Performance check between whole building thermal performance criteria and exterior wall measured clear wall R-value, thermal bridging, thermal mass, and airtightness

J. Kosny, J. E. Christian, A. O. Desjarlais, E. Kossecka, L. Berrenberg

Research output: Contribution to journalConference articlepeer-review

26 Scopus citations

Abstract

The dynamic thermal performance of an insulated concrete form (ICF) system was analyzed based on a dynamic guarded hot box test. The same wall configuration was modeled for dynamically changing boundary conditions using the finite difference computer code HEATING 7.2. Thermal mass validation of the model was made by comparing model heat flow predictions to the hot box measured heat flow through an ICF clear test wall exposed to dynamic boundary conditions. Good agreement was found between test and computer modeling results. A series of response factors, heat capacity, and R-values were computed using finite difference computer modeling. They enabled a calculation of the wall structure factors and estimation of the simplified one-dimensional 'thermally equivalent wall' configuration. The usage of the equivalent wall theory provides a direct linkage from dynamic hot box test to accurate modeling of buildings with walls that contain considerable three-dimensional heat flow within the structure. The equivalent wall generated for the ICF system was used in a whole building computer model to simulate a single-family residence in six representative U.S. climates. The heating and cooling loads generated from these building simulations were used to estimate the R-value that would be needed in conventional wood-frame construction to produce the same loads as the ICF system. The resulting R-value is considered an effective R-value for the ICFs, which not only accounts for the steady-state R-value but also the inherent thermal mass benefit. A second major benefit of this ICF system is the airtightness. This paper also analyzes the impact of a 20% reduction in uncontrolled infiltration for the ICF house compared to the wood-frame structure.

Original languageEnglish
Pages (from-to)1379-1389
Number of pages11
JournalASHRAE Transactions
Volume104
Issue number2
StatePublished - 1998
EventProceedings of the 1998 ASHRAE Annual Meeting - Toronto, Can
Duration: Jun 21 1998Jun 24 1998

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