My brother-in-law and I installed new kitchen cabinets last spring. Everything turned out great, except for one oversight. A few wall cabinets have dead space in between them, and they are open at the bottom. It’s allowing outside air to come through the bottom of the cabinets. What kind of insulation might you recommend to fill these cavities? Would fiberglass be safe to use?
I assume you do not have solid drywall at the top of the cabinets to the attic and this is allowing air movement. You can seal the gap with anything that’s solid – drywall, wood, metal, or plastic. Fiberglass or insulation will not stop air movement.
You should also have a complete air seal from the heated space to the attic. In fact, you must have an air seal to prevent heat loss and moisture damage into the attic.