Contractors lead deep dive into retrofits

BostonCAN recently announced its new campaign to promote deep energy retrofits of Boston’s existing buildings. What do these retrofits entail, and what are the challenges associated with them? On May 9, we hosted “A Discussion of Deep Energy Retrofits” in order to learn more. The event featured Paul Eldrenkamp, Kerry Kostinen, and Mike Duclos, contractors and energy efficiency mavens with years of experience retrofitting homes and tracking the energy savings achieved.

Boston’s Climate Goal and the Role of Retrofits

Before summarizing the event, let’s put retrofits in the context of Boston’s overall carbon neutrality goal. The Carbon Free Boston Summary Report 2019 outlines three broad strategies: increasing energy efficiency, electrification, and shifting the electric grid toward renewables. Buildings are one sector where these strategies will be applied. The report defines a deep energy retrofit as “a whole-building approach [that] improves both the building envelope—its roof, walls, windows, and doors—and replaces heating/hot water systems that currently rely on gas and oil with systems that run on increasingly zero-GHG electricity . . .” (p. 13).

Increasing Energy Efficiency with Air Sealing and Insulation

On May 9, Kostinen and Duclos showed photos of projects to “improve the building envelopes” of private homes. In a deep energy retrofit, the house’s sheathing is stripped off, air leaks are sealed, insulation values are increased, and a dedicated ventilation system is added. As Duclos demonstrated, the house then becomes more energy efficient. It is also more comfortable, with reduced drafts and cleaner air. However, retrofits are expensive: Kostinen showed examples costing $40,000 or more. In his experience, monetary return on investment is not a reasonable expectation.

According to Eldrenkamp, return on carbon investment is also an issue. Retrofitting a building requires producing materials, transporting them, and using power tools to install them. All of this releases greenhouse gases (GHG), which constitute the “embodied carbon” of the project. How long it takes for the savings in “operating carbon”—the emissions from day-to-day activities in the building— to make up for this embodied carbon depends partly on the materials used. While spray foam has a huge carbon footprint, there are actually some materials that sequester carbon. But another key factor is the project’s duration. Eldrenkamp has concluded that “we cannot do projects that last months and months” because the carbon payback period can be 75 years.     

Electrification with Heat Pumps

Eldrenkamp was more optimistic about the potential of electrification (replacing a gas or oil heating system with an electric one), now viable because of heat pumps. Per unit of energy delivered to a home, electricity is much more expensive than gas or oil, because a lot of energy is lost during generation at a fossil fueled power plant and in transmission to our homes. For the same reason, conventional electric heaters are the most carbon-intense way to heat a home. Heat pumps are different. They move heat outdoors in summer (like air conditioners) and indoors in winter (yes, there is enough heat outside then.) Heat pumps are 280% efficient on average—a unit of electrical energy used to run a pump moves almost three units of heat energy. Oil and gas heaters, on the other hand, average about 80% efficiency. With heat pumps, electric heat can be competitive in price with propane, oil, and (in some cases) gas heat systems, and it emits less than half the carbon.

These comparisons assume the current mix of power sources in the New England grid. For Eldrenkamp, greening the grid is a top priority: as the grid approaches 100% green, the GHG cost of powering a home with heat pumps approaches zero, regardless of other measures. Unfortunately, as Duclos pointed out, the United States is far behind Europe in the development of renewables.

Eldrenkamp also stressed that the climate movement needs to do a better job of tracking energy usage, before and after interventions. “If you don’t keep score,” he said, “you don’t know whether you’re winning.”


As BostonCAN mulls over what we learned, three principles stand out:

  1. We must green the grid. Although BostonCAN’s new campaign focuses on the buildings sector, the energy sector remains crucial.
  2. How we retrofit matters, not just how much or how fast. Poorly planned projects can backfire.
  3. We must track energy use. Data is knowledge, and knowledge is power.

See the entire presentation, “A Discussion of Deep Energy Retrofits,” on YouTube.