During the schematic design phase, the team investigated several levels of thermal performance. Wall and roof system options were evaluated based on expected energy performance, initial construction cost and long-term operating costs. Three alternatives for wall construction were analyzed for performance and capital and operating costs.
• Leave the existing exterior brick in place and insulating from the inside by using spray foam behind the existing veneer.
• Demolish the existing exterior brick and insulate from the outside using rigid foam, plus installing a new metal panel rain screen.
• Demolish the existing, exterior brick and insulate from the outside using rigid foam, plus installing a new ventilated brick-veneer rain screen.
The design team investigated each of these wall options with multiple levels of insulation. Comparing the potential return on investment for each of the options, it was determined that the optimum value was achieved by demolishing the existing brick and installing 4” of polyisocyanurate board insulation under a combined brick-veneer and metal-panel rain screen wall assembly.
In addition to the high thermal performance achieved by the wall assembly, a combined air/moisture/vapor barrier was applied continuously over the entire building envelope. This spray-applied barrier combined with membrane layers, used at corners and non-adhesive surfaces, was specifically detailed to ensure that the resulting building would be one of the tightest commercial buildings in Vermont. In final blower door testing the building reached a result of 0.11 cfm50/square foot exterior surface area, which put this building in the top 10 percent of buildings tested in Vermont.
Retrofit - 3" new EPS insulation
New - 4" EPS insulation
Slab edge assembly
4" EPS to 36" deep
Slab edge R-value
Above grade wall assembly
4" polyiso rigid insulation
Above grade wall R-value
Retrofit - 6" new polyiso and 4.5" existing polyiso
New - 9" polyiso
Windows and Doors
Accurate Dorwin triple pane windows. Wasco skylights in the offices U 0.1, SHGC 0.54, VT 0.5
Average window U-factor
Solar Heat Gain Coefficient
Visible Light Transmittance
Space heating - Manufacturer & Model
Open-loop ground source shallow aquifer with plate and frame heat exchangers and console heat pumps.
Domestic hot water - Manufacturer & Model
Solar Thermal ~60% of the load, propane for the remaining
Ventilation - Manufacturer & Model
Thermotech enthalpy wheel -70% effective
Lighting Manufacturer and Model
High-efficiency florescent and LED lamps throughout, open-loop daylight harvesting in all third-floor conference and courtrooms and north-facing offices, dual switching in all other rooms, Lutron GRAFIK Eye with EcoSystems.
Mechanical Equipment Installation Details and Comments
Full building mechanical commissioning by Cx Associates.