U.S. buildings are a significant source of energy consumption (about 50%) and carbon emissions (about 40%), and providing conditioning to building interiors is a major portion of that expenditure. Improving building envelope performance can reduce the amount of energy used for heating and cooling, since external walls provide an important barrier between occupied building spaces and variable ambient conditions. In general, multi-layer exterior walls tend to perform better than single-layer walls, even for the same overall R-value and thermal capacitance. This work addresses practical choices in multi-layer wall design to minimize internal temperature swings that result from outside, or ambient, temperature fluctuations. An electrical analogy is used to model one-dimensional heat conduction using RC circuits. A frequency response analysis is conducted based on a period of one day. For a fixed wall thickness, four features are optimized: materials, proportion of materials, number of layers, and material distribution. Key design features include pairing insulating and thermally massive materials, distributing layers evenly, and positioning the insulating layers at the inner- and outer-most layers of the wall (i.e., near the indoor and outdoor environments). Methods for determining the optimal proportion of each material and number of layers are also presented. Combined, these easily implemented features can reduce interior temperature fluctuations by several orders of magnitude compared to ambient temperature variations. This helps maintain steady indoor temperatures, which is more comfortable for building occupants, and supports energy management strategies, like reducing peak heating and cooling loads.
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