How To Insulate A Warm Flat Roof

Both these variants require different approaches to insulation which will be covered in this guide.

How to insulate a warm flat roof.

The correct method for a flat roof is under the current regulations to have a warm roof. Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses. Insulation material is placed on top of the roof rather than in between the ceiling and the decking. In the case of a flat roof insulation is usually either a rigid board above the deck or a mineral glass wool quilt immediately above the underdrawn ceiling depending on the type of roof design and construction.

The material that works best depends largely upon preference in a given situation. Many times i answer the phone and customers ask me to give a price for a new flat roof. When a homeowner really needs to cut down on costs some contractors may suggest the following. With a warm roof the usual process is to split the insulation into two layers.

You would only do this however if replacing the roof covering on top and you have the height above the roof to do this. Proper ventilation in flat roofs. Add an additional layer of osb over the sheathing. The only point of putting the insulation on top of the waterproof membrane is when you can t take it off as when for example it is bitumen.

It should be installed on tapered 2x furring strips in order to slope the surface of the roof to drains. Ventilation is necessary to allow moisture accumulated inside to escape. In a nutshell you would sandwich 130mm of solid insulation between two decks allowing to place a vapour barrier on top of the first deck. It also lets hot air escape in the summer.

Insulation is placed in between the joists underneath the roof surface above. Then install r 30 fiberglass batts between the rafters. Insulation can either be put below the weather proof membrane which is called a warm roof deck construction or above the waterproof membrane which is called an inverted warm deck.