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Old 06-12-2011, 01:45 PM   #1
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1 1/2 inch foam insulation


Hello,
I am in the process of re-doing my basement. I tore down the paneling and removed the bat insulation do to flooding. The insulation was R-7 1 1/2 inch thick. I can't find R-7 1 1/2 thick bat. Is it ok to use the Styrofoam sheets that are 1 1/2 thick?

Thanks in advance

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Old 06-12-2011, 02:18 PM   #2
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1 1/2 inch foam insulation


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Originally Posted by jburchill View Post
Hello,
I am in the process of re-doing my basement. I tore down the paneling and removed the bat insulation do to flooding. The insulation was R-7 1 1/2 inch thick. I can't find R-7 1 1/2 thick bat. Is it ok to use the Styrofoam sheets that are 1 1/2 thick?

Thanks in advance
I'd install the amount of insulation your region suggests as opposed to what was there. Insulation requirements have increased since that work was done due to the increased cost of energy.

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Old 06-12-2011, 02:27 PM   #3
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1 1/2 inch foam insulation


Styro stuff is not fire rated and can actually melt. I wouldn't use it in an interior space.
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Old 06-12-2011, 07:03 PM   #4
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1 1/2 inch foam insulation


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Originally Posted by sdsester View Post
Styro stuff is not fire rated and can actually melt. I wouldn't use it in an interior space.
Worse than melt, it catchs fire very easily, and spews out toxic fumes. Defintely not recommended unless its then covered with something fireproof.
inch per inch styrofoam products dont provide the same insulative value (I think less than half), plus they are way more expensive.
R12 is pretty standard for batts, if the area they are going into is a bit narrow, squeezing them flat reduces the R value, but they are still probably more insulative than foam, safer and cheaper...
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Old 06-13-2011, 01:42 AM   #5
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1 1/2 inch foam insulation


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Originally Posted by phantasm72 View Post
Defintely not recommended unless its then covered with something fireproof. ••Yes. Like sheet rock.

inch per inch styrofoam products dont provide the same insulative value ...•• Compared to what? He has fiberglass (I assume, not rock wool, etc), which is next to useless for anything but insect and rodent nests. Basements are a great place for EPS or XPS. There is a far better R value, inch per inch, in rigid foam than FG, for a couple of reasons. (
See after the bullets.
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Old 06-13-2011, 01:52 AM   #6
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1 1/2 inch foam insulation


I will be covering with sheetrock.
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Old 06-15-2011, 08:58 AM   #7
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1 1/2 inch foam insulation


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Originally Posted by jklingel View Post
See after the bullets.
Compared to fibreglass batts.
batts have a R value of about 4.5 / inch and styrofoam is about 3.8
Which is actually a lot more than I originally thought it had when I made the original post, but my point still stands, batts, inch per inch are still more effective, a lot safer to have in a home and way more cost effective.
And yes, I do know you can get even better rigid foam board with superior 4-ratings and even stuff that has fire retardant coatings on it, but you will be paying the big bucks for that.

Last edited by phantasm72; 06-15-2011 at 09:00 AM.
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Old 06-15-2011, 01:26 PM   #8
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1 1/2 inch foam insulation


I think you have your numbers backwards. I have never seen FG listed with a R value exceeding 3.5. Check here, for ex. http://www.allwallsystem.com/design/RValueTable.html Rigid foam is far superior for 3 reasons: One, the R/inch. Secondly, when you look at the whole wall assembly, as typically installed, FG R's drop way off because it is impossible to install perfectly and it is inconsistent in its structure. Finally, FG batts are not dense enough to prevent internal convective loops, further eroding the advertised R value. Sure, you pay a little more for rigid foam. What is your goal, though, when insulating? To put in something cheap or something that will pay for itself time and time again? If you want batts, get mineral (rock) wool, cellulose, cotton, or wool. Read about insulation on buildingscience.com, greenbuildingadvisor.com, ORNL site, etc. FG batts are a marginal insulation, but not good, by any means. Dense packed FG is good stuff, but batts, basically, stink. I have 13" of batts in my walls (installed in 1980, as I did not know better then) and they are doing a pretty good job, partly because of how they were installed. However, I have no use for them anymore, as there are better products readily available, as noted above; I will be dense packing cellulose, which is far superior to FG batts in a few ways. So, that is the skinny on FG batts as I see it.
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Old 06-15-2011, 09:59 PM   #9
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1 1/2 inch foam insulation


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Originally Posted by jburchill View Post
Styrofoam sheets that are 1 1/2 thick?
Id check with both your insurance company and local building codes prior to installing them. Some places you may find they arent legal inside a house.

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