Existing Roof Insulation

How to install insulation board over an existing roof membrane.

Existing roof insulation.

Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. Single ply roof insulation. The proportions do not matter but this arrangement helps to eliminate any draughts caused by gaps between the insulation and the rafter. Alternative options for insulating old roofs.

There is a good deal of controversy around these systems. Water is insulation s enemy. Single ply roof systems can provide an easy to install seamless roof assembly. Here s how to insulate your new or existing roof.

Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense. Lay the wood perpendicular to the roof joists and use roofing nails to fasten it in place. Now comes the really really big point. Rockwool multifix is a mineral fiberglass faced stone wool product that can be installed under many single ply membranes.

Place layers of building paper over the sheathing. Gable end detail overhang cut and then rebuilt to hide the thickness of the over roofing rigid insulation. It is an acceptable practice to install a new roof over an existing roof membrane system provided that the roof deck is. Hack n stack sealed foam board between the rafters would be better since it s at least an air impermeable insulation but even that would require a vent gap below the roof deck to meet code and you d still be under r38 on that 2x6 rafters unless you fattened it out per holladay s recommendation.

Install plywood to act as structural roof sheathing. Box out light fixtures. The 6 inches of rigid insulation added to the top of the existing roof deck needed to be done in a manner that was invisible. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow.

One modern option for existing buildings is sprayed foam. Portions of an existing building that are altered in the course of additions alterations renovations or repairs must be brought into conformance with the code with the following exceptions applicable to attic roof retrofit.