I get the design part, but is it really sustainable?
We have always admired the tough, gutsy work of Olson Kundig; when we gave them our first Best of Green award I called it "low tech and low impact." But I have not shown much of it lately; they have often been big second homes out in the country, which we tend to avoid. However one of their recent projects just won an AIA COTE (Committee on the Environment) Top Ten award for "setting the standard in design and sustainability." It's a big second home in the country.
Set in California’s harsh Mojave Desert, Sawmill offers a new model for the sustainable single-family home. The client brief called for a self-sufficient home that maximized connection between architecture and nature, and between family members inside. The 5,200 SF concrete block, steel and glass home is designed to stand up to the severe climate of the fire-prone Tehachapi Mountains. Demonstrating that high design can also be high performance, Sawmill is a net-zero home that operates completely off the grid.
There is a lot to unpack here. Whether it is a new model for a sustainable home, whether it is truly self-sufficient (people have to eat), and whether it is really net-zero (does that mean anything when you are off-grid?) are all questionable, but let's just revel in a gorgeous bit of Olson Kundig first.
Like much of Tom Kundig's work, there is a lot of salvaged and recycled materials used. Concrete Masonry Units (CMU) have a far lower embodied carbon than poured concrete. The blocks often look utilitarian but they can have their own beauty (I am surrounded by them in my office here because I like the look of them). They leave it exposed- an inexpensive, durable finish.
Being in the desert, there are the kind of diurnal swings in temperature that make thermal mass useful, so it has lots of concrete and masonry to hold the heat. Cooling is mostly done passively by catching the canyon winds. A ground source heat pump warms or cools the radiant floor and an 8.4 kW array with batteries provides all the power that's needed.
The Jury says "This is an excellent example of the potential beauty in a holistic passive approach. The house is completely off-grid with a light environmental footprint." It's too nice a house to complain that 5200 square feet of concrete construction does not have a light environmental footprint. But really, just because something is off grid doesn't make it green.
It's off-pipe too, with a well supplying water that's pumped up to a water tower. They don't bother collecting rainwater because there is so little of it and call that a virtue too, noting that "it made more sense to return rainwater to the ground to recharge the water table rather than build a site cistern that would be used only sporadically." They even make what looks like a bog-standard septic tank and leach field sound sexy and environmental because it "minimizes pollution by utilizing the natural filtering processes of the soil" and "replenishes the regional watershed." The jury bought this line totally, noting:
The team is commended for their site-specific analysis, as evidenced by the decision to let rainwater recharge the water table rather than collect it. If a single-family dwelling is to be built in a desert climate, this is how to do it.
This makes no sense. If the well water is returned to the water table through the septic tank, then the collected water would be too, it doesn't just disappear. Really, whoever wrote the Olson Kundig submission deserves an award for even turning the fact that they didn't do something into an environmental plus.
COTE used to stick pretty close to LEED criteria but Wellness is an increasing concern. Buttons pushed here: It maximizes connections between inside and out; "Strategic placement of glazing frames views of the surrounding mountains, promoting health by enticing occupants to take advantage of nearby hiking trails."
Then there are the healthy materials "selected to promote indoor air quality, wellness and health. The interior palette employs natural materials such as reclaimed wood, oiled steel plate, and ground fly ash concrete with earth-toned aggregate."
The EPA has concluded that fly ash concrete is safe but there are many skeptics. Fly Ash is toxic waste containing "numerous hazardous substances including heavy metals such as mercury, arsenic, and cadmium." The industry claims that it is "encapsulated" when it is in concrete but others are not so sure. On Green Building Advisor, Robert Riversong writes:
Although recycling fly ash into building materials may seem to be a viable alternative to disposing fly ash into waste dumps where it can leach into the soil, using a hazardous material in building products is actually waste disposal masquerading as recycling. A fundamental rule of recycling is similar to that of medicine, that is, "First, do not harm." However, the use of fly ash in construction materials is far from safe.
The use of fly ash significantly reduces the need for Portland cement and the carbon footprint of the concrete. Notwithstanding Riversong, the consensus is that it is probably safe when mixed in concrete. But I would hardly tout it in the Wellness section.
There is no question that Olson Kundig has designed a beautiful house, and written a brilliant award submission. But is it really setting the standard in sustainability? I don't think so.
Thousands of people have been living off-grid in the desert for decades, usually sucking propane for heating and power. Modern technologies like efficient solar panels, big battery packs, LED lighting and heat pumps have made it possible to live better electrically off-grid with zero carbon, but it is not with zero impact. That is a lot of hardware, needed to power a lot of house. If this is, as COTE suggests, "a new model for the sustainable single-family home" then we are in a lot of trouble.