HO-82-03-4 -- The Determination of the Dynamic Performance of Walls

The thermal performance of building walls, in situ, is largely unknown. Until now, most wall performance measurements have been done in laboratories, typically by using large hot-boxes. In-situ performance is considerably more difficult to measure, for the experimenter usually has little control over temperature, solar radiation, or wind conditions. The task of accurately measuring surface temperatures and heat fluxes over significant lengths of time is not easy. Furthermore, once measurements have been obtained analysis of the data is not a trivial matter. As illustrated by a review of measurement techniques and wall performance models compiled by Carroll, most existing models contain too many parameters to be suitable for direct analysis.

A simplified model of dynamic thermal, performance that allows the characteristics of a wall to be quantified on the basis of measured surface temperatures and heat fluxes has been developed. The model, uses a set of simplified thermal parameters (STPs) to characterize the thermal performance of walls from an arbitrary temperature history. In addition, the STPs can be used to arrive at a physical interpretation of the behavior of a wall. This model is applicable to any set of data. In this report, however, its applicaton to the analysis of data collected by the Envelope Thermal Test Unit (ETTU), is demonstrated. Accordingly, laboratory measurements using ETTU are included as part of the validation procedure.

Citation: ASHRAE Transactions, Volume 88, Part 1, Houston, TX



Product Code(s): D-HO-82-03-4