How Much Roof Insulation Is Enough

For these locations i recommend intermediate insulation values between those for cold climates and hot climates.

How much roof insulation is enough.

I suggest a 4 5 10 30 60 rule. R 4 windows r 5 under slabs r 10 foundation walls or slab perimeter r 30 above grade walls and r 60 in the attic or roof. Recommended insulation levels for retrofitting existing wood framed buildings. If you need to add four inches approximately r23 with polyiso insulation or r15 with expanded poly styrene there may not be enough room between the membrane at the roof penetrations.

Where you live different climates require different insulation r values. How much insulation should you install. For these locations i recommend intermediate insulation values between those for cold climates and hot climates. Input length and width of area to be insulated.

Have loose fill insulation blown in on top of existing insulation. How well a particular insulation works is expressed by the r value which ranges from 2 0 to 8 0 per inch of insulation. Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam.

R 4 windows r 5 under slabs r 10 foundation walls or slab perimeter r 30 above grade walls and r 60 in the attic or roof. Having enough insulation in your attic is one of the best ways to save energy on both heating and cooling your home. What about existing houses. Existing 3 4 inches of insulation.

The higher the r value the better job the insulation does at preventing the transfer of heat. The amount of insulation recommended for your home will vary depending on a number of factors. As a general rule the attic needs to have 12 inches of insulation warner said. This calculator is to be used as an estimating tool only.

That s my rule of thumb in any climate zone if you have a crawlspace or unheated basement make sure there is insulation between the floor joists. You will need a higher r value of insulation if you live in the northeast than if you live in southern california. Membrane manufacturers as well as various building codes require 8 inches of space from the flat roof membrane up to a penetration.