Straight Green: Advanced Energy Design Guides
June 27, 2011
A series of design guides developed to help building designers and owners achieve 50 percent energy savings over ASHRAE Standard 90.1 - 2004 are now being rolled out. The first in this series of design guides, Advanced Energy Design Guide for Small to Medium Office Buildings from up to 100,000 square feet is available now, free of charge. The guide was developed jointly by the US Department of Energy, The American Society of Heating, Refrigerating and Air-Conditioning Engineers, American Institute of Architects, U.S. Green Building Council and the Illuminating Engineering Society of North America.
The 50 percent energy design guide series picks up where the original series left off. The original series includes guides for six building types, and were developed for an energy savings of 30 percent beyond the 1999 version of ASHRAE Standard 90.1.
In addition to the newly released design guide for small to medium office buildings, 50 percent AEDGs are planned for the following building types:
- K-12 school buildings (planned for second quarter 2012)
- Medium to large box retail buildings (planned for first quarter 2012)
- Large hospitals (planned for second quarter 2012)
Fifty Percent Energy Savings Made EasyASHRAE claims that the design guides will allow practitioners to design buildings that achieve 50 percent energy savings simply by following the prescriptive recommendations contained in the guides:
“The recommendations in the guides allow those involved in designing or constructing the various building types to easily achieve advanced levels of energy savings without having to resort to detailed calculations or analyses.”
The guide presents prescriptive design “packages” that are chosen by a design team based on a project’s climate, site, building use, code requirements and other factors. The introduction to the guide states that not all options presented will be appropriate for every project. Design recommendations included in the guide for 50 percent energy savings achievement include the building enclosure, lighting, heating, ventilation, air-conditioning, building automation and controls, water heating and plug and process loads. Additional “bonus” savings recommendations not required to meet 50 percent energy savings are addressed in a separate chapter of the guide and include additional daylighting, natural ventilation and renewable energy systems.
The guide stresses the importance of adopting an integrated project delivery process in achievement of the 50 percent energy savings goal. The guide states that simply following a list of prescriptive recommendations (contained in the guide) is not enough and that IDP must be an integral part of the process for success. An entire chapter of the guide is dedicated to IDP, its definition, main principles, and organizational charts, and phases. It mirrors the AIA IDP documents A195, A295 and B195.
Do the Guides Work?For built and occupied buildings, available evidence that following the prescriptive recommendations of the energy guides is limited to a handful of case studies on the ASHRAE website for the original AEDG series. The five case studies presented add up to less than 100,000 square feet of conditioned space. There is no evidence presented in the case studies that show a connection between the various prescriptive measures employed and corresponding energy savings. Without this information, the guide’s effectiveness is impossible to evaluate. There is no way to know, for example, how much impact the solar PV array or the super-insulated walls, or the triple paned glazing had in getting the building to its energy guide goal of 30 percent better than Standard 90.1-1999. Also missing is anything showing the cost of these measures (and impact each had on overall energy efficiency).
For the 50 percent energy guide series, technical support documents using computer simulations were done by Pacific Northwest National Laboratory for a small and medium sized office building in each of the eight climate zones. The support documents include information on how additional costs of the prescriptive energy savings recommendations were calculated and, for the two heating systems studied, the payback period. Unfortunately, there is no comprehensive list of costs for each recommendation with an accompanying payback estimate. The support document concludes that payback values for the advanced energy measure “packages” for the climates zones modeled do not create an unreasonably high economic burden in pursuing the 50 percent energy savings goal. We have to take the author’s word for it.
Some of the most interesting information in the support documents is contained in the review comments and responses, included in the Appendices.
ConclusionWhat I was hoping for in the guide was more of a recipe approach to 50 percent energy savings: In climate Zone 4, add one part super-insulated wall, with 25 percent glazing at U value 0.37, one water source heat pump and voila. Fifty percent energy savings. Unfortunately, the opening promise that using the Advanced Energy Savings Design Guide allows a design team to achieve 50 percent energy savings “without having to resort to detailed calculations or analyses” seems too good to be true.
There are many choices offered to the design team, but no “if-then” flow chart that assists in the decision making process. The guide allows a designer to choose from 20 to 40 percent window-to-wall ratio, steel, wood or mass wall construction and several HVAC system packages, for example, but it does not offer any guidance on what impact different combinations of these choices will have on the goal/promise of 50 percent energy savings. The only way to know how much energy savings can be expected with various combinations of the recommendations presented is energy modeling. As a source of energy savings information, the guide is excellent. As an easily followed prescriptive pathway to achieving 50 percent energy savings in buildings, it falls short.