Configuring wall layers for improved insulation performance
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External walls provide an important barrier between occupied building spaces and variable ambient conditions. Building insulation is often optimized for static performance based on its R-Value rating, but a growing body of literature has begun to assess the dynamic thermal performance of multi-layer walls. The focus of this work is to provide fundamental insight into configuring wall layers for improved insulating performance. Thirty-three different walls are evaluated based on four primary configurations with fixed volumes of insulation and thermal mass. Only the layer distribution is varied. Because the total volume of each material is fixed, the overall thermal resistance and capacitance are equivalent for all configurations studied. An electrical analogy is used to model the one dimensional heat conduction through the wall and determine the magnitude ratio and phase of the frequency response evaluated at the frequency corresponding to a period of 1. day. The two temperatures used to quantify the wall system transfer function are the inside and outside surfaces of the wall (i.e., two surfaces exposed to the indoor and outdoor environments, respectively). The best insulating performance is achieved when insulation layers are positioned as close as possible to the inside and outside layers of the wall (i.e., near the indoor and outdoor environments). In addition, optimal results occur when both the insulation and thermal mass are distributed evenly throughout the wall. Using this optimized configuration, each material is then divided into an increasing number of thinner layers. Results indicate that an optimum number of layers exist such that the magnitude ratio is maximized. 2013 Elsevier Ltd.
