How To Insulate A Flat Roof Cold Deck

Insulated roof assemblies can be vented or unvented.

How to insulate a flat roof cold deck.

Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior. A roof over a vented unconditioned attic does not need to include any insulation. Quinn therm qrfr ffr insulation is a foil faced insulation board which helps further improve the thermal performance to help achieve the desired u value. The target should be to achieve a u value of 0 25w m2k or better.

Run vertical 2 3 boards battens over roof sheething 16 o c. There are a number of quinn therm roof insulation boards which will suit a warm deck flat roof construction built with a concrete deck each with different facings. To produce a cold roof the insulation has to be fitted inside below the weatherproofing support beams brickwork etc with a ventilated air gap. A cold flat roof is one where the insulation is between or between and below the roof joists.

Refurbishing an existing timber joisted flat roof which has no insulation. This is used for refurbishment e g. 1 get insulated panels with osb board attached to iso insulation you will then screw this over current roof deck. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity.

In warm climates zones 1 through 4 low density open cell spray foam insulation is the typical choice since it is vapor permeable and will allow drying of the exterior sheathing and roof framing if they happen to get wet via diffusion into the interior of the building. The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation. With this kind of roof the insulation follows the slope of the roof. The insulation is below the deck but above the plasterboard.

However most cathedral ceilings and low slope flat roofs are insulated roof assemblies. Where insulation depth is restricted by the flat roof construction it may be necessary to install the roof insulation between and below the joists to create a cold deck structure. And then install 1 2 minimum recommended is 5 8 or thicker plywood on top of battens.