"R" for insulation????

R is for resistance to heat movement. Some info here

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.

"cece e." wrote on 11 Jul

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).

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

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

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.

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

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.

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.

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

Nick

Wrong.

Nick

That would be closed cell.

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.

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

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.

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

Nick

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

Nick

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 -

Unlike your arrogance, your ignorance may be curable :-)

You might buy an old copy of the ASHRAE Handbook of Fundamentals and look at the table on R-values of plane airspaces, or look into "System R-values."

Nick

Labeling and Advertising of Home Insulation (R-Value Rule) CFR 16CFR460

(From the U.S. Government Printing Office via GPO Access)

Source: 44 FR 50242, Aug. 27, 1979, unless otherwise noted.

Sec. 460.1 What this regulation does.

This regulation deals with home insulation labels, fact sheets, ads, and other promotional materials in or affecting commerce, as "commerce" is defined in the Federal Trade Commission Act. If you are covered by this regulation, breaking any of its rules is an unfair and deceptive act or practice or an unfair method of competition under section 5 of that Act. You can be fined heavily (up to $10,000 plus an adjustment for inflation, under Sec. 1.98 of this chapter) each time you break a rule...

R-value measures resistance to heat flow. R-values given in labels, fact sheets, ads, or other promotional materials must be based on tests done under the methods listed below. They were designed by the American Society of Testing and Materials (ASTM). The test methods are: All types of insulation except aluminum foil must be tested with ASTM C

The tests must be done at a mean temperature of 75 deg.Fahrenheit. The tests must be done on the insulation material alone (excluding any airspace). R-values ("thermal resistance") based upon heat flux measurements according to ASTM C 177-85 (Reapproved 1993) or ASTM C 518-91 must be reported only in accordance with the requirements and restrictions of ASTM C 1045-90, "Standard Practice for Calculating Thermal Transmission Properties from Steady-State Heat Flux Measurements."

Aluminum foil systems with more than one sheet must be tested with ASTM C

Single sheet systems of aluminum foil must be tested with ASTM E408 or another test method that provides comparable results. This tests the emissivity of the foil--its power to radiate heat. To get the R-value for a specific emissivity level, air space, and direction of heat flow, use the tables in the most recent edition of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers' (ASHRAE) Handbook. You must use the R-value shown for 50 deg.Fahrenheit, with a temperature differential of 30 deg.Fahrenheit.

For insulation materials with foil facings, you must test the R-value of the material alone (excluding any air spaces) under the methods listed in paragraph (a) of this section. You can also determine the R-value of the material in conjunction with an air space. You can use one of two methods to do this:

You can test the system, with its air space, under ASTM C 236-89 (Reapproved

You can add up the tested R-value of the material and the R-value of the air space. To get the R-value for the air space, you must follow the rules in paragraph (c) of this section.

For aluminum foil: the number of foil sheets; the number and thickness of the air spaces; and the R-value provided by that system when the direction of heat flow is up, down, and horizontal.

For insulation materials with foil facings, you must follow the rule that applies to the material itself. For example, if you manufacture boardstock with a foil facing, follow paragraph (b)(4) of this section. You can also show the R-value of the insulation when it is installed in conjunction with an air space. This is its "system R-value." If you do this, you must clearly and conspicuously state the conditions under which the system R-value can be attained.

Also see: