Insulation is not just for attics and outside walls. Many areas of a home that are often overlooked include ceilings with unheated spaces above (including dormer ceilings), knee walls of attic spaces finished as living areas, sloped walls and ceilings of attics finished as living areas, cathedral or vaulted ceilings, perimeters around slabs, floors above vented crawl spaces, floors over unheated or open spaces such as over garages or porches, basement walls, band and header joists, floors over unconditioned basements, soffits
below cantilevered second-floor rooms, knee walls of closets in “bonus” rooms, and even areas where acoustical dampening is required such as laundry rooms or bathrooms.
Gaps and voids are areas where insulation should be installed but is omitted, thereby causing conductive and convective heat loss. A gap is a place where the insulation does not come all the way to the edge of the space to be insulated. A void is a hole in the envelope of the building. Examples include plumbing chases, wiring penetrations, fireplace cavities, dropped ceilings, soffits, and venting.