In the last two installments of this blog, I covered what builders need to know about key adjustments in the 2015 International Energy Conservation Code (IECC) and how those changes will affect new home construction. In the next two posts, I’ll explore the non-energy benefits of complying with the most recent building energy codes and the several areas where they align with other building requirements.
Building energy codes--which establish minimum requirements for the components within a building that affect energy consumption--typically take a backseat to building safety, health, and fire codes. However, many builders and code officials are realizing that compliance with the most recent energy codes helps produce a structure that’s not just energy efficient, but one that’s safe, comfortable, resilient, and free of defects for occupants.
Provisions within the energy code touch most aspects of residential construction including the building envelope and the heating and cooling system, and the benefits that accompany energy code compliance have outsize impacts on everything from the safety of the air that occupants breathe to the prevention of fire spreading through draft openings. Increased durability, reduced potential for premature equipment failure, and a more comfortable environment for the occupant—these things all add to assisting builders with meeting other health and life safety codes and the expectations of home buyers.
Let’s dig into some of the most important issues energy code compliance addresses:
Ice dams. For homes in colder climates, ice dams are cause for headache and an abundance of insurance claims filed by homeowners—news reports indicate there have been a spike in them this winter. According to the Insurance Information Institute, “water damage and freezing” is the second most frequent homeowner’s insurance claim and accounts for 20% to 25% of all insurance losses. The average cost of each claim is $6,965.
The simple solution to this costly problem is air sealing and properly insulating the ceiling assembly as required by the energy code. The 2015 ICEE requires a ceiling insulation value of R-49 for Climate Zones 4-8 (the colder regions of the U.S.), and an envelope air leakage rate not to exceed three air changes per hour. By complying with these tenets of the code, builders prevent their future customers from having to deal with ice dams and potential callbacks to address the problem.
Air leaks. Other air leaks and uncontrolled airflow through the building envelope can have a severe effect on a home’s durability. They can carry moisture into framing cavities and lead to mold growth, rot, pests, and damage to the building envelope. Air leaks into the house can also bring contaminants, such as exhaust from a car parked in a garage and other pollutants that are stored outside of the conditioned space.
Complying with the air-sealing requirements in the energy code increases the durability of the building; cuts down on potential moisture, mold, rot, and pest problems; improves indoor air quality; and prevents the financial and health issues that can be associated with these problems.
In addition to the envelope air leakage limit listed earlier, the 2015 IECC also requires that the building envelope have a continuous air barrier and requires air sealing between a garage and conditioned space. These requirements can be found in Table R402.4.1.1 of the 2015 IECC.
Condensation on windows. Moisture can condense on inefficient windows when warmer moist air comes in contact with the cold surface of the glass or the frame during colder months. This condensation can damage wall and ceiling materials and, if prolonged, can promote the growth of mold and mildew if mixed with dirt and other nutrients.
Complying with energy code requirements to install efficient windows that will perform well in the climate zone they are specified for can significantly reduce these condensation issues. The 2015 IECC U-factor requirements range from a 0.32 in climate zones 5-8 to no requirement in zone 1 (i.e. Miami, Fla.).
Fire blocking and combustible construction. In wood-framed residential construction, the code requires that fire blocking be provided to cut off all concealed draft openings (both vertical and horizontal). The fire blocking must also form an effective fire barrier between stories, and between a top story and the roof space. Fire blocking is required in concealed spaces of stud walls and partitions, and at intersections between concealed spaces.
R402.4.1.1 of the 2015 IECC lists the air barrier and insulation criteria for 16 individual construction components. Complying with air-sealing and insulation requirements of the energy code not only increases the efficiency of the house, but also helps meet fire blocking requirements of the International Residential Code by requiring that insulation be installed in exterior walls and that all penetrations be sealed between conditioned and unconditioned space. Concealed spaces are also required to be sealed off from each other to prevent air leakage.
Slab-on-grade and mold and mildew. Slab-on-grade floors built in cold climates are typically very cold, especially if they are not insulated properly. Energy codes require slab edge insulation in most climate zones, which reduces the risk of condensation on the surface of the slab and the potential growth of mold, mildew, and other unwanted pests. Table R402.1.2 of the 2015 IECC requires slab edge insulation of R-10 for a depth of 2 feet. In climate zones 6-8 the R-10 insulation must extend to a depth of 4 feet.
Issues with rim joists. The rim or band joist is a framing member that is relatively easy to insulate but difficult to air seal. Warm air passing through the insulation will condense on the rim joist during the heating season and be held against the surface. The moisture can cause mold growth and eventually can lead to rotting out the rim joist.
Energy codes focus specifically on the rim joists to ensure they include an air seal and are properly insulated. The 2015 IECC requires the air barrier to include the rim joists and requires the rim joists to be insulated. (Refer to Table R402.4.1.1 for air barrier and insulation installation requirements.) Complying with energy codes can increase the durability of wood framed construction.
As you can see with the above issues, complying with energy codes has lasting positive effects on residential construction. It’s also what home buyers are now looking for: A recent study by the National Association of Home Builders showed nine out of 10 buyers would rather buy a home with energy-efficient features than a home that doesn’t have those features and costs 2% to 3% less.
In part two of this blog installment, I’ll share some of the benefits of mechanical and water heating system compliance, as well as some real world examples that demonstrate what can happen if provisions of the energy code are not met and how construction practices were changed to mitigate issues that affected durability and indoor air quality.
