An Overview of Energy-Efficient Homes
By: Robert Marino | Director of Clean Energy and Infrastructure
As Washington state moves towards electrification, our buildings landscape will have a lot of changes from energy efficiency in new construction to retrofits. In the next year I will be writing a series of articles to share about energy efficiency in new construction and retrofits. Let’s look at an overview of a high-efficiency home. Building a new home or retrofitting an existing one using these practices can help you get your home close to “net zero energy,” meaning your home produces as much energy as it uses. Thanks to the Zero Energy Project for many of the ideas in this article, and you also might like this video from Whidbey Island builder Ted Clifton that covers similar topics.
- Building orientation, (for new construction) if you are building a new home, definitely work with your architect (if possible) on orientation. An east-west orientation will form a southern facing roof slope for installation of a solar array to power your house. South facing windows bring in the warmth of sunlight in the winter and can be shaded by eaves in the summer. Of course, if you have an existing home, orientation is no longer a consideration. If you don’t have a south facing roof, you still might be able to install solar. It is worth consulting an installer to find out more.
- Simple design. “Complexity adds cost.” Go for “BBB” (boxy but beautiful). A cube is a practical shape that is easier to heat and cool evenly, and simple roof lines make solar installs and maintenance easier. Simple design primarily applies to new construction, but could influence your design of an addition as well.
- Tight building envelopes limit air leakage and are required to maximize the energy efficiency of your home. Air sealing refers to using one or more materials to create a continuous barrier around the space that you will heat or cool in your home, as if you were to wrap a six-sided box with plastic wrap. Air sealing reduces airflow, just like insulation reduces heat transfer. An attached garage is the place to start in order to keep fumes out of your living space, followed by the ceiling/attic and the ground floor (assuming no slab). Air sealing is about the most cost-effective energy efficiency measure you can take.
- Energy modeling can help you predict how a given efficiency upgrade would affect your house and can suggest the most cost-effective upgrade while also taking into account the law of diminishing returns.
- High performance windows minimize heat gain and heat loss. Windows are measured in U-factor. U-factor is the measure of heat transfer, the opposite of R-value, and values range from .10 to 2.00. The lower the number the less heat transfer. Here is a tool for selecting windows based on your climate.
- Balanced insulation levels throughout the building. Insulation is measured in R-Value. The R in R-value stands for resistance and means how well a given material is at blocking the transfer of heat. The higher the R-Value, the better the material is at trapping heat. There are significant diminishing returns when adding additional insulation: R-20 insulation is only slightly less efficient than R-40 insulation. Modeling a home’s energy performance is a good way to balance insulation for the whole building envelope, for example balancing the amount of ceiling insulation with wall insulation.
- Mechanical ventilation. In a tightly sealed, energy efficient building, air must to be brought in via mechanical ventilation and then distributed throughout the house. Ideally incoming air is filtered through a HEPA or similar filter. Stale air is removed from the building. It may be appropriate to use a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV). HRVs and ERVs improve energy efficiency by taking heat and in some cases moisture in outgoing air and returning it to your home. Clean air is a climate adaptation for housing in the Pacific Northwest where we can now expect wildfire smoke in many years.
- Heating and cooling equipment. Once the envelope is sealed, it’s now time to add a heat pump for heating and cooling. Since the building envelope is maximizing efficiency, you’ll now be able to get a heat pump sized for smaller loads. Having air conditioning is a climate adaptation in the Pacific Northwest where we can expect more hot days and more heat waves.
- Hot water is typically the second highest energy expense after heating and cooling. Solar water heaters used to be the standard for energy-efficient homes, but these days a heat pump water heater (HPWH) will be more cost effective unless you need hot water for several people. A HPWH would work well in our temperate Western Washington climate. HPWHs need good airflow wherever they are placed and tend to slightly cool and dehumidify the area where they are located. Go here to see an amazing retrofit that uses a HPWH to heat the whole house.
- Efficient appliances. Look for ENERGY STAR certified appliances. ENERGY STAR appliances require that an appliance be 15% more efficient than a standard appliance. You can often find more efficient appliances at the same price points as standard appliances if you shop around.
- Efficient lighting. LEDs are the most efficient lights currently available and can last for 20 years. Focus on lighting horizontal work surfaces like countertops, more so than spaces.
- Alternative energy. Solar is the last thing to add once everything else is done correctly. If not done correctly, you’ll never get to net-zero energy use as there is not enough roof space for all the solar panels required. Since you now have a super energy-efficient home, you can right size your solar array to supply a smaller energy load while still meeting all your needs. You could also put additional panels on your roof to power an electric vehicle for example, creating a positive energy house (a house that produces more energy than it uses). In a future article I will discuss the use of small wind turbines to power homes, if solar is not an option.
One last resource to mention is a book called the Pretty Good House. The authors take a practical approach to energy-efficiency and building high quality houses without getting preoccupied with perfection which helps stay within a budget. The book focuses on new construction, but is still helpful for retrofits. Please feel free to reach out with questions or comments at .