Building Codes Assistance Project

Inadequately sealed building envelopes can lead to significant air leakage that decreases the comfort of a residence by allowing moisture, drafts, and undesired noise to enter. Air leakage may also reduce indoor air quality by permitting dust and airborne pollutants to infiltrate the building. According to the Environmental Protection Agency, air leakage in a typical home accounts for 25% to 40% of its heating and cooling energy use -- a substantial loss of energy and money.

Air sealing the building envelope is one of the most critical features of an energy efficient home. Heating and cooling account for 50% to 70% of the total energy used in the average American home, in which air leakage can be a significant cause of energy waste.

A building envelope constructed with proper air sealing can provide many benefits, including:

• Increased comfort: A tighter building envelope reduces the amount of unconditioned air, drafts, noise, and moisture that enter your home. Proper air sealing will also minimize temperature differences between rooms. As a result, tight envelopes can maintain a more consistent level of comfort throughout a house.
• Improved indoor air quality: A tighter building envelope reduces the infiltration of outdoor air pollutants, allergens, dust and radon as well as moisture infiltration from outdoor air in humid climates. Properly sealing the building envelope will also eliminate paths for pests to enter.
• Lower utility bills: Air leakage accounts for 25% to 40% of the energy used for heating and cooling, hampering the performance of other building systems, including HVAC, fenestration, and insulation. All building systems must perform well together to optimize the energy efficiency of a home.
• Fewer condensation problems: In hot, humid climates, moisture can enter into wall cavities through exterior cracks, resulting in mold and mildew problems that can lead to costly damage to framing and insulation. In cold climates, gaps in the interior walls allow moisture from warm indoor air to enter wall cavities and attics, which can condense on cold surfaces and lead to similar damage. Proper air sealing can significantly reduce the incidence of these problems.

Professional energy auditors employ blower door tests to measure the airtightness of buildings. This diagnostic tool helps identify leaking areas in the home that need to be addressed. Other online resources detail many techniques for properly sealing different leaky parts of the typical home.
Consult WNC Green Building for an air sealing checklist.

There are many new and innovative air sealing products -- like low-VOC fastenings and foam joint and caulk joint sealants -- that are not specified by the model codes that can save energy, money, and enhance thermal comfort. For more information, visit www.BuildingGreen.com.

The following section provides examples of these types of code improvement language or methodologies in these areas.

Policy Options

• Offer Alternative Compliance Option Through HERS Rating

  Massachusetts Building Code for One- and Two-Family Dwellings, Seventh Edition (780 CMR): Chapter 61, Section 6101.1 amending 404.7 such that a building with a HERS score of 100 or less will be in compliance in lieu of building to 2006/2007 IECC specifications:
  "A proposed building, for which the builder or the buyer obtains a Home Energy Rating by an accredited Home Energy Rating System (HERS), will be considered to comply with the intent of Section 4 if the rating score on the building is 100 or fewer points."

• Blower Door Guided Air Sealing

More coming soon!

**Image 1 and Image 2 courtesy of Building Energy Codes Resource Center. Image 3 courtesy of Headwaters Energy & Finance.