Radiant Barrier/ insullation Delima

[glatt]

Originally Posted by Pooka

Ok... I'm still torn. I've seen to this magical website of which you speak... and it is a bit more technical than I can handle at the moment.

I just saw your post over there and the responses. I'd consider giving the most weight to the posts made by Andy Engel. He's one of the editors at Fine Homebuilding magazine and is quite knowledgeable. That Piffin guy is also pretty experienced, but he's from Maine, so I don't think his greatest expertise is in Texas insulating needs.

[Flint]

glatt is stalkin' mah wife

[footfootfoot]

Originally Posted by Flint

glatt is stalkin' mah wife

We need a lolcat image for that caption

[JuancoRocks]

Cellulose insulation has it's own drawbacks, most of which are not well publicized.

Cellulose is made with chopped newspaper that is hammermill treated with boric acid and borax.

While it is cheaper than rock wool or fiberglass it has it's own design defects. Under extreme heat conditions as here in Arizona the boric acid and borax migrate down in time and then leave an attic full of exposed unprotected chopped paper. Makes a beautiful flashover when exposed to fire. There is also the fact that the boric acid and borax mixture is corrosive and should not come in contact with metal ducts, pipes or light fixtures.

Yeah, I know, in many cases it has a UL listing. Well, many things that are listed work well in other climates and other parts of the country but Arizona seems to be the ultimate test facility and by default many of those things fail here. We did an accelerated life test and ended up with exposed newspaper. Not what I want in my attic.

[tw]

Originally Posted by Pooka

Ok... I'm still torn. I've seen to this magical website of which you speak... and it is a bit more technical than I can handle at the moment. Figured... as there seem to be at least several of us hot Texans here I'd continue my thoughts on the topic.

Fiberglass remains the industry benchmark for insulation. Other types are used when installation makes fiberglass difficult.

Your first problem is the hottest or coldest part of the building exposed to outside (attic) air. That is where the insulation must be thickest. Four inches of any insulation is 1950 standard when energy was cheap. Six inches minimum. Around heating (cooling) ducts, insualtion must be thicker than in other locations. Three or four inches of insulation in ceiling regions is unacceptable anywhere in America - except where the rooms are unheated or uncooled.

Since insulation around ducts must be high (not flat) and not compressed, then fiberglass around those ducts is a simplest solution. Insulating around those ducts would be the first task regardless of what type insulation gets used in flat sections.

Thermal barriers (ie paper backing or metal foil) are the vapor barrier. A vapor barrier must exist where insulation meets inside air or touches sheet rock. In your case, insulation already exists. Putting insulation with a vapor barrier over top of existing insulation does nothing good for you; may create a problem. Obviously blown insulation does not have that vapor barrier. Fiberglass bats without a vapor barrier is purchased where fiberglass gets installed over existing insulation.

Air ducts are all but exposed. Insulation with a vapor barrier is installed here; would be useful and make the task easier to attach that insulation to a frame around those ducts. That paper backed or foil backed insulation gets stapled to a frame around air ducts (and anything else that requires separation from insulation such as embedded light fixtures).

Do you have large light fixtures embedded in the ceiling and exposed in the attic? These should also have insulation over them - not insulation blown into them. IOW before installing blown type insulation, some formed insulation (ie fiberglass) should be installed over these fixtures so that blown insulation is not blown into these light fixtures. Electrical light fixtures must breath. Many blown insulation installers don't do this; don't keep their insulation out of those embedded light fixtures.

If any electrical junction boxes are not properly covered, those covers MUST be installed before installing insulation. Insulation (especially blown type) inside any electrical junction box can only create a future hazard.

Your insulation will be higher than existing ceiling beams - typically 2x6s. Therefore insulation will pile up to the roof where ceiling beams meet rafters. This is a major vapor problem. A problem typically alleviated by installing styrofoam air channels. These channels hold the insulation maybe one inch away from the roof so the roof does not rot.

Insulation above those ceiling beams means attic spaces no longer are storage areas. To use the attic for storage, wood is placed above the ceiling beams. Then insulation installed. Now a floor (ie plywood) can be nailed above that insulation so that attic storage is possible.

Insulation works by expanding. Any insulation that is compressed becomes closer to no insulation. One problem with some blown insulation is that it compresses with age. Another advantage of fiberglass. It does not compress with age. As insulation compresses, its R rating decreases. Higher R means better insulation. Compressing insulation (with age or with storing items on top that insulation) reduces its R rating.

Attics must breath. Air from the soffit must flow up into the attic via those air channels, then out via roof vents or attic fan. Note the previous reference to an attic fan or another's reference to roof vents. You must have that ventilation so that air flows up through the inside of roof wood.

Cellulose or other blown materials can only be used where insulation lies flat. Where insulation is on an angled or curved surface, then fiberglass is typically used. Therefore the fiberglass is installed over those curved surfaces before blown insulation is layer into flat surfaces.

Any hole in the insulation means insulation around that hole is compromised. Properly installed insulation also takes scraps to fill any gaps. These gaps are why blown insulation is easier to install. No one must carefully fill holes between insulation bats or cut the fiberglass so that it encases (goes around) wires and other existing items. If the wire crosses from beam to beam, then fiberglass bats must be cut or separated so that insulation lies uncompressed on both sides of that wire. Inferior installers will just lay insulation over that wire and press the insulation down.

Insulation laid over any wires must also not press that wire to the sheet rock wall. Wires must always remain two inches away from every sheet rock wall so that nails hammered in any wall years later do not penetrate that wire. This workmanship is why many avoid fiberglass bats; use blown insulation.

Any type of insulation must be installed wearing a mask. All insulations fill the air with unhealthy materials when being installed. Mineral type insulations continue to fill air with hazardous (asbestos equivalent) materials after installed. Stable materials such as fiber glass, fiber boards, and some blown type insulations tend to be safe after installed. However outgassing from some blown type materials remains a problem denied by those manufacturers - ie formaldehyde. Outgassing is especially problematic where insulation is installed in confined spaces (ie walls). That outgassing goes into a house; not outside through the vapor barriers. Another reason why fiberglass is so highly recommended - no outgassing.

Just a few pointers to consider. Other responsible sources should have discussed these and other facts.