Spacing Between Insulation And Roof

Spacing of furring strips for metal roof when installing a metal roof over an existing roof insulate the spaces between the wood strips with rigid insulation to prevent condensation before.

Spacing between insulation and roof.

The idea here is after you have your high quality metal roof installed you will want to prevent the space underneath from heating up. In vented cathedral ceiling assemblies a minimum 2 inch clear airspace is recommended between the underside of the roof deck and the top of the cavity insulation. The gaps do not have to be more than 1 8 inch but they are important to the health of the roof the insulation and the house as a whole. The same concept holds true for roof trusses.

The solution is not to ignore the insulation but to add one component. When there are gaps or channels between the pieces of insulation you allow the air to flow between each one. If there is a leak the air flow ventilation will help dry out the moisture. Instead a dead space exists between the roof system and the top floor ceiling typically comprising of an acoustic tile system and no roof ventilation is provided.

For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. This ventilation offers another benefit. An air space between the insulation and the bottom of the roof sheathing is desirable.

Place between purlins if using them. The code calls for a minimum of 1 in. A roof must be able to breathe. In the winter humidity from the house s interior will get past the insulation and come in contact with the cold roof sheathing where it will condense into water.

This not a code requirement but ought to be only 1 inch is typically specified. Of airspace between the top of the insulation and the back of the roof sheathing.