Low-energy office buildings using existing technology: simulations with low internal heat gains

Flodberg et al. International Journal of Energy and Environmental Engineering 2012, 3:19 http://www.journal-ijeee.com/content/3/1/19 ORIGINAL RESEARCH Open Access Low-energy office buildings using existing technology: simulations with low internal heat gains Kajsa Flodberg1*, Åke Blomsterberg1 and Marie-Claude Dubois1 Abstract Although low-energy and nearly zero-energy residential houses have been built in Sweden in the past decade, there are very few examples of low-energy office buildings. This paper investigates the design features affecting energy use in office buildings and suggests the optimal low-energy design from a Swedish perspective. Dynamic simulations have been carried out with IDA ICE 4 on a typical narrow office building with perimeter cell rooms. The results from the parametric study reveal that the most important design features for energy saving are demand-controlled ventilation as well as limited glazing on the façade. Further energy-saving features are efficient lighting and office equipment which strongly reduce user-related electricity and cooling energy. Together, the simulation results suggest that about 48% energy can be saved compared to a new office building built according to the Swedish building code. Thus, it is possible, using a combination of simple and well-known building technologies and configurations, to have very low energy use in new office buildings. If renewable energy sources, such as solar energy and wind power, are added, there is a potential for the annual energy production to exceed the annual energy consumption and a net zero-energy building can be reached. One aspect of the results concerns user-related electricity, which becomes a major energy post in very low-energy offices and which is rarely regulated in building codes today. This results not only in high electricity use, but also in large internal heat gains and unnecessary high cooling loads given the high latitude and cold climate. Keywords: office building, low energy, dynamic simulations, cooling, electricity, lighting, building envelope, HVAC, internal heat gains Background According to the European Union's Directive on Energy Performance of Buildings, all new buildings within the union must be nearly zero energy by the end of 2020 [1]. The most recent statistics for Sweden show that the total delivered energy to existing office buildings was around 210 kWh/m2/year in 2005 [2], whereof the first half was electricity and the other half was district heating and cooling. Regarding new office buildings, the energy performance has been improved, in terms of reduced heating loads, but the electricity for lighting and equipment is still high. The high electricity use results in large primary energy demands in general and also in internal * Correspondence: Department of Architecture and the Built Environment, Div. of Energy and Building Design, Lund University, Box 118, Lund 221 00, Sweden heat gains and heat surplus, leading to unnecessary cooling loads given the high latitude and cold climate. Good examples of low-energy and nearly zero-energy residential houses have been built in Sweden during the past decade [3,4]. However, at the time of writing, there are very few examples of low-energy office buildings. In Germany, on the other hand, a number of passive and low-energy office buildings have been constructed and evaluated (see examples of demonstration projects in [5,6]). Also, research on energy efficiency potential for a passive office building in Germany has been carried out with dynamic simulations by Knissel [7]. Knissel shows that the primary energy requirement of an example building in Frankfurt can be reduced by 70% with high insulation levels in the building envelope, low electricity consumption for equipment and lighting, no active cooling, heat and humidity recovery and earth-to-air heat © 2012 Flodberg et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Flodberg et al. International Journal of Energy and Environmental Engineering 2012, 3:19 http://www.journal-ijeee.com/content/3/1/19 exchangers. These German experiences are clearly important for the development of future zero-energy office buildings. However, they must be adapted to a Swedish context, as building techniques, climate conditions and indoor comfort criteria differ between the countries. For example, the sum of heating and cooling degree days is larger and the amount of useful daylight is smaller in Sweden compared to Germany, which affects the heating, cooling and lighting strategies. In order to bridge this gap, the project ‘Energy-efficient office buildings with low internal heat gains: simulations and design guidelines’ was initiated. The overall aim of the project is to provide knowledge to the Swedish building industry, supporting the development of cost-effective office buildings with good indoor climate and very low energy use. The main goal is to reduce the annual energy use by 50%, compared to the requirements in the Swedish building code. This paper describes the second phase of the project, a parametric study carried out with dynamic simulations on a typical office building. The objectives of the study are to: Page 2 of 9 case solution and simulated in order to obtain the maximum energy saving potential with a proven technique. The parametric study did not include the study of different heating and cooling systems. Only the building's actual heating and cooling demand was investigated and district heating and cooling with a coefficient of performance (COP) of 1.0 was assumed. The simulation software IDA ICE 4 is a dynamic multi-zone simulation program for the study of indoor climate of individual zones within a building as well as whole-year energy consumption for the entire building. It uses the neutral model format language and hence enables the user to change and write new models. IDA ICE was developed in the mid-1980s at the Royal Institute of Technology (KTH) in Stockholm, Sweden, and now serves a global market. The simulation tool is provided by EQUA Solutions AB (Solna, Sweden), and it has been validated according to CEN 13791, ASHRAE 140–2004, CEN 15255, CEN 15265, CIBSE TM33, RADTEST and Envelope BESTEST [8]. The base case  Reveal important design features when designing a low-energy office building  Present an office building with a good indoor climate, which uses less than half the energy compared to a new office building, including userrelated electricity. The obvious advantage with such reduction in energy is that the remaining demand can be met by renewable sources like wind, solar, geothermal or biomass, enabling a net zero-energy office building. The paper discusses recommendations for architects and e (...truncated)