Re: What's in your attic?
Start at the Owens Corning website. There is an insulation calculator there based on DOE recommendations for your zip code. You do not want Owens Corning product, tho. Just go there to use the calculator to determine the R-value you will be installing. As was already mentioned the blown paper has a better insulating quality, its cheaper, quicker and easier to install, and has the added benefit of a bromide additive as a fire retardant (required by law) that is also fantastic at resisting pests. They dont like it, rats/mice love fiberglass insulation.<br /><br />As was mentioned, you need to build some dams to prevent the blown insulation from interfering with the air vents. Do the same around any recessed lights you have poking up into the attic, min of 3-in away from the fixtures. If your recessed fixture are rated IC (insulation contact) you dont have to build the dams around them, but I would. Also build a dam around your doorbell transformer if its in the attic.<br /><br />There is no significant diff between brands of blown paper insulation. Pass on all of the gimmicky additives, aluminum chips, etc. They just cost more than what is returned with your energy bill savings. I think the bags at Lowes are 40sq ft at R19. Good news, the only diff between R19 and R30 or R38 is how thick you pile the stuff up when you blow it in. The R-value for the thickness is not linear, i.e. R38 is not twice as thick/much as R19. New home construction is R30 in the attic, the min of what I would blow in. The DOE recommends R38 in the SF Bay Area, thats 11.8-inches of blown.<br /><br />Disadvantages of blown insulation will be realize if you ever have to remove it. Not a practical DIY project, but doable, and really expensive to have someone do it for you. It would cost almost twice as much to remove as it does to pay someone to install it. Also, debris is the killer for blown insulations. If you will be re-roofing consider covering the blown ins with plastic, then remove the plastic and all of the roofing shrapnel on it.<br /><br />If you have hot summers and/or you use air conditioning frequently, I would consider also installing a radiant barrier under the roof before blowing the ins. Its basically aluminum foil adhered to something (like paper or mylar) to prevent it from tearing, it reflect incoming heat back out toward the roof surface. Its cheap and extremely effective, enough so that if a houses ceiling framing was designed for it, radiant barrier could be used instead of rolled or blown insulation to radiate as much as 90% of the heat loss back into the home. Let us know if you need info on that stuff.<br /><br />Also, check with your utility company for rebates. PG&E (in Calif) rebates $0.15 per sq foot for ceiling insulation installs. Starting Jan 2006 the fed gvt will allow you to deduct a certain percentage of the cost of the insulation directly from the bottom line of your fed income tax, i.e. you dont take it as a deduction from your income but rather as a straight rebate off the taxes.<br /><br />Let us know what you decide to do and maybe we can give you some how-to tips on installing it.
