For optimal energy efficiency, your home should be properly insulated from the roof down to its foundation. The illustration above shows all the areas of the home where there should be insulation. The numbered areas shown in the illustration are as follows:
1. In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below. If the air distribution is in the attic space, then consider insulating the rafters to move the distribution into the conditioned space.
(1A) Attic access door
2. In finished attic rooms with or without dormer, insulate (2A) between the studs of "knee" walls, (2B) between the studs and rafters of exterior walls and roof, (2C) and ceilings with cold spaces above.
(2D) Extend insulation into joist space to reduce air flows.
3. All exterior walls, including (3A) walls between living spaces and unheated garages, shed roofs, or storage areas; (3B) foundation walls above ground level; (3C) foundation walls in heated basements, full wall either interior or exterior.
4. Floors above cold spaces, such as vented crawl spaces and unheated garages. Also insulate (4A) any portion of the floor in a room that is cantilevered beyond the exterior wall below; (4B) slab floors built directly on the ground; (4C) as an alternative to floor insulation, foundation walls of unvented crawl spaces. (4D) Extend insulation into joist space to reduce air flows.
5. Band joists.
6. Replacement or storm windows and caulk and seal around all windows and doors.
In addition to insulation, consider moisture and air leakage control in each area of your house. If radon is an issue where you live, you’ll also need to consider radon and radon-resistant construction techniques as you research foundation insulation options. In addition, if you live in an area with termites, you’ll have to consider how termite protection will affect the choice and placement of insulation in your home.