Rigid Insulation Above Roof Deck

Second you can take the opportunity to make the roof deck airtight.

Rigid insulation above roof deck.

I m considering a roof design that would place all the insulation above the roof deck with no insulation below. Insulation board should be added between the old and new roof systems to ensure proper insulation and to reflect heat from the outside. After the roof deck is prepared the rigid foam boards need to be cut to size to fit snugly together on. Attach to deck board.

If the sheathing is boards it s a good place for a self adhered membrane. Placing a layer of fluffy insulation below the roof deck would needlessly complicate the. Available in both foam and rigid form choose the board type. The main issue people encounter with insulation above sheathing is when it expands.

Add insulation above the roof deck this approach fits current building science thinking in terms of putting the thermal control layer on the outside of the building structure. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing. High moisture areas may benefit from leaving a small air space between roof sheathing and the rigid foam insulation panels. The bottom layer of a single ply membrane roofing system is the roof deck or substrate.

Generally 40 of the total assembly r value should be above the roof deck. There are lots of different ways to insulate this type of roof but one of the best methods calls for the installation of rigid foam insulation above the roof sheathing. If plywood or osb sealing the panel edges with acrylic tape over primer or a fluid applied membrane would be good options. However for the best performance and for when space comes at a premium it s tough to beat rigid foam insulation.

Rigid foam insulation installation prepare roof deck. The right thickness would need to be calculated to move the dew point above the plywood deck where air infiltration is minimized. Typically this would be achieved by adding polyiso insulation above the plywood deck. The project is in climate zone 4 seattle area and i want to have an open beam look in the ceiling.