Thermal Performance of Uninsulated and Partially Filled Wall Cavities
Wall cavities are widely present in the construction of low rise homes since wood framing is the most common type of construction for residential buildings in the United States. The primary function of such wall construction is to provide a stable frame to which interior and exterior wall coverings can be attached and by which a roof can be supported. The existence of wall cavities increases the thermal resistance of the enclosure, particularly when they are filled with insulating material. Several design guides provide data for prediction of the thermal resistance of uninsulated wall cavities of varying internal geometries. However, U-value coefficients provided in these guides do not account for partially insulated cavities or for variations in aspect ratio. Whole building energy simulation tools, like DOE2 or Energy Plus, use simplified, 1-D characterization of building envelopes. For the most part, this characterization assumes a fixed thermal resistance over the range of temperatures experienced by the enclosure. In reality, the thermal resistance is dominated by convection and radiation and is a function of several parameters, including the temperatures and emissivities of the cavity surfaces and the aspect ratio of the cavity. This study describes detailed CFD modeling to evaluate the thermal performance of uninsulated or partially filled wall cavities accounting for conduction through framing, convection, and radiation. The resulting correlations can serve as input for DOE2 and Energy Plus modeling of older homes, where the walls are either uninsulated or partially insulated due to the settling of the insulating material. Parameters of the study are the ambient temperature outdoors, emissivity of the cavity surfaces, cavity aspect ratio, and height of the insulation level. The outcomes of this study provide: An understanding of the thermal performance of uninsulated or partially insulated wall cavities, which is an essential aspect of energy conservation in residential buildings. Accurate input for whole building simulations models like DOE2 and Energy Plus in various climate zones. Recommendations on retrofit measures.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1045726
- Report Number(s):
- NREL/CP-5500-54454; TRN: US201215%%109
- Resource Relation:
- Conference: Presented at the 2011 ASHRAE Annual Conference, 25-29 June 2011, Montreal, Quebec, Canada; Related Information: Paper No. ML-11-C012; See NREL/CP-5500-50925 for preprint
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMBIENT TEMPERATURE
ASPECT RATIO
CAVITIES
CLIMATES
CONSTRUCTION
CONVECTION
DESIGN
EMISSIVITY
ENERGY CONSERVATION
OUTDOORS
PERFORMANCE
RADIATIONS
RESIDENTIAL BUILDINGS
ROOFS
SIMULATION
WALLS
WOOD
residential
heat transfer
thermal performance
wall cavities
insulation