How Much Air Space Between Insulation And Roof

The solution is not to ignore the insulation but to add one component.

How much air space between insulation and roof.

Insulation is technically a solid with a lot of air in it therefore it is not an air gap. 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. You can then apply batt insulation around the foam without worrying too much about the air space. With a warm roof the usual process is to split the insulation into two layers.

Apply a 2 inch layer of spray foam insulation r 10 to r 12 directly to the interior surface of the roof sheathing. Most building codes require a ratio of 1 150 ventilation space to attic floor space. It is important that air is allowed to circulate between the roof covering and the insulation to avoid condensation a gap of at least 50mm 2 inch must be left between the insulation and the inside of the roof covering. You can also contact your local municipality to check on building code in your area.

The code calls for a minimum of 1 in. Air gaps larger than this work well too they promote ventilation on the foil and help keep the air dry and the air temps lower. Generally spray foams have to be applied by a professional. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

If the roof felt is breathable then you need to leave a 50mm gap between it and any cellotex etc you shove in between the rafters sinewave mar 2 2009 2 big jumbo new member. In principle use of cavities is similar to use of a insulating material. This will keep the surface warm and help minimize condensation. Cavities air spaces.

Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. Factory built metal chimneys should be kept from contacting insulation by a minimum 75 mm 3 in unless otherwise specified by manufacturer or local authorities. If there is a leak the air flow ventilation will help dry out the moisture. By leaving an air space between the insulation and the sheathing we can have air flow over the framing.