OR-20-013 -- Home Envelope Performance Evaluation Using a Data Driven Method

Envelope performance evaluation, namely evaluation ofthe thermal properties (thermal transmittance and capacity)and airtightness are becoming increasingly important forachieving energy efficient homes. Unlike traditional evaluationmethods—such as those based on initial design data,measured structure data from sampling, and in-situ measurementsusing a heat flow meter—the model-based envelopeperformance evaluation method proposed in this paper isbased on a simplified home thermal model. This method canevaluate the overall home envelope thermal performance, i.e.,the integration of thermal properties and airtightness, using ashort period of indoor and outdoor air temperature data.Depending on the availability of the wind or not, this methodcan also evaluate the airtightness of an envelope. Threesequential experiments were conducted to validate the effectivenessof the method. The first experiment showed the windeffect can cause around 15% difference in envelope thermalproperty estimations; the second experiment suggested winddata collected from a city weather station might not be accurateto represent the local wind conditions near the test home;and the third experiment, using data collected from 1,676homes, demonstrated that the envelope performancedecreased proportionally as the home age increased for homesthat were 5 to 40 years old, while there were no distinctivepatterns for homes older than 40 years due, perhaps, to a smallsample size. The demonstrated results of the third experimentalign well with the expectation that younger homes experiencebetter home envelope thermal performance. Although moreexperiments are needed, with knowledge of the ground-truth ofthe test home envelope conditions, the results of this papershow that the model-based envelope performance evaluationmethod can be an efficient, practical, and effective alternativeto the traditional methods by eliminating physical heat flow orconstruction material property measurements.