Foil Insulation R Value

What is the r value or r rating of radiant barrier foil insulation.

Foil insulation r value.

The r value is in essence the measurement of an insulation sheet s ability to resist heat flow. Polyiso is typically used with a foil facing and it has an r value of 7 0 to 8 0 per inch of thickness. Worth mentioning to get the equivalent r value to what the manufactures claim on the packaging the installer has to use spacers under the insulation to keep the prescribed air gap between the ducts and the foil. Other materials may only have a fifty percent increase in r value when their thickness is doubled.

Each sheet is created with different r value ratings. Most metallic bubble wraps are about an r 1. Air inherently has an r per inch value of 5 6 and is an excellent insulator when radiation and convection are controlled. The sheets themselves are not created equally.

As a foil faced polyisocyanurate foam insulation enerfoil tm s r value actually more than doubles when it is twice as thick as you can see from the chart above. It s a measure of how long it takes a heat absorbing product to absorb 100 of its potential and begin to transfer that heat out the other side of the product. This testing to designate an r value only applies to conductive heat flow not radiant heat flow. R value is a term to describe how quickly heat will pass through or be absorbed by a product.

It provides about r 5 per inch. An r value is a measure of an insulation product s resistance to thermal heat transfer. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. Just as the absorbency of a raincoat is unrelated to its ability to repel water the r value of rfoil does not fully measure its ability to insulate and redirect heat energy.

The astm c236 1224 tests that determine a products r value yield the following results for rfoil reflective insulation. This material offers the highest r values about r 6 to 6 5. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. Smaller sizes are also available.

Products with foil facing help the panels resist moisture vapor. Working with home insulation boards insulation panels typically come in 4x8 foot sheets. Basically r values range from 1 5 to 7 and the higher the number is the more effective the insulation sheet is at increasing thermal efficiency and thereby insulating your home. Heat flow down r 10 6 heat flow horizontal r 6 8 heat flow up r 5 3.