"R" for insulation????

[cece e.]

My last question before I get started with insulating my crawl space. Remember this is my first time doing this. What does the "R" mean for insulation. I was going to insulated my crawl space with fiberglass insulation but a man from the big orange box told me that for a crawl space I could use (i forgot the exact name) styrofoam and glue it to the walls and it would have an R10 rating (or something like that). What did he mean and is styrofoam just as effective as insulation (in Colorado) for keeping the heat in?

[Edwin Pawlowski]

R is for resistance to heat movement. Some info here

Styrofoam is about R4 per inch, same with expandable polystyrene.

[Jeff]

R is the fraction of heat loss compared to an air gap the same thickness. So R-19 insulation will conduct 1/19 as much heat as an air gap the same thickness. If you place two pieces of insulation on top of each other you can add the R value. For example two 6" fiberglass bats (R-19 each) equals R-38.

[Doug Boulter]

"cece e." wrote on 11 Jul

2006:

We're talking two different strategies for insulating a crawl space here, I believe. You intended to put fiberglas batts between the floor joists, and he wants you to insulate the walls of the crawlspace.

The difference is how the crawlspace functions. In your system, it stays close to the temperature (and humidity) of the outside air. You open the small vent windows in the summer and block them off in the winter. In his system, the crawlspace is insulated space -- warmer in the winter and colder in the summer. The crawlspace isn't ventilated at all in any season.

So it seems to me you and he are talking apples and oranges. Both methods are routinely used these days. You might want to talk to your local utility and get their recommendation for what works well in your area -- and, if you seal the crawlspace, how to deal with heating equipment in the crawlspace (needs an intake air duct for combustion air).

[nicksanspam]

Resistance to heat flow. Specifically, Ohm's law for heatflow says I = E/R Btu/h, where E is an F temp diff and R is the R-value of 1 square foot of insulation. For A square feet, multiply the heatflow by A.

For instance, a 2'x8' R5 Styrofoam (vs R4 beadboard) wall that's 70 F on one side and 30 F on the other will have I = (70F-30F)2'x8'/R5 = 128 Btu/h of heat (38 watts) flowing through it.

Nick

[maradcliff]

And here I always thought it meant "Rob". The higher the R value the more money they ROB from your wallet. :)

[m Ransley]

Styrofoam is R4-4.5" Blue or pink foamboard is R5" Foil faced Polyisocyanurate foamboard is R7.2" R value is resistance to heat flow, foam costs more, in certain areas it is better where area to insulate is minimal, it also provides a vapor -air infiltration barrier.

[zyberengel]

[nicksanspam]

m Ransley errs again:

Same thing. All R5 per inch. Open cell expanded polystyrene (white coffee cup material) is R4 per inch...

These days, it's often stamped "R6.8" (per inch.) Add about R3 per foil, if the foils are exposed.

Nick

[m Ransley]

Nick, White Styrofoam is not R5", extruded polystyrene, the pink Owens Corning or blue Dow is R5" . White Styrofoam board is sold just like R5 extruded polystyrene board, in the same manner, but is inferior in R value, workability and stability.

Polyisocyanurate foilfaced newly used rating of 6.7"-6.8" is the aged or mature R value after R 7.2" polyiso outgasses.

Perhaps you could provide us with some detailed mathematicals of your opinion.

[m Ransley]

Nick, foilfaced does not increase R value by 3R per foil, or R6 for both side, please provide proof of your statement. At most it contributes R-.5, if that.

[nicksanspam]

Where can we buy this "white Styrofoam board"? :-)

Nick

[Nick Pine]

Wrong.

Nick

[Edwin Pawlowski]

That would be closed cell.

[Edwin Pawlowski]

Styrofoam is the blue material extruded by Dow Chemical. Styrofoam is a registered trademark of Dow but often the name is mis-used when referring to any other type of polystyrene foam board, extruded or molded and wire cut such as the CLOSED cell expandable polystyrene board, sometimes called bead board.

[m Ransley]

Alright nick, post Proof foil increases Polyisocyanurate by R3, You Can`t dipshit.

[Chris Lewis]

According to zyberengel :

And has _zero_ insulation value. Except inosofar as it may seal air leaks. He's trying to insulate it, not improve its fire resistance.

R is insulation factor. Not fire retarding rating.

[nicksanspam]

EPS is open cell. X (extruded) PS is closed.

Nick

[nicksanspam]

Sorry. I have other things to do than correct your many mistakes.

Nick

[m Ransley]

Right Nick, you post numbers but cant prove anything, because foil does nothing of real merit to R value, it is a Radiant barrier, no R value of significance. If as you say it increases each side by R3 then R 7.2 -

1" of polyiso would come out near R 13, kind of dumb, yes, maybe you have numbers to prove your dream.