Will new energy codes change the way you build?
With new requirements for insulation, ventilation, and a tighter envelope, the 2012 IECC is likely to affect the way you approach residential construction.
By Selby Frame
The latest iteration of the International Energy Conservation Code (the 2012 IECC) ratchets up energy performance standards for residential construction by about 15 percent over 2009 standards and roughly 30 percent over 2006 standards. Depending on where you’re located, the updated standards could significantly change how you build your homes.
Administered by the International Code Council and updated every three years, the IECC is the most widely adopted model energy code throughout the U.S., with roughly 41 states using some version as the basis for the statewide energy code. Currently, only Maryland and Illinois have fully adopted the 2012 IECC, but more than a dozen other states are expected to adopt it or an equivalent in the next two years.
The new code includes changes in requirements for a home’s insulation, ventilation, and building envelope that are intended to improve the durability, safety, and comfort of homes and lead to energy savings that increase a home’s value over time. It will also have a noticeable impact on how builders and engineers approach construction, budgeting, and inspection processes on new homes and in some retrofit scenarios.
The 2012 IECC had a number of important changes in both format and requirements. For the first time, the code was clarified by splitting residential and commercial construction into separate sections, with residential defined as buildings of up to three stories.
The updated standards for residential construction had several key components:
- Wall insulation requirements have become more stringent in all but the hottest climate zones; for the first time, builders in the coldest climate zones will be required to install exterior rigid foam or other comparable wall insulation.
- Nearly all homes will be required to have a whole-house mechanical ventilation system.
- Window glazing U-factor and solar heat gain coefficient (SHGC) requirements are more stringent in many climate zones.
- Seventy-five percent of lighting fixtures in a new home must be so-called high-efficacy fixtures that use compact fluorescent lamps (CFL) or other energy-efficient lighting (up from 50 percent in the 2009 IECC).
- Duct tightness requirements have become more stringent.
- The airtightness requirements for the building shell are more stringent, and airtightness testing is required on all homes. The 2009 airtightness level of 7 ACH50 (air changes per hour, or ACH, under 50 pascals of pressure) has been ratcheted down to 3 ACH50 for homes in most climate zones.
Many of the 2012 IECC standards will look familiar to builders already designing for above-code certification, such as Leadership in Energy & Environmental Design (LEED), Energy Star certified new homes, or DOE Challenge Homes. But even green builders will be affected. “The bronze level of the National Green Building Standard is probably a little shy of the 2012 IECC,” says Craig Drumheller, director of Codes and Standards for the National Association of Homebuilders (NAHB), “whereas the silver is now exceeding it.”
“Some [builders] have had to change the way they do construction,” notes Don Mock, plan review chief for the Howard County (Maryland) Inspections Office. “They have done 2×4 studs in the wall in past construction and now need to build with 2×6 studs to get major insulation in the wall. That’s probably the really big sticking point – that and duct testing and pressurized testing.”
Although earlier tradeoffs that allowed builders to install high-efficiency appliances to help comply with codes were eliminated in previous editions of the IECC, you need not forgo installation of Energy Star appliances, high-efficiency propane or natural gas furnaces, and tankless water heaters, which remain in high demand among consumers and play an important part in achieving other efficiency ratings, including improving a home’s Home Energy Rating System (HERS) Index scores.
High-efficiency propane furnaces, for instance, offer best-in-class efficiency, with annual fuel utilization efficiency (AFUE) ratings as high as 98 — well above the 78 AFUE minimum of the current code. Direct-vented units can help builders decouple the heating system from the home’s air by drawing their combustion air directly from outdoors. This feature is particularly important for highly air-sealed homes built under the 2012 code and will also improve indoor air quality.
Because of the 2012 IECC’s more stringent requirements for air leakage, many homes will be required to adopt mechanical ventilation to address one of the potential dangers of supertight homes, the ability to “breathe” sufficiently to expel pollutants that accumulate indoors.
“When you make a house that much more airtight, it changes how a house works as an entire system,” explains Jamie Lyons, senior engineer at Newport Partners, a Maryland-based housing consulting firm. “Builders need to think more closely about how air gets in and out of the house, how pressure changes. Typical homes built five years ago were probably twice as leaky as [2012 IECC compliant] ones in many ways. Changing houses this remarkably is going to have an effect on other systems.
“A tight house is kind of like a shoebox,” he says. “A big furnace or dryer sucking air out of the house can make the house have [overly] negative pressure and make combustion gases have a harder time escaping out of the flue.” Houses with highly efficient propane or natural gas furnaces, boilers, and water heaters have added safety against the shoebox effect, Lyons says: “They are going to be direct vented or power vented, so they force the combustion gases out of the house under fan power.” In a supertight house, he says, that ventilation is important to help avoid backdrafting combustion gases.
The tougher standards in the 2012 IECC are also likely to lead to higher construction costs. According to a Department of Energy study, moving from 2009 to 2012 IECC standards will increase construction costs by an average of $1,659 to $2,797, depending on the climate zone.
The good news? Most consumers who purchase homes built to the standards will see their down payment and other upfront construction costs recouped in as little as one year. The study predicts building to the updated code will result in positive annual cash flow savings (energy savings minus mortgage increase) averaging between $102 and $444 as a result of energy efficiencies, mortgage tax deductions, and property taxes. And for builders, these more energy-efficient features should help their new homes stand out even further from existing homes on the resale market.