Roof guide

Roof insulation thickness guide

Roof insulation thickness is driven by thermal target, available depth, and the existing resistance of the roof deck and finishes.

Target first

Start with the U-value you want the roof to reach.

Roof build-ups often have a fixed structural depth that limits insulation thickness.

Enter existing resistance and lambda to get a fast thickness estimate.

Open the calculator for a custom roof build-up.

See a roof-specific target-U example.

Read the broader thickness planning guide.