Insulation, moisture, and ventilation practice questions

Aluminum and other metals transfer heat readily, giving them a high U-value, so a break in the frame is used to slow that transfer. A material with a high R-value would already resist heat flow and would not need a break. A low U-value describes a material that transfers heat slowly.

Carbon monoxide is not among the pollutants the manual lists. VOC come from manufactured products in the building and its furnishings, and combustion products and tobacco smoke are listed apart from them. Carbon dioxide is the pollutant the manual ties to breathing.

Condensation inside wall cavities in these zones has been shown to be usually not a problem, so no retarder is required. The water and air barrier on the exterior is not a vapor retarder, and nothing in the manual prohibits a retarder in these zones; it is neither required nor recommended.

A powered attic fan depressurizes the attic. Where openings connect the crawl space and the attic, it can pull moist crawl space air and conditioned house air upward, and the vapor can condense in the walls or where the chase enters the attic. Pressurizing the attic is the opposite of what the fan does.

UFFI hidden in a wall cavity cannot be judged by looking at the house. Shrinkage and breakdown are the present concerns with the material, but neither can be seen through a finished wall. The formaldehyde off gassing has already subsided.

Loose fill is sold in bags and is usually blown into place by a machine, so it also goes by the names blown-in and blown insulation. Blanket is another name for batt insulation, which comes in rolls.

Insulation should be trimmed to fit around obstructions, for example plumbing pipes and electrical boxes and cables. Joists and truss bottom chords are the framing that insulation fits between, which is a different defect when the batts are the wrong width.

Radiant barriers do their best work in the Desert Southwest and the Deep South, climate zones 1 and 2, on houses with significant solar heat gain. They reach maximum effect in an attic that holds HVAC ducts and equipment. Each other choice lacks the climate, the solar heat gain, or the attic ducts that this effectiveness depends on.

A ridge cover is meant to sit over an opening cut in the sheathing at the ridge. A cover with no opening under it, a cover not set directly over its opening, and an opening that is too small are all typical defects to report. End caps keep water out of a ridge device but do nothing to create air flow.

Finishing and insulating should wait until it is reasonably certain that all liquid water entry has stopped. Grading, drainage, gutter, and irrigation faults cause most of it, so fixing them is the first step, and checking the exterior foundation drain is another. Foam on the walls does not stop the water.