Is refllective insulation a good choice for our home?
We have a 1st floor room with no insulation in the ceiling. Over it is a large unheated walk-in attic with insulation between the roof rafters. Where we have a second story, the ceilings are insulated with fiberglass, but nothing in the roof. A contractor has recommended a reflective radiant barrier both for the floor of the unheated walk-in attic and to be put over the fiberglass insulation on the second floor plus wrapping the ducts. This is new technology to me. Is this a sound recommendation?
In short - no, especially not in your climate zone which is primarily focused on keeping heat in, instead of cooling.
- In your area a well sealed (to stop air from below coming up into the attic spaces) and well insulated attic is what is needed.
- A sound recommendation - get a real energy auditor or contractor in there that understands Building Science and renovations - not a salesmen.
As for the unheated walk-in attic with insulation between the rafters that is generally considered a hot roof and the attic space is considered conditioned (truthfully it is semi-conditioned but the "correct" term is conditioned). You didn't mention what type of insulation material or thickness there is and that is something that needs to be looked at to prevent ice dams and boiling summers.
- Should your ducts be sealed and insulated to R8 or better - yes.
- Do not buy into the radiant bubbles wrap - that only has an effective R-Value of .5 (not 11 / 13 / 30).
As for the second story - while a radiant barrier can reflect heat back down in that configuration, it loses its effectiveness as it gets dusty and if you haven't airsealed really well you are looking at having some major moisture issues which could lead to mold.
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Check our best attic insulation Q&A to see what other homeowners and contractors are saying about foam insulation, duct sealing, radiant barriers, etc.