How Much Air Space Between Insulation And Roof

Most building codes require a ratio of 1 150 ventilation space to attic floor space.

How much air space between insulation and roof. You can then apply batt insulation around the foam without worrying too much about the air space. 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. In principle use of cavities is similar to use of a insulating material. With a warm roof the usual process is to split the insulation into two layers.

Generally spray foams have to be applied by a professional. 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. 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. The solution is not to ignore the insulation but to add one component.

Insulation is technically a solid with a lot of air in it therefore it is not an air gap. You can also contact your local municipality to check on building code in your area. Apply a 2 inch layer of spray foam insulation r 10 to r 12 directly to the interior surface of the roof sheathing. 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.

Install a non flammable radiation shield that maintains a 75 mm 3 in air space between the chimney and insulation. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca. Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. If an air space is left between two layers making a wall or roof in any building the air trapped between two layers being poor conductor of heat acts as a barrier to heat transfer.

By leaving an air space between the insulation and the sheathing we can have air flow over the framing. Cavities air spaces. This will keep the surface warm and help minimize condensation. If there is a leak the air flow ventilation will help dry out the moisture.