Building Envelope Theory

Building Envelope Theory Topics
The last 50 years have brought about changes to the way we build, insulate, and operate buildings. Major changes include:
  • Wider use of thermal insulation.
  • Tighter building enclosures.
  • Introduction of forced-air heating and cooling systems.
  • Increased need for proper ventilation of buildings.
  • Reduction in the number (amount) and function of active chimneys.

A building envelope is the combination of the foundation, wall, and roof assemblies all working together to provide a comfortable and safe environment in a building. It also preserves the structural integrity of the building. The building envelope works in conjunction with the heating, cooling, and ventilation systems to perform several major functions:

  • Controls the comfort level inside by managing temperature and relative humidity.
  • Reduces heating and air conditioning cost.
  • Prevents problems such as pipe freeze-ups.
  • Prevents insect and vermin infestation of the building.
  • Prevents condensation inside of the building’s foundation, walls, and roof assemblies.

Tighter building envelopes have resulted in lower exchange of air between interior heated or cooled space and the exterior environment. The lower exchange between the indoor and outdoor environment has led to some serious problems:

  • Moist air from inside condensing on the inside of wall cavities, which can lead to the wood rotting or metal rusting.
  • Condensation on the inside of wall cavities that can lead to mold and mildew growth, which can be unhealthy for building occupants.
  • An increase in the level of interior pollutants such as volatile organic compounds from cleaning products.
  • An increase in the concentration of soil gas like Radon in basements, crawl spaces, and slabs.

References

Bynum, Richard, 2001. Insulation Handbook, McGraw-Hill, New York, NY

Lstiburek, Joseph and John Carmody, 1993. Moisture Control Handbook, Van Nostrand Reinhold, New York, NY

Lstiburek, Joseph, 1998. Builders Guide: Cold Climates, Building Science Corporation, Westford, MA