If you spend enough time in the environmental movement, you'll undoubtedly get wrapped up in the philosophical discussions of what is the most “green.” Paper, or plastic? Off-grid, or grid-tied? Such debates are naturally going to arise in a movement whose goal is to improve the way people live on this planet, because the act of living affects our natural world many varied ways. Sometimes, improvement in one aspect of environmental impact has unintended consequences in another.
Green building is not without its own debates of this ilk. Should a new insulation product capable of drastically dropping energy consumption be used, even if it is manufactured with chemicals whose toxicity is not well studied? Should I stay in my existing energy hog of a home here in town, or build a new green home in a location that requires me to drive many miles each day to work and the nearest grocery store? Any project that successfully transforms from dream to reality is going to have to accept some compromises between competing environmental concerns. I work with customers every day who must contemplate these trade-offs, and have observed that green home projects are often guided by one of two very different general philsophies, each with their separate focus on what it means to be a truly green residence.
The Resilient, Self-Sufficient Approach
This school of thought is the older of the two. The goal is to disconnect the home altogether from the environmentally problematic systems that modern homes depend upon, supporting its own needs in a more sustainable manner.
This kind of green home has a plan for everything. Not connected to the electrical grid at all, a solar array, wind turbine, micro-hydro generator, or any combination of the above will charge batteries to power the electrical essentials of this house—although a propane generator is in place when even these systems fail. Heating for this home also often comes from propane, (it is generally too far away from town to have natural gas service) in combination with a trusty wood stove. Water comes from wells, greywater, and rain barrels; much of the food comes from the site. This home likely features strong passive solar design, and will be well insulated—although preferably with natural insulation materials such as cotton or sheep’s wool. Some modern conveniences, such as air-conditioning, are likely foregone, although enough will remain to satisfy the particular wants and hobbies of the homeowner.
This home in Colorado exemplifies the philosophy of resilient green design. It uses natural materials (adobe, wood-framed construction, interior tile and brick for thermal mass) and off-grid systems (solar electric system, solar hot water system for domestic hot water and assistance with hydronic radiant floor heating, all with propane backup) to remain resilient in an very remote area with common snowstorms and power outages.
The High-Tech Approach
This philosophy embraces technology to improve connections to the existing infrastructure. This home may look on the outside very similar to a standard home—minus the solar array--and it will use whatever technology is available toward the goal of ultra-low resource consumption. It likely uses mass-produced building products like spray foam insulation or structurally insulated panels (SIPS), to achieve exceptional levels of insulation. It will be extremely air-tight with the help of caulks, gaskets, and tapes, and will incorporate a mechanical fresh air system to keep the occupants healthy. It will likely be both heated and cooled, using ultra-efficient technology like a ductless mini-split heat pump or a ground source heat pump with variable speed blower and desuperheater for water heating assistance. It will likely be all-electric---the better to be powered by an on-site solar array—and hooked up to the existing electrical grid so as to allow the homeowner to use her solar when the sun shines, pull electricity from the grid when it is not, and send any excess generation from the solar back out to the grid as a credit against later grid use. It will use passive solar design whenever it can, with special coatings on south-windows to allow more heat transfer, and triple pane windows on other sides of the home.
The National Institute of Standards Net Zero Test Facility, pictured here, is one example of such a home. Using thick walls, air-tight construction, and high efficiency systems, the it was built to use 60% less energy than standard construction before the addition of the 10 kilowatt solar array and separate solar water heating system. It was also designed fit in with the look of the regular suburban homes around it.
Low-Loads Is What They Have in Common
Though the means to get there may differ, the common theme in both of these philosophies is low energy use--the first philosophy because of necessity, as the on-site systems must be able to supply all the home’s needs--and the second because of the cost benefits of negating electric bills. This means houses insulated above and beyond code levels. This means passive solar design principles used to their fullest extent whenever possible. And in either case, there is some portion of modern living that demands electricity: whether for an array of consumer electronics or just for a well pump. That means on-site renewable energy will always have a role to play, at least until the utilities start getting serious about deploying renewables for widespread grid generation.
All Of the Above!
As a green building consultant, I can usually tell which philosophy my clients are more likely to identify with after a few conversations—although of course, in real life, many projects take on aspects of both. My preference is for neither. Every attempt at green building can teach us something new about how to reduce our environmental impact. Every new green building advances the goal of a less impactful building stock in some capacity. A project really wins when it can find ways to accommodate multiple environmental goals. Low energy loads, and healthy, non-toxic materials. Resilience against what may come, without requiring the sacrifice of all modern luxury. Arriving at a product or process that benefits the environment, benefits people, and remains economical can sometimes be a long, iterative process. As an environmentalist, I believe it is a process that is essential to undertake.
Which philosophy do you identify with more strongly?
photo 1 credit: John Janus
photo 2 credit: NIST