Decarbonizing our homes is challenging, but has become much easier than in the past.

With the discovery and use of plentiful fossil fuels, builders forgot lessons learned over thousands of years. People living in the northern hemisphere historically built their homes facing south to let the sun, low on the horizon, in to warm their homes in the winter, while the summer sun, higher in the sky does not need to overheat the house when there is a good roof-line overhang .  But by In the early 20th century, builders had forgotten this useful habit. Additionally, using as little fossil fuel as possible was not a high priority, so they installed a minimum of insulation, did not pay attention to air sealing, and often installed electric baseboard heating, rather than oil and gas furnaces and boilers, because it was cheap to install. But it was incredibly expansive for the user.

With energy scarcity during and after World War II, there was renewed interest in facing homes south to take advantage of the winter sun. This was called passive solar design. In 1947, Bruce Anderson published Your Solar House which showcased existing projects.

This crisis catalyzed the interest in solar.  Builders, architects, and engineers expanded experimentation with passive solar design and more.  In 1973, with government funding, the University of Delaware built “Solar One,” the first house to integrate solar photovoltaic (PV) cells and use them for both electricity and heating.  In 1974: The U.S. government passed the Solar Energy Research, Development and Demonstration Act, committing to making solar energy more viable and affordable.  President Jimmy Carter installed solar panels on the White House roof in 1979 to increase visibility to this new technology.

Oil prices dropped, and President Reagan removed the solar panels from the White House.  But “hippie builders” and others continued to experiment with facing homes south, adding more insulation, and more thermal mass to store heat for nighttime use.  In 1982, physicist William Shurcliff published a book that coined the term “Passive House,” which he used to describe the combination of passive solar and super-insulation.  However, the terms “zero-net-energy home,” (one that makes at least as much energy as it consumes, such as by having on-site solar panels) or a “zero-carbon home,” (one that does not use fossil fuels because its heating system is electric, such as an air source heat pump) had not yet been coined.

Building a new zero-carbon home is cost effective, and the Massachusetts building code comes close to requiring this standard. 

Although rehabbing an existing home to be a zero-net-energy home is expensive, many of the same techniques used to build zero-carbon homes can be used to dramatically reduce energy use, provide better comfort, and reduce utility bills in an existing home. If an existing heating system is replaced by an electric heat pump and solar panels are also installed, then the house can become a zero-net-energy home.  As grid electricity becomes less reliant on fossil fuels,  as required by Massachusetts law to become zero-carbon-emitting by 2050, all homes that switch to electric heat and appliances will become increasingly less dependent on fossil fuels.

To learn more, click here.