How Much Space Between Insulation And Roof

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.

How much space between insulation and roof.

Apply a 2 inch layer of spray foam insulation r 10 to r 12 directly to the interior surface of the roof sheathing. Typically fiberglass or cellulose are the material choices. Here are four approaches i recommend you investigate for insulating your attic. With a warm roof the usual process is to split the insulation into two layers.

Insulation is technically a solid with a lot of air in it therefore it is not an air gap. 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. The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies. 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.

Typically we suggest you have an air gap between 1 2 and 3 4 for the radiant barrier to work. This is one of the two most common types of insulation. 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. R value for loose fill per inch is between r2 and r4 higher value with.

You will however have to follow up with great stuff foam to ensure filled gaps if you go that direction. Often installed into wall cavities as a way to retro fit walls lacking insulation it can also be blown into unfinished attic spaces.