As state building codes continue to adopt additional energy saving measures into their standards, sustainable and green building programs are driven to find new and innovative ways to continue to build even better homes with increased comfort, savings and superior quality. What makes a home super-efficient? Explore the different components of energy efficiency in each of the following types of homes.
- Average 1965 Home
- New Code Home
- ENERGY STAR® Certified Home
- DOE Builders Challenge
- Super Efficient Homes
- Net Zero
Average 1965 Home
Homes built in the 1960s began utilizing insulation in the walls and ceilings, but the insulation levels were still quite low and often filled only half of the wall cavity. Under-floor insulation was still rare, and framing used much more lumber than we use today. Homes were also built without much attention to air sealing. Inefficient oil furnaces and single-paned windows contributed to high energy usage compared with even the most basic home today. During this period, the average annual energy consumption was roughly 35,000 kWh*.
*Assumes translation of all energy use to electric
New Code Home
The first national energy codes were written in the mid-1970s and were widely adopted in the 1980s. At the same time, however, the average house size in America steadily increased. The average home is now more than twice the size of the average home in the 1950s. The current energy codes still fail to capture many existing opportunities for improved efficiency. A home built to code in the Northwest will require insulation in the walls, floors and ceiling. There are some requirements for framing and air sealing, but these are by no means extensive. Energy codes also require HVAC sizing and design to be done correctly, but verification is rarely required.
ENERGY STAR® Certified Home
ENERGY STAR certified homes incorporate building practices and technologies that capture energy savings well beyond the basic energy codes. Compared to a modern home built to code, an ENERGY STAR certified home is at least 15% more energy efficient. The savings can be attributed to a wide range of improvements to the building envelope (walls, floors, ceiling and windows), heating and cooling equipment, water-heating equipment, lighting and appliances.
DOE Builders Challenge
The Department of Energy’s Builders Challenge encourages builders to go beyond ENERGY STAR requirements. Depending on the relevant state’s energy codes, a Builders Challenge home is roughly 30% more efficient than a home built to code. Builders accomplish this level of efficiency by following prescriptive guidelines that are similar to, but more stringent than, the ENERGY STAR certified home program, or by using energy modeling software that helps them determine how to meet the 30% savings.
Super Efficient Homes
While most super-efficient homes are built by custom builders, production builders are exploring cost effective ways to reach this standard. Advanced framing, super-insulated envelope systems (ICFs, SIPs, exterior rigid foam, etc.), triple-paned windows, heat pump water heaters, ductless heating and cooling systems, heat recovery ventilators (HRVs) and compact fluorescent lighting all provide huge energy savings. Passive House is one of the most advanced certification platforms in this category, due to the rigorous nature of its requirements.
Net zero is a paradigm shift in residential construction. Homes in this category consume no more energy than they produce throughout the course of a year. This can only be achieved when generating energy on-site – typically with photovoltaic panels (PV), or, in rare cases, wind turbines and/or water mills. In most climates, net zero homes consume a small amount of power in the winter, and then make up for it during summer when the PV panels maximize their output. In many cases, electricity not used on site can be sold back to the utility and rerouted elsewhere through the electrical grid. Net zero homes still incorporate many of the same features found in other energy-efficient homes. Before utilizing on-site renewable energy, it is important to maximize energy savings through improvements to the envelope and mechanical systems.