Spray Foam Underside Of Roof In Attic

The main concern with spray foam insulation and shingle warranty is proper attic ventilation.

Spray foam underside of roof in attic.

The installer sprayed foam directly on the metal flues. Lstiburek takes blame for bad language. This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope.

Unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. The attic will be a conditioned space and i m planning to apply spray foam insulation to the underside of the roof sheathing. When spray foam is installed on the underside of the roof deck the attic space is insulated from heat that otherwise would be entering the attic. An attic that is properly vented has 50 intake of fresh air and 50 exhaust of the hot air.

If you look closely you ll see two exhaust flues on the left side. The roofing materials are installed and consist of timberline shingles and full coverage ice and water barrier the entire roof. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. Unvented roofs with spray foam applied to the underside of the roof deck have been used since the mid 1990s.

It s not coming from above the roof and it s not some new moisture source resulting from the spray foam. If you do not have proper ventilation you are in essence cooking your shingles. You ll also see another safety hazard and code violation. Polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters and attic walls in much less time than is needed for other materials.

Open cell spray polyurethane foam or closed cell spray polyurethane foam ccspf insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in all climate zones see figure 1. You should never do this. Most people do not realize the requirements for proper venting of an attic. In this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within the building envelope.

The insulation reduces wildly high temperature spikes and so the attic becomes a conditioned part of the home like any other room. The attic you see in the photo here is a different home but it does have one feature in common besides the spray foam.