New houses with net-zero energy use are getting to be increasingly common. On the other hand, New England is full of old houses that really should be preserved for their historic value. We rarely see a house that fits into both groups. There is a reason for that. A “deep energy retrofit” to bring a house to net-zero energy use while preserving historic value is not easy.
Kent Hicks, owner of Kent Hicks Construction in West Chesterfield, Massachusetts has made a study of the problem of deep energy retrofits in historic buildings. This is quite literally true, as he had one employee spend six months just researching insulation to find out what has the best results, with the least environmental impact, for given situations.
Hicks’ company recently completed a job that shows what is possible when the deep energy retrofit is combined with building restoration. The work may have produced the oldest electrified house with net-zero energy usage in the United States.
The house, whose owners wish to remain anonymous, is in a historic neighborhood of Deerfield, Massachusetts. It is not really known when it was built, but there were alterations made to it sometime in the 1730s, so perhaps it was built in the late 1720s.
The original plan was to start with an energy retrofit on an apartment in the barn on the property, which had been built during the 19th century. Then the owners could live in that while the work on the house was being done. As work on the barn progressed, however, it became clear that the condition of the barn was not good enough to make that task practical. Since it was clear that old lumber would have to be found for parts of the house restoration, it was decided to deconstruct the barn, putting its timbers aside.
Catherine Truman Architects, which was working on the project, managed to find a barn that was nearly the same size and shape. That barn was also deconstructed, with its timbers brought to Deerfield to build a replacement barn. When that was in place, it was set up to use net-zero energy and the owners moved in.
The barn roof had a 12-kilowatt photovoltaic system installed, to supply all needed energy for both buildings. Since both buildings would be highly efficient, the solar system could provide heat as well as lighting and power for appliances.
We might mention that the present barn sits on a concrete slab and has a polished concrete floor. The long-lasting quality of this material can make it environmentally attractive to use, despite its high embodied energy. An article on this appeared in the October, 2017 issue of Green Energy Times (bit.ly/GET-concrete-house).
Once the owners were comfortably set in the new quarters, work could begin on the old house. The three-century-old building’s problems were very much in evidence. Many of its timbers were in direct contact with the soil. Nevertheless, Hicks could easily see that while significant parts of the wood were rotten on one side, the other side was often both sound and capable of being rendered beautiful for re-use. And these could be polished to have the patinas of aged wood, cut from forests unlike nearly any we have left today.
The building was taken down to the frame. New wiring and plumbing was installed. As the walls were rebuilt, they were covered on the outside by a layer of insulation consisting of polyisocyanurate, with foil on both sides, and this was covered by reused siding. The envelope had to be sealed as well as possible at the windows and doors, and care has to be taken that any intruding moisture ducted back outdoors, which entailed use of an inner layer of polyisocyanurate insulation. Hicks explained the importance of this, “As long as we can keep the shell dry, we are golden.”
Inside, there is additional insulation of cellulose. Hicks said this has an environmental impact that is about as low as you can get. The final measurement is R-40 for the walls and R-60 for the roof.
Windows were replaced with new ones that were not as efficient as some that are available today. This was to preserve their appearance. If they had the same number of lites in each, they appeared too deep, when compared to the original glazing.
The ventilation system Hicks chose for this project is from Zehnder, a German company. He told us, “The ventilation system is inexpensive insurance that your family is breathing fresh air.” Simple vents in the bathroom and kitchen are good enough for neither heating nor health.
Because the house is a restoration, as well as a retrofit, the project was not fitted with the usual mini-splits. The Mitsubishi heat pumps were instead fitted to a ducted system to avoid having clearly visible heating units inside the house.
In the end, the grid-tied PV system is enough to cover the energy needs of both the barn and the house. Performance is expected to be very like that of newer net-zero buildings. When I asked about a backup for the heat, Hicks told me there was none, adding, “We built a passive house a couple years ago, and at 10 below, the heat was shut off for two days as an experiment. The temperature went down two degrees.”
Hicks believes this house is probably the oldest in the country that uses net-zero energy. Nevertheless, it remains true to its historic presence. “Buildings are really important to the fabric of the community,” Hicks said. “This is what we do well. If you look at the Deerfield house you would probably not realize it was net-zero.”