Mundane but essential; energy-efficient HVAC for Town Hall
For years Town Hall staff have commented and, from time to time, complained about the heating and air conditioning in the Town Hall building. In the old brick section there can be frost on one wall of the Police Department unless electric heaters are plugged in to supplement the heating. Come summer, that section is hot, stuffy, and airless. In the white clapboard wing of Town Hall, the Listers shiver in their office in winter while the Town Clerk’s office is cosy.
The root cause is an inadequate and poorly-designed HVAC system (Heating, Ventilation, Air Conditioning) that was cobbled together to save money. There are only two thermostats for the whole building. The Listers do not have a thermostat, and on sunny days their office may run 10 degrees hotter than the other offices. In winter the choice is either plug in electric heaters to keep the Listers comfortable, or turn up the thermostat to warm that office and overheat the Clerk’s office. A similar situation bedevils the old brick section. And overall, air exchange in the building is almost non-existent and certainly not up to code.
HVAC systems do not last forever, and this one is nearing the end of its life. One of the two air conditioners has been broken for some time, and the propane furnaces are 19 years old. In 2020 the Town began the process of selecting a contractor to design and install a new system, one that would be consistent with the Town Plan goals of reducing energy costs, lowering greenhouse gas emissions, and decreasing reliance on fossil fuel.
The Selectboard, in consultation with Intermunicipal Regional Energy Coordinator Geoff Martin, went through a competitive process to select Energy Efficiency Investments (EEI) as the contractor. EEI is a locally owned company that provides energy services to clients in northern New England. They have a track record with municipalities including Addison, VT, and the City of Manchester, NH, and with schools including Bennington, VT, and Keene, NH.
EEI drafted a series of proposals in 2021 and 2022. The Selectboard balked at one costing $382,000 and at another for $282,000. After further input, both from Geoff and the Town Energy Committee, they returned a third time with a proposal costing $227,215. The price was brought down by removing a centralized, remotely driven, integrated controller system and retaining the Town’s existing backup generator instead of buying a new one, plus other changes. The project qualifies for rebates from Efficiency Vermont and Green Mountain Power that are not figured into the final quote. A majority of the Selectboard approved this proposal on September 19th, with one member opposed.
What Town Hall will get for this price includes comfortable offices year-round thanks to advanced heat pump technology with a tried-and-true model from a leading manufacturer. Each office will have its own heat pump with an individually programmable control to regulate its temperature and turn down the heat when the room is not in use. In summer the heat pumps will also cool and dehumidify indoor air, eliminating the need to purchase new air conditioner units.
Heat pumps are extremely efficient. Typically, with 1kW of electrical energy put in, a heat pump will put out around 4kW of heat energy. This efficiency is represented as a COP (Coefficient of Performance), and a good heat pump, operated correctly, will have a COP of around 4. When outdoor air temperatures drop to minus 14 degrees F, the heat pump efficiency drops to a break-even point at which heat energy captured from the air equals the electrical energy input to the unit.
Because heat pumps are electric, a backup heat source is necessary. The two aging furnaces will be replaced with a single propane furnace that will only be fired up if there is a power outage. It will mostly function to provide air exchange through existing ductwork, working in concert with an Energy Recovery Ventilator (ERV) that will save energy by transferring heat between warm outgoing air and cold incoming air. The ERV can also directly warm incoming winter air as necessary. The building will finally have proper, healthy air exchange, something we value highly now that we have the experience of living with COVID.
As mentioned, the existing backup generator will be wired into the new system. While it can’t supply enough power to run the heat pumps, it is needed to keep the lights on, because Town Hall is listed as an emergency shelter.
EEI will be the design engineer and overseer of subcontractors and will perform quality control of the installations. They will also train Town Hall staff in operating the climate controls of the heat pumps. Lastly they will “commission” the whole system, which means balancing the air flow throughout the building to deliver even ventilation and heat distribution.
One more thing: the Selectboard voted unanimously to order energy-saving “Window Dresser” window inserts for all the Town Hall windows. The inserts double the insulating value of a window and cut down on drafts caused by convection currents. They also block air infiltration from poorly sealed glass or gaps between the window and frame.
While it is not as glamorous as some other approaches, numerous experts point to energy efficiency as the cleanest, most cost-effective means to reduce emissions and combat climate change.
Photo credit: Li Shen