Low temperature heating: A ‘no regrets’ step on the road to net zero

Heat pumps will play a primary role in the future heating market thanks to their high levels of efficiency and use of ever-greener electricity, says Heat Pump Association Chair Phil Hurley

Festival Net Zero 2021

Most people know that changes are required to reduce carbon emissions in line with the UK’s net zero carbon target but while people are able, and on the large part willing, to make greener choices to reduce their individual carbon footprints, many are unaware that 14% of UK carbon emissions come from household heating.

Domestic households represent the second-largest energy consumer after transport, and with a substantial 83% of homes connected to the gas grid, more must be done to support the shift away from carbon-intensive heating towards low carbon, energy efficient alternatives. Yet over 1.7 million fossil fuel boilers are still being sold in the UK every year, and a large proportion of homes are not prepared for the installation of alternatives.

Implementing change on this scale is not easy, and while we cannot reasonably expect all 24 million UK homes to become ‘net zero ready’ overnight, steps can be taken to level the playing field between heating technologies and prepare homes for the inevitable installation of low temperature heating systems. This is essential to both the legislated net zero target and the commitment to deploy 600,000 heat pumps per year by 2028.

Heat pumps will play a primary role in the future heating market thanks to their high levels of efficiency and use of ever-greener electricity, but their installation requires considerations on top of those typically needed for ‘traditional’ heating systems. For example, heating emitters – such as radiators – are commonly sized for significantly higher flow and return temperatures than those heat pumps require for optimal operation. This is because gas boilers can operate efficiently at temperatures of around 70°C; however, it is important to note that their efficiency also improves at lower temperatures. As such, upgrading heat emitters so that they can condense more consistently than at higher temperatures is a ‘no regrets’ step on the road to net zero. Not only will it allow us to lower fuel bills and carbon emissions from heating systems in homes today, but it will also prepare homes for the inevitable installation of low carbon heating in the future.

The Heat Pump Associations (HPA) 2020 report, Retrofitting Homes for Net Zero Heating, advocated for the Domestic Building Services Compliance Guide to be adjusted so that a maximum 55°C flow temperature is a ‘Minimum Standard’ for the installation of all heating systems from 2026. More immediate changes can of course be made in advance, such as a requirement within the Building Regulations for any full replacement of a heating system, including heat emitters, to be designed to operate at 55°C.

The Government’s response to the Future Homes Standard (FHS), complete with Draft Guidance for 2021 Approved Document L, has thankfully stated that newly installed or fully replaced heating systems should operate at a flow temperature of 55°C or lower (unless ‘it is not feasible’). This is an important interim step in the preparation for the implementation of the FHS in 2025, not just because it will minimise the installation cost of heat pumps in future and limit barriers to uptake, but because it will improve the efficiency of any heating system put in place at the time.

New insight into how prepared existing UK homes are for low carbon heating has been provided through a study commissioned by the Department for Business, Energy and Industrial Strategy (BEIS). Findings quantify the number of homes for which changes to the heating emitters are required to accommodate a low temperature heating source, such as a heat pump.

On a peak winter day, the study finds that just 10% of UK homes are suitable for heat pumps with a 55°C flow temperature, with no changes to their heat emitters. When considering the average temperature for the coldest winter month, this rises to 55% of homes, with no changes to their heat emitters or flow rates for most of the heating season. Provided that the heat pump is able to meet the maximum required flow temperature for the peak heat demand (kW), the flow temperature could in fact be reduced for much of the season to increase overall efficiency. However, these figures are significantly reduced when considering additional heat demand above what is calculated by SAP or reductions in radiator performance over time. While the study highlights that heat pumps with additional heat sources can be installed even without changes to heat emitters in a proportion of UK homes, it provides an important indication of the share of homes that still require improvements in preparation for low carbon heat. It is essential that these improvements are made as soon as possible.

The study also highlights that heat emitters are rarely hydraulically balanced to ensure that the distribution of water in heating systems is optimised. The HPA and other key industry players have called for a Low Carbon Heat Course to be introduced as part of accreditation refresher courses for heating installers. This course would include practices such as heat loss calculations, heat emitter sizes and hydraulic balancing, which – as confirmed by the recent BEIS study – is not commonplace as part of the installation of traditional heating systems. It is therefore essential that policies are put in place to mandate the training installers need to support the shift to low temperature heating across this decade.

This is a promoted article.

 

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