It's a reasonable question to ask, considering that some homes with open-cell spray foam insulation installed on the underside of the OSB roof sheathing have reported moisture problems. There's also a pretty reasonable answer to will spray foam will rot your roof: No spray foam will not rot your roof.

Will spray foam rot my roof?

Studies show that open-cell spray foam is risky in colder climates. Indoor moisture diffuses through the foam and comes in contact with the cold roof sheathing. The spray foam traps the moisture against the roof, which results in eventual decay.

Why you shouldn't spray foam your attic?

Because spray foams contain highly reactive chemicals called isocyanates, exposure can cause severe breathing and skin problems.

Is spray foaming your roof worth it?

If you see the benefit of insulating your new construction home correctly from the start for long-term comfort, energy savings month after month, and fewer headaches while you live in the house, then spray foam insulation may very well be worth the extra cost to you.

Does spray foam devalue your house?

In fact, according to Heritage House, they have seen entire roofs rotted and unrecoverable after SPF has been used. They state that by using SPF in your roof, '…you will devalue your home by the amount that a new roof will cost, and more. ' And we agree.

Spray Foam Insulation — The Ugly Truth?

Can I spray foam the underside of my roof?

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).

Does spray foam hurt shingles?

With this experience, we know the spray foam we use isn't going to damage your roof or shingles. We also know that in many applications, insulating the roof deck is the best way to seal the envelope of the home.

Does a spray foam roof need to be vented?

By using an air-impermeable insulation, like spray foam, on the roof deck will stop any air movement. If the home's building envelope is completely air sealed, then the air traveling up to the attic won't be unbearably hot, and there will be no need to cycle it out with vents.

Can spray foam cause rot?

We already know open-cell spray foam is risky in cold climates. Moisture from indoors can diffuse through the foam and find the cold roof sheathing, where it accumulates and eventually rots the roof.

How long does closed cell spray foam last?

Take a look at the following: Foam is more energy efficient. The R-Value of closed cell foam is 300% that of fiberglass. It's estimated to last for 80 years.

What is the downside to foam insulation?

On the downside, spray foam insulation comes at a price that is considerably more expensive than fiberglass. Often times, spray foam is triple the price of fiberglass and sometimes it can be more. Applying spray foam insulation is also something that is not advised to do by yourself unless it is a very small job.

How long does a spray foam roof last?

Spray foam roofs are generally expected to last around 20 years at installation. The roof will last much longer than 20 years, but this is the standard warranty period. This all depends on the thickness of the foam and the coating, and applying more of either of them will generally extend the warranty term.

Should you insulate the underside of your roof?

roof insulation is no-contest. The floor wins every time. Insulating the floor is standard practice for an unfinished attic space. The exception to this rule takes place when families opt to convert an unfinished attic space into something usable or livable.

Does spray foam shorten shingle life?

As it relates to spray foam in your attic, spray foam will have little to no effect on the temperature of your shingles.

Are hot roofs bad?

As for the “hot” roof theory, the unvented attic system could make the temperature of your roof go up a little, but fear not. This possible temperature increase of a couple degrees won't cause damage to your roof or shingles at all.

What's a hot roof?

A “hot roof” means that insulation is installed closely beneath the roof decking, without space for ventilation. In some cases, this design allows the attic space to be usable like any other room in the house by bringing it into the thermal envelope of the home.

How thick should spray foam be in attic?

Now generically speaking, we usually recommend open cell spray foam to be 6- to 10-inches on a roof deck or ceiling and 3-inches in the walls. Closed cell spray foam should be 4- to 5- inches on the ceiling and 2- to 3-inches in the walls.

Does spray foam trap moisture?

Moisture Barrier

Open cell spray foam is not a moisture vapor barrier, and will allow moisture to pass. So, if you're considering spraying foam to the roof deck of your new or existing home, you want open cell. If there's a roof leak, water will pass through the foam, and you will quickly be able to find your problem.

Is closed cell spray foam a vapor barrier?

Quality closed cell foam insulation acts as a vapor barrier and does not absorb moisture; at the same time, the insulation prevents leakage by closing air gaps. With proper installation of foam insulation, the house should be well sealed and allow the house to breathe.

Can mold grow behind spray foam insulation?

Adding spray foam insulation in potential problem areas is a great way to insulate your home and goes a long way towards mold prevention. It is mold-resistant because it expands when it gets wet, meaning there's no room for mold or mildew!

Why do mortgage companies dislike foam insulation?

So why is it a problem for mortgage lenders? By sealing the roof space with this material, air circulation can be restricted to the roof and timbers. This can lead to condensation, which in turn can eventually lead to the rotting of the wooden roof supports.

How do you remove spray foam insulation from a roof?

Lacquer thinner is an excellent solvent and highly efficient for removing spray foam roof insulation that has cured. This can be obtained from most paint shops or DIY stores. As with Acetone, it must not be used in confined spaces without considerable ventilation.