Nate Huygen, and John Sanders
i Research Associate, National Brick Research Center, Clemson University, nhuygen@clemson.edu
ii Director, National Brick Research Center, Clemson University, jpsand@clemson.edu
ABSTRACT
Cool walls are designed to reduce energy consumption by having a high solar reflectance which minimizes the heat energy absorbed from solar radiation. This strategy is more effective for light-weight wall systems than for more thermally massive walls due to the ability of the mass to act as a buffer against heat transfer. In this study, three different wall systems were analyzed – fiber cement cladding, brick veneer cladding, and brick veneer over typical concrete masonry unit (CMU) – to cover a spectrum of thermal masses typical in residential and commercial buildings. Using a 2D finite element program, along with typical metrological year (TMY) climate data, these walls’ performance was simulated. The influence of climate zone, wall orientation, and solar reflectance was studied. It was found that the thermal performance of the light-weight wall had the highest sensitivity to changes in solar reflectance due to its minimal capacity to store and buffer solar energy. Conversely, increasing the wall’s thermal mass not only made the thermal performance less sensitive to solar reflectance, but also significantly reduced the energy usage of dark-colored walls. A brick veneer wall was found to have a 22% decrease in cooling energy and 44% decrease in peak cooling load as compared to a fiber cement wall in climate zone 1. A brick veneer wall over CMU was found to have a 28% decrease in cooling energy and a 66% reduction in peak cooling load as compared to a fiber cement wall in climate zone 1. If a wall has enough thermal mass and is in a favorable climate, there are conditions where a darker colored wall has a lower total energy usage. These results emphasize the need for holistic design of the building envelope when trying to optimize energy efficiency.
KEYWORDS: Thermal Mass, Solar Reflectance, Energy Modeling, Wall Envelope.
093-Huygen.pdf
