Case studies of cavity and external wall insulation retrofitted under the Irish Home Energy Saving Scheme: Technical analysis and occupant perspectives

Abstract

a b s t r a c tThe residential sector represents 27% of primary energy consumption in Ireland. This paper examines the case study of the Irish government's national grant scheme to encourage energy efficiency retrofit in private housing. That is the Home Energy Saving (HES) Scheme, later rebranded the Better Energy: Homes (BEH) Scheme. The methodology involved monitoring several homes immediately before and after retrofit alongside discussions with occupants. The examination focused on specific measures commonly introduced through the HES/BEH programme − cavity and external wall insulation. It has been found that a significant decrease in heat loss through the walls was measured in all cases. Regardless, the occupant played a considerable role in the change in energy use in the buildings, and the main motivation for retrofit was found to be comfort and not energy savings or environmental concerns. As a result, the actual energy savings are notably less than the potential savings had the pre and post comfort levels remained the same.

Compact facility for testing steady and transient thermal performance of building walls

“…Although heat transfer delivered by conduction only is more common for small or single material testing [21][22][23][24][25], these apparatus have not been built on a scale or to a design that could incorporate a building wall sample. Heat transfer through the wall alone can also be examined in situ or in the laboratory, using heat flux sensors and thermocouples placed on the wall surface [38,39]. However, this method can only determine the heat flow at a particular location, which may not give an accurate reflection of the wall's true behaviour, particularly for inhomogeneous wall types such as the cavity block wall.…”

“…Hollow blocks possess a lower thermal mass than solid walls of the same thickness. It has, therefore, been shown that lighter internal layer thermal mass results in less benefit during insulation retrofit [38,39]. The following sections detail the specifications for the rig before examining the results of testing on the wall as compared to calculated and published values for this wall type.…”

Rarefied flow and heat transfer characteristics of rectangular cavities with heated concave surface

“…22 Cavity utilization in thermal insulation was investigated heavily in the literature; for example, Byrne at al. 23 investigated cavity as insulation in Irish homes, and the results were compared with external wall insulation. They concluded that small concaved cavities could be utilized in layers inside walls to improve thermal insulation.…”

Assessing the quality of retrofits in solid wall dwellings

“…The issues that Lowe and Bell identified almost 20 years ago are still seen today in new builds but also in retrofits and, as a result, measured performance remains below design standards (Byrne et al, 2016). It is difficult to infer industry performance from a small sample of case studies, however De Selincourt (2015) interviewed a range of industry experts and retrofit surveyors and found they consistently observed inadequate detailed design and poor workmanship, resulting in homes being left with substantial thermal bridges and potential thermal underperformance and moisture risks.…”