Replies

1. 
   DavidThomas | Nov 08, 2002 10:15am | #1

   I presume you refer to the build up of dust on the top surface of horizontal reflectix which eliminates the claimed advantage of outer silvered layer.

   My gripe about the stuff is two-fold. 1) it is expensive. I use R-11 or R-19 FG batting which is cheap and behaves fine in the long run in a horizontal application. It can't fall down like it often does when there is sheetrock below it. And 2) they are lying scumbags. In the large print on the package, they claim R-values like 14.3 No way! Only in the fine print do you discover that they are taking credit for all the airspaces, the sheetrock, plywood, and the silvered surfaces which will get ducty over time. That is like saying that a $200 steering will carry five people around in comfort. Sure, as soon as I attach it to a Toyota Camry! For Reflectix, R-3 or R-4 is more like it.

   The stuff is sometimes helpful in a retrofit (you can slip it down a joist bay through a smallish opening) or where space or removability is important (a motor vehicle to be serviced, perhaps?). But in new construction, save your money and get more R-value with the traditional alternatives.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska
1. 
   Paularado | Nov 08, 2002 08:37pm | #2

   David, thanks for replying to this message. We decided to use FG batts in our basement ceiling for our radiant heat system above. We are going with gypcrete. I'm glad to hear that others think this is a good idea. We did it because we are currently living in the basement and needed something to try to contain the heat down there. R13 isn't much, but since the house above is somewhat closed in, it will have to do. Someday soon we hope to move upstairs!

   We have been buying the 32 ft long rolls of R13 encapsulated batts (Home Depot, ugh). It works out to be 22 cents/square foot and the plastic encapsulated stuff is a little nicer to work with than kraft faced in this application. It looks like the reflectex costs 2x as much at about 45 cents/square foot. If you buy FG batts at Home Depot right now, be sure to ask at the service desk for the rebate offer. You get a $20 home depot gift card if you buy $100 worth of Johns Manville insulation.

   Our local lumberyard only has short-length batts, so that's why we were stuck with home depot. Amazingly, we can fit 20 rolls of the stuff in our 8 ft pickup bed, so it was 2 trips to the orange box for us.

   David, do you remember over a year ago when I posted "How would you heat this house and why" about our proposed log home in Colorado. I appreciated your comments back then and we moved forward with radiant heat. We now have the slab on in the basement and I sure do like it. Our first gas bill was only $10. I really don't know how this could be since it included 2 weeks of heating our basement without any insulation anywhere. Is is possible that radiant heat is THAT efficient?

2. 
   Mongo | Nov 08, 2002 09:31pm | #3

   Skip, you wrote it's a "retrofit" radiant system. Does that mean a staple-up?

   Underneath staple-ups, I like to use half-inch foil-face polyisocyanate insulation. It comes in 4' x 8' sheets. Rip the sheets slightly wider than the joist bay (measure the bay where the insulation will go, not at the bottom edge), then friction-fit them up against the subfloor, holding them about 1.5" or so off the underside of the subfloor. Normally the staples used in a staple-up will act as spacers to hold the polyiso a good distance off the bottom of the subfloor.

   The tight friction-fit will hold them in place. If you want added security you can run a couple of drywall screws into the sides of the joists right at the bottom edge of the polyiso.

   The polyiso is R 7.2 per inch, and with the tight friction fit you'll eliminate any convective flow. That will help the heat go where it's supposed to...up to the living space.

   Just another option...

1. 
   billyg83440 | Nov 08, 2002 10:00pm | #4

   foil-face polyisocyanate insulation.??

   Just curious, I've never heard of this type of foam insulation. R 7.2/in. is a lot. Best I've ever seen claimed was R 5/in. w/ other foams.

   Where do you get this? What color is it? It sounds like it would be a great option. I am going to put some staple up radiant in the basement ceiling to heat my upstairs, so I will also need to use some insulation to help it heat the upstairs.

   Also, what's the cost of this stuff, and is it available in thicker widths?

   Thanks for any help.

   Bill

1. 
   Mongo | Nov 09, 2002 12:52am | #5

   Billy,

   It's available at every lumber yard around here, as well as HD. Don't know if Lowe's has it, I've never been to one.

   It comes in 4' by 6' sheets. I use it in thicknesses from 1/2 to 2". It's a cream-colored insulation, it comes with different facings. I use foil-faced.

   Celotex makes TUFF-R, and Homasote makes ULTRA-R. Those are the two available to me in CT. Carefulk about mixing and matching brands, as when you get to the 2-inch thick product, the thickness differs by about an eighth of an inch from TUFF-R to ULTRA-R. That's only a factor in certain situations.

   A while ago I did get a flyer that one of the polyiso manufacturers was going to start using a different blowing agent. I think it mentioned that it would result in abouyt a 10% reduction in R-value, to about R 6.5 per inch.

   Cost? For foil-faced, the half-inch is about $8.50 a sheet, the 2" about $19.

   You can order the 2" thick stuff tapered, for use on exterior decks, etc. Runs from 2" to zero for a quarter-inch drop per foot. Cha-ching!

1. 
   BillHartmann | Nov 09, 2002 03:39am | #6

   Mongo

   Does it still come with the Celotex name?

   The Celotex company split up a year or 2 ago. Dow ended up with the insulation division. The fiberborad and the shingles ended up with other companies.

1. 
   Mongo | Nov 09, 2002 03:48am | #7

   I've got some 2" of each out back that I bought just a few weeks ago. Homasote has big black graphics on the foil, Celotex uses red. Both names prominently displayed.

   Edit:

   Wanted to add, last spring I had to call all over CT to find some 2". Asked for them by name. "Celotex Tuff-R" and "Homasote Ultra-R". No clue. Asked about "4x8 sheets of foil-faced polyisocyanate" insulation.

   "Oh, yeah, we've got stacks of that stuff..."

   Edited 11/8/2002 7:52:58 PM ET by Mongo