Addressing energy use in existing buildings is essential to combating climate change. The renovation and adaptive reuse of Dartmouth College’s Anonymous Hall offers a blueprint for transforming both building use and energy use to meet today’s needs.
Dartmouth College’s Anonymous Hall uses five highly effective strategies to reduce the building’s energy footprint within a tight construction budget. The renovation reuses the concrete and steel structure of the original 1962 Dana Hall Biomedical Library building, implements highly insulating walls and roof, makes use of ultra-high-performance glazing, uses an efficient space-saving mechanical system and incorporates a photovoltaic shading canopy to reduce the energy used in construction and reduce predicted energy use by 90% compared to baseline.
Dana Hall was originally constructed in 1962 as a brick clad cast-in-place two story building. In 1971, a brick clad steel addition added a floor, a penthouse and cantilevered projections. Consistent with construction of the time, the building envelope incorporated materials we know now to be unhealthy and had dismal thermal performance. The building systems were woefully out-of-date energy hogs and the building was not truly accessible. However, the structure built to support stacks of books was sound and the former library’s column grid flexible. Additionally, its location in the campus helped to frame and form outdoor spaces that could be remade as campus assets. Dana Hall had potential.
The design strategically adds a new combination shear-core and braced-frame lateral system and attaches a steel-framed addition at the south. These interventions bring the structure up to modern codes and allow for the reprogramming of the building. The reuse of existing structure reduced the amount of new high embodied energy materials like steel and concrete used in construction. The project salvaged over 20,000 cubic feet of concrete, reducing CO2 emissions by at least 1237 metric tons based on NRMCA estimates for carbon emissions from concrete alone. The salvaged steel as well as the reduced demolition and construction activities associated with the structure further reduce energy demand associated with the building.
Insulation is tremendously cost-effective as an energy efficiency measure. Supporting a light terracotta rainscreen facade, the lightweight stud framed exterior walls combine 6″ of continuous dual density stone wool insulation with 5 1/2″ of stone wool batt in the cavities to provide an effective U-Value of 0.033, double code required thermal resistance. The roof system provides a minimum R-60 continuous insulation with an average effective U-value of 0.014 or almost triple code required thermal resistance. Continuity in the envelope is maintained by projecting the wall beyond the slabs, using structural thermal breaks at projections and incorporating an additional outboard vapor permeable water barrier to protect the integrity of the continuous insulation.
The glazing strategy for Anonymous Hall combines careful proportions, locations, recesses, canopies and topography with advanced technologies. The triple-glazed punched windows on three sides of the building are tall and set deep in the wall with two low-E coatings to minimize solar heat gain and winter heat loss. Continuous curtainwall glazing at the ground floor is under cover from the floor above. The penthouse is shaded by the photovoltaic canopy.
The new south addition is clad in an advanced fully-glazed curtainwall facade system designed with passive measures and active controls to produce a thermally efficient envelope responsive to its environment. The glass facade is made of 2″ triple-glazed insulated units and high-performance vacuum insulated glass panels arranged in response to orientation and to maintain visual connections to the landscape beyond. Both units have integral expanded metal mesh shading and are silicone structurally glazed to a thermally-improved aluminum curtainwall frame. Each component is optimized for thermal performance with a whole system U-value of 0.17, more than four times more efficient than the latest energy code requirement. The system also pairs automated vent windows with daylight-responsive shades to allow simultaneous daylight control and natural ventilation.
Energy Efficient Mechanical Systems
Served by central chilled water and hot water loops, a highly responsive radiant heating and cooling system with dedicated outside air and fan assisted natural ventilation fits to the tight constraints of the salvaged structure and to a conducive program with a high percentage of offices and analytical labs. Through individual controls, the system provides ventilation air in volumes and to spaces only as needed to dramatically reduce the size of air handling equipment and the energy it consumes. Additionally, manual and automated windows allow natural ventilation when outside conditions permit to further reduce energy use. Finally, the fenestrations and glazing are carefully calibrated to the available radiant panel cooling to eliminate the need for expensive and energy consuming supplemental systems.
The small penthouse at the roof of the existing building allow for a terrace roof garden with a solar canopy above. Covering nearly the full existing roof area, the 67kw photovoltaic panel canopy reduces the building’s predicted energy use index (pEUI) from 25 to 10 kBtu/sf/yr.