Residential commissioning to assess envelope and HVAC system performance
Houses do not perform optimally or even as many codes and forecasts predict. For example, Walker et al. (1998a) found large variations in thermal distribution system efficiency, as much as a factor of two even between side-by-side houses with the same system design and installation crew. This and other studies (e.g., Jump et al. 1996) indicate that duct leakage testing and sealing can readily achieve a 25 to 30% reduction in installed cooling capacity and energy consumption. As another example, consider that the building industry has recognized for at least 20 years the substantial impact that envelope airtightness has on thermal loads, energy use, comfort, and indoor air quality. However, Walker et al. (1998a) found 50% variances in airtightness for houses with the same design and construction crews, within the same subdivision. A substantial reason for these problems is that few houses are now built or retrofitted using formal design procedures, most are field assembled from a large number of components, and there is no consistent process to identify problems or to correct them. Solving the problems requires field performance evaluations of houses using appropriate and agreed upon procedures. Many procedural elements already exist in a fragmented environment; some are ready now to be integrated into a new process called residential commissioning (Wray et al. 2000). For example, California's Title 24 energy code already provides some commissioning elements for evaluating the energy performance of new houses. A house consists of components and systems that need to be commissioned, such as building envelopes, air distribution systems, cooling equipment, heat pumps, combustion appliances, controls, and other electrical appliances. For simplicity and practicality, these components and systems are usually evaluated individually, but we need to bear in mind that many of them interact. Therefore, commissioning must not only identify the energy and non-energy benefits associated with improving the performance of a component, it must also indicate how individual components interact in the complete building system. For this paper, we limit our discussion to diagnostics in areas of particular concern with significant interactions: envelope and HVAC systems. These areas include insulation quality, windows, airtightness, envelope moisture, fan and duct system airflows, duct leakage, cooling equipment charge, and combustion appliance backdrafting with spillage. The remainder of this paper first describes what residential commissioning is, its characteristic elements, and how one might structure its process. Subsequent sections describe a consolidated set of practical diagnostics that the building industry can use now. Where possible, we also discuss the accuracy and usability of these diagnostics, based on recent laboratory work and field studies. We conclude by describing areas in need of research and development, such as practical field diagnostics for envelope thermal conductance and combustion safety. There are several potential benefits for builders, consumers, code officials, utilities, and energy planners of commissioning houses using a consistent set of validated methods. Builders and/or commissioning agents will be able to optimize system performance and reduce consumer costs associated with building energy use. Consumers will be more likely to get what they paid for and builders can show they delivered what was expected. Code officials will be better able to enforce existing and future energy codes. As energy reduction measures are more effectively incorporated into the housing stock, utilities and energy planners will benefit through greater confidence in predicting demand and greater assurance that demand reductions will actually occur. Performance improvements will also reduce emissions from electricity generating plants and residential combustion equipment. Research to characterize these benefits is underway.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Energy Efficiency and Renewable Building Technologies; California Energy Commission through the Public Interest Energy Research program under Contract No. 500-98-033. (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 820646
- Report Number(s):
- LBNL-47412; R&D Project: 474401; TRN: US200405%%55
- Resource Relation:
- Conference: Performance of Exterior Envelopes of Whole Buildings VIII: Integration of Building Envelopes, Clearwater Beach, FL (US), 12/02/2001--12/07/2001; Other Information: PBD: 31 Aug 2001
- Country of Publication:
- United States
- Language:
- English
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