Too Hot for Net Zero

Phil Hurley - Chair of the Heat Pump Association

A recent Heat Pump Association Installer Survey has revealed that more than 70% of heating systems are set to temperatures over 66°C.

The Heat Pump Association published a report last year on the steps that should be taken to retrofit homes for net zero heating. The paper advocated for a maximum flow temperature of 55°C for the installation of all heating systems from 2026 in addition to important steps to instigate more immediate progress.

Since then, the Government has set out Draft Guidance that aligns with these interim recommendations by stating that newly installed or fully replaced heating systems, including all heat emitters, should operate at 55°C or lower.

But what changes are needed to support the necessary shift to low temperature heating? To help answer that all important question, the HPA recently surveyed 182 heating installers, each providing valuable insight that will hopefully help to inform important decisions in the years ahead.

Phil Hurley, Chair of the Heat Pump Association, summarises some of the survey’s headline findings below.

There is a Huge Opportunity to Improve the Efficiency of Heating Systems

As is to be expected, most heating systems are set to operate at flow temperatures above 66°C, with less than 10% set to perform at the recommended 55°C or lower. This is no surprise considering that fossil fuel boilers are the dominant heating system and that they can operate at temperatures of around 70°C.

However, it helps to crystalise a huge opportunity for improvement. All heating systems, be it a low carbon heat pump or a fossil-fuelled gas boiler, are more efficient when operating at lower temperatures – and yet over 90% of heating systems are currently set to operate at temperatures above 55°C. Even though the condensing point for boilers can be met at these higher flow temperatures, there are still considerable efficiency gains to be made beyond this point. Improving their efficiency is an opportunity that therefore cannot be missed.

Heat Emitters Must Be Upgraded to Allow Low Temperature Heating

To achieve lower flow temperatures, upgrades to heat emitters may be needed. Several radiators, for example, may need to be replaced with larger more modern efficient ones so that they allow the boiler to condense more consistently that at higher temperatures.

The Government’s decision to require all newly installed or fully replaced heating systems, including heat emitters, to be designed to operate at a flow temperature of 55°C or below is a promising ‘no regrets’ step on the road to net zero. Upgrading heat emitters now will not only save households money on fuel bills but will also reduce carbon emissions regardless of the heating system in place. This is shown in the below table, which was extracted from the HPA’s 2020 report: Retrofitting Homes for Net Zero Heating.

Net Present Value of Achieving Lower Flow Temperatures During a Full Radiator Upgrade

Upgrades to heat emitters so that they can perform at low flow temperatures will not just deliver immediate improvements in energy efficiency but will also provide the future proofed heating system infrastructure that would allow low carbon heating technology like heat pumps to be installed at a later date.

This key consideration in preparing homes for net zero heating was further demonstrated by our recent survey results, with installers indicating that over 70% of radiators within a home would need replacing or resizing when installing a heat pump. The analysis above demonstrated a benefit for the consumer even where 100% of the radiators were changed. Upgrading emitters now will therefore help to turn the Government’s 600,000 heat pump deployment target into a reality by 2028.

Most Heating Installers Have Limited Experience Installing Low Temperature Heating Systems

While some installers already understand practices such as heat loss calculations, heat emitter sizes and hydraulic balancing, they are not currently commonplace as part of the installation of traditional boiler heating systems.

With the majority of heating installers indicating that they have between 0-5 years of experience installing low temperature heating systems, it is clear that there is a need for training to ensure that they have the skills and confidence they need to ensure that heating systems can operate correctly at temperatures of 55°C or below.

As such, the HPA and other key industry players have called for a Low Carbon Heat Course to be introduced as part of mandatory accreditation refresher courses for heating installers which would include training on the practices mentioned above. This course is not just necessary to upskill and train the workforce; it also has the backing of installers. This was confirmed by a recent research report published by BEIS, which found that 76% of installers were very or fairly supporting of mandatory low carbon modules in traditional heating and plumbing qualifications.

New Training Route Being Developed For Heat Pump Installers

Turning Evidence into Action

As Chair of the HPA, I am pleased to have seen so many heating installers have engaged in our survey and to have received responses from both those who do and do not install heat pumps. All 182 respondents have helped us to gather important insight into the changes needed to shift towards lower temperature heating.

We hope that this evidence will be used to improve the efficiency of all heating systems and to help establish the heat emitter infrastructure required for the rollout of heat pumps. While there is a huge challenge at hand, there is also an incredible and cost-effective opportunity for us to prepare homes for the low carbon future.

For more information on the Heat Pump Association visit:

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