Jan 29, 2015
Mention the words “sustainable living” to anyone and one of the first things that comes to mind is energy efficiency. In addition to producing one’s own food, what sustainable living home would be complete without attempts on all fronts to reduce the amount of dirty energy needed to heat, cool, or power that home? The FLAT is well aware of this and has, from the very beginning, made energy efficiency a primary consideration in its mission.
It’s important to remember that a sustainable home doesn’t work if it’s not really a “home.” People need some level of comfort in order to want to live somewhere, and the FLAT aims to demonstrate a normal, comfortable life in the most sustainable way possible. That means we still take hot showers, have massive cooking parties, host events, wash our clothes (from time to time), and anything else a normal group of university students would do. “Cold beers and hot showers,” as they say in the biz.
We do this in several main ways, namely through energy-efficient appliances, producing our own electricity, and experimenting with passive solar and thermal envelope techniques.
This is probably the easiest area to demonstrate. These appliances are increasingly available and visible on the market and are even voluntarily rated with systems like EnergyStar. And, given a few minutes with algebra, it’s simple to calculate the cost and carbon savings over time. The FLAT uses many of the common efficient appliances, such as CFL bulbs (with a mind to switch to LEDs); an efficient refrigerator, washer, and dryer; and so on. Two Kill-a-Watt meters help us track the energy and power usage of various individual appliances so that we can make conscious choices about what we use and how often we use it. In general all of the FLAT residents are very mindful about turning off or unplugging devices when not in use to avoid wasted energy via phantom loads or unnecessary lights.
The FLAT roof hosts a 2.8 kW solar PV array. This array is grid-tied and net-metered, meaning that any energy not used by the house is exported to the grid and paid for by the utility. Instead of using storage, we simply buy from the utility when the array is not producing power, and export when it is. As a result, and in conjunction with the efficient appliances and conservation measures, we use less than 10% of the utility power of an average household in Montana, and pay nothing for electricity between March and November in an average year.
The array itself was paid for by a loan from the KRELF (Kless Revolving Energy Loan Fund), a fund available to any students interested in doing energy projects at the University, at an upfront cost of $33,000. FLAT residents pay off the loan over time, and the University itself keeps the savings from the utility bill. On a purely simple-payback basis, the system is not cost-effective as it will take slightly longer than the 25-year lifetime of the panels to pay the loan off. However, the cost of solar PV systems has come down considerably since the system was first installed, and federal and state subsidies continue to make solar more viable in Montana. In addition, the carbon savings (which are approaching 10,000 kg CO2e) go towards the University’s goal of bringing its scope 1 and scope 2 carbon emissions to zero by 2020. The FLAT array also acts as a demonstration to the University, which is considering various solar arrays of its own.
The biggest challenge facing the solar PV demonstration is accessible and visible monitoring. A display on the side of the house gives a realtime reading of the power production, total energy produced, and total carbon offset. However, the FLAT is pursuing alternatives to this display that will be more accessible to those who are not familiar with electrical terms, and more visible for the hundreds of people who walk past the display every month.
Another challenge, as with any Northern system, is snow. The rooftop panels are only accessible via a long, heavy pole with a glorified mop on one end that we use to scrape snow off the panels, or at least the half we can reach. It is also not a pleasant task to march out into the snowdrifts on a frigid January day. Thankfully PV systems are designed with the assumption that they will be covered in snow for some part of the year, and homeowners are not typically expected to scrape them.
Passive Solar and House Envelope
Like many homes in Missoula, the FLAT was constructed somewhere between the 1950s and 1970s, bestowing on its residents the associated charm and headache. It poses a challenge, particularly in the area of remodeling, but serves as an ideal demonstration for neighbors rather than a “look what you could do with a million bucks” type of demonstration house.
In general residents of the FLAT, indeed the University itself, cannot touch the walls of the house except to apply a coat of pain (which we did, using toxin-free organic paints). Inside the walls is asbestos, used heavily through the 1970s and subsequently banned. The cost of removing asbestos is beyond the means of most homeowners and so we are limited in our options for working with the house envelope. We apply insulation to our windows every winter, seal the bottoms of doors, and have blown several additional inches of cellulose insulation into the attic to reduce heat loss through the roof (generally the single greatest source of loss other than windows due to its surface area and poor insulation). Other than that we try to keep south-facing windows clear, turn our thermostat to the low-50s, and operate a pellet stove in the living room for those really cold days.
Where we really get to focus, however, is on our studio space in the back. Formerly a garage, the building was torn down and started anew with help from the Missoula College energy and carpentry programs as well as local suppliers. Using fly ash for the floor (high thermal mass) and recycled materials for everything else (courtesy of Home Resource and Heritage Timber), we made a studio space that has a cob and hay-bale wall on one end, cellulose insulation on two other walls, and large operable windows with thermal curtains covering the south wall. The space regulates its own temperature very effectively for 8 or 9 months of the year, and is heated for the cold months with a pellet stove (pellet stoves burn compressed pulp from paper mills nearby, thereby reducing waste and avoiding the use of fossil carbon). More information on the studio can be found in the Studio project link.