A home’s building envelope is the physical barrier that separates the inside of the home from the outdoor environment. It includes the foundation, exterior walls, roof, insulation, windows, and doors. These components help control the movement of heat, air, and moisture between the home and the outside environment.
A “tight” building envelope is one that limits how much conditioned air escapes outside the home. A tight building envelope plays an important role in creating a comfortable, healthy, and energy-efficient home. It helps maintain more consistent indoor temperatures, reduces drafts, limits moisture problems, and protects the home from outdoor conditions such as rain, wind, and temperature changes.
Heat naturally moves from warmer areas to cooler areas. During the winter, heat from inside the home moves toward the colder outdoor environment. During the summer, heat from outside moves into the cooler indoor space.
The building envelope helps slow this heat movement by addressing two primary inefficiencies: heat transfer and air leakage.
Heat transfer refers to the movement of heat through walls, roofs, windows, doors, and foundations. The rate of heat transfer depends on the types of materials the heat is moving through.
Air leakage occurs when conditioned indoor air escapes through gaps, cracks, and openings, while outdoor air enters the home. Common sources of air leakage include:
Creating a tighter, better-insulated building envelope by reducing heat transfer and air leakage can significantly reduce the amount of energy required to heat and cool a home. By decreasing the amount of energy required to heat or cool a home, smaller and cheaper heating and cooling systems can be installed to maintain indoor comfort levels.