How Much Roof Insulation Is Enough

Input length and width of area to be insulated.

How much roof insulation is enough.

This calculator is to be used as an estimating tool only. Membrane manufacturers as well as various building codes require 8 inches of space from the flat roof membrane up to a penetration. For these locations i recommend intermediate insulation values between those for cold climates and hot climates. Having enough insulation in your attic is one of the best ways to save energy on both heating and cooling your home.

For these locations i recommend intermediate insulation values between those for cold climates and hot climates. You will need a higher r value of insulation if you live in the northeast than if you live in southern california. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam. 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.

I suggest a 4 5 10 30 60 rule. The higher the r value the better job the insulation does at preventing the transfer of heat. Existing 3 4 inches of insulation. 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. How well a particular insulation works is expressed by the r value which ranges from 2 0 to 8 0 per inch of insulation. The amount of insulation recommended for your home will vary depending on a number of factors. Have loose fill insulation blown in on top of existing insulation.

I suggest a 4 5 10 30 60 rule. Click the button to calculate the amount of insulation in square feet and man hours wall and ceiling fiberglass insulation needed for this job. As a general rule the attic needs to have 12 inches of insulation warner said. 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.

What about existing houses. Add insulation to attic. 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.