I fail to see how spraying the underside of the roof deck to the same R Value as the alternative of insulating above the ceiling is "the way to go." (Unless, of course, you have HVAC equipment in the attic.) R30 in the attic and R13 in the walls is the minimum requirement in Florida. If you're considering spending $6,200 more for foam, spend a fraction of that and insulate to R60 in the attic, asrecommended by building scientist Dr. John Straube. In case moisture moving into the attic in severe weather is a concern, I'd use blown cellulose, which is more tolerant of moisture than fg.

Since you're in the planning stage, consider the energy savings advantages of white roofing tiles.

This post was edited by worthy on Tue, Apr 16, 13 at 19:31

Thanks Worthy. Read some of Dr. Straube's articles and he def. know his stuff. HVAC equipment will not be in the attic. Attic will now be insulated to R60 as Straube reccomends. What would you reccomend in regards to the wall insulation? If I upgrade to cellulose I don't think I gain that much over fiberglass batts. Would it be worth it to foam the walls?

no to foaming the walls.
a much better and affordable option is to
use 1" foam sheathing board on exterior
of walls, conventional insulation in walls,
and air tight drywall approach for sheetrock.

so where are ducts located?
unvented attics also make houses more
hurricane resistant.

best of luck.

While I agree most attics should have R60 in the US, its tough to justify in actual practice in climate zones below 5 or so. John Straube is in a cold climate but many other building scientists recommend those levels for most of the country.

As for foam in the walls, I heartily agree with energy rater as to the importance of exterior insulative sheathing, but think you should price both cellulose and OC foam for the cavities. In our area they are very close in costs. I say no to batts almost always due to their difficulty to properly install.

The new ZIP R product is tough to beat for its labor and air sealing properties. Reducing thermal bridging is usually more important than R value.

If you are concerned about R value and insulation, you should be more concerned with the airtightness as measured by the blower door test.

Airtight is much more important than R value!

Blower door test numbers reveal much more than the "R values" of building components.

Energy Rater - Would you recommend replacing the osb or plywood woth the foam sheathing and having some support braces throughout or using in addition to the osb or plywood? Articles I've read said it can be done both ways as long as you provide adequate bracing.

Brian - Thanks for your input as well. The Zip R product looks interesting I'm just not sure how the pricing will compare to foam sheathing or osb. Zips website says their system is easier to insall than house wrap so it saves on labor cost. I will also try and find someone local who could do a blower test once we get to that point. Do you know what someone would usually charge for that?

I'm in a hurricane climate, so we have done
it both ways, foam board over solid sheeting
and solid sheeting to interior, with foam
sheathing to exterior.

I prefer the latter myself, not as much confusion
about window & door framing. and structrual strentgh
is same. Home owners like the fact that it isn't hard
to hang stuff on solid sheeted walls on interior.

we also use Simpson Strong Tie products to add
strength to walls & minimize uplift of roof rafters.
not difficult to install, you should take a look at
their products.

I read good stuff about zip sheathing, but have
never seen it locally.

best of luck.

Thanks again Rater. The framer will use Simpson Strong Ties (HDU2 - SDS2.5). So if we use OSB to interior then foam sheething to exterior (installed correctly) and cellulose or foam to insulate the walls I think I'll be pretty happy with the results. Still going to check out the zip system and see what I get from a price and experience stand point from the installer. Even if it's a great product I don't want my house to be the first time the sub has used it.