Energy design by computer modeling is only an approximation and can never completely account for variations in occupant behavior and lifestyle. Still, our Energy-10 modeling predictions came very close to reality. There is still much to be learned as we monitor the house’s performance over the long term. We can safely say, however, that we demonstrated that the Passivhaus philosophy works well, and that builders can achieve tremendous energy-efficiency improvement with just a change in techniques and a modest increase in cost (see “Cost Comparison” sidebar).
Comfort and safety are very important, too. A home like ours is not for a “hands-off” family that insists on the narrow 68°F to 72°F comfort range that Americans have grown accustomed to since the widespread use of air conditioning. A passive solar home requires getting used to slightly wider temperature swings, and requires hands-on participation to occasionally open and close shades and windows to maintain comfort.
We also were pleased that humidity problems did not occur. Because of our dry climate, we purposely used an ERV for ventilation, rather than a heat recovery ventilator, because an ERV also transfers humidity between incoming and exhaust air. This worked extremely well—throughout the winter, the house remained between 25% and 35% relative humidity, the heart of the comfort zone in cold weather.
The challenges of detailed design and frustrations during construction began fading the moment we watched the electric meter run backward—and at the first of many 0 kWh electricity bills—and the first time the outside temperature dipped below 0°F, but we could sit in a 72°F house, with no heater turned on. It has been a fun and worthwhile adventure!
Jim Riggins is the owner and principal analyst of EnerSmart Energy Solutions (enersmartenergy.com), a Building Performance Institute (BPI) building analyst, EPA WaterSense home inspector, and a Residential Energy Services Network (RESNET) certified home energy rater. Jim and his wife Elise showcased Heliospiti in the 2011 Pikes Peak Tour of Sustainable Buildings to show the benefits of affordable energy-efficient construction to the Monument and Colorado Springs, Colorado, communities.
Products & Companies:
Accurate Dorwin • accuratedorwin.com • Windows
ACT • gothotwater.com • D’Mand hot water recirculator
Enphase Energy • enphase.com • Microinverters
Habitat for Humanity ReStores • habitat.org/restores • Recycled building materials
National Renewable Energy Laboratory • 1.usa.gov/PVWatts • PVWatts solar calculator
Onset • onsetcomp.com • Hobo data loggers
Passive House Institute U.S. • passivehouse.us
Professional Solar Products • prosolar.com • PV & SHW mount rails
Rampart Custom Homes • rampartcustomhomes.com • Builder
REHAU • bit.ly/ECOAIR • ECOAIR earth tube
Sharp Solar • sharpusa.com • PV modules
Sun Earth • sunearthinc.com • Solar hot water collectors
Sun Plans • sunplans.com • Passive solar building plans
UltimateAir • ultimateair.com • RecoupAerator ERV
WaterSense • epa.gov/watersense