CRES Jefferson County Chapter
Architecture defines our lives in many ways, affecting our mood, our wallet, and our health. Perhaps more importantly as a society we need to succeed in reducing the carbon footprint of our buildings to bring it in line with a livable climate.
On August 25 the Jefferson County chapter of the Colorado Renewable Energy Society invited two architects — Peter Ewers from Boulder and Brian Fuentes from Boulder — on the subject of green architecture. We’ll limit ourselves here to the presentation by Peter Ewers and will feature Brian Fuentes next month.
Peter Ewers, AIA, LEED AP BD+C, has designed dozens of sustainable homes, commercial buildings, two net-zero-energy homes, and several net-zero-energy-ready homes. Over the years he’s become a proponent of the solar PV powered all electric home.
As Ewers lays it out, the process of designing a net zero home is quite straightforward. It all starts with: 1) orienting the building toward the sun to optimize heat gain, 2) creating an extremely tight building envelope, 3) designing a heating and cooling systems to match the needs, and 4) creating power using geothermal or photovoltaic solar panels.
But there are obstacles. Perhaps the main one is that the architect has to convince his clients that the extra effort and initially higher expense is worth sticking with the concept. Ewers jokes that the Rocky Mountains are sometimes “on the wrong side.” Everyone wants mountain views, alas, large windows will let too much heat escape.
South facing windows are key, as long as you plan for shading overhangs to protect from overheating. A lesser known method, especially for net zero homes in harsher climates is designing to get substantial thermal mass inside — such as a room dividing stone wall which will heat up and then slowly radiate that heat back.
As for the building envelope much has been learned about how to keep the warmth inside but it remains tricky: thermal bridges let heat escape where walls are penetrated, joists meet, or pipes and cables are routed.
That’s were insulation comes in, and for net zero, builders must pull out all stops. The weakest and most expensive links are the windows, and there isn’t yet a lot of choice for triple pane Argon filled windows that meet top criteria. But for insulating below the slab, the walls below and above the grade as well as the roof there are many options, including spray foam, fiberglass batts, riding, and double layered gypsum board.
As the Russian proverb says: Trust but verify. After all the insulation is in place but before the outside walls are finished Ewers administers a blower-door test to pinpoint anyway points, as it’s much easier to fix heat leaks now — whether the home ‘works’ depends on getting really close to perfection.
The heating and cooling systems play a big role, bolstered by passive solar gains and careful shading — the latter not an easy taks as Colorado’s intense winter sun blazes in below protruding shades designed for summer when the sun stands much higher.
Firing up a masonry heater embedded in a large inside stone wall once in the morning can heat the home for most of the day, but even a single wood pellet stove may suffice as the single active heat source.
Another way to provide both heat and cooling is an electric ground source heat pump, which geothermally uses the constant temperature of the earth as the exchange medium instead of the outside air temperature. Ewers considers GSHP as the best option, despite the cost, which at present is lessened substantially by a 30% federal tax rebate.
Price is again an issue when selecting an evaporative cooler but the top models really do deliver.
A decade ago Ewers was still installing solar hot water systems but changing technology – and changing cost – now has him take a different route: where a $7500 solar hot water system can only cover 75% of the need, today a new breed of heat pump water heaters from Siebel or GE, paired with additional solar PV, deliver 100% of the water for $2000 less for a virtually maintenance free operation.
The final net zero element is power generation, which is where solar photovoltaics shines. It turns out that in Colorado a slight eastern orientation of the panels is best due to afternoon clouds, but even if the panels can’t be aligned perfectly a 90 degree deviation still works well.
The big caveat, however, remains the higher up front cost for a net zero design, as well as life style choices of the clients which may overrule a perfect design. Panoramic windows in the energetically wrong place or an always-on hot tub will make net zero impossible; however, it is often possible to at least meet near zero specification.
But with the right attitude, concludes Peter Ewers, “net zero energy buildings for residences and small commercial are easily within reach.” After all we’re simply talking about thicker walls, better insulation, passive solar orientation, efficient heating and cooling systems, and on-site power generation.
Harder than your average cookie-cutter home designed to maximize the developer’s profit, but not that hard. And unlike the latter, a net (or even near) zero home will provide minimal maintenance cost with maximum comfort, while bringing its ecological and climate footprint way down. An architectural practice that needs spreading.