Replies

1. 
   David_Thomas | Jan 03, 2001 08:35am | #1

   *
   "Northern Comfort - Advanced Cold Climate Home Buildling Technigues" by The Alaska Home Program, Inc. has a chart on page 66 giving the R-value per inch of 11 types of insulation. As do many other books. To that, you'd have to add your local prices. Or just wander the aisles of Home Depot with a calculator noting the R-values and prices of what is available. Then call a few cellulose and urethane spraying companies for quotes.

   Generally, most people use fiberglass batts because the materials and installation cost is the lowest for an acceptable R-value. And if your building code has energy-efficiency requirements, there are likely exactly what can be achieved with FG batts (R-11 in an 3.5" wall or R-19 in a 5.5" wall).

   Do you have some concern, goal, requirement, or condition that is not the norm? Very expensive fuel? Very cheap fuel? You love to chop wood? Going all-electric for some stupid reason? Extreme climate (like me)? A desire to have a very tight house? A Y2K wacko who wants to heat the house of the grid? I opted to spray 2 inches of urethane foam onto the sheathing (high R-value/inch but also higher $/R-value) to achieve very, very low air leakage (tested at 0.07 air changes per hour). And then used FG batts in the rest of the bay for the lower $/R-value. -David

1. 
   Frank_H._Biscardi | Jan 03, 2001 06:44pm | #2

   *David,Thanks for your note. The motivation is that I live in central Virginia and my current house gets pretty cold upstairs despite the standard fiberglass insulation. I don't mind spending a little more for better insulation. I am also a little worried about what the cost of heat will be in 20 years.I am planning a Brick veneer house @ 3,000 sq feet with a Tempcast (masonary heater)stove. I am in the middle of the country and we have lost our electricity for up to three days in the past.Wood is plentiful and I get it from my wood lot. I am leaning toward urethane foam vs wet blown cellulose, but I need to learn a little more.How do you like your urethane? What is the R /inch.ThanksFrank

1. 
   David_Thomas | Jan 03, 2001 09:03pm | #3

   *The R-value of urethane is R-7 per inch - twice that of FG batts. But I see the big advantage as being how well it seals up all those nail holes, gaps between sheets of plywood, and plumbing and electrical penetrations. Half your fuel bill now may well be from air leakage though the house. The other half being from conductive losses through the walls and ceiling.I've been happy with it, although I banged heads a bit with the installer. Kind of like a tar and gravel roofer - our conversations went better after he'd had his daily dose of fumes. But in the morning when he relatively chemical-free, he was an irritable cuss. You DO NOT want to be in the house while spraying is going on, IMHO.I was also concerned about heat during electric failures. (Extreme winters, high winds, and a lot of dead spruce trees around). Because I have a radiant concrete slab-on-grade, it takes 1-2 days for 50,000 pounds of concrete to cool down in a tight house and it only starts getting cool after 48-56 hours. Because I'm heating off DHW heater (no electricity), all I need to hot-wire my heating system is 100 watts to run a curculator pump and I can do that from an invertor from a car battery. But if you are planning on a wood stove, then you've got the power failures covered. Sounds like your current house may not have good circulation of the heated air if you've got significant cold spots. You might consider cutting a duct in between up and down stairs, possibly with a fan. Where is the warmest air in the house? Where is the coldest? Can you connect the two? Something to consider when laying out the duct work in the new place. -David

1. 
   Frank_H._Biscardi | Jan 04, 2001 08:36am | #4

   *David,Thanks for your post. I have a three floor Cape Cod.Lots of air circulation around the top floor and only standard insulation. I really need a two zone arrangment for the heat as the wood stove usually gets the downstairs so hot it shuts off the thermostat. Overall not a good arrangment and that is why I want the new house thought out a little better. Thanks for the advice. I will buy the books you listed.Regards, Frank

1. 
   Brenda_Deese | Jan 25, 2001 02:58am | #5

   *We'll be building in NW Florida and researching insulation information. We understand that cellulose and fiberglass costs about the same thing (info obtained from two sources). Question: does the cellulose attract insects/bugs? Thanks!

2. 
   Andy_Engel_ | Jan 25, 2001 03:59pm | #6

   *Cellulose is loaded with borate salts that make it fire and bug resistant. Standard cellulose installation techniques generally yield the stated R-value. Standard FG installation techniques are more problematic. For example, for insulation to insulate best, it must fully contact the back of the drywall with little room for convective currents to develop. Because cellulose is blown in, it does this. FG batts are typically installed with their paper faces nailed to the sides of the studs, which creates little convective chimneys, even though it makes it easier for the drywallers to find the studs. FG must be closely fitted around pipes and electrical boxes, a rare display of workmanship. Cellulose flows around these obstructions nicely.A common problem on houses such as capes that have knee walls between the conditioned space and the attic is that these kneewalls are frequently open to the attic. Unconditioned air can flow right through the typical FG insulation. The backs of knee walls must be air sealed with cheap plywood or caulked-in houswrap for insulation to do any good at all here. Cellulose forces this detail on you. FG gives the installer the chance to say, "I ain't never seen that done. Somebody who don't know much about how we run insulation is filling you with dumb ideas." Also, some sources say that cellulose blocks radiant heat gain in the summer, while FG doesn't. They also say that at temperatures around 0 and below, FG loses much of its effective R-value. They also tout cellulose's ability to block small air leaks in the walls or ceilings. I could be wrong, not having a research lab to verify these claims, but I paid extra to insulate my house with cellulose. I'm warm in the winter, and have no air conditioning for the summer.Andy

3. 
   Gene_Leger_ | Jan 25, 2001 06:27pm | #7

   *Andt, a few comments. Stapling the Kraft paper facing to the insides of the studs is a code violation and a fire hazard.The reduction of blown-in FG R-value as temperature drops was measured and verified by Oak Ridge National Laboratory (ORNL)Cellulose is more effective in blocking radiant heat than is fiberglass. This phenomenon has been verified by ORNL--David Yarbough. If you need more information please advise. GeneL.

4. 
   Andy_Engel_ | Jan 26, 2001 04:02pm | #8

   *Gene, thanks, that was just the sort of verification I hoped for.Andy

5. 
   Frank_H._Biscardi | Jan 27, 2001 10:09pm | #9

   *Andy,Sounds like I should nail 1/4 plywood on the roof side of the knee wall. I had thought of that but was afraid I'd cause a moisture trap.Would just stapling up heavy plastic work?Frank

6. 
   Andy_Engel_ | Jan 28, 2001 06:37am | #10

   *Frank, I think you'd be much less likely to create a moisture trap with plywood or some other sheathing that's somewhat permeable than with plastic. Remember, if you use a vapor barrier, it goes on the warm side of the insulation. In the south, that means outside, though. Andy

7. 
   Frank_H._Biscardi | Jan 28, 2001 08:07am | #11

   *Thanks to all who answered my post.RegardsFrank

8. 
   Bill_Conner | Jan 28, 2001 05:44pm | #12

   *Andy, I respectively disagree about the warm side. I believe a vapor barrier should be on the moist side. I agree that in the attic situation discussed here and assuming a heating climate, the warm side is almost certainly the moist side.

9. 
   Andy_Engel_ | Jan 29, 2001 05:31pm | #13

   *That's interesting Bill. I'd never thought of it that way. I know the moisture drive is from warm to cold and from moist to dry. I'd always focused on the warm to cold aspect, because, I guess, pinpointing the warm and cold takes less subtlety than pinpointing the moisture can. Andy

2. 
   Frank_H._Biscardi | Jan 29, 2001 05:31pm | #14

   *
   Folks,

   I am planning a house. I would like to learn more about the different insulating options- especially cost/inch/R-value.Can anyone please point me to a good book on this?

   Thanks

   Frank