Cellulose in a basement

[Master Brian]

I am in the process of trying to finish off my basement in my 1915 Bungalow.

My foundation walls are cinder block and about the top 2' of the wall is above grade. I am keeping the wood studs about 1-2" off the block walls. Originally, I though about using fiberglass batting with mold resistant sheet rock, but am a bit worried about the batting taking on moisture. The blocks have been painted, I am thinking it is paintd with a masonry paint, but can't think of the name of paint.

I called one of the cellulose companies and asked if it was ok to use in the basement and they said if I had a vapor(?) barrier against the block wall it was ok. The lady said heavy mill plastic, special paint or even rigid foam would be fine.

Does anyone have any experience with this? I have had moisture in my basement during heavy, heavy rains, but I am making progress on eliminating the moisture as most of it is from poor drainage.

I looked at a lumber yard and they had 3/4" white foam sheets for about $3-4 a sheet, which wasn't too bad. The problem is I don't know enough about the difference in the rigid foams. Do I need a special type? What do I "tape" the seems with. Would something else be better?

I just feel the cellulose and foam would provide a very draft free basement with pretty consistant temps all year round.

A contractor friend of mine said all he thinks I need is the rigid foam and thinks I'd be wasteing my money on the cellulose. I figure total cost of foam and cellulose would be max $200 for the area in question.

[jadnashua]

Corning has some foam insulating panels specifically made for basement walls that interlock to provide the vapor barrier...you may want to look at them. If you ever got moisture up from the floor, the cellulose would be a big problem in the walls...the foam generally doesn't absorb anything.

I would think you wouldn't need that much space behind the studs, and you might think about buying a kit to spray the foam in after you get the wiring in place. You might want to consider plastic conduit for it, but that may be overkill. The R factor can vary significantly between different foam boards and the type of spray on, should you choose one of those. I think I'd avoid batt fiberglass where there have been moisture problems.

[garyl53]

Here is a good reference for insulation basements.

http://www.buildingscience.com/docum...nt-insulation/

[Master Brian]

I'll read what the link has to say, in a minute.

As for the rest, I've looked into the foam and that just doesn't seem cost effective. We are probably talking $1000-$2000+ to do it myself vs. $100-$200+ to add cellulose and foam board.

I agree if the cellulose gets very wet, it would likely be a problem, but I would think if the foam can keep the moisture off the cellulose on the wall side, I should be good there and most likely if I decide to use the cellulose, I'd probably run foam only along the bottom 1' of the walls. That way, moisture would really have to travel up to reach any cellulose and I do believe it can handle a little bit of water. Unless I'm mistaken.

[Master Brian]

Oh yeah, and I've looked into the owens corning panel as well. They do look very nice, but again too pricey in my opinion. Maybe in some parts of the country or areas where water infiltration is a big big problem, they might be worth it, but honestly my basement stays pretty dry except where the grade was bad. All of those areas are being delt with and fixed.

[jadnashua]

Cellulose is mold food..all it takes is a little moisture. Since it is packed fairly dense, it would take forever to dry out. Depends on how much insulation you want. Foam would give you the most/inch, with cellulose probably second, then fiberglass. But, if you are willing to lose that much floor space with the studs out there, then fiberglass may be the least expensive per R-factor. Not sure how many cubic feet you need, but the fairly big self-install kits for foam spray on are not too dear. it's messy, and depending on how much needs to be done, the break-even point from having it done may mean adding their labor and materials becomes cheaper than you can buy the materials for yourself.

Since you don't have to worry about air infiltration as you might in the attic or an upstairs wall, the fiberglass may be the best bang for the buck.

[Master Brian]

I don't think, being in a basement, that R-factor is a huge factor. My main thought in using the cellulose was that I thought it was mold resistant, could handle a little dampness and it keeps insects/rodents away a bit better than fiberglass batting.

You guys are saying it breeds mold? Maybe I've misread something.....

I also kind of figured the cellulose would be fairly inexpsive to blow in and provide a very quiet/draft free room. The plan is the basement will be used for a media/game room area.

I did read the article linked above and it sounds like my original plans were fairly close, but they say not to use faced fiberglass. I would think not having the face on it, would make it difficult to hang. Another reason I think the cellulose would be a good fit. Hmmm....

I will be loosing some floor space with the studs, but not enough to worry about in my opinion. I need room to possibly run some duct work, etc. I figure I may loose 2" the entire length of 2 walls. A third wall has the sewer lines ran midway up, so that wall is going to become a floor to ceiling bookcase. Then the 4th wall is an interior wall and I am using fiberglass batting on that wall just to somewhat deaden the sounds from a laundry and mechanical room.

[jadnashua]

Cellulose insulation is essentially ground up newspapers with some chemical addatives. Paper - mold, they go hand in hand. Otherwise, we'd be overrun with dead trees and leaves that didn't rot into a good mulch. It's packed denser than typical fiberglass, but they make blow in fiberglass, too.

The soil sucks heat out of the building, so something to slow it down is very useful. The part above ground is probably one of the worst heat sinks in the house.

If you don't mind the texture, the paint addative from www.insuladd.com is neat. Used more in industrial applications, and sold by others already mixed with paint, but much more ecconomical if you 'roll your own'. Just make sure you mix in a large enough bucket - it doesn't dissolve!

[Master Brian]

Cellulose insulation is essentially ground up newspapers with some chemical addatives. Paper - mold, they go hand in hand. Otherwise, we'd be overrun with dead trees and leaves that didn't rot into a good mulch. It's packed denser than typical fiberglass, but they make blow in fiberglass, too.

Makes since except everything I read about cellulose says "Cellulose will not rot, decay or mildew, and it does not support fungus or mold growth." I've seen moldy and mildy fiberglass batts. Another thing, they occaisionally spray cellulose into open walls wet. It's actually supposed to be better when applied that way. I understand your point, but our houses don't decay, unless they sit in constant wet/dry/wet/dry areas.

The soil sucks heat out of the building, so something to slow it down is very useful. The part above ground is probably one of the worst heat sinks in the house.

That would be my thoughts as well, which is why I'd love to insulate the basement. I would think a well insulated basement wouldn't need heated or cooled much at all. My basement is cool in the summer, but cold in the winter as it is, in an uninsulated state.

If you don't mind the texture, the paint addative from www.insuladd.com is neat. Used more in industrial applications, and sold by others already mixed with paint, but much more ecconomical if you 'roll your own'. Just make sure you mix in a large enough bucket - it doesn't dissolve!

Not planning on painting the walls. The lower portion will be beadboard paneling or stips, which will be painted, but the upper sections will be papered most likely. This is an old house and I want it to seem like this was a basement finished along with the rest of the house.

I know it sounds like I'm sold on cellulose, maybe I am to an extent, but I really am looking for any valid arguments against what my thoughts are. Spray in foam is just too expensive. I might get a DIY kit, just to do the areas around the rim joists, but not sure. I know Great Stuff isn't horribly inexpensive, but I kind of wonder how it would work in the rim joist area....

[jadnashua]

The small spray cans (around 16oz) would be horribly expensive, and lead to a poor install...I'm talking about the 25-50# cannisters.

Paper facing on insulation will support mold...celluose is the primary ingredient of paper. Drywall used under tile in a shower is a disaster waiting to happen. It would take some extended time being damp, but also consider that once the wall is closed up, any moisture that may get in there will take a long time to evaporate, too. There can be a fair amount of moisture that comes up through the slab.

Try an experiment...take a few 2x2' squares of plastic and tape them down over a few sections of your basement floor and others on the walls and let them sit for several days. See if you get any condensation accumulating behind them.

If you ever get any standing water on the floor during an extended rain storm, or winter snow melt, anything that traps moisture will be a problem.

[frenchie]

Only foam in basements.


I can't believe someone is trying to pitch you cellulose in a basement - that's downright unconscionable. Fiberglass, I disagree, but okay... But cellulose? In a basement? That's just wrong.




1. Basements are humid.


2. Cellulose is hydrophilic - it sucks up & stores any available moisture - like a giant paper towel.

Cellulose is wood fiber. The insulation's been chemically treated to not rot as easily, not feed mold as easily, and not burn as easily, as plain old ground-up newspapers would... but it's still, in essence, a giant paper towel. It doesn't have to "get very wet". Just give it some high humidity, it will "get very wet" all by itself.

3. Bad combination.






Fiberglass can grow mold, in the sense that mold will grow ON it. But the mold is actually "eating" whatever organic material is on the fiberglass... usually, that's whatever gunk was dissolved in the water that flooded/leaked; it can also just be dust that got on it during manufacturing, shipping, retailing, purchasing, transportation, instalation, and/or construction. All you need to do it add moisture.

Aside from that, fiberglass itself is pretty neutral to airborne humidity - just goes right through. But unless you want the sheetrock being damp, you'd still have to use the plastic sheeting. But... plastic sheeting in a basement always grows mold. "Always" isn't something I say very often. I have never seen plastic in a basement, that didn't have mold on the backside. Not once.

So - foam only, in basements.

The ideal basement finish? Glue foam insulation board to the walls, glue paperless sheetrock to the foam. Tape using full-weight, setting-type joint compound, and fiberglass tape. That'd be moisture-resistant... pretty much forever. Even if it got flooded, worst case scenario all it'll need is wash the walls & maybe a fresh coat of paint.

[hj]

Why would the below ground portion of the basement need insulation in the first place. It is like an "earth banked house" which uses the ground as insulation. AND, moisture barriers are usually between the heated area and the insulation, to keep the moisture out of the insulation, not behind it.

[frenchie]

Why would the below ground portion of the basement need insulation in the first place. It is like an "earth banked house" which uses the ground as insulation.

If you want the finished room at a constant 55 degrees... sure. But if you want it any warmer than that, you need to insulate from the ground.

AND, moisture barriers are usually between the heated area and the insulation, to keep the moisture out of the insulation, not behind it.

The vapor barrier or retarder goes on whichever side is "wettest". In the Norteast, in winter, that's the inside. But in Georgia, in summer, it's the outside...

In a basement, it's usually the ground side, not the living side. Even though the inside is being heated, the ground is much more damp than the living side.

[Master Brian]

The ideal basement finish? Glue foam insulation board to the walls, glue paperless sheetrock to the foam. Tape using full-weight, setting-type joint compound, and fiberglass tape. That'd be moisture-resistant... pretty much forever. Even if it got flooded, worst case scenario all it'll need is wash the walls & maybe a fresh coat of paint.

Frenchie, you've given me something to think about, but do you mind giving me a bit more feedback??

I am using the 2x4 framing because I need to go around some drain pipes, possibly need to run some HVAC ductwork and I am installing electrical. I was planning on using something like 1/4" or 1/2" foam panels, then building my wall and insulating with the cellulose or fiberglass, but after what you posted, I'm wondering, if I would be better going with a thicker foam panel and just forgetting any other insulation.

Also, I was told that mice will eat the white foam panels, but not the pink/blue panels. I was also told the pink/blue has about twice the R value @ of course twice the price. Is that true?

What about the studs on the exterior walls? Treated or untreated? They will not touch any concrete, there will be a treated lumber bottom plate and I'll be using paperless rock on the exterior walls.

I will add that years ago, I framed houses for a few years and we always used untreated studs in the basement, don't know how they insulated is what I don't know. Most were probably unfinished basements... Seems like we'd just hilti gun the furring strips to the walls if it called for it. ???

[frenchie]

Frenchie, you've given me something to think about, but do you mind giving me a bit more feedback??

I am using the 2x4 framing because I need to go around some drain pipes, possibly need to run some HVAC ductwork and I am installing electrical. I was planning on using something like 1/4" or 1/2" foam panels, then building my wall and insulating with the cellulose or fiberglass, but after what you posted, I'm wondering, if I would be better going with a thicker foam panel and just forgetting any other insulation.

Yes.

I like to stick to moisture-resistant materials below grade.

Also, I was told that mice will eat the white foam panels, but not the pink/blue panels.

That's true for termites - not sure about mice.

You can also get the white foam treated, to prevent... not sure how that holds up over time, though.

I was also told the pink/blue has about twice the R value @ of course twice the price. Is that true?

Yes. Kinda. Expanded foam (white) is R-3.5 per inch. Extruded foam (the pink or the blue) is R-5 per inch. Around here, they work out about the same price, per R-value.

What about the studs on the exterior walls? Treated or untreated? They will not touch any concrete, there will be a treated lumber bottom plate and I'll be using paperless rock on the exterior walls.

I will add that years ago, I framed houses for a few years and we always used untreated studs in the basement, don't know how they insulated is what I don't know. Most were probably unfinished basements... Seems like we'd just hilti gun the furring strips to the walls if it called for it. ???

Not too worried about non-PT for studs, especially if they aren't touching the concrete. Just the bottom plates are an issue, IMO.




Side note: the new PT they brought in a few years back, eats regular nails - it uses copper as its main ingredient, which causes galvanic corrosion.

Use hot-dipped galvanized ONLY, in that stuff. Plain, or electrogalvanized, will rust away very, very, very fast.