Roof Deck Foam Insulation

Joined jan 17 2009 313 posts.

Roof deck foam insulation.

So applying this insulation product can actually give you added protection from roof leaks. You may also need to inspect the foam at intervals to see whether any shrinkage has. Discussion starter 1 jun 24 2009. Generally more insulation is needed for condensation control in colder climates.

Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. The secret to high performance insulation is stopping air infiltration. With enough closed cell spray foam under the deck or enough rigid above the deck interior moist air can t condense if the there is no condensation you don t need drying thus no need to vent. We then vented that space through the roof deck as was the normal practice for roofing.

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. So your attic is sealed and insulated to protect your home against energy loss. 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. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions.

On one project in kansas we installed 1 x 1 along both sides of the rafters and then added 3 8 plywood to them. So there are very few if any air gaps voids channels where energy can escape. To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. This gives a 1 air space between the roof deck and the insulated area.

Even small gaps can allow the passage of warm air through the foam rendering the foam all but useless as an insulator. This type of insulated roof assembly limits thermal bridging through rafters. The plywood was fastened through the rigid foam to the rafters with long screws. Because the properties of foam insulation are like epoxy glue it tenaciously adheres to the surface of your roof deck.

The amount of closed cell spray foam or rigid insulation is somewhere between 20 to 50 of the r value of the overall cavity insulation depending on your climate zone. Jump to latest follow 1 9 of 9 posts. One huge difference between spray foam insulation and other types of insulation is that it is an effective air barrier. Also the higher the indoor humidity the more insulation is needed to avoid condensation.

Closed cell foam which is used as insulation on the underside of your roof deck is not air or water permeable. After installing several layers of rigid foam above the roof sheathing these workers installed plywood above the rigid foam. What happens to an insulated roof deck it when to comes time to replace the shingles and bad wood is found.