How To Insulate A Flat Roof Attic

This old house general contractor tom silva and host kevin o connor demonstrate the proper way to insulate an attic.

How to insulate a flat roof attic.

Rigid foam panels are available in thickness. If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters. The materials used to insulate under the roof include batts of mineral or glass wool insulation held in place by battens of wood attached to and across the rafters. The simplest and cheapest solution for attic insulation is the so called cold attic.

Sealing bypasses bypasses are anywhere that there is a break in the insulation. This technique involves placing insulation directly between the ceiling of the upper floor and the attic floor which prevents heat from penetrating the attic. It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains. In either case you will need to follow the general steps below to insulate your garage roof.

With this method only the attic floor is insulated. Use rigid foam insulation panels on your flat roof before applying the final roof covering or inside the house before adding sheetrock or paneling. This is best done when the roof covering needs replacing anyway. See below for a shopping list and tools.

A layer of rigid insulation board can be added either on top of the roof s weatherproof layer or directly on top of the timber roof surface with a new weatherproof layer on top of the insulation. Then install r 30 fiberglass batts between the rafters. With a warm roof the usual process is to split the insulation into two layers. With flat roof insulation a vapor barrier should sit between the joists and ceiling panels and the insulation on top.

However if you have a cathedral style garage roof you will need a scaffolding to get into the upper areas of the roof.