How To Vent Closed Cell Insulated Roof

Unvented roof here again the choice of what insulation to use and whether to install it over or under the roof deck depends on the condition of the present roof the depth of rafters the r value you must attain and cost.

How to vent closed cell insulated roof.

For roof ventilation to be successful a few conditions must be met. Temporarily secure long plastic forms between the rafters on the inside of the ceiling. How to vent a foam insulated roof. Cost aside the most straightforward route is spraying closed cell polyurethane foam on to the underside of the roof deck.

Proper air movement from soffit vent to ridge vent is not always possible. Allow it to escape. Moisture is also another huge issue when it comes to spray foam insulation in an attic. For best performance the airspace in the vent chute should be a minimum of 2 in.

Closed cell foam can also add to the structural strength of the roof system which can make it a more appealing choice in locations that frequently endure high winds. Unless you live in climate zones 2b or 3b desert area s in texas new mexico arizona california the codes and common sense will point you to closed cell foam. Unless you re bulk filling rafter bays between 2 10 or 2 8 rafters with closed cell spray foam this approach will likely require you to fur out the rafters to accommodate additional insulation to achieve desired r values. Intumescent coatings are not always needed to coat spray foam in the attic in order to meet code thermal barrier requirements.

Leave a gap on both sides of the roof near the ridge. 2 another question on the use of sprayfoam is what happens when an applicator unintentionally sprays foam to wet lumber particularly wet framing members. It has been said that insulating with spray foam insulation at the roof line will lead to moisture problems with the roof sheathing. Whereas too little spray foam insulation can leave for thermal bypass because of the complete lack of insulation in the attic.

When using a hybrid insulation system such as ccspf covered with fibreglass or cellulose insulation a greater thickness of closed cell foam is needed to reduce the potential for condensation. These forms are. Closed cell or open cell foam.