Energy Saving Strategies and Architectural Design

Thursday, November 13, 2008
The Library Renovation project includes dozens of changes that will dramatically improve the energy performance of the building. Many of these initiatives are outlined in the library's "Green Initiatives" program, which can be found elsewhere on the library's website. I am writing to discuss some other aspects of the project, from the perspective of the architects and engineers working on the design of the renovations.
During the course of our early design work we studied many different strategies to find out which improvements would be most cost effective and yield the best long term energy savings for the City of Portland. We studied one idea that included a 2,000 SF photovoltaic system on the front of the building. We were very excited about this possibility, given the library's south facing front wall, but when we ran the calculations we discovered that even with tax breaks it would take over twenty years to pay for itself. We studied another idea that used a SolarWall metal panel system on top of the stone facing, to generate pre-heated fresh air for the mechanical systems, which are located on the top level of the building. This system worked and had a short payback time, but it covered up a good looking material (the granite veneer) with a not so good looking material (black perforated metal). This idea led us to another, the idea of a solar greenhouse chimney, which you see illustrated on the front of the library in our latest renderings. The tall angled glass curtainwall on the front of the library (the uppermost portion) is actually a greenhouse that generates pre-heated air for the mechanical system. The sun penetrates the single glazing, heats up the air and stone behind it, then rises naturally to the top of the chimney where it is drawn into the air mixing chamber in the mechanical system as heated fresh air. Without this system the cold outside air has to be mechanically pre-heated before it is mixed with the inside air, which uses a lot of energy. The glass curtainwall greenhouse saves enough energy to pay for itself in less than ten years.
One of the most dramatic features of the new library design is the glass curtainwall enclosing the new cafe space. With this glass wall, the space in the front of the library that is currently outdoors will be dramatically transformed into the front living room of the new library, overlooking Congress Street and Monument Square. Visitors to the library will be able to sit in the new cafe, immediately adjacent to the sidewalk on Congress Street, bringing new life and activity to the street. The curtainwall also replaces the original skylights and windows on the front of the building, which were built in the 70's and not as efficient as today's windows and glazing systems. The new enclosure will have high performance, low-E, argon and krypton gas filled insulated glass, which will significantly improve the energy performance of the building overall. Phase One of the library renovation project will replace 40% of all the windows and glazing in the building. Additional window replacement is planned for future phases.
The greatest energy savings will come from replacing the existing electric radiators with high efficiency hydronic baseboard heating along the perimeter walls of the library. New high efficiency boilers will be installed to produce the hot water for this
system. This improvement will produce the greatest energy/cost benefit for the library, and will result in the most noticeable improvement in comfort for the library patrons. We will also be replacing all the lighting in the library, installing motion sensors that will turn the lights off when the rooms aren't occupied, and light sensors to allow the lights to stay off when daylighting is enough to light the space.
Many other energy saving improvements have been included in the design of these renovations. I invite you to visit the "Green Initiatives" section of the Reach for the Stars website to learn more about the project.
Scott Simons