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Hybrid ventilation research for houses
Reardon, J. T.; Ouazia, B.
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H ybrid ve nt ilat ion re se a rc h for house s
R e a r d o n , J . ; O u a z i a , B .
N R C C - 4 8 7 1 3
A version of this document is published in / Une version de ce
document se trouve dans: Solplan Review, No. 130, Sept.
2006, pp. 18-19
Hybrid Ventilation Research for Houses
by James Reardon and Boualem Ouazia
Buildings represent 30% of total energy consumption in Canada. In thermally well-insulated buildings, ventilation and air-conditioning may account for more than 50% of the energy consumption. Improvements in the energy efficiency of ventilating buildings can therefore make a real impact toward reducing Canada's overall energy consumption and GHG emissions.
Ventilation provides air for occupants and removes indoor air pollutants generated from indoor sources, e.g., carbon dioxide and water vapour from occupant activities, and volatile organic compounds (VOCs) from modern furnishings and consumer products. Natural ventilation, through openings in the building envelope, is driven by natural forces: wind and temperature differences between indoors and outdoors, not requiring fans powered by electricity. Those natural driving forces vary with weather, and so may not be reliable, causing too little or too much fresh air exchange. Discomfort due to cold drafts, uncontrolled air distribution, and impractical heat recovery or filtration are some of the other disadvantages.
Mechanical ventilation, on the other hand, is easily controlled, lends itself to
straightforward application of heat recovery and filtration, and is reliable. However, it consumes electrical energy and thereby causes GHG emissions. As modern
construction trends are creating Canadian houses that are more and more airtight, concerns about inadequate natural ventilation have led to increasing requirements for mechanical ventilation in Canadian building codes. NRC-IRC is conducting a research project one part of which is an examination of the natural ventilation rates typical in existing Canadian houses.
Hybrid ventilation strategies, combining the advantages of both natural and mechanical ventilation strategies and using each to offset the disadvantages of the other, may offer an approach to reduce the energy required to provide necessary ventilation in Canadian buildings. Houses and other small buildings covered under Part 9 of the National Building Code are a logical place to start developing these strategies.
With a good design, a hybrid strategy should be able to minimize the excess energy consumed from overventilation and avoid the indoor air quality problems associated with underventilation. Intelligent control systems that automatically switch between the natural and mechanical ventilation modes, modulate fan speeds and vent openings to ensure a steady ventilation rate and adequate interior distribution of the supply air should be able to minimize energy consumption and maintain a satisfactory indoor environment.
The objective of this research is to develop innovative energy-efficient hybrid ventilation strategies for single-family residential buildings and to evaluate their performance for reliable standards compliance, indoor air quality, and occupant satisfaction. The performance of each hybrid strategy and control algorithm in terms of providing
adequate ventilation and its energy consumption and impact on thermal comfort will be
HybridVentilation SolplanReview Final Sept2006.doc 1 / 2 10/13/2006 10:41 AM
assessed through experiments in the recently upgraded NRC ventilation research house facility for a full range of weather conditions.
A parallel study of hybrid heating, combining radiant floors and forced-air heating systems is also underway in this facility (see Solplan Review, July 2006). This provides the opportunity to ensure that innovative hybrid ventilation strategies will be suitable for houses both with and without the good indoor air distribution that results from continuous low-speed operation of forced-air furnace fans (as shown by previous IRC research). Ventilation rates and air distribution patterns will be measured under different modes of operation over a range of weather conditions and system operation states in order to assess the variability and reliability of ventilation as functions of these conditions. The energy consumption will be monitored for all strategies and operating conditions. Results from the study will demonstrate the potential of hybrid ventilation strategies in houses for reducing energy consumption and peak electrical load, and improving building ventilation.
Participation by one or more manufacturers will improve collaboration between industry and researchers, and facilitate industry uptake of the technology developed.
The study results may lay the foundation for further development of residential strategies for free cooling, a proposed research topic for the near future.
Readers can obtain more information from these websites:
Hybrid ventilation research: http://irc.nrc-cnrc.gc.ca/ie/iaq/factsheet8_e.html Research house facility:http://irc.nrc-cnrc.gc.ca/ie/facilities/testhouse3_e.html
_____________________________
James Reardon is a Senior Research Officer and Boualem Ouazia is a Research Officer with NRC-IRC’s Indoor Environment program.
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