Jim Coddington, the chief conservator at the Museum of Modern Art (MoMA) in New York, presented some trends that were found from analyzing the environmental data that was collected at MoMA over the past six years. This was particularly interesting because it compared two relatively new or newly renovated buildings with different types of usage/functionality and HVAC systems. The building on 53rd street, Jim admits, is very leaky from a number of sources, including the many doors through which thousands of people pass, and has a steam and electric HVAC system. The building in Queens (QNS) on the other hand is mostly concrete with very little glass and has a gas powered HVAC system. The data that Jim presented was collected from across the museum including finance, operation, conservation, and vistor services. Needless to say there are a lot of people invested in this.
Jim showed mostly graphs and charts. These included data showing the temperature and %RH outside, inside the buildings, dew point, and comparing this energy usage. I’ve included images of the graphs that I found most interesting or informative.
In QNS there is a large expenditures of gas in august and dips in winter. This is because that are able to use free cooling to extract excess heat for 8 or9 months, or 3 out of 4 seasons, through a heat exchanger on the roof. In this process, heat is absorbed from the condenser water by air chilled water. The length of time they are able to use free-cooling is based on set points of T and RH (see second image) and is affected by air temperature, relative humidity, and water supply temperature. Non-free cooling with the RH set at 50% happens over the summer and is longer at lower temperatures. So during the summer the temperature set point is allowed to drift to 22 degrees C. Jim mentioned that having a narrower set point may actually equal cost savings, but they have no data for that.
On the analysis for the 53rd street building, Jim highlighted that this is a very different situation. It is a high use building, with lots of leakage points and demand on the systems- steam and electric principally. Therefore, the energy usage is much higher.
It has been asked whether heat from visitors is significant? In Chris McGlinchey’s calculation, the 360 kJ/hr given off by the visitors with a typical stay of 4 hours, this is not a huge contributing factor.
In Jim’s summary and conclusions- The expected was stated that they are consuming more energy in the 53rd St building than QNS. This is mostly in winter (see the third image). The QNS building is more efficient because of the free cooling, lower set point temperature and equates to lower energy usage thanks to an efficient building design. Online Resources:
- Steam- natural gas utility converter: http://www.coned.com/steam/default.asp
- NIST Guide for the Use of the International System of Units (SI) 2008: http://physics.nist.gov/cuu/pdf/sp811.pdf
- Humidity converter: http://www.cactus2000.de/uk/unit/masshum.shtml
- NOAA, National.ncdc.noaa.gov/