South Florida spray foam insulation

[36tbird]

Hi all, I'm researching the idea of spray foam insulation for a house in south Florida that I just bought. I looked into the attic to see 2' on center trusses with plywood decking so I think that the foam would stick well to that. The living room has a cathedral ceiling but there looks to be about a 15" crawl space through there. So, what I am learning from you guys is that I need to get closed cell so that I do not need to worry about a vapor barrier and that 2" is about the norm. Is that correct? I'm not worried about insulating for cold but trying to make the house as efficient and economical to fight the summer heat. I like the way they mount the A/C units in the ceiling for that purpose. Anybody in the south done the foam like I'm thinking and seen good results? Any contractors in the Fort Myers/Naples area that anyone can recommend? Thanks in advance.

 

[36tbird]

Really, no one?

Well, in case there are lurkers on here trying to learn as I am, I discovered a bit on my own based on some postings here on other threads that I will pass along. Please, anyone knowledgeable that can correct my assumptions, please step in.

I saw where one new school of thought is that in humid/hot climates, you might spray in foam in the attic sealing everything. The thinking here is, if you have a vented attic, humidity from the air may come in through the vented attic and that is why you should have vapor barriers. But, if you spray foam everything and seal it up, then your attic will be protected from the humidity and, therefore, no vapor barrier is required. Furthermore, your sealed up attic with your air conditioner system installed there with its ducting will be more efficient as it is now part of your "conditioned air space".

Please correct me if my deductions about this are incorrect.

Now, here is a little bit of reasoning that I have reached on my own. Having just bought this house in S. Fla. I learned that when you get insurance on it you can get an inspection to see how your roof trusses are tied down to possibly save money. It is called a "Wind Mitigation Report". New regulations require that the inspector takes pictures of the attic and the straps in your attic, if you have them. Seems to me that if you go and have foam sprayed in your attic to make it an "unvented attic" because it would require shooting the eves, you might cover up the straps and not be able to take pictures of them. Don't know if it matters, but just something I thought of.

 

[CUSTOMMANCAVES.COM]

Not sure about the spray foam insulation, but last summer I was working in a home (SoFLA) that had the attic space heavily insulated and they blocked off all the soffit/ridge vents. The air handler was installed in this space. The return air(?) ducts condensed heavily and that leaked down through the ceilings. I think you need attic venting, no matter what, in a humid climate.

 

[kb2tha]

I am in NYS. My research found that a vapor barrier is needed even with closed cell, UNLESS you spray at least 3". Do not know if or how this would apply in your state's climate conditions. I ended up with open cell, 3" in walls covered by 1" R7 rigid urethane and poly barrier under 1/2" sheetrock.
Ken

 

[36tbird]

Thanks gents, that's the kind of valuable info I was looking for. Custommancaves, besides the sweating problem, was the efficiency and/or economy of the air conditioning during the summer enhanced? Might be a moot point because I am not sure if there is a way to overcome the condensation.

Here is south Texas where we have the same sort of humidity, my house has gable vents and I've never seen any problem with air conditioner condensation. The Florida house has ridge and soffit (sp?) vents. I have a solar powered gable vent and really like that. I am wondering about installing one of those on that Florida house in conjunction with the spray foam insulation. I might be trying to re-invent the wheel here, though.

 

[Underdog]

"The living room has a cathedral ceiling but there looks to be about a 15" crawl space through there."

There is no way to get in that crawl space to insulate it. Usually the drywall is nailed or screwed to the trusses. It will hold the weight of fiberglass insulation nothing more, other words nothing to crawl on. Leave it alone unless you want to rip the drywall down.

 

[36tbird]

Thanks,Underdog.

I thought I would learn from the spray foam insulators how that should be treated. It seems to be a pretty common style down there to have those type of ceilings in the common living/dining room area. The access hole I was looking through was from the now enclosed garage side. But, I was thinking that if there isn't one on the other side where a closet in a bedroom is located, it would be pretty easy to put one in. Need to check next time I go visit. Again, thanks to all for the info and ideas.