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Primary energy implications of ventilation heat recovery in residential buildings
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development. (Ecotechnology)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development. (Ecotechnology)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development. (Ecotechnology)
2011 (English)In: Energy and Buildings, ISSN 0378-7788, Vol. 43, no 7, 1566-1572 p.Article in journal (Refereed) Published
Abstract [en]

In this study, we analyze the impact of ventilation heat recovery (VHR) on the operation primary energy use in residential buildings. We calculate the operation primary energy use of a case-study apartment building built to conventional and passive house standard, both with and without VHR, and using different end-use heating systems including electric resistance heating, bedrock heat pump and district heating based on combined heat and power (CHP) production. VHR increases the electrical energy used for ventilation and reduces the heat energy used for space heating. Significantly greater primary energy savings is achieved when VHR is used in resistance heated buildings than in district heated buildings. For district heated buildings the primary energy savings are small. VHR systems can give substantial final energy reduction, but the primary energy benefit depends strongly on the type of heat supply system, and also on the amount of electricity used for VHR and the airtightness of buildings. This study shows the importance of considering the interactions between heat supply systems and VHR systems to reduce primary energy use in buildings.

Place, publisher, year, edition, pages
2011. Vol. 43, no 7, 1566-1572 p.
Keyword [en]
Mechanical ventilation; Heat recovery; Heat supply systems; Electric resistance heating; Heat pump; District heating; CHP plant; Primary energy
National Category
Environmental Biotechnology Civil Engineering
Identifiers
URN: urn:nbn:se:miun:diva-13330DOI: 10.1016/j.enbuild.2011.02.019ISI: 000292231600008Scopus ID: 2-s2.0-79956354126OAI: oai:DiVA.org:miun-13330DiVA: diva2:401141
Available from: 2011-03-01 Created: 2011-03-01 Last updated: 2012-08-14Bibliographically approved
In thesis
1. Life cycle primary energy use and carbon emission of residential buildings
Open this publication in new window or tab >>Life cycle primary energy use and carbon emission of residential buildings
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, the primary energy use and carbon emissions of residential buildings are studied using a system analysis methodology with a life cycle perspective. The analysis includes production, operation, retrofitting and end-of-life phases and encompasses the entire natural resource chain. The analysis  focuses, in particular, on to the choice of building frame material; the energy savings potential of building thermal mass; the choice of energy supply systems and their interactions with different energy-efficiency measures, including ventilation heat recovery systems; and the effectiveness of current energy-efficiency standards to reduce energy use in buildings. The results show that a wood-frame building has a lower primary energy balance than a concrete-frame alternative. This result is primarily due to the lower production primary energy use and greater bioenergy recovery benefits of wood-frame buildings. Hour-by-hour dynamic modeling of building mass configuration shows that the energy savings due to the benefit of thermal mass are minimal within the Nordic climate but varies with climatic location and the energy efficiency of the building. A concrete-frame building has slightly lower space heating demand than a wood-frame alternative, because of the benefit of thermal mass. However, the production and end-of-life advantages of using wood framing materials outweigh the energy saving benefits of thermal mass with concrete framing materials.

A system-wide analysis of the implications of different building energy-efficiency standards indicates that improved standards greatly reduce final energy use for heating. Nevertheless, a passive house standard building with electric heating may not perform better than a conventional building with district heating, from a primary energy perspective. Wood-frame passive house buildings with energy-efficient heat supply systems reduce life cycle primary energy use.

An important complementary strategy to reduce primary energy use in the building sector is energy efficiency improvement of existing buildings, as the rate of addition of new buildings to the building stock is low. Different energy efficiency retrofit measures for buildings are studied, focusing on the energy demand and supply sides, as well as their interactions. The results show that significantly greater life cycle primary energy reduction is achieved when an electric resistance heated building is retrofitted than when a district heated building is retrofitted. For district heated buildings, the primary energy savings of energy efficiency measures depend on the characteristics of the heat production system and the type of energy efficiency measures. Ventilation heat recovery (VHR) systems provide low primary energy savings where district heating is based largely on combined heat and power (CHP) production. VHR systems can produce substantial final energy reduction, but the primary energy benefit largely depends on the type of heat supply system, the amount of electricity used for VHR and the airtightness of buildings.

Wood-framed buildings have substantially lower life cycle carbon emissions than concrete-framed buildings, even if the carbon benefit of post-use concrete management is included. The carbon sequestered by crushed concrete leads to a significant decrease in CO2 emission. However, CO2 emissions from fossil fuels used to crush the concrete significantly reduce the carbon benefits obtained from the increased carbonation due to crushing. Overall, the effect of carbonation of post-use concrete is small. The post-use energy recovery of wood and the recycling of reinforcing steel both provide higher carbon benefits than post-use carbonation.

In summary, wood buildings with CHP-based district heating are an effective means of reducing primary energy use and carbon emission in the built environment.

Place, publisher, year, edition, pages
Östersund: Mittuniversitetet, 2011. 165 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 115
National Category
Civil Engineering Environmental Sciences
Identifiers
urn:nbn:se:miun:diva-14942 (URN)978-91-86694-57-9 (ISBN)
Public defence
2011-11-08, Q221, Campus Östersund, Östersund, 12:00 (English)
Opponent
Supervisors
Available from: 2011-11-28 Created: 2011-11-28 Last updated: 2012-07-30Bibliographically approved

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