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

Abstract

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.

Thermal transmittance effect on energy consumption of Mediterranean buildings with different thermal mass

“…In addition to different geometries, the generated buildings also have random pairwise values of thermal transmittance for the opaque and transparent elements of the building envelope. This approach of generating synthetic datasets was used in the past to study the relevance of geometry-based indexes as thermal performance indicators [25]; to determine the impact of thermal transmittance variation in building design practice in eight climate regions in Europe [26]; to find the most adequate thermal transmittance values for heavyweight construction in sixteen locations in the Mediterranean region [27]; and to foster lightweight steel-framed construction in hot arid climates [28].…”

Energy Design Synthesis: Algorithmic Generation of Building Shape Configurations

“…In a comprehensive review, more than 100 studies about diverse building energy, comfort, and environmental design optimization (BECEDO) issues were evaluated [8]. The analysis states that most BECEDO studies' focus is set on the HVAC system and envelope parameter, and occupancy behavior optimization [9][10][11][12]. Even though the building geometry's positive effect on comfort and energy performance is more and more proven [13][14][15], over 60% of energy demand [16], as well as 80% of environmental impact reduction [17] is achievable with the combined optimization of the shape and further variables.…”

Performance-based design of multi-story buildings for a sustainable urban environment: A case study

“…Besides being helpful to building design practitioners, performance-based approaches can also be used to study some building performance phenomena, such as the impact of different building indexes [31,32], to compare alternative construction systems [28], and to determine the best thermophysical properties of building elements [33][34][35].…”