Tompkins Weekly     6-20-16

By Jon Harrod

I own a company that installs insulation and energy-efficient heating and cooling systems. While most of our projects involve existing buildings, we also work on new homes.

Building a house is an act of imagining a personal future. I’ve heard our clients talk about the living room where their yet-to-be-conceived children will play or the bedroom they’ll use when they no longer want to climb stairs. Houses are also expressions of our larger social and environmental vision. The longevity of houses requires us to think ahead and build in a way that will make sense in decades to come.

To avoid the worst consequences of climate change, we must curtail our use of fossil fuels and keep most known reserves of gas, oil and coal in the ground. This transition needs to occur in the next 15 years. Knowing this, does it make sense to build houses that rely on fossil fuels for heating, cooking and hot water? Does it make sense to invest in energy systems that will soon need to be abandoned? Keep in mind that we’re talking not just about a furnace and ductwork, but the pipelines, storage and transportation infrastructure, and extraction wells that support it.

Recent developments have converged to make fossil-free homes not just possible, but affordable. We’ve been privileged to work with visionary clients and builders who have helped demonstrate that this approach is ready for the mainstream.

Improvements to insulation, windows and airtightness have dramatically reduced heating and cooling requirements, allowing for simpler, smaller mechanical systems. This approach is taken to an extreme in “passive houses” like those in the Third Neighborhood at EcoVillage at Ithaca. With 12-inch thick walls, triple pane windows, and 24 inches of attic insulation, these homes need no central heating system.

Winter sunlight, plus the heat given off by human bodies, lights and appliances, provides much of these houses’ heating requirements. Electric baseboards provide supplemental heat in cold, cloudy weather. With modest solar arrays, these houses can produce as much electricity as they consume.

Modern heat pumps provide another way to heat without on-site fossil fuels. Electric resistance heaters, like the baseboards mentioned above, are 100 percent efficient at converting electricity into heat. For each unit of electricity consumed, one unit of heat is produced. Heat pumps, as their name suggests, use electricity to move heat into the house in winter and out in summer, allowing them to deliver two to four units of heat for each unit of electricity consumed.

Ground-source, or geothermal, heat pumps circulate fluids through buried tubing, taking advantage of relatively constant soil temperatures. In the winter, they extract heat from the soil. In the summer, they pump unwanted heat out of the house, either into a hot water tank or back into the earth.

Air-source heat pumps are another option for our region. They can be thought of as reversible air conditioners. In the summer, they extract heat (and humidity) from the living space and dump it into the outdoor air. In the winter, they concentrate heat from the cold outdoor air and deliver it to the living space. Air-source heat pumps are less efficient than ground-source systems (delivering about two units of heat for each unit of electricity, versus three to four for ground-source systems), but are cheaper to install. Small, well-insulated houses are good candidates for electric resistance or air-source heat pumps; for larger houses, the expense of a ground-source system is often justified.

Even at current low prices for natural gas and propane, the lifecycle cost of a fossil-free system (including installation, fuel, maintenance and meter charges) can be lower than that of a fossil fuel furnace or boiler. Fossil-free heating also has a smaller carbon footprint, even when the electricity used comes entirely from the grid. More than half our regional electric supply comes from low-carbon sources: solar, wind, hydro and nuclear. As renewables continue to boom, grid emissions will decline further.

Of course, reducing fossil fuel use isn’t enough; we need to eliminate it entirely. Drops in the prices of solar panels and innovations in siting and finance, including community solar farms and pay-as-you-go contracts, are making solar easier and more affordable.

The formula for a zero-energy, fossil-free home goes something like this: build a tight, well-insulated envelope, install an efficient heating system matched to the building’s down-sized requirements and install enough solar panels to zero out the energy use. Want zero-emission transportation as well? Add an electric car and more solar panels.

The approach is simple, scalable and it works. Which is good, because we don’t have time to waste. In the next 15 years, we need to transition all our housing stock, new and existing homes, away from fossil fuels. Every home built fossil-free from the start is one less we will need to retrofit later.

Jon Harrod is a City of Ithaca resident.