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) Insulate the attic access door.
(2) In finished attic rooms with or without dormers, insulate (2A) between the studs of “knee” walls, (2B) between the studs and rafters of the exterior walls and the roof, (2C) and ceilings with unconditioned spaces above.
(2D) Extend insulation into joist space to reduce air flows.
(3) Insulate 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 in heated basements.
(4) Apply insulation to floors above unconditioned space, such as vented crawlspaces 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 crawlspaces. (4D) Extend insulation into joist space to reduce air flows.
(5) Do not forget to insulate band joists.
(6) 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 have 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 will affect the choice and placement of insulation in your home and plan for a means of inspection.