Foam vs. Fiberglas in basement ceiling
jgold723
| Posted in Energy, Heating & Insulation on
We’re renovating an 1860s era house here in southern Maine.The house has a full basement with granite rubble walls. I’m assuming I should/need/must insulate the ceiling overhead. I’m considering foam, but I’m wondering if it’s worth the extra cost. I can do it reasonably cheaply myself with the pink stuff. What’s the prevailing opinion?
Thanks,
John
Replies
What is your present heating system?
We have a reasonably new and efficient forced hot water system.
I just finished my basement. I foamed the joist bays that had HVAC ducts in them and the band board area at the perimeter. I used FG in all other bays using bats taller than the joist to make sure I got contact all the way to the bottom of the subfloor. Jay
Is the cellar damp?
what condition are the rubblestone walls in?
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The cellar is fairly damp. We poured a new concrete floor, but the walls are pretty porous. I plan to ventilate heavily in the summer to reduce condensation.
I don't know about where you are, but here the worst time to 'ventilate' is in summer, because the outside air is heavy and damp, but the cellar walls are much cooler, so wet air comes in and condenses, making things wetter, not drier.I am about to recommend spraying foam tpo the rubble walls like the others, but you haven't answered my other question yet - about what condition they are in. You need to do any repairs they might need structurally first.FG batts in a damp basement become a breeding ground for hiding mold growth. There are a couple places where I have got the opportunity to tear it all out after 10-15 years and it ain't pretty
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Structurally, the walls seem to be OK (mostly large blocks of granite), but there are a lot of voids and they are very uneven. I suppose they could be sprayed with foam, but it would be similar to spraying the side of a mountain.I hear what you say about condensation -- but I don't think there's any way to seal that space well enough to condition it. And running a dehumidifier down there would be prohibitively expensive. I figure I'm better off keeping good air movement down there and hopefully raising the temp enough to reduce condensation.But I'm not an expert here, so I'm open to ideas.The basement, BTW, is only partially underground. About 2 feet of it is below grade.
" I don't think there's any way to seal that space well enough to condition it. "you have just been told how to do that. Plastic on floor was mentioned. You already have a slab now and plastic should have been placed under that.
So just spray a ccouple inches of foam up the walls amnd the rim joist/sill and you are tight - good to go.My first impressionwas that your walls are rubble but this sounds like cut granite blocks. Just repoint them first.
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I couldn't agree more about re pointing the walls. To suggest spraying foam with the cost, uglyness,and possible need to cover in case of codes is crazy when a simple pointing job will solve the problem.
I suspect that pointing would be the way I'd go -- at first anyway. Is there a way in inject mortar into the voids? Keep in mind that these are not well-fitted blocks of granite. They appear to have been dumped rather haphazardly, so some of the voids are quite large -- up to 1-foot square in a couple of spots.Also -- is there a more cost-effective way to spray the foam (one that doesn't require a professional), should I decide to try that route? I can't imagine buying enough cans to do it that way.
If you have gaps as big as a sq ft then they should be filled with smaller stones. May be worth while to get a mason in there for their opinion.Here is the DIY option. Not cheap but may be cheaper than the pros in your area.http://www.rhhfoamsystems.com/http://www.tigerfoam.com/?gclid=CMD7sZespo8CFRFSagodWlt5Rw
Read this as well:http://www.coastalcontractor.net/cgi-bin/article.pl?id=181
gaps as large as that should be laid in with brick and parge coated first. There are also epoxy injection companies but that can get pretty expensive.tigre-foam and Fomofoam are internet suppliers of home kits for small spaces.
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Sorry I haven't responded I lost track of this thread somehow. You can inject the mortar, But the purists here are going to jump all over me.
I can't remember who the manufacturer is but I have a sort of caulk gun that I use from time to time. It has a closed cylinder that you can fill with mortar and then bassically caulk the joints. Much faster and you can fill the voids better.
Now before I get beat up here's the draw backs. The wetter the mortar the more shrinkage you get and the weaker the end product. This gun requires rather wet mud to function.
So I don't do this if structure is an issue (Pointing won't solve that kind of problem anyway).
As far as shrinkage I finish the joints much like I do stone. Fill voids and let it set up. I Waite until it is rather hard and past the smearing stage. Then compress and strike the joints using a jointer or striker. The last stage would be just before it is unworkable I brush the joints.this really creates a cohesive surface with the stone and is rather attractive.
This is not the traditional method and I wouldn't say 100% proper. That said it works well when pointing dry laid basement walls and where there are large and numerous voids.
Reading this it sounds like a lot of work, but in fact this triples my speed.
Thanks for that reply -- I'm thinking I'll go that route. Now I just need to find one of those guns.Structural integrity isn't an issue -- at least as far as I can tell. These blocks aren't going anywhere. I just want to fill in the gaps to keep as much water (and critters) out as possible.John
albioneng.com I am iced in my property so there is plenty of time to dig out my tools and look.
I have the basic model and works fine. It cost about $60.00. Use type "S" mortar ( it seams to jam the gun less).You will get jamming, don't bother getting frustrated it's part of the game.
pointing only solves one of three problems. yes it might create other problems. That is not my descision, only a suggestion to answer the OP as the best way to solve that one.
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Can't say as I have all the answers, just think making a horror show out of a two hundred year old basement can't be the way to go.
Have a 1835 stone farm house in MD-- I run a dehumifier year round but it is on a timer 6 hrs a day and it keeps up with the moisture -- all the best - Dudley
FG makes nice home for mice and other critters bound to get through the rubble walls. The conventional wisdom is to insulate your basement floor and walls and "condition" the air in the basement. Not likely to happen in your case which is similar to mine. Here's what I did about 12 years ago in my 1850 cape with rubble basement walls (and dirt floors). Laid down 60 (yes, 60) mil poly (was containment membrane leftover from a landfill cap, 6 mil poly would have probably worked as well). About 4" of pea stone to hold it all down. Chinked all the gaps above grade with foam to keep out drafts. These need to be touched up every few years. R-30 unfaced batts in-between the joists. Don't used any kind of faced batts, you'll want the FG to breath as best it can. I stapled 1" chicken wire to the undersides of the joists to support the batts. Seemed like a good idea at the time but it's a pain whenever I need to pull some insulation down for whatever reason. So far, it's working. It's not textbook, but old houses rarely are.
Assuming there's some utilities in the basement (water service, boiler, etc) and it's likely a damp basement, I would recommend the spray foam but not in the floor system.
Though I rarely recommend petrochemical foams, this is one of the few ideal applications: brush down the inside of the stone walls and have them sprayed with a couple inches of closed-cell foam. This will stabilize the walls, waterproof them, keep out drafts and mice and insects and allow the basement to be partially conditioned space, preventing freezeups and keeping the floor system accessible for maintanence.
If the floor is dirt, then I would agree that a protected and well-sealed VB is the first thing to do. Curl the VB a few inches up the walls and cover the edges with the foam.
I'm dealing with this issue today actually. House circa 1820, fieldstone foundation. Inspector here won't let there be exposed foam in a cellar. Must be covered with plywood or sheetrock. I decided to cut 2" rigid foam between the joists, leaving it a little loose, foam the gaps at the edges and cover with thin plywood. Don't like FG in open floor systems (don't like fiberglass in much of anything actually). because you don't get air seal, plus it's hard to keep it in good repair in a cellar. The loose fibers aren't good for you. I think Riversong's suggesting of foaming the walls is probably the best thing to do in terms of health and performance, but I really hesitate to cover a nice exposed fieldstone wall. And as I said, the inspector here would requite it be covered with something flame retardant, requiring a lot of extra expense.Steve
Mmoogie,Check with the foam co. and see if thy have a fire barrier paint. Firefree 88 is one brand.If applied to spec. it provides the required fire barrier. I have use similar products in application where access is limited or mounting surfaces are irregular (rock basement).The foam company wanted to sell the foam so they helped me work out the code issues.Now with that product foam is approved.Garett