Natural gas, primarily used for building heating, constitutes 16% of the greenhouse gas emissions in the City of Seattle. As I noted in a previous post, a city seeking carbon neutrality can shut down the natural gas distribution system, bringing these carbon emissions to zero in one fell swoop. Building heat and hot water can be provided by several energy sources, including electricity.
But where will all the electricity to replace natural gas come from? In Seattle, we are blessed with carbon-free hydropower. But we have a limited supply, and any additional electricity would need to be purchased on the open market or come from new generation. However, the cheapest electron is the one you never need to generate, due to energy efficiency.
Passivhaus is an emerging standard for buildings that uses up to 90 percent less energy than conventional construction; a maximum of 4.75 kBTUs/square foot/year for heating. The Passivhaus standard uses thick insulation and high-performance windows to prevent heat losses, and recovers heat from exhausted air through a Heat Recovery Ventilator (HRV). A 300 square foot Passivhaus, the Mini-B, is on display at the Phinney Neighborhood Center in Seattle.
By building new construction to Passivhaus standards and developing cost-effective Passivhaus remodeling strategies, the electric demand for building heating can be vastly reduced. Which will leave the hydropower electricity available for other uses when we move away from fossil fuels in buildings.