Before starting any retrofit project, it is important to assess all potential environmental hazards related to the project.

While almost every part of an old building can be better insulated and made more airtight, it is important to know which energy efficiency measures could have the largest effect on the performance of the home. The first concept to understand is the role that stack effect plays in the air movement of the house. At the bottom of the house, cold air is drawn in as shown in the adjacent schematic, and at the top, warm air is pushed out into the attic. As a result, air sealing and insulating at the bottom (i.e. basements and crawlspaces) and at the top (i.e. attics and roofs) of a house should be prioritized, and these areas are also often the easiest to access in unfinished spaces.