Net-zero energy homes possible in the nation’s icebox. Why not everywhere?
by Allen Best
If a house can be net-zero in Fraser, Colorado, then net-zero is possible anywhere. Fraser calls itself the icebox of the nation, although the icebox ain’t what it used to be. It’s gotten much warmer in recent decades, particularly on winter nights. They still get down to 30 below occasionally, though, which is why the achievement explained at the Colorado Renewable Energy Society meeting deserves mention.
Peter Ewers, an architect in Golden, spoke at the meeting last evening, explaining his work to advance net-zero energy building. First, what is net-zero? California is requiring that as of 2020 all new homes be net-zero-energy capable. Their definition of energy is electricity.
But in most of the country, three-quarters of energy comes from natural gas, for heating. Achieving net-zero is a harder, more complicated proposition than just throwing PV panels on the roof, although that’s invariably part fo the proposition. In most places, getting to net-zero involves figuring out how to site the house, to maximize solar gain, but then making sure you don’t over-heat the house in summer.
Beyond siting, the task is to ensure the building envelope is as tight as it can be, which means a lot of insulation but also means you pay attention to a lot of little things called thermal bridging. Only after you have figured out all of the above do you worry about adding renewable energy, mostly solar panels, though ground-source heat pumps can be very effective, too.
Net-zero homes sen to be mostly in the high-rent districts, created for people of a certain affluence. But Ewers and Brian Fuentes, also an architect specializing in net-zero homes, indicated they think that net-zero energy homes aren’t that far from the mainstream, especially in multifamily building projects (where shared walls can reduce heat loss).
Why does this matter? Ed Mazria of Architecture 2030 puts it very well. Given how much our greenhouse gas emissions result from buildings, we simply have to do a better job of our buildings. It’s not just a matter of replacing coal-fired power plants. It’s transportation, of course, but buildings, which are responsible for something like 35 or 40 percent of all of our energy use.
But are we heading in the right direction of this building transformation. Building codes are inching forward with their requirements for energy efficiency. But what about all the skyscraper sheathed in glass? In June, touring Toronto and Vancouver, I was struck by how many of the tall buildings in these two cities, both of which seek to burnish their sustainability credentials, are encased in glass.
Glass, under the best of circumstances is not a good insulator. You can hit R-60 insulation in our attic pretty easily, but an old-fashioned window (such as my house) has just a R-1 value. But even high-tech (adn expensive) windows n net-zero energy homes have only R-12.5.
Recently, The Denver Post reported about a 12-story luxury residential tower on the city’s western margins, near Sloan’s Lake. Trevor Hines, chief executive of NAVA Real Estate Development, told the newspaper that 70 percent of the building’s skin will be glass.