Cold Roof Insulation Between Joists

A cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof.

Cold roof insulation between joists.

Refurbishing an existing timber joisted flat roof which has no insulation. This is used for refurbishment e g. The insulation is below the deck but above the plasterboard. Unless the joists are exceptionally deep there is also likely to be a requirement to install insulation to the underside of the joists as the upper 50mm of joist space is usually required to be left clear for ventilation purposes.

Ventilation is required for these roofs. The rule of thumb for foil faced boards like thermapitch tp10 or kooltherm k7 in this scenario is that you can have no more insulation under the joists than you have between the joists. Insulation between the joists keeps warmth in your living space below and creates a cold loft while insulation in the rafters allows you to keep warmth in the roof space as well. To form a vapour control layer seal the joists between the boards.

The majority of domestic cold flat roofs use insulation between and under the joists. Other benefits of roof insulation include. It is preferred to have the bulk of the insulation between the joists to reduce any risk of condensation. Poly to the underside of joists.

Install quinn term ql kraft insulation boards below the joists using suitable mechanical fixings. A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. Cold roof a cold flat roof is one where the insulation is between or between and below the roof joists.