A high-performance home combines a variety of building materials and practices to create an integrated, energy-efficient system. Advanced framing, high R-value insulation, air-sealing and triple-paned windows keep heat in during the winter and out during the summer. Heating and ventilation systems work in conjunction with the home’s outer shell to maximize comfort and improve indoor air quality. Heat pump water heaters and LED lighting ensure that daily tasks consume the least amount of energy possible.
These super energy-efficient features make it possible to build a home that exceeds current national and state standards for energy efficiency or even better, a “net zero” home that produces as much energy as it uses.
Conventional framing choices such as wood, concrete and metal often act as thermal bridges and directly transfer heat from interior walls to the outside. Framing techniques that significantly improve energy savings include:
- Advanced framing: reduces material waste and heat transfer by arranging materials to increase areas of insulation and reduce pathways for heat to leave the house
- Staggered stud walls: interrupts thermal bridging by alternating studs along the wall, never completely connecting the inside wall to the outside wall
- Double wall assemblies: layers two smaller walls filled with insulation next to each. Constructing walls with 2x6" instead of the standard 2x4" studs creates a deeper wall cavity, allowing for more insulation
- Insulated Concrete Forms (ICFs) and Structured Insulated Panels (SIPs): Integrates a high level of insulation with an all-in-one wall system incorporating pre-fabricated framing materials
- Raised heel trusses extend the space where the roof meets the wall of a house, adding areas that can be insulated
High performance homes reduce heat loss by creating more surface area to insulate and using better insulating materials. Advanced framing opens up areas in walls, floors and ceilings, allowing for added insulation. Insulating materials that have a high resistance to heat flow, also known as R-value, increase the advantage.
Two other effective insulation options, spray foam and blown cellulose, are applied with high-pressure, forced air and densely pack the entire wall cavity, completely filling gaps around framing materials. Another efficient method, exterior rigid foam, adds a layer of insulation to the exterior of the house. This increases the total R-value of the wall, reduces pathways for conduction (thermal bridging) and prevents condensation that leads to mold and dry rot.
Traditional single-pane windows allow heat to quickly escape to the outside, wasting energy.
Double-pane windows, the current building standard, add a sealed air cavity between two panes of glass that acts as an insulating layer and reduces the heat transfer to the outside. High performance triple-pane windows are the superior energy efficient solution. With three panes of glass separated by two sealed air cavities, heat transfer is minimal.
Air sealing augments the energy savings captured with advanced framing and high R-value insulation, supports the efficiency of HVAC systems and maintains air quality.
Areas of leakage include windows and doors, gaps in framing materials and areas where mechanical systems bridge interior and exterior walls. Once prescriptive framing elements are in place, contractors can identify problem areas and seal leaks with caulk or a liquid or foam-applied air barrier to make the home airtight.
Success can be demonstrated with a blower door test. A blower door test pressurizes a home and measures air leakage by determining how many times outside air is replaced throughout the house. In an ENERGY STAR certified home, a measurement of four full air changes per hour (4 ACH50) is the required standard. A high performance home may test as low as two full air changes per hour.
A high performance heating, ventilation, and air conditioning (HVAC) system delivers comfort, maintains air quality and saves energy.
Traditionally, HVAC systems have relied on ductwork to deliver heating and cooling throughout the house. However, air leakage and heat loss from air ducts is very common. When ductwork is installed in attics, crawlspaces, garages or other unconditioned spaces, the amount of energy wasted can be as much as 30 percent.
Today’s high performance homes often feature a tightly sealed HVAC system that incorporates the ducts inside a conditioned space or is without ducts all together. Due to both the ducts being in conditioned space, as well as a more efficient process of transferring heat, a ductless heating and cooling system is up to two times more efficient than a traditional heat pump.
Many high performance homes also have internal filtration systems that trap odors, pollutants and allergens.
While a properly insulated and air sealed home greatly increases energy savings, air sealing also restricts the replacement of stale, inside air with fresh, outdoor air.
A Heat Recovery Ventilator (HRV) improves Indoor Air Quality (IAQ) by periodically exhausting out stale air and indoor pollutants and piping in filtered, fresh air.
Before entering the house, the outdoor air is warmed to room temperature by the indoor air as they travel side-by-side in a heat exchanger that conducts heat between the two. This maintains the quality of the incoming fresh air and also pre-heats it without using the home’s furnace or heat pump.
In most homes, water heating accounts for 15–25% of all energy consumed. Heat pump water heaters pull warmth from the surrounding air and transfer it to water in the storage tank. This technology uses up to 50% less energy than traditional electric hot water heaters.
Compact Fluorescent Lights (CFLs), the first energy savers to replace the century-old technology of incandescent bulbs, are quickly being eclipsed by Light Emitting Diodes (LEDs). LEDs produce light by passing electricity through a microchip and can produce over 100 lumens per watt of electricity. When compared with an incandescent bulb that produces 10-20 lumens per watt or a CFL that produces 40-100 lumens per watt, the energy savings is significant. Although more expensive up-front, the average LED lasts years longer than a CFL or incandescent bulb. Many local utilities also offer cash incentives to lower the cost.