humidity, and the mix is right, this can lead to foam cracking, falling off and worse shrinking.
Keeping in mind that condensation does not form on or inside wood that is warm - above "dew" point, you get a better result boxing in the entire floor, this keeps the wood warm and dry and saves most of the heat that would otherwise escape downwards.
Sheets of polystyrene or similar closed cell insulation, fitted between the joists and below the joists will ensure that your wooden floor stays perfect for the life of the building.
Yes, BatMouse might be into that, but usually mice don't hang upside down to chew on insulation with any regularity unless there is something for them to stand on while they are doing it.
installing anything UNDER the insulation that affords them purchase would only make the issue worse.
By now he could have easily installed maybe $50 worth of hardware cloth, carefully fastened at the edges, and with all gaps closed, and he'd not have a problem.
no problem
other than the fact that his existing insulation would be pretty poor. If you think the hardware cloth is necessary, by all means, spend the money, but I wouldn't (and didn't, without regret) bother, and it doesn't change the fact that fiberglass is a really poor choice for this application. lots of air movement. thermal bridging. impossible to seal. less effective at extreme temperatures. not that great in any case where convective currents can occur anyway.
fiberglass is certainly better than nothing but much better can be had here.
Yeah, I would have used faced insulation with the face down, to cut convection. But the stuff he has would be reasonably effective if it stayed in place.
I can't get behind that
the foil face is a vapor barrier and you'd have it on the wrong side of the insulation in this application, which would create a potential moisture issue IF you could seal it really well.. but even with the face batts are impossible to really seal and convection can still occur within the batts themselves. their rating plummets in exterior conditions like this when it's as cold as it gets up here as well.
fiberglass is junk and should be used for interior soundproofing only, IM so very HO, in cold climates. and probably not even that. the following link is about loose fill but I can't see why it wouldn't apply even moreso to batts which additionally have the batt to joist connection point to provide additional leakage paths.
http://web.ornl.gov/info/reports/1994/3445603820925.pdf
Hardware cloth
Dan, bought any lately? $50 won't go far. Joe H
Yep, $50 of hardware cloth will cover about 82 sq ft. (including tax of 7.5%).
I would sheath it with the cheapest weather resistant material available. Probably flake board, or OSB.
Fiberglas without something solid to impede the movement of air is BARELY better than useless.