Equinox Data
One of the most important aspects of the Equinox House project is our effort to make sure that people don’t have to take our word for how good it is. Too often we hear about a new “green” home being constructed that is “environmentally friendly” and “energy efficient”, but when it comes down to it, they very rarely show any actual hard data to prove any of their performance claims. Sure, using bamboo may be a nice material, but how environmentally friendly is your house if it is over-windowed and requires loads of extra cooling capacity in the summer time and has large temperature swings throughout the day (check out our Windows section of Equinox Features and Technologies)? And is your air really fresh? Opening and closing windows for “natural ventilation” sounds nice, but the reality is that relying on people or “natural” systems to purge unhealthy gases from your house will not keep your indoor air free of odors, mildew, mold, radon and VOCs. And, shouldn’t zero energy mean that the energy a renewable energy system produces meets or exceeds the energy a “net-zero residence” requires? While energy is an important factor, even more important is water. The current cost of water in the US is much lower than its real value. We sorely need information to help home owners and building managers understand how they can integrate cost effective rainwater harvesting and storm water management techniques into their buildings.
Various home ratings are nice for providing an awareness of considerations that are important to follow for design and construction of net-zero residences, but these ratings and certifications need to be followed up with real data. We believe that if a house claims to be energy efficient, data should be published to back it up. So here we are, with our data. Equinox House is not only an energy efficient, true net-zero energy home, but it is also a comfortable house with healthy air, and a rainwater harvesting system that contributes significant water for our everyday use while helping to minimize the effects of storm water runoff on our neighbors.
Below you will find data plots related to comfort, indoor air quality, energy and rain water. If you return to this site periodically, you will be able to see updates as well as new information we will be adding (eg, water condensation from comfort conditioning, appliance energy usage). We will also be adding event tags to the charts to explain activities and special occurences in the data.
Indoor Comfort-Temperature/Humidity/Light
Follow the temperature and humidity, prime indicators of comfort inside Equinox House. Temperature and humidity are only part of the story. Air velocity and surface radiation are also important. During the winter, because the interior surfaces (walls, roof and floor) are relatively warm compared to conventional homes and because the humidity naturally stays in a comfortable range (40 to 60% relative humidity), and because the fresh air ventilation rate has an undetectable velocity, a comfortable wintertime temperature in Equinox House is 68F. As we move into summer, the temperature that feels “comfortable” will be adjusted to whatever the occupants desire for the best comfort. The light intensity level is a qualitative indication of sunny days versus non-sunny days. Light levels in Equinox House are approximately 1000lux during sunny winter days with the addition of direct sunshine, and 400lux during sunny summer days when direct sunshine is omitted by the “equinox” overhang.
Equinox Energy-Solar Energy Collection/House Energy Usage
The plot below shows the trends in solar energy harvesting coupled with Equinox House energy requirements. Similar to farming, we harvest most of our energy in the warm months, and with a “grid-tie” solar system, we feed our excess into the electric grid which needs extra help in the warm months to meet air conditioning demand. In November, the more overcast, shorter, colder days require more energy than collected by the solar energy system. Energy credits built up during the warm weather months are used to meet the extra house energy demand. Equinox House lives off its energy credit until April when solar energy production is again greater than house energy requirements.
Solar Energy Production and Equinox Energy Consumption
Rainwater Harvesting -Cistern Level/Cistern Water Usage/Precipitation
Follow the rainwater harvesting and usage since the system startup in August, 2010. From August to the beginning of November, rainwater was used to establish some garden areas around Equinox House. At the beginning of November, plumbing for toilets in Equinox House were connected, inspected, and approved for usage. The rainwater hearvesting data shows how much water has been collected in the 1700 gallon cistern. A water usage plot tracks the daily toilet water usage. Weather station precipation reports are used to determine the amount of rainwater shed from Equinox House roof. The difference between the precipitation and the cistern’s capture for a rain event is the amount of water delivered to the raingarden. The raingarden has a nominal 2000 gallon capacity.
Rainwater Collection and Usage
Indoor Air Quality-Carbon Dioxide/VOCs/Radon
The potential emission of volatile organic compounds from home furnishings is a concern to one’s health. Radon is the second leading cause of lung cancer after cigarettes. And, carbon dioxide levels from respiration and combustion sources should be maintained below1200 to 2000ppm (parts per million) on average. The fresh air ventilation system in Equinox House operates 24 hours per day, 7 days per week. The attached plots track these gases in Equinox House. Periodic events such as parties or our experimentation with the ventilation system quickly recover to desired levels. Overall results indicate exceptional indoor air quality. Radon levels are always less than 2-3 pC/l, long term carbon dioxide levels are below 1200ppm, and VOCs are not emitted by house furnishings at a rate that exceeds background fresh air levels. That is, all VOCs emitted in the house are from human sources. The human generated VOCs, while important to control to minimize human odors, are not the harmful ones of concern such as formaldehyde or benzene. During time periods without human occupancy, the human generated VOCs self-destruct within one day, leaving the indoor air at a level comparable to the background VOCs in fresh air.
