Warm Flat Roof Insulation Between Joists

So a solution i would like to propose is.

Warm flat roof insulation between joists.

A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. Here the roof deck is maintained at the same temperature as the external conditions hence cold deck roof. Making a warm flat roof construction but instead of putting the insulation above the structure joists as seems to be normal i propose to include the joists effectively as insulation i believe wood is quite good for that and install a proper vapour control layer underneath the joists. How to install insulation in a flat roof with timber deck insulated above the joists.

The vapour control layer is above the decking but below the insulation. As to your warm roof to me that looks like a hybrid roof with pir insulation above the structural joists a warm roof but also between the joists a cold roof. This will enable the airflow to circulate freely. If insulation is being added to an older building then it is common practice for the ceiling itself to be taken down.

A cold flat roof is defined by insulation being installed between and if necessary underneath the timber joists. Here the roof deck is maintained at the same temperature as the internal conditions hence warm deck roof. A warm flat roof is defined by insulation being installed on top of the roof deck. 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.

The insulation is immediately below the waterproofing layer. Warm deck insulation 1. If you put insulation under the decking and between the joists you lower the temperature of the decking and lower the due point thus bringing it closer to the danger point of being in the building. Set the quinn therm qrfr ply insulation boards onto a wide 30mm bead of vapour resistant sealant applied to the upper surface of all the joists and cross noggins.

Good question theoretically when building a warm roof the vaper control layer goes on the warm side of the insulation. The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation.