Foam Insulation Questions

[fox1]

Ive had two different companies come out and give me quotes on spraying my insulation. Both companies say they don't spray the ceiling rafters in the attic but instead spray the underside of the roof. They also want to spray over my ridge vent and my gable vents, said that doing a complete thermal envelope is the way its done these days.
This is new to me, has anyone had any experience on this ?

[4x4 AG]

we have it in our new house. what they are telling you is what is done on ours. the attic essentially is sealed with the rest of the house. it stays really cool, even though not necessarily vented with ducts.

[IowaHunter]

Your house has to breathe. Sealing it is not a good thing and I would cover the ridge vents either.

[sjaaaz]

Back in my framing days, when a house was using spray insulation, we would put no Cornish vents or ridge vents.

[fox1]

Your house has to breathe. Sealing it is not a good thing and I would cover the ridge vents either.

Thats my thoughts as well but the guy that was out this morning said that is taken care of with the HVAC fresh air intakes. I paid extra to have those ridge vents installed. LOL

[BrianL]

In the early days they encapsulated the entire house, but really no need to heat and cool the attic. My buddy in HVAC said if he builds again, he will spray ceiling not roof.

[yanta61]

All the builders I've talked to say no vents when using spray foaming.

[Cookiemonster1]

Buddy of mine is a builder and he is in a law suit over this. Something about houses not able to breath and moisture problems. I dont know all the facts but Im building one now and I'm doing the attick in foam but not the walls.

[Plan B]

When we built we knew we were doing spray foam, so I didn't have my framing contractor install ridge vents or soffit vents.

[4x4 AG]

Thats my thoughts as well but the guy that was out this morning said that is taken care of with the HVAC fresh air intakes. I paid extra to have those ridge vents installed. LOL

It does breathe through the fresh air intakes installed. i am not the best at explaining in words, but the attic above the conditioned space below is semi-conditioned as well. there are fresh air vents to the outside that bring in fresh air and allow the house to breathe.

What they are telling you is the practice as i understood it when i built. and i researched with several builders. Just different practice than batt insulation.

[fox1]

Buddy of mine is a builder and he is in a law suit over this. Something about houses not able to breath and moisture problems. I dont know all the facts but Im building one now and I'm doing the attick in foam but not the walls.

Ive heard this before but everything i seen was in really high humidity areas, my new place is west of Tulsa Ok.

[Samson]

Buddy of mine is a builder and he is in a law suit over this. Something about houses not able to breath and moisture problems. I dont know all the facts but Im building one now and I'm doing the attick in foam but not the walls.

Water can leak into a home do to say a faulty window or because it is lacking a particular flashing, or even maybe a caulked joint failed. When you completely cover a wood structure with foam, when the water comes in it has no place to drain or evaporate. The wood will stay saturated and will rot from the inside out. This is why your buddy is probably getting sued. That deck failing in California last month that killed the Irish failed because the builder did not put in the required flashing. The stucco that enveloped the deck did not allow the water to escape and the beams rotted out. It's not the foam or stucco's fault, but rather the fault of the builder for not waterproofing correctly and not leaving a way for the water to drain out of the structure. Foam is a great insulator, but can be very problematic if the builders don't know what they are doing.

Here is a great writeup with pictures. All are stucco applications and not foam but the same rules apply. All of the homes in the pictures were less than 10 years old.
http://mgault.com/leaky-rotten-stucco.htm

[tremman78]

that's what they are doing to my new house, I also paid for soffit and ridge vents,lol

[super_dave]

Foam Insulation Questions

Your house has to breathe. Sealing it is not a good thing and I would cover the ridge vents either.

If it's done the old way, this is correct. However, when you seal the roof and soffit vents, your attic becomes a part of your interior and it will breath just like any other part. The soffit vents are just to move warm air up and out of the attic

I will say this, there's no way I would have it done unless I was absolutely positive there were NO leaks of any size anywhere on my roof

[Kcwwcb]

As someone stated above, the common practice with spray foam is in the bottom of the roof deck and to NOT vent the attic spaces. I am still not convinced this is a good idea in the southern high humidity states, up north is a different story. The most important thing about spray foam being used is you MUST work closely with the Mechanical Engineer that designed the HVAC system. R values are different, therefore tonnage can be greatly affected. Fresh air vents are typically incorporated as well. The moisture problems come from the system not running long enough to remove the humidity. The temperature drops too fast since the unit is oversized and does not have the run time to remove adequate moisture from the air. It is basically the reverse up north, due to the extended run times of furnaces, it is typical to have a humidifier on the system to add moisture. Being a little further north in Tulsa, I would not think that you would have the humidity problems. Just make sure the builder involves the mechanical engineer. I would ask for a letter from the Mechanical Engineer that states the house HVAC system was designed with the knowledge that spray foam construction methods were going to be utilized. just my $0.02