Now showing 1 - 5 of 5
  • Publication
    Net energy analysis of domestic solar water heating installations in operation
    (Elsevier, 2012-01) ;
    The potential of solar water heating systems to reduce domestic energy use is frequently acknowledged. However there are two factors that are rarely discussed when studying this technology. Firstly the real performance of the installed systems in operation, and secondly a life cycle perspective of its energy use. These two issues are reviewed in this paper, and a field study in Ireland is also presented. In the review, some studies show that measured real performance of domestic solar water heating systems can be lower than expectations. Concerning their life cycle energy performance, existing studies show that the initial energy investment for the systems (their embodied energy) is a small portion of the energy savings over their lifetime with calculation paybacks generally lower than 2 years. On the field study carried in Ireland, representative of a maritime north European climate, the ‘energy payback’ based on the expected energy savings is between 1.2 and 3.5 years, values comparable to previous studies considering the less favourable climate and installation characteristics. However the measured energy savings generally worsened the life cycle energy performance of this technology and thus increased the energy payback period. The study concludes that while there is a real potential for life cycle energy savings through domestic solar water heating installations, devising mechanisms to ensure proper design, installation and operation of systems is essential for this technology.
    Scopus© Citations 41  2833
  • Publication
    Energy ratings based on measured energy consumption : a practical approach for implementation of EPBD and identification of high-energy use buildings.
    (University of Minho, 2007-09-12) ; ;
    Article 7 of the EU Energy Performance of Buildings Directive requires Member States to implement energy certification for buildings, and particularly for large public buildings, requires an energy certificate to be displayed in public. This paper outlines a simplified procedure for the certification of existing public buildings based on measured energy consumption, which is applicable even in countries where information on the building stock is not currently available. Energy consumption data collected for a number of buildings is used to develop energy benchmarks for typical and good practice energy performance. The rating procedure is based on a comparison between the energy consumption of each building and the derived benchmarks; a process that is illustrated in a sample of 88 Irish primary schools. The paper concludes with a discussion on the next steps to a more detailed measured rating procedure.
      267
  • Publication
    Life Cycle Energy Performance: Exploring the limits of passive low energy buildings
    (ASN Events, 2008-09-21) ;
    There is an increasing trend in reducing energy demand of buildings by improving building envelope thermal characteristics. Proven construction examples as used with the German PassivHaus standard achieve substantial reductions on the heating demand compared to mainstream construction, generally by using high levels of insulation together with ensuring excellent air tightness and minimizing of thermal bridges. However, the limits to which levels of insulation in a building can be increased and still represent overall life cycle energy savings are not clear. Particularly for temperate climates, adopting very-high insulation standards can lead to a danger of over specifying construction elements: once we reach certain levels of insulation, any extra material used can have larger energy costs or “embodied energy” than the energy it saves in the life cycle of the building. This paper presents the heating energy use of sample houses in the Irish maritime climate, and analyses the life cycle energy use including the embodied energy of the materials used. A 50-year perspective is presented, and conclusions about the limits to which the heating energy consumption can be lowered by “passive” means on a particular climate are drawn. This paper demonstrates the life-cycle benefits of optimizing the building design ensuring a correct orientation and sizing of the openings, but respecting certain limits when using energy intensive insulation materials.
      305
  • Publication
    Defining Zero Energy Buildings - A life cycle perspective
    (University College Dublin, 2008) ;
    A simple definition of a zero energy building (ZEB) is a stand-alone building which does not use any offsite energy source for its operation. The definition is easily extended to buildings with a net-zero annual on-site energy balance, where a building is connected to the electricity grid and annual energy use is the same as energy exported to the grid. In this paper we expand the ZEB definition adding a life cycle perspective including the embodied energy (cradle to site) of materials, which is considered as an additional off-site supply. The consideration of embodied energy adds a level that will help discern the life cycle benefits of different demand or supply side building design strategies to achieve ZEBs. Calculations of operational energy use and embodied energy for different house design options are presented, analyzing what options would move closer to this ZEB definition. Results show how the achievement of extreme reductions on energy demand by using high quantities of energy intensive materials are not an optimum solution over the life cycle of a building, active technologies becoming a better option after certain limits.
      642
  • Publication
    Optimising Life Cycle Energy Performance of Housing: The Value of Occupancy Control
    (Les Presses de l'Université Laval, 2009-06-22) ;
    There is a trend towards reducing heating and cooling requirements of buildings by using high levels of insulation, minimizing thermal bridging, and ensuring excellent air tightness, together with the operation of efficient mechanical ventilation heat recovery (MVHR) systems. In temperate climates, this approach has already raised questions about potential risks of over-specifying some construction elements and installations. This study argues that in maritime climates, appropriate building design with occupant controlled natural ventilation could provide an optimum life cycle energy performance. A heating demand analysis of a sample case study house with MVHR and of the same case study with naturally ventilation is presented, testing different levels of insulation for each case. Embodied energy data of the additional envelope insulation and the MVHR system is added to the operational energy , and the options are compared from a life cycle perspective.
      317