By Eric Doub, Founder & CEO
“Can BIG be green?” is a question that we are continually asking ourselves. Here are some of our thoughts, prompted by an emailed concern by a web visitor:
If you claim to be a zero net energy, environmentally conscious builder, how can you promote a home that is over 9,000 square feet? Such a home is neither ‘responsible’ nor ‘environmentally friendly’ – to be such, it should have both a small carbon footprint and physical footprint.
I have given much thought to this topic, and share the same concerns, but when asking about environmental impacts, is size of home the only factor to consider?
In the case of this 9,000 sf home, we did not determine the size. We were the consultants on energy and comfort systems. Through our efforts, it became possible for the home to be a net energy producer by about 150% — enough to power the entire house and also drive an all-electric vehicle some 24,000 miles per year. We achieved this using standard materials, off-the-shelf technologies, and commonly understood methods easily repeatable by construction trades.
How many years will it take for the carbon emissions from the construction of a larger home compared to a smaller home to be made up for by the larger home being a net energy producer, being net carbon negative? This kind of thing has been calculated. Of course, if people can be influenced to build a smaller home by the principles in the Not So Big House series, that’s a better place to start.
My own background in renewables and efficiency dates to the early 1980s, and when I see people building homes that could comfortably house dozens of people, many questions arise. One is: If a home of any size is to be built, how do we measure its impacts?
RMI’s Green Footstep is a good place to start, to assess ecological footprint. Running that 9,000 sf home through such an assessment, or those of Scientific Certification System’s life cycle impact systems would likely result in some discouraging figures.
Yet I look at the 1,200 sf Habitat/NREL 2005 net zero energy home in Denver, a home that is a net energy producer to the extent that the single mother of two who lives there could have driven 15,000 miles for free if she had had an electric vehicle these last three years, and I have to ask how many planets would be required if half the people in China had a stand-alone, suburban home like that. Size alone does not determine ecosystems and climate impacts. Carrying capacity and LCIA analyses do.
If one building is constructed using building science best practices, and by proper energy and water and air and moisture management is made to last hundreds of years, whereas one smaller building is built to last 50 years, then there is an interesting comparison to consider. Durability is a crucial component of sustainability. So is universal design, so that layout works for people in all stages of life and for future generations’ tastes and needs. Smaller homes that people don’t want to keep as they are can generate more severe environmental impacts than larger homes that remain unchanged over long periods of time (because they are built to last, be operated with energy bills next to nothing, and because they serve the residents’ needs and meet their desires).
(When people build these large homes, I like to joke that it is all in order: When the coasts flood some decades from now and refugees stream inland to Colorado, these prairie mansions will be ready to accommodate 20 to 30 people — and be operated as net carbon neutral! For such net-zero energy residences the challenge will not be energy, but fresh water.)
The principles and practices in this Showcase for Carbon Neutrality are applicable to homes of any size in any climate. With this HERS 0 home being publicly verified by real-time, online energy and home performance monitoring systems, the bar will be set quite high for the building industry. We already did this with our flagship project, Solar Harvest. This next project is to go one significant step further: Not only be net zero energy on a site basis, but also be a net producer, AND have all materials and methods pushed through the stringent filters of Life Cycle Impact Assessment (we were on track to hire SCS to lead this analysis). Eco-effectiveness, not eco-efficiency.
