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Homeowner Forum / Construction / March 2005What is the best insulation?
What is the best insulation to use in a new home? Fiberglass bats, blown celulose, sprayed foam? Has anyone used isynene or Sealection? Foam will seal the best for walls on air infiltration an remain more constant in R value as fiberglass can loos R value at extreme lows. Icynene is only R 3.5 ? as is fiberglass per ". Polyurethane foams can be R 7 per inch but need a recomended gas out time, I will guess several weeks. For walls foam is best. Celulose is paper, it settles, decomposes, is a dust issue and I believe looses it fire effectiveness eventualy. Fiberglass is good for attics. You dont say where you live but remember codes are minimums , not what would be optimal. Optimal ratings can be found even Owens Corning, Dow, Johns Mansville, have better optimal Zone insulation guides. There is a relativley new way of spraying Cellolose in the wall with a glue binder that is OK. Depending on where you live -Zone, 2x6 walls and R 7 foam can give a good payback. Im zone 5, to -20 and have R 100 attic and R 30 walls on a 110 year old rehab, For 1800 sq my total Ng was 340 $ last year with gas cooking, dryer and water heater. There are alot of ways to save if you are building and are open to ideas. Would a hot desert AZ location somehow influence the choices ? The builder is suggesting cheaper Certainteed or more expensive Icynene. I noted that Icynene will get only R20 in 2x6 walls. What is more important in arid climate, air tightness or isolation capacity ? Thanks Dave Icynene is apx R 3.5 polyurethane foams are apx.R 6-7, but need to outgass times. Both R value and infiltration are important. I hope you are also looking into an air exchanger. Where heating or cooling loads are high get the highest R value you can afford. Even upping attic past code minimuns usualy gives fast payback. > Icynene is apx R 3.5 polyurethane foams are apx.R 6-7, but need to > outgass times. Local BASF rep cites a Canadian study which found that sprayed polyurethane foam had no outgassing after 48h. An US study is planned for later this year, too late for me. >Both R value and infiltration are important. I hope you > are also looking into an air exchanger. Definitely, if anything to let the outgassing out ;-) Also, with a possibly 700-1400 CFM range hood ventilator I am concerned about how to mobilize the fresh air when cooking on full throttle. Maybe the ventilator should be connected to the air exchanger to avoid downdrafts via fireplace chimneys ?? >Where heating or cooling loads > are high get the highest R value you can afford. Even upping attic past > code minimuns usualy gives fast payback. The building is a central cathedral ceiling and flat roof at sides. LOT of glass (North-South with overhang). Still, realizing that the high R foam insulation would be the most expensive, is it worth with all the heat gain via windows ? I heard about people who in order to save cost had a R 12 2 inch foam layer supplemented with fiberglass. I like the flexibility of having space for later wiring retrofits (in contrary to icynene where one needs to fill full 6 inches). What I am afraid is the cost of having two crews to come. Need to do some cost analysis whether it is not better to spray 3.5 inch (R21) and just to swallow the material cost. I was looking on the site of the local distributor http://www.dasproducts.com/ and was confused by so many brands/options. The contractor suggested by the builder apparently works with just one system http://www.youngbuilders.com/what.htm Opinions ? Dave You need an air gap at the roof deck but im sure the contractor knows that. What Zone is house-area and temp swings. Heat rises so yes insulating to over code by 100% is smart. Ok now I see you are Arizona? Im midwest where it goes to -20f so your needs are different then my area. But for real efficiency it is in the design and insulation and windows. There are im sure local sites that will give optimum designs for your area. Also consider R5 cellular shades but be sure they dont voild window warranty. I would personaly go with the highest R per inch since you can never add more later, that means poly foam. Your roofing material choise can help also. Have you picked windows by SHG solar heat gain? Look at Hurd. Designing for the desert is not what I have alot of info on. There are many ways to pick your own upgrades that will save you every day in utility costs. ...But for real efficiency it is in the > design and insulation and windows. There are im sure local sites that > will give optimum designs for your area. Also consider R5 cellular > shades but be sure they dont voild window warranty. Yes, I thought about even the triple ones esp. on the big west oriented window (together with Scotch tinting) Have you > picked windows by SHG solar heat gain? Look at Hurd. Not yet. When I was in some model homes, even now on a sunny March noon, you can't hold your fingers to an aluminium frame how hot it is. This made my mind for aluminium clad wood windows (enter Marvin) but I will check other companies as you are suggesting Dave An off topic idea look into Rinnai gas tankless water heaters. Look at the Building Science Corporation web site for climate specific, researched information. Often, the kind of insulation is less important than the way it is used. TB > What is the best insulation to use in a new home? Fiberglass bats, > blown celulose, sprayed foam? From an insulation standpoint, I would think the cellulose or sprayed foam would be best. They can fill in all the little spots around pipes, behind wires, etc. and can drastically reduce air leakage. However, when we built our house, I chose fiberglass bats. Widely available, inexpensive, and easy for a DIY to install. Another issue for me was future repairs and modifications. If I ever have to open a wall/ceiling/floor to repair or modify wiring or plumbing. I can pull the batts out, make my changes, and reinstall the fiberglass batts. This would be very difficult to do with foam or cellulose. I've already had to do this twice in our crawlspace since we moved in about 5 months ago. The first was to install cable TV wiring (didn't think we would EVER get cable out here when we built the house), and the second was to replace some plumbing hangers that were making noises. In both cases, it was a simple matter to take the insulation out and reinstall it. Air leakage is often a bigger problem than insulation efficiency, so I caulked around the sole plate of the walls, around windows and doors, etc. I also used that expanding foam insulation anywhere pipes or wiring passed through the floors/ceilings. Take care, Anthony |
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