Low carbon heating in domestic buildings - technical feasibility: report

1 Introduction

1.1 Background

In April 2019, the First Minister declared a global climate emergency - calling for action from Scotland and the world - and committed Scotland to net-zero greenhouse gas emissions by 2045, in line with the UK Committee on Climate Change (CCC) recommendations.^[2]

The Climate Change (Emission Reduction Targets) (Scotland) Act 2019 has been passed by the Scottish Parliament setting in law very ambitious targets to reduce greenhouse gas emissions, requiring Scotland to reach net-zero emissions by 2045, with 75% reductions by 2030 and 90% reductions by 2040.

Scotland's Climate Change Plan set an ambition for emissions from buildings to be near zero by 2050, and targets 35% of domestic and 70% of non-domestic buildings' heat to be supplied using low carbon technologies by 2032. This Plan is due to be updated in 2020 to reflect the new emission targets. Scotland's Energy Strategy includes a separate target for 50% of Scotland's energy across heat, transport and power to be supplied using renewable sources by 2030. The Energy Efficient Scotland programme, launched in May 2018, sets out a wide range of measures, including funding, pilot projects and information provision, to promote low carbon heating alongside energy efficiency improvements in Scotland's buildings.

Meeting these targets will require almost all households in Scotland to change the way they heat their homes. There is a wide range of potential low carbon heating options, and as yet there is no clear consensus on the most appropriate technology or mix of technologies. It is therefore imperative to advance our understanding of the suitability of the available low carbon heating options across Scotland's building stock.

1.2 Objectives

The aim of this work is to assess the suitability of low carbon heating technologies in residential buildings in Scotland.

There is large variation across the building stock in Scotland, leading to significant differences in the most suitable and effective low carbon heating options and the additional improvements required to install low carbon heating.

Numerous factors influence the suitability of one or more of the available heating technologies. Concerning the building itself, this includes the building construction type and energy efficiency level, the existing heating technology and heat distribution system, listed or conservation area status, internal and external space constraints and other factors.

However, the factors influencing suitability of low carbon heating options relate not only to the building itself, but also to the location in which the building is situated. For example, the potential for a heat network in the vicinity of the building presents a potential means of decarbonising heat even where deep energy efficiency retrofit could be difficult, as does the presence of a gas network, through which low carbon gas could be delivered. The ease of physical access to the building may have an impact on the cost or technical feasibility of applying new, prefabricated insulation approaches, and the exposure of the building to coastal or other more severe environmental conditions might impact the cost of materials.

In order to deliver a useful analysis of the suitability of low carbon heating technologies in Scottish homes, this study aims to produce:

• A set of archetypes representative of the Scottish housing stock, segmented according to the most material attributes influencing the suitability of low carbon heating;
• An assessment of the technical feasibility of the considered low carbon heating options within each of the archetypes;
• An overall assessment of the suitability of each low carbon heating option across the Scottish building stock.

The outputs generated through this work will form a key part of the evidence base on low carbon heat which the Scottish Government will use to further develop and strengthen Scotland's low carbon heat policy, in line with the increased level of ambition of achieving Net Zero by 2045.

1.3 Methodology

This research and analysis for this study were carried out in three key stages, illustrated in the following chapters.

Review of technical feasibility of low carbon heating in homes → Creation of a model representing the Scottish domestic building stock in 2017 and 2040 → Analysis of the suitability of low carbon heating in current and future Scottish homes

The first stage, reported in Chapter 2, focussed on the review of technical feasibility of low carbon heating in homes. A comprehensive literature review of the factors influencing suitability and of the barriers to deployment of low carbon heating in domestic buildings was performed, including any features that could be relevant in the Scottish context. The information thus collected was utilised for the identification of the most relevant attributes that should be considered in the following stage for the creation of a stock model. Some of the most relevant sources utilised are the recent work on 'Hard to Decarbonise Homes' for the CCC^[3] and the Evidence gathering for electric heating options in off gas grid homes for BEIS.^[4]

The second stage, described in Chapter 3, aimed at the creation of a model representing the Scottish domestic building stock. Initially, a review of the data on Scottish homes found in Home Analytics Scotland Dataset and various other sources was performed. Based on the available information on the buildings stock offered by Home Analytics and on the relevant suitability parameters determined in the previous stage, a set of useful attributes influencing the suitability of low-carbon heating technologies in Scottish homes was identified. The existing domestic building stock in 2017 could therefore be mapped to a list of archetypes, characterised by these selected attributes. Finally, a scenario for the deployment of energy efficiency measures was developed according to the targets of the Energy Efficient Scotland Route Map, allowing for a comparison between of the characteristics of the current building stock in the year 2017 and of the likely building stock in 2040.

In the last stage, outlined in Chapter 4, an analysis of the suitability of each of the archetypes representing the Scottish domestic building stock for a set of 26 low-carbon heating systems was performed. The suitability of the current and future Scottish domestic building stock for low-carbon heating could therefore be tested and the characteristics and number of homes that are suitable only for a restricted range of low-carbon heating technologies was more closely examined.