Originally completed in 1908, Unity Temple is one of Frank Lloyd Wright’s greatest works and one of the world’s most important 20th Century buildings. It is a National Historic Landmark and one of the ten “Key Works of Modern Architecture by Frank Lloyd Wright” nominated to the World Heritage list. It was a featured work in the 1910 Wasmuth Portfolio which profoundly impacted contemporary European architects, giving birth to modern architecture.
The $25M restoration encompassed every aspect of the building and returns this internationally significant work of architecture to its original appearance while giving it new life to successfully serve its original congregation and the thousands of tourists who come from all over the world to see it.
The project had numerous challenges, but the design and construction team spent nearly a year in research and development of treatment strategies that allowed for one of the most comprehensive and authentic restorations of a Wright building completed anywhere. The final photography only gives a hint at this truly transformational intervention that must be experienced in person.
Main components included:
• Complete restoration of the concrete exterior. Matching of 1970s shotcrete was particularly challenging.
• Complete restoration of all interior surfaces using original exposed sand plaster and extremely thin paints that fully replicate Wright’s beautifully soft interiors.
• All original oak trim was documented, removed, cleaned, and reinstalled in its original locations.
• All new code compliant MEP upgrades including new conduit routed into the concrete.
• All art glass was documented, removed, restored and reinstalled.
Prior to the restoration Unity Temple only had heat via radiators. A nearly yearlong study of the environmental behavior of the building recommended that a comprehensive HVAC climate management system be installed to help control temperature and humidity. This would not only better protect this historic structure but also provide a more comfortable interior environment for the occupants. A primary goal was to minimize the energy impact of adding this HVAC climate management system into the building.
Due to the nature of the historic building materials which could not be changed (uninsulated concrete walls and single-pane glazed art glass windows), the only opportunity to enhance the envelope performance was through adding roof insulation and insulated glass (IG) skylights. New roof insulation met or exceeded energy code requirements and the skylights were also improved with IG Units that exceeded energy code. This resulted in the best envelope thermal performance possible given the limitations of the material realities of this historic structure.
One area where significant sustainable practices could be implemented was with the lighting and HVAC systems. All historic lighting was converted to dimmer controlled LED lamping and any new supplemental lighting was high efficiency LED or fluorescent. This not only improved lighting levels throughout the building but also significantly reduced the energy use associated with lighting the building.
For the HVAC system, the solid concrete construction limited the choice of system to a distributed air handling system served by chilled and hot water allowing simultaneous temperature and humidity control. High efficacy motors with variable frequency drives were used throughout the systems whenever possible, using variable pump and variable airflow strategies to best manage the environmental needs of the spaces. Ventilation for the building is provided by energy recovery style make-up air units that recover waste heat from exhaust air and also CO2 demand control ventilation that only brings in fresh air when the interior air quality demands.
A heat recovery modular chiller complete with variable speed compressors provided the production of all chilled water, primary hot water, and domestic hot water except for the kitchen. A high efficiency boiler provides supplemental heating for hot water. A HW reset schedule maintains heating hot water at the lowest possible level to still provide any required supplemental heating.
The heat recovery chiller is connected to a ground loop heat exchanger to provide the most efficient operation possible. This loop field consists of nine 500 feet deep Rygan heat exchangers offering highly efficient heat transfer to the adjacent ground with a manufacturer reported increased performance of up to 200% of a standard U-Bend style ground heat exchanger.
A building automation system helps to ensure proper operation of the systems and maximizes the opportunities for enhanced system performance and energy conservation.
The net effect of the increased envelope performance and reduced interior lighting loads is a properly sized and efficient HVAC system capable of meeting the needs of the occupants and also the unique historic fabric of the building.
Unlike with a new building, trying to quantify and compare energy and carbon reduction for the restoration of Unity Temple with standard metrics such as Energy Star Target Finder or the Architecture 2030 Challenge Targets is very challenging. Unity Temple is a National Historic Landmark. It was built as an uninsulated solid concrete building with single pane metal framed art glass and single glazed skylights. It had heating only with no forced ventilation or air conditioning and poorly lit spaces using historic fixtures with low wattage bulbs. The restored building envelope has roof insulation, insulated glass skylights, and restored metal frame art glass windows. Using storm windows for the art glass was studied, but the ROI and the visual impact resulted in this option being rejected. All non-art glass windows have IG units. The solid concrete walls are exposed on the exterior and finished with a decorative plaster and paint on the interior offering no opportunity for insulating the walls. All historic lighting was changed to dimmable LED lamping, as were the few new additional fixtures. Furthermore, to help protect the historic building fabric, a fundamental goal was to install a HVAC system that could simultaneously control temperature and relative humidity within a narrower range of operation. This type of HVAC is more energy intensive since it is based on the process needs of the building rather than the comfort of the building occupants.
Understanding that adding systems that would improve human comfort and the longevity of the historic materials would also be more energy intensive then the original configuration of the building, strategies were sought to minimize the energy increase of the restored building including:
- Improving building envelope performance within the high standards of restoration required.
o Adding better than code compliant roof insulation above the roof deck and replacement of large single pane metal framed skylights with new thermally broken, insulated glass skylights.
o All art glass metal framed windows were removed and restored which improved overall air infiltration into the building.
- Improving the lighting energy intensity by using LED lamped fixtures throughout the building reduced energy consumption while increasing illumination levels and reducing maintenance.
- Adding a process level environmental management system that includes:
o A geothermal based chilled/hot water system that provides simultaneous heating and cooling with heat recovery mode using waste energy recovery to enhance efficiency.
o Variable speed pumping that uses minimal pump energy to provide the required flow.
o Variable air flow to reduce energy consumption and provide the needed temperature and humidity control.
o Energy and demand control ventilation that only ventilates when required and captures waste heat energy from the exhaust air stream.
o Building automation system that controls the systems to optimize the opportunities to save energy.
The net result of the effort is a building which provides significantly enhanced environmental control without significant additional energy consumption.
Unity Temple is located in the heart of downtown Oak Park within walking distance of numerous shops and restaurants. The building has an excellent walk score rating of 93 and is only 0.3 miles from the Oak Park Blue Line CTA stop. Unity Temple is open to the surrounding community and offers religious services as well as organized tours through the Frank Lloyd Wright Trust. In addition, there are numerous special events such as lectures and concerts held throughout the year. As the historic condition of the building and its construction on the site, there are no parking spaces on site. There is on street metered parking along both sides of Lake Street as well as some limited free parking on Kenilworth Avenue. There is also public parking available in the Oak Park Public Library parking lot directly across the street. However, rather than relying on cars, congregation members and tourists are encouraged to walk, bike, and use public transportation. Bike racks provide spots for 10 bikes. The number 309 and 313 Pace buses stop in front of the building on Lake Street.
This project did not change the fundamentals of the plumbing system except in the replacement commercial kitchen. Toilet room fixtures including water closets and lavatories were reused or remained in place throughout the project. The commercial kitchen that replaced the kitchen in place at the time of restoration uses code compliant fixtures including a 3-compartment sink, a 2-compartment prep sink, condensing style dishwasher, and hand sink. These fixtures replaced similar fixtures as part of the process.
Storm water management also remained the same before and after the restoration project although all interior storm drains pipes and roof drains were replaced due to deterioration. Site conditions for storm water were also not changed as part of the project with the same amount of permeable surface available for storm water percolation before and after the restoration.
21.6% of precipitation is managed onsite through percolation. The balance of precipitation is directed to the Village sewer system
0% waste water is reused onsite
100% of potable water used onsite is metered and regulated
0% reduction in regulated potable water since this type of work was not included as part of project
The most sustainable building is one that already exists. Due to Unity Temple’s historic significance and landmark status, great care was taken to preserve as much original historic fabric as possible. This, in turn, reduced the amount of building material that entered the waste stream as well as the embodied energy used in creating new building materials. Materials selection was necessarily related to historic authenticity rather than the short term issues of indoor environmental quality although whenever possible the more environmentally selection was made. Recyclable materials such as old rebar from the removed failed roof slabs were segregated and recycled. The 1970s shotcrete material removed for restoration was saved and reused as the aggregate material in the sealing of all crack repairs.