High Performing Buildings - Spring 2009 - (Page 27) Lessons LeArned • Extracting heat from the borefield during the a problem for the Normand-Maurice Building winter requires below-freezing fluid temperasince it sits on bedrock). Careful manageture. Because the borefield was used both for ment of the construction site is required, as heat rejection and extraction and was thus is protection of the horizontal runs. (Here, connected to both the hot water and chilled they are encased in concrete.) water loops, propylene glycol was used as • Classical water-cooled chillers shouldn’t be antifreeze throughout the water loops (the used as heat pumps during the heating seaalternative was separating the borefield loop son, especially with a geothermal borefield. with a heat exchanger, reducing the energy They are designed to maintain the chilled water savings due to increased lift on the waterloop temperature, while the hot water loop temcooled chiller). This led to major difficulties in perature should be the active control parampurging the air from the loops, pressurizing the eter. Specialized systems or equipment would system and fine-tuning its operation, as the be much easier to commission and operate. glycol appears to hold more air than normally • Ceiling radiant slabs in cooling can be really expected (unconfirmed, since the local chemieffective. In this case, the underfloor air discal manufacturer representatives don’t agree tribution system, which is partly variable air with our conclusions). It is felt that it is much volume, maintained its boxes almost closed better to limit the glycol to where it is needed to prevent over-cooling the spaces (which and separate those loops from the others. lead to IAQ dissatisfactions). Current tube • A geothermal borefield underneath the buildspacing in the slab is 12 in. and could posing is feasible, workable and effective, though sibly be increased to 18 in. without affecting it must be designed and operated to prevent performance. freezing of the underground soil (this is not of the Canadian government, has served as a case study for professionals and students seeking to incorporate sustainable features into other projects. Its significantly lower than average operating costs demonstrate that an energy-efficient building makes economic sense and can serve a variety of purposes. • About the Authors Ashly lyons, junior engineer at Pageau morel, was the lead writer. frederic genest, leed AP AsHrAe , HBdP and associate at Pageau morel, was project engineer and served as heating/cooling system designer. Jacques de grace, leed AP engineer, , and principal associate at Pageau morel, served as project manager and conceptual designer. HPB.hotims.com/25005-5 spring 2009 HigH Performing Buildings 27 http://www.energygauge.com http://www.energygauge.com http://HPB.hotims.com/25005-5
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