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Recommended Ventilation Strategies for Energy-Efficient Production Homes
Because low-infiltration homes often need mechanical ventilation to maintain indoor air quality, the US Environmental Protection Agency's (EPA) Energy Star® Homes program asked our research team in the Energy Analysis Department of Lawrence Berkeley National Laboratory (LBNL) to recommend the most appropriate mechanical ventilation strategies for new, single-family Energy Star® production (site-built tract) homes in four climates.
Mechanical ventilation is uncommon in US single-family homes because until recently it was thought that residential buildings were leaky enough to provide adequate air exchange. However, as homebuilding materials and practices have changed, building air leakage (infiltration) levels have decreased, and it has become obvious that mechanical ventilation is a residential design issue. This report does not address whether mechanical ventilation is necessary or what level of air exchange is appropriate. It does evaluate and compare the cost and effectiveness of nine residential ventilation systems and recommends the most suitable systems for new single-family production homes in cold, moderate, hot humid, and hot arid climates.
Our analysis is based on computer simulations of ventilation systems in prototypical homes and requires assumptions about climate, home characteristics, indoor pollutants, and occupant behavior that do not necessarily apply to every situation. Besides making climate-specific recommendations for mechanical ventilation of new homes, we also provide information that can enable contractors to determine the most suitable ventilation strategy for each set of circumstances.
We compared residential ventilation strategies in four climates according to three criteria: total annualized cost (the sum of annualized capital cost and annual operating cost), predominant indoor pressure induced by the ventilation system, and distribution of ventilation air within the home. The mechanical ventilation systems modeled deliver 0.35 air changes per hour continuously, regardless of actual infiltration or occupant window-opening behavior.
Based on the assumptions and analysis described in this report, we recommend independently ducted multi-port supply ventilation in all climates except cold because this strategy provides the safety and health benefits of positive indoor pressure as well as the ability to filter and dehumidify ventilation air. In cold climates, we recommend that multi-port supply ventilation be balanced by a single-port exhaust ventilation fan, and that builders offer balanced heat-recovery ventilation to buyers as an optional upgrade.
For builders who still install forced-air integrated supply ventilation, we emphasize that (1) forced-air ductwork should be airtight or within conditioned space, (2) systems should include a control that automatically operates the forced-air fan at least 20 minutes during each hour that the fan does not operate for heating or cooling, and (3) because of high operating costs and other disadvantages of operating a standard forced-air fan for ventilation, home buyers should be given the option of upgrading to an efficient, variable-speed forced-air fan with an integrated-control motor (ICM).
Appendix A. When is Continual Depressurization of Homes Safe? (an outline of the conditions in which exhaust ventilation is suitable) Word 97/98 file: AppndixA.doc
Appendix B. Itemized Capital Costs (estimated costs to install and maintain various mechanical ventilation systems) Excel 98 file: AppndixB.xls
Appendix C. Itemized Operating and Total Annual Costs (estimated operating costs of ventilation fan energy and tempering of ventilation air, for representative cities and houses) Excel 98 file: AppndixC.xls
Roberson, Judy A., Richard E. Brown, Jonathan G. Koomey, and Steven E. Greenberg. 1998. Recommended Ventilation Strategies for Energy-Efficient Production Homes LBNL-40378. Abstract
Roberson, Judy A., Richard E. Brown, Jonathan G. Koomey, Jeffrey L. Warner, and Steven E. Greenberg. 1998. "Ventilation Strategies for Energy-Efficient Production Homes." Proceedings of the ACEEE 1998 Summer Study on Energy Efficiency in Buildings. American Council for an Energy-Efficiency Economy, Washington DC. Abstract | 66K PDF
Bower, John. 1995. Understanding Ventilation. The Healthy House Institute, Bloomington IN.
Stevens, Don T. 1996. "Mechanical Ventilation for the Home". Home Energy. Mar/Apr, p 13-19.
EFI, the Energy Federation Inc: a not-for-profit catalog, outlet, and source of objective information on residential ventilation equipment
The Home Ventilating Institute: a division of the Air Movement and Control Association, independently certifies and publishes an annual directory of performance data for balanced heat-recovery ventilation equipment. Phone (847) 394-0150 or e-mail: email@example.com.
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