Thickest Insulation for 3.5"

[CThomp]

I've got to figure out the best insulation to get into my eating nook ceiling.

I've only got 3.5". I'd like to get something more than r-13 into it. Do I have any options? the ceiling area is 5'x10ft.

Spray foam would be my best option but I don't want to call a spray foam place for 50sqft. That doesn't seem to make much sense.

Maybe a reflective barrier and then some r-13? Can the insulation be pressed directly to the reflective barrier?

[David]

Probably expensive, but R-15 batts:
http://www.jm.com/insulation/product_availability/Residential_Commercial_Construction_Prod_Availabil ity_List.xls

Reflective barrier needs needs air space for radiation.

Rigid (insulative) foam can be used quite effectively. Cut it in strips with a table/contractor saw, stick it in, fill any gaps with expanding foam rated for insulation.

There are spray foam DIY kits that do ~ 200sf. Not sure R-value of them.

[CThomp]

I was thinking the rigid foam as well. Lowes has 1/2" sheets that are r-3. I could get r-21 out of glueing 7 layers together and then glueing it to the underside of the roof. That may be the way to go. Then filling in the gaps with great stuff.

Yeah the radiant barrier I could do in other parts of my attic once my new roof is on. It'll have a ridge vent and probably an attic fan.

Those DIY kits are a bit expensive for such a small project.

[David]

I was thinking the rigid foam as well. Lowes has 1/2" sheets that are r-3. I could get r-21 out of glueing 7 layers together and then glueing it to the underside of the roof. That may be the way to go. Then filling in the gaps with great stuff.
Get a quote from a supply place for rigid foam. Lowe's will price match.

Yeah the radiant barrier I could do in other parts of my attic once my new roof is on. It'll have a ridge vent and probably an attic fan.
Not sure I follow. The radiant barrier needs to be roof decking. And why have a ridge vent and an a fan?

[CThomp]

Ridge vent and a fan just to keep the air moving. It's an old house.

Reflectix radiant barriers show them mounted between rafters with empty attic space below and the roof decks above.

http://www.reflectixinc.com/script/products/product.asp?ID=79

[rabadger]

What county you in?

[CThomp]

Lee County

[rabadger]

Lee county - zone 1 in 2003 IRC.

Ceilings R-13
Walls R-11
Floors R-11
Basement walls R-0
Slab perm. R-0
Crawl space walls R-0

If my memory serves me correctly 1" of styrofoam from the big box stores is equal to R-4. 4X3.5=R-14. You can get R-15 batt for 2X4 framing.
Or you could use the r-14 foam then lay down the R-15 batt over the rafters.

Lay the foam now and after you get the HVAC figurered out line sets, and any ducts installed, lay the R-15 batt over it. That way you will not be crawling around the fiberglass trying to install items.

Check with the local guys. They may require more than what is in the 2003 IRC

[David]

Ridge vent and a fan just to keep the air moving. It's an old house.

Reflectix radiant barriers show them mounted between rafters with empty attic space below and the roof decks above.

http://www.reflectixinc.com/script/products/product.asp?ID=79


You have a new roof. Why not use TechShield?
linky too slow right now.

[CThomp]

The little space in question isn't going to be exactly accessible.

It's kind of a cathedral ceiling type of thing. Basically I'll have the eating nook, then drywall up against the rafters, insulation, and then roof deck. So only 3.5" to put anything.

No duct work involved. The space will be conditioned as part of the kitchen.

Lowes carries DOW 1/2" stuff that is r-3. If I do rigid foam i'll probably use that.

[CThomp]

I'll have a new roof deck when I get to the addition. Right now I have an old roof that will have new shingles and underlayment.

So techshield may be an option then. But right now everything is retro-fit.

[CThomp]

How much is a sheet of techshield anyhow?

[David]

not sure. Lowe's carries a generic of it.

[CThomp]

I'll be in Lowes probably this weekend. I'll check then.

[David]

IIRC, it wasn't 3/4 though, but they could probably order it.

[CThomp]

I won't be using 3/4" for the new roof deck when I get to the addition. I'll be using regular 1/2" stuff.

I've only been using 3/4" lately because I have to so the new wood will match up to the 3/4" t&g planks on the old roof.

[David]

The IBHS suggests 3/4 rated to 40/20. Just in case you were curious. :)

[CThomp]

Whats that mean... 3/4 rated to 40/20?

[CThomp]

Nevermind...figured it out. They say 19/32" rated to 40/20. 19/32 is 5/8" or just shy of it.

23/32" is 3/4" or just shy of it.

What does 40/20 mean though? I'm sure it's probably a standard.

So far I think everything i'm doing is at code. At least i'm trying to be.

[David]

My bad. You're right, 19/32". The 40/20 means max span between rafters/floor joists, respectively.

[CThomp]

Ah. Building is hard. LOL.

[spence]

There are spray foam DIY kits that do ~ 200sf. Not sure R-value of them.Do you have a link or name of a supplier for such a product?

[David]

Only via google.

http://www.google.com/search?sourceid=navclient&aq=t&ie=UTF-8&rls=GGIE,GGIE:2006-39,GGIE:en&q=diy+spray+foam+insulation

I can't vouche for any particular product because I've never used them. I only know that it can be done. I wouldn't hesitate to DIY it over a small area though. It's got to be as good as f/g and people still use f/g.

You must be careful though.
- Wear old clothing (long sleeves, pants, head covering, gloves, ..) that can mostly be thrown away (would your wife really want that in her washer, and would it be worth the ensuing arguement with her :) )
- Wear safety goggles and have a helper with an eye rinsing kit nearby in case you really mess up