Documenting Energy Efficiency: From Design, to Constuction, to Occupancy
This case study for Ramona Apartments building provides a comparison between the designed parameters and the actual energy use, after the building was completed and occupied. The reason this case study is exceptional is because energy efficient design does not guarantee performance in use, and that the actual performance is rarely documented.
Achieving energy efficient and sustainable buildings requires commitment all the way through the value chain of a building design and construction. It starts with a committed owner and investor, it continues with an energy efficient design and quality craftsmanship during the construction, and results in tangible dollar savings for the building occupants. One such example is Ramona Apartments, a 138-unit family-friendly building in the Pearl District, in Portland, Oregon, home to 133 children (and a total of 361 residents).
The construction started in December of 2009 and was completed in March of 2011. What is remarkable about Ramona Apartments was, not only that the building was designed and built as energy efficient, but also that the performance has been validated after two years of occupancy and will continue to be recorded for at least the first five years of occupancy. This is the first case I am aware of in which building energy performance was documented from design, to construction, to occupancy, and actually measured.
Most energy efficiency at Ramona can be attributed to focusing on the building’s fundamentals, especially building an airtight and well-insulated envelope. There has been extensive discussion in the industry about the impact of airtightness on building’s energy efficiency and the effectiveness of a continuous air barrier in achieving an airtight envelope. However, this has been received with skepticism, since most research to date documenting energy savings from airtightness is based on energy simulation models which compare the energy performance of an airtight building with a “leaky” building, often code minimum.
This case study documents not only how a continuous air barrier could achieve an airtight building envelope, but also how an airtight building envelope can reduce the energy use. The actual energy use is close to that predicted by energy simulation models, which included air leakage control as one of the critical energy efficiency measures. Based on experience with previous buildings, the design team had assumed an infiltration rate of 0.16 ACH in energy model simulations. Blower door tests conducted on 36 of the apartments at Ramona, in addition to whole building airtightness testing, averaged an air leakage rate of 0.14 ACH.
Further monitoring for the next 5 years will provide additional information on maintaining building envelope airtightness years after its initial installation. No such data exist in the industry.