If you leave the insulation in the attic floor after insulating the roofline the attic will be cooler in winter than if you remove the insulation.
Spray foam attic roof deck.
Moisture generated indoors or that infiltrates into the home is responsible for the bulk of the moisture in an attic insulated with spray foam on the underside of the roof sheathing.
The main concern with spray foam insulation and shingle warranty is proper attic ventilation.
Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e.
The most common spray foam product used to insulate attic roof decks is open cell spray foam insulation sometimes referred to as half pound foam or icynene seen in the images on this page.
If the intent of installing spf to the roof deck was to create a conditioned attic non vented then the recommendation would be to first remove any insulation and vapor retarder from the attic floor then to install spf on the roof deck and gable walls.
And vented or unvented attics that are insulated above the roof deck with rigid foam.
Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope in this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within.
High efficiency attic insulation helps provide added thermal protection lessens wasted energy and increases enhanced comfort and quiet.
If you do not have proper ventilation you are in essence cooking your shingles.
An attic that is properly vented has 50 intake of fresh air and 50 exhaust of the hot air.
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.
It is important to note that icynene is a brand name similar to how a tissue is referred to as kleenex.
Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.
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.
Most people do not realize the requirements for proper venting of an attic.
Unvented attics that are insulated on the underside of the roof deck with blown spray foam.
Thus the air in the attic is connected with the air in the house.
Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly.
In a normal household where the occupants take a few showers and do some cooking some of the water vapor may well find its way into the attic.