High-temperature heat pumps could be the game changer we need for retrofit

You only need to look at the volatility in gas prices over the past few years to understand why the transition to more sustainable heating solutions, which will mitigate this volatility, is crucial to reducing household susceptibility to fuel poverty. It’s vital that housing providers continue to make their homes warmer, more affordable and comfortable for their customers.

We’ve been on this journey for some time, using our Homes and Place standard to guide our thinking, determine investment priorities, and bring more of our homes up to the levels of comfort we want for our customers, while mapping a pathway to net zero.

When you take these arguments together, the rationale for retrofitting homes with sustainable alternatives, such as heat pumps, is obvious even without the legal obligation.

But as we know, the need to install low-carbon heating was never really in question.

“It is possible to retrofit homes and keep the existing radiators and pipework. It’s an exciting development, and a potential game changer for the sector”

Instead, the challenge has been the installation in existing homes, which was costly, time-consuming and disruptive as it was believed that especially old microbore (small-diameter) pipework had to be replaced. 

Not only that, but to install a low-temperature heat pump, which is all that existed on the market until recently, you had to replace most of the pipework. This meant lifting or replacing carpets, removing radiators and carrying out plenty of redecoration work afterwards.

Understandably, many of our customers found this disruption off-putting.

But there is good news. Our recent pilot with Mitsubishi Electric has turned the assumption that heat pumps cannot be fitted with legacy microbore pipework firmly on its head.

The early findings from this trial, in which we retrofitted six of our homes with high-temperature air-source heat pumps (HTASHPs), show that it is possible to keep the existing radiators and pipework. It’s an exciting development, and a potential game changer for the sector.

By significantly reducing the level of disruption to the customer and allowing existing pipework, radiators and floor coverings to remain, it mitigates a significant time and cost barrier to large-scale heat-pump retrofitting in our homes.

The findings to date also tell us that the installation of a high-temperature heat pump can take as little as two days, which is around 40% quicker than it currently takes SNG to install a low-temperature heat pump, pipework and radiators.

Then there’s the cost. Keeping the existing pipework and radiators while reducing the need to redecorate means we could save up to £2,000 per house that we retrofit. Across our gas-heated portfolio, this could represent significant savings. As a not-for-profit, this means we can invest more in our customers’ homes and provide greater value for money.

“The findings from this trial open the door for more providers to scale up their net-zero efforts in the knowledge that they don’t have to compromise on the comfort of their customers”

SNG is investing £500m over the next 10 years to retrofit 1,500 homes every year to reach a minimum Energy Performance Certificate rating of Band B or better. In addition to our own funding, we’re using £9.8m from the Social Housing Decarbonisation Fund (SHDF) Wave 2, over £19m from SHDF Wave 2.1, and £36.5m from the Warm Homes: Social Housing Fund.

While the introduction of medium to high-temperature air-source heat pumps will create a small drop in efficiency and therefore generate slightly higher running costs in comparison with low-temperature ones, no heating technology is completely without its limitations. It is, however, possible to mitigate some of this by ensuring the HTASHPs can adjust to weather conditions and do not operate at a fixed flow.

In addition, we can invest the money saved from lower installation costs into measures that would generate and store electricity for the home, saving residents more on their bills.

The findings from this trial open the door for more providers to scale up their net-zero efforts in the knowledge that they don’t have to compromise on the comfort of their customers or incur unnecessary costs.

Early next year, we will have additional data from more retrofit pilot projects we’re carrying out in 110 occupied homes. These explore differing heating, hot water and energy generation, distribution and storage systems, including HTASHPs.

For now, we’re excited by the potential of high-temperature heat pumps. We’ll use the data from all our trials to understand the optimal technologies for retrofit, to inform our approach to making our customers’ homes more efficient and comfortable.

Richard Young, technical director, Sovereign Network Group