By DON NEFF
Designing and building an energy efficient home is not rocket science, but requires knowledge, experience, and expertise, including careful coordination of your team. According to a National Association of Home Builders survey, energy efficiency is becoming the most sought-after feature for homebuyers. In response, builders are creatively embracing new technology solutions and re-engineering old processes.
Quality construction by skilled workers is important and necessary, but alone it is not enough. Achieving or exceeding the standards set by the U.S. Green Building Council (LEED for Homes) or the U.S Department of Energy’s Energy Star program requires more advanced systems and new knowledge. Tracking installation practices through software such as CaptureQA®, for example, provides builders with helpful dashboard metrics on how their trades and field team members are performing during the construction cycle. If deficiencies in insulation installation are found and documented, they can be corrected before that work is covered up.
The goal of net-zero in 2020 by the California Energy Commission is a case in point and re-thinking building envelope insulation is one of the keys for success. Long established practices of using fiberglass batt insulation by itself in 2×4 framed wall cavities will not provide enough R-value to achieve the stated goal. Improper installation can create convective air flow loops in interior walls that result in under-insulated assemblies and thus more energy usage.
Insulation standards have been raised by stakeholders, and the industry is moving towards higher performing rigid exterior foam products. Rigid foam boards can be used to insulate almost any part of the home. According to the U.S. Dept. of Energy, “they provide good thermal resistance — up to two times greater than most other insulating materials of the same thickness.”
Dr. Joe Lstiburek of Building Science Corp is a proponent of the “Perfect Wall”, which integrates exterior rigid insulation products. The benefits include eliminating “thermal bridging” (heat conduction through structural elements) as rigid foam wraps the house like a sweater. Quoting Dr. Lstiburek, “When you are cold, you pull on a sweater, you don’t eat it.”
Variations of this thermal control layer include combinations of interior (stud bay cavity) spray foam and fiberglass batt insulation. Blown in fiberglass fibers (“spider insulation”) are another product, applied in the same way that damp-spray or wet-spray cellulose is installed. The key considerations with any of these solutions are the labor and material costs, availability of products, and ease of installation. However, regardless of the type of insulation used, it needs to be installed by skilled and experienced tradesmen who understand the thermodynamic processes of insulated walls and roofing systems.
Homebuilders are constructing progressively tighter building envelopes to achieve energy conservation objectives, such as those in California, with a goal of maximizing energy efficiency while minimizing building system defects. Use of blower door testing is commonly used to identify air and energy leaks and provide guidance to implement proper sealing of the envelope.
In addition, improperly installed roofing systems are particularly vulnerable because the components are out of sight and consequently create longer term performance issues through air and vapor infiltration with potentially resultant building assembly deterioration. Where homebuilders integrate better water, vapor, and thermal control layers in their roofing systems, construction quality, durability, and energy efficiency can improve. Windows and doors are prime suspects in energy losses because they are really just big holes, filled with dissimilar materials of lower performance specs than the adjacent assemblies. Other contributory factors are incorrect installations, not following architectural plan details, broken window seals, and even the wrong window types for the climate zone.
Roof-mounted solar panels are becoming increasingly common on homes and apartments as component pricing declines. Unfortunately, solar system design, location, and orientation (to the sun), as well as installation errors prior to the line side connections, can similarly compromise overall system performance.
One solution is to install the panels on a so-called “cool roof.” Because of their lighter color, cool roofs reflect sunlight and reduce thermal radiation. Combining a PV system with a cool roof can improve the performance of a solar photovoltaic system by as much as ten percent.
Whatever measures are taken, the goal of building energy efficient homes is to lead in the marketplace with state-of-the-art architectural designs and construction methods combined. By so doing, builders can construct and sell homes that consumers want, and our environment needs.
Don Neff is the President/CEO of LJP Construction Services, which has been at the forefront of the quality assurance movement on behalf of builder and insurance clients for 25 years. For more information, visit www.ljpltd.com