Answers to Insulation Questions #2 Answers to Insulation Questions #2

Q. I have a 30-year-old brick ranch house in Atlanta, about 2,000 sq. ft. with a full basement. I want to add an attic fan and more insulation. So, how much is enough to add? Do I add R-13, R-19 or R-25? I've been told the amount to add but I do not want overkill. Here is what it cost to add the additional insulation: R-13 - $253.00; R-19 - $366.50; R-25 - $586.00. At what amount am I wasting dollars on insulation?

A. The cost of the insulation itself is not a determining factor when it comes to the cost effectiveness of insulation. The installation costs will determine it. Since you intend to do-it-yourself, the more insulation the better.

Q. My township needs FIRESTOP to be done for newly built walls in my finished basement. Has anyone dealt with this before? How expensive are they?

A. The most common type of mineral fiber used for insulation is known as "Rock Wool." If you search the web for manufacturers, you will find a few. Then ask them for a distributor nearest to your home. The price should be competitive to fiberglass or may be slightly more. You should also check with your local building supply store because if it is mandated, they will surely carry it.

Q. I have moved into a newly built home and have since noticed that the humidity never drops below 70 percent and has been as high as 82 percent. The AC keeps the temperature at 70 but doesn't seem to be able to drop the humidity. I suspect there is no vapor barrier in the attic. It has what I think is called Feather Lite insulation. It is a white fluffy substance. Is there a way to now put a vapor barrier over the blown in insulation?

A. If you just turned on the AC in a new home, it will take some time for it to dry out. Just let the AC run. Everything in the home is new, wet and green right now. You might want to let the fan run 24/7 for it to help. It's more in the wintertime you think about V/B. For sure, don't put batts with a V/B over what you have up there now.

Q. I am looking for information on the rebates and incentives available in Dallas, TX. I know they are out there, but information on the actual process is scarce, I get bits and pieces. What I need is insulation blown in my attic. It has original insulation from 1967 and is in desperate need of a better barrier.

A. You might start with bids from contractors to blow fiberglass or cellulose and start from there with negotiations with them. If you mean to blow the insulation yourself, negotiate with the suppliers in town. Generally, you can get suppliers' names and contact information from the manufacturers of the products.

Q. I need to put insulation in a cathedral ceiling in my attic. I have been told that I need to have ventilation space between the roof and the insulation. How do I do this? The spaces between the rafters is 18.5 inches, and I have found that insulation comes in 23 or 15 inch widths. What do I do?

A. As far as the insulation size is concerned, most retail store will not carry odd sizes. It does not mean that manufacturers do not make it. I recommend you go to or search for insulation manufacturers and request the size you require. Then ask them for the nearest distributor in your area so you can pick it up.

Q. I'm finishing my basement. I plan to build 2x4 walls with R-12 fiberglass. I will place my 2x4 walls 2" out from the cement walls to create a 2" dead air space. I know I need to vapor barrier the side facing the interior of my home between the drywall and the studs, but I'm thinking I should vapor barrier both sides. I'm concerned that the fiberglass could fall back or slouch and then sit up against the cement walls. This would create a breeding ground for mold. Other than a little extra cost, is there any reason I shouldn't vapor barrier both sides?

A. Doing a vapor barrier directly on both sides of insulation is more likely to breed mold from condensation than the scenario you mentioned. If you plan to allow the airspace, I would attach the other V.B. directly to the basement wall. It's possible to develop condensation between the V.B. and the wall too. If condensation were a problem in your basement, I would be inclined to do the air gap thing, use the V.B. at inside only and use one or more dehumidifiers in the basement.

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