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Tom7227

Insulation in basement

18 posts in this topic

I'm helping my brother build out his basement. A big issue is what design/products should we use for insulation.

Two options are on the list - about R12 or so spray foam or closed cell polywhateverthepinkstuffis.

It is 105 feet of 8 foot block walls with no real moisture problems to date. The area is going to be two bedrooms, a bathroom and a rec room with a fireplace.

So far the only thing I have learned is an opinion from a guy who said keep the R to around 12 or so because if you go higher the frost will get too close and could screw up the blocks.

If you foam to you stud out, install wiring and then foam, put the studs out 1/2 or 3/4 from the block, what? If you used the pink polywhatever would you attach it directly to the wall and then fur strips? Someone mentioned using foil faced - why? Do you need a moisture barrier with these products? Why?

We want to comply with any codes so if there's something special on this please let me know about that as well.

As always, thanks for any input.

Tom

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I'll be interested to here the replys as I am thinking of redoing my basement as well. Right now its got the standard old knotty pine boards on the walls with no insulation behind it. I want to tear that out and drywall so I'm interested to know what I should use to insulate behind it.

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As I am doing something similar with the spray foam job, I just did a bunch of research on it. Please keep in mind I talked with the local building officials, so this may not fly with you local inspectors. I found all inspectors are learning the foam products and may give contradictory information.

The open cell spray foams can be considered a vapor barrier between 1-1/2 and 2" thickness. This allows you to use standard electrical boxes instead of the vapor proof ones ($1 compared to $4-8). This also seals ALL air flow from the block with a much better seal then poly could ever do. Closed cell can also provide a water barrier, but costs a lot more for materials. Closed also can hold moisture which could cause problems if you cannot see water from a problem (think roofs) I would run this past your contractor for clarity on the specific situation you have.

I was also told the "R" values of insulation cannot compare batt and spray foam because of the seal spray gives you. You only need 3" of spray to equal a 2x6 stud wall construction of R-19.

If I were you, I would install 2x4 (green if touching) tight to the block walls, spray in 2-3" of insulation, and be done with it.

Talk with the local insulation contractors and make up your own mind on Open cell/Closed cell foams. They can give project specific information when I can only guess about the situation.

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Could you give some cost numbers for the various options so I can begin to get an idea what this may cost.

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Open cell spray foam DOES NOT give you any sort of vapor barrier. If you use open cell you must use a vapor barrier in conjunction with it. Plastic sheeting or a vapor retardant primer applied either directly to the foam or on the drywall would suffice. Closed cell foam will give you a vapor barrier. Closed cell foam is about an r-7 per inch while open cell is slightly less. You could use the foam that comes in sheets against the block and seal all the seams and along the floor with caulk and then build your walls on the inside of that. The latter would probably be the cheapest. If we do it that we usually use foil faced thermax sheeting. I have a sheet that illustrates some of the methods to do this if you are interested.

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I asked both my Bldg inspector, and the contractors, and they told me open cell provides a vapor barrier. Maybe they look at it differently in your jurisdiction. I was told the same thing in the past, so they may look at it differently now.

I was also told that to meet minimum energy requirements, you only need 3" max of spray foam. If pinching pennies, you can save the labor to shave excess insulation and "underspray".

Tom, The square foot prices are very dependant on the thickness you want installed. I found that on average, it is costing me about $1.50-2.75 depending on what we are spraying. A 2x4 wall is on the lower end, but I have some crawl spaces, rim joists, and ceilings that I need to have done that are on the upper end of that.

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Open cell spray foam DOES NOT give you any sort of vapor barrier. If you use open cell you must use a vapor barrier in conjunction with it. Plastic sheeting or a vapor retardant primer applied either directly to the foam or on the drywall would suffice. Closed cell foam will give you a vapor barrier. Closed cell foam is about an r-7 per inch while open cell is slightly less. You could use the foam that comes in sheets against the block and seal all the seams and along the floor with caulk and then build your walls on the inside of that. The latter would probably be the cheapest. If we do it that we usually use foil faced thermax sheeting. I have a sheet that illustrates some of the methods to do this if you are interested.

We just built a place, and the thermax (silver foil wrapped around foam) at 1" think is what our contractor used. He attached it to block walls using big plastic washered nails (.22 style) and then foil taped all seams. He said it gives the vapor barrier and still allows the blocks to "breath". Then he said when I wanted to finish basement just put up studs on inside with NO insulation or additional vapor barrier and that's it.

We did the rim joists in spray foam, and the framed in walls (walkout) in glass bats.

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If we do it that we usually use foil faced thermax sheeting. I have a sheet that illustrates some of the methods to do this if you are interested.

Why foil faced? I don't know what it adds? If you could send me the sheet I would appreciate it. weyandt one two three four (used the numbers not the words) @ yahoo and you know the rest.

Thanks alot.

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The foil faced Thermax is flame retardant so the builder can leave it exposed. If the foam is drywalled over you can use pretty much any R-5 foam. The fact that you get a variety of opinions from building inspectors is a clue to get the info from a professional who has successfully insulated block walls without causing moisture/condensation problems.

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Only closed cell gives you a vapor barrier. That is the main difference between OPEN and CLOSED cell. It is in the name. OPEN cell lets vapor through while CLOSED cell does not. Open and closed cell will give you an AIR barrier but only one gives you a vapor barrier. As a contractor I have dealt with both. Speak with someone who specializes in spray foam and they will gladly explain the differences between the two.

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Gotta correct myself, I did not use Thermax, but "TUFF-R", but I think same stuff. Good luck Tom. I have pics of it if you would like to see how they attached/sealed/taped etc.

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Just went to Menards and the main thing the staff said was to check with the city for what they require. Seems odd to me that there would be any variance from place to place. I thought that's why there was a state building code - to keep thing uniform and simple.

The city in question requires R10 in the walls and the only thing at Menards that meets that spec was the 2 inch pink stuff - and I forgot to check and see if that was open or closed cell.

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I would be interested to see how it was installed.

Here are a couple pics, not the best, sorry.

Not totally installed, shows edge. This was 1" stuff.

IMG_9027_800x600.jpg

This shows how they went around the staggered block wall where it meets up to framed wall.

IMG_9037_800x600.jpg

And here is a link to a pic that shows it maybe a bit better angle for big picture. We still haven't finished basement, and will take several years at best to do that, ha! (from slide show I did for my wife of the place):

Basement insulated wall using Tuff-R on block

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Right now my basement has old knotty pine tounge and grove panels on the walls. Behind them I assume there is some sort of wood strips attached to the concrete already to attach the paneling to.

I am not 100% sure if there is insulation back there already but if not would it work to cut this down and put it inbetween existing strips of wood that is already there?

Would you want to cover with a vapor barrier before installing dry wall or can you then just drywall over it as is?

I have also considered just drywalling over the existing paneling since is appears to by 100% with no moisture issues and it is SOLID. The paneling is the older pine boards probably 3/4 inches thick.

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The pink sheet goods are closed cell. When we were talking about open and closed cell it was in reference to stuff they come out and spray in place.

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Seems like a shame to take out the knotty pine. If you do take it out carefully and see if someone else can use it - I bet you can sell it without any trouble.

As I wrote you need to check with the city you live in to see what they require. Where I'm doing it they want a R10 put in place. If you just rock over what you have you won't get much insulation out of it at all. So far the 2 inch pink board looks like the winner for me but I haven't priced out the spray foam yet.

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The knotty pine isn't a bad look its just not the look we are going for in the basement. At one point before we bought the house we were told the water heater broke and all the water flooded the basement leaving a little water damage on the bottom of the boards. Nothing to serious just a alittle stain on the bottom where the water was trying to wick up.

I'll be able to pull them out in pretty good shape so I do plan on seeing if someone wants them. A little sanding and they would be good as new.

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