How Much Space Between Insulation And Roof

Spray foam insulation is the most expensive option with the highest roi.

How much space between insulation and roof. The table below shows what levels of insulation are cost effective for different climates and locations in the home. Unvented hot roof design cathedral ceilings are also an option. 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. Of airspace between the top of the insulation and the back of the roof sheathing.

The higher the r value the better the thermal performance of the insulation. For example cathedral ceilings built with 2x12 rafters have space for standard 10 inch batts r 30 and ventilation. R value is a measure of insulation s ability to resist heat traveling through it. If you already have insulation but it was put in some time ago it is worth checking the.

Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense. Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. The hot roof design allows more insulation to be installed in the roof cavity as the need for a vent space is eliminated. The recommended depth of blanket style insulation glass or mineral wool for a loft is 250 to 270 mm.

They come with or without a paper or foil facing that acts as a vapor barrier. Generally spray foams have to be applied by a professional. Apply a 2 inch layer of spray foam insulation r 10 to r 12 directly to the interior surface of the roof sheathing. You can then apply batt insulation around the foam without worrying too much about the air space.

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. This will keep the surface warm and help minimize condensation. Insulation costs between 1 400 and 2 300 blown in insulation is a little cheaper than batting fiberglass and radiant barrier insulation which cost 1 600 on average.

This flexible insulation material is most often packaged in rolls that come in various thicknesses and standard widths usually 16 inches and 24 inches to fit between joists or studs in a house s framing.