By Walker Wells
Multi-family housing is seeing a major shift toward all-electric design. Greenhouse gas commitments, renewable portfolio standards and decreased cost for wind and solar energy are causing the electrons on the grid to become increasingly carbon-free or renewable. As the grid cleans up the source, it is important to address the end users of energy – appliances, water heaters and HVAC – rather than locking in years of fossil fuel use.
Affordable housing developers are among the leaders in this transition. The shift to all-electric buildings is a “back to the future” moment, as modern, all-electric homes were a major trend of the 1970s. The technology at that time was not energy efficient though, as both space heating and water heating relied on resistance technology. With rising electricity costs, many developers shifted to gas for cooking, clothes dryers, water heating and space heating, with electricity still used for lighting, fans, air conditioning, washing machines, and dishwashers.
This mixed fuel approach remains common, but trends are shifting quickly. Multiple California cities have adopted energy “reach codes” that either require all-electric design or place additional requirements on mixed fuel building, like installing the electric circuitry even if gas appliances are provided.
Single-family homes can make the switch fairly painlessly, without returning to yesterday’s outdated technology. Highly efficient heat pumps are already the preferred approach for most space heating and cooling. In most cases the biggest hurdle is adjusting to induction cooktops. Heat pump water heaters fit into the same spaces as conventional units.
Multi-family design is a bit trickier, particularly in the hot water system design. Providing each apartment with a heat pump water heater is a common option. But there are considerations. The units require make up air, so it needs to be on an exterior wall, and in the process of creating hot water they generate cold air.
To benefit from the ability to share system capacity among the dwelling units, another approach is to install three or four water heating units in a utility room on each floor, combined with a recirculating loop that serves multiple apartments. Centralized heat pump hot water systems, as a replacement for a central boiler, represent the most significant shift in design practice. Storage tanks that allow for water heating to occur when renewable energy is plentiful and electric rates are lowest, can operate as a “thermal battery.”
A number of affordable housing developers are pursuing all-electric designs. Why are they going all electric? Partly out of commitments to innovation, green building and climate action. Partly due to benefits associated with all-electric design.
Residents benefit from eliminating sources of combustion and the associated carbon monoxide from the living environment. The air quality benefits are especially valuable to children that struggle with asthma or other respiratory issues. Electric appliances can talk over wifi networks with energy management systems to reduce demand during peak periods and reduce utility costs for residents.
Building developers avoid the cost of running gas lines and providing meters. The broader community benefits from reduction in the release of oxides of nitrogen, a component of smog. Over time the greenhouse gas emissions associated with the project decrease as the grid gets cleaner. In areas with access to 100% renewable energy, through the utility or a community choice aggregation, building operation can be carbon-neutral, with photovoltaic panels reducing energy costs and pouring additional clean electrons onto the grid.
The inherent qualities of multi-family construction – smaller units, reduced energy loss through exterior walls, in-fill development at densities that can support walking, biking, transit use and mixed use development – further augment greenhouse gas reductions in building operations.
The shift to carbon-free sources of energy, in tandem with efficient and integrated end uses is essential, whether it is to comply with next generation building codes, support local or regional climate action plans, or to contribute to meeting the commitments of the Paris Climate Agreement. By being able to literally plug in to clean energy, all-electric buildings are like messengers from the future decarbonized built environment and low-carbon economy.
Walker Wells is a Principal at Raimi + Associates, a mission-driven urban planning and sustainability consultancy.