Renewable and zero emissions heating systems in affordable housing projects: evaluation

An evaluation of renewable and zero emissions heating systems in 21 Scottish affordable housing projects. This study assesses the estimated, actual, and counterfactual costs of the projects’ heating systems and determines the drivers behind decision making.

4. Overview of affordable housing projects

An overview of the projects participating in the evaluation is presented in Table 4. The table shows their locations by local authority area; the type of heating system; the target sustainability standard; construction status and project size (the number of affordable housing units). Several technologies are abbreviated here and throughout the report, with GSHP, ASHP and MVHR denoting Ground Source Heat Pumps, Air Source Heat Pumps and Mechanical Ventilation with Heat Recovery, respectively.

Table 4: Overview of projects included in this study.
# Local Authority Area Heating system Sustainability Target Status Size
1 North Ayrshire Solar PV & Electric boilers Bronze + Silver aspects On site 34
2 North Ayrshire Solar PV & Electric boilers Bronze + Silver aspects On site 18
3 North Ayrshire Solar PV &
Heat battery
Silver + Gold aspects Complete 4
4 North Lanarkshire Solar PV &
Heat battery
Gold Complete 2
5 Perth & Kinross ASHP Bronze + Silver aspects Pre-construction 4
6 Argyll & Bute ASHP Silver On site 300
7 Angus ASHP SAP - 81 Complete 10
8 Scottish Borders ASHP Silver + Gold aspects Pre-construction 4
9 Highland ASHP Bronze Pre-construction 14
10 South Ayrshire ASHP Unconfirmed Delayed 14
11 Perth & Kinross ASHP Unconfirmed Delayed 50
12 Dundee City ASHP & MVHR Unconfirmed Delayed 30
13 Highland ASHP, Solar PV &
Heat battery
Bronze + Silver aspects Pre-construction 117
14 Glasgow City ASHP, MVHR & Heat battery Platinum Complete 2
15 Dumfries & Galloway ASHP, MVHR & solar thermal Silver On site 5
16 Scottish Borders Shared ASHP Silver + Gold aspects Pre-construction 21
17 Edinburgh City Shared ASHP 100% above Silver Pre-construction 41
18 West Lothian Shared GSHP Silver Pre-construction 16
19 Edinburgh City Shared GSHP Bronze + Silver aspects On site 84
20 Fife Shared Biomass Bronze + Silver aspects On site 85
21 North Ayrshire Shared Biomass Bronze + Silver aspects On site 123

Of the 21 projects initially included in the evaluation scope, three were not able to participate due to delays. As such, we were not able to confirm all of the information for these projects, hence they are not referenced in any further sections of this report.

The project locations are shown below in Figure 2, where they are categorised according to the type of heating system. Where the category includes a '+' symbol, this indicates that there are several additional technologies included in the heating systems. The markers also give an indication of the size of each development (not to scale).

Figure 2: Project locations and heating system types
A map showing the location of the housing projects and their heating system types.

Figure 2 shows that the majorty of the projects participating in this evaluation are located close to or within the Central Belt of Scotland. There are also several remote, rural projects, including three located on Scottish islands.

Figure 3 demonstrates the split between settlement types according to the Scottish Government Urban Rural Classification, as well as the significant variation in project size. Whilst most projects have no more than 20 homes, there are a few with more than 100 homes, the largest having 300 homes. In Figure 3(c) projects are classified as 'large' if they comprise more than 20 affordable housing units. These factors have been presented here as they are likely influencers of a housing project's design, including its heating systems. The given distribution of size and settlement type indicates the variability in the sample and the potential broad range of factors that could impact heating technology choice.

Figure 3: Size and settlement classifications
Charts showing which settlement types the projects are in and their size.

Figure 2 also indicates that there is a broad variation in the heating systems specified across the various projects. This is further demonstrated in Figure 4, which shows the chosen technology, fuel type and composition of the 21 heating systems across the original projects. Clearly, heat pumps are used across the majority of the projects, with indvidual ASHPs being the most common.

Figure 4: Heating system classifications
A chart showing the heating technology, fuel type and composition of heating systems for the housing projects.

The projects are classified by what sustainability standard their energy systems are designed to achieve in Figure 5. The three delayed projects have not been included here as the targets were not confirmed and some of the other targets may be subject to change. The information provided indicates that the vast majority of the projects have heating systems that are designed to meet Silver Standard. Projects achieving Silver or a higher standard will meet the Affordable Housing Supply Programme's greener standard.

The two projects denoted as 'Higher' in Figure 5 include one Platinum project (which is notably the only project in this study to employ hybrid gas boiler air-source heat pump systems) and another which was yet to select a sustainability standard but aimed to be "100% improved versus Silver standard". The project listed as 'Other' was devised before the standards became mandatory, but (based on the target SAP score of 81 for the homes) would likely achieve Silver standard for its heating systems. The single 'Bronze' project was not able to afford Silver standard within the project budget.

Figure 5: Standards specified for heating system aspects of the Scottish building regulations' sustainability levels
A chart showing the sustainability standards that the housing projects are targeting.

The Bronze and Platinum projects were not able to provide cost breakdowns for their heating systems for work package 1 of this study. The other project aiming to meet a 'Higher' standard than Gold had not designed its heating systems yet and therefore had not yet costed this. The cost data presented in subsequent sections of this report relates only to projects that meet Gold and Silver (or equivalent) sustainability standards.



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