Do U-value insulation? England's field trial of solid wall insulation

Panel: 5A. Cutting the energy use of buildings: Projects and technologies

This is a peer-reviewed paper.

Authors:
Geoffrey Stevens, Energy Saving Trust, United Kingdom
Jaryn Bradford, Energy Saving Trust, United Kingdom

Abstract

The Energy Saving Trust is completing the largest UK field trial to monitor the in-situ performance of retrofit solid wall insulation. We have gathered building performance data from over 75 houses in England, including: monitoring of external/internal temperature and humidity; wall surface temperature; and gas and electricity usage at 5 minute intervals. Thermal imaging, u-value and air tightness measurements have also been captured, and all measurements have been taken before and after insulating.

U-value measurements show that pre-insulation thermal performance of solid walled buildings in England varies widely. The average pre insulation U-value for the sample was 1.4W/m2K, well below the assumed value for a solid wall of 2.1 W/m2K. Further, based upon temperature measurements, almost half of the properties in the trial were considered to be under-heated.

Partners from across the insulation industry committed to insulate a third of the properties in the field trial. A number of challenges and barriers to installing solid wall insulation were identified, including technical, social and legal challenges encountered during the process of installation, which are discussed in further detail.

Post-insulation data, presented in early 2013, will give crucial insight into achieved energy and carbon savings and consumers’ perceptions of comfort and control. Post insulation u-value measurements will also be investigated to reveal possible gaps in estimated performance of insulation systems based on lab testing and modeling versus observed performance.

This paper therefore will present the baseline energy consumption measured at the 75 properties; demonstrate the measured u-values and thermal efficiency of solid-walled buildings; and discuss the energy savings and changes to internal temperature recorded at monitored properties as a result of the installation. Further, the paper will discuss the barriers encountered to retrofitting solid wall insulation in the UK.