Batt insulation contact with attic floor
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After air sealing the attic, random sections of batt insulation are no longer in contact with the attic floor. The plan is to add more blown-in fiberglass on top.
Does it matter if random parts of the batts don’t touch the attic floor? For example, where there are wires, the batts are now resting on top of the wire so it’s not touching the floor. Same is true for the batts at the edges of the exterior walls. Many batts weren’t pushed down completely after air sealing.
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Replies
For insulation to be effective, it needs to be in contact with as many sides of the framing/finish material as possible. In walls, this is all 6 sides, for vented attics, this is usually 5 sides. Gaps such as the ones you describe in your question are insulation deficiencies that I see often when conducting thermal imaging scans. These spots are hotter or colder than the rest of the ceiling, resulting in poorer performance than the rest of the ceiling. I recommend cutting the insulation around the wires and other attic obstacles so that the insulation is in contact with the ceiling finish material.
Randy
You are supposed to "split" the batt and fit it around wires. Wires should not be deforming the shape of the batt significantly if installed correctly. The usual way to do this is to split the batt, then fit the batt above and below the wire so that the wire ends up going through the batt in an approximately straight line along it's original path. In practice, this isn't all that difficult to do.
I wouldn't worry too much about small gaps here and there, with "small" being around 1/4" to 1/2" or so, especially if the gap is completely contained (i.e. not open to the air on one or more sides). Ideally you want to eliminate ALL such gaps, but in practice it's very difficult to get a perfect installation, so do the best you can. Batts should be fit into the cavities they're installed in as well as possible, pressed into place to get all the way in, then "fluffed" a bit to fill the cavity up to the top, or at least as far up as the batt's thickness allows.
Bill