The potential impact of low thermal transmittance construction on the European design guidelines of residential buildings

• Published in: Energy and buildings 2018-11, Vol.178, p.379-390
• Main Authors: Rodrigues, Eugénio, Fernandes, Marco S., Soares, Nelson, Gomes, Álvaro, Gaspar, Adélio Rodrigues, Costa, José J.
• Format: Article
• Language: English
• Subjects: Building design; Building envelopes; Building geometry; Buildings; Climate; Construction; Design engineering; Dynamic simulation; Energy consumption; Energy demand; Energy efficiency; Generative design method; Geometry; Guidelines; Housing; Performance indices; Residential areas; Residential buildings; Residential energy; Simulation; Surfacing; Thermal cycling; Thermal transmittance; Transmittance
• ISSN: 0378-7788; 1872-6178
• DOI: 10.1016/j.enbuild.2018.08.009

•The U-value impact on the thermal performance of residential buildings was analyzed.•96,000 buildings were randomly generated and evaluated using dynamic simulation.•Six geometry-based indexes were correlated with the buildings performance.•Low U-values can increase energy consumption in warm and moderate climates.•Adequate U-values allow designers to explore new building forms and window designs. European countries impose regulations for low thermal transmittance envelopes to improve the buildings’ energy efficiency. However, in scientific literature, evidences are surfacing that such low U-values are affecting the validity of traditional design guidelines. The purpose of this paper is to analyze the implications of lowering the envelope U-values. To achieve this, 96,000 residential buildings were generated, with random geometries and U-values, and their energy consumption evaluated for eight European locations. The buildings were grouped according to the envelope elements’ thermal transmittance and the results statistically analyzed. For each group, six geometry-based indexes were correlated with the energy performance. As U-values decrease, the performance variation amplitude was found to reduce, making the geometry less important. However, in warm/moderate climates, low U-values tend to actually increase the energy consumption and also rise the performance variation, meaning that geometry regains importance. In this case, instead of helping reducing the heating demands, solar exposed windows and compact geometries raise the energy consumption. It is concluded that, for each climate location, there is an ideal U-value range for which the energy demand is low and the geometry effect becomes less significant, thus freeing designers to further explore building forms and window designs.