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Heat pumps, are they really the solution to low carbon heating in the UK?

By November 12, 2021 No Comments

It is possible to heat a building in many different ways. A traditional UK home is likely to have a gas boiler, this gas boiler heats water and drives it through radiators to heat each room.

Although this is the norm for UK homes, other countries employ other heating practices. For example, North American households rely on a central furnace to deliver their heat. These furnaces work by transferring heat to air, this heated air is then pushed through vents into living spaces. In Russia, the pechka – comparable to the AGA cooker – is a large stove, used for centuries in the Soviet states for food both preparation and for household heating. A pechka is a brick and clay stove that absorbs heat quickly but cools slowly, and often only needs to be lit twice a day to warm the entire home.

Heat pumps, extract warmth from the air, the ground, or water – a bit like a fridge running in reverse. Heat pumps are driven by electricity, if the electricity comes from a low-carbon source, then they provide greener heating. In this post we look at how feasible it would be for UK households to switch to heat pumps amid the news that there will be heat pump grants available for households

Over a fifth of the UK’s overall greenhouse gas emissions are attributed to the heating of buildings and dwellings, it, therefore, comes as no surprise that the government’s Heat and Buildings Strategy is under pressure to deliver effective reductions.

However, it isn’t always straightforward, for older UK homes the switch to heat pumps would require significant extra insulation to be fitted. Homes with combi-boilers would also require the installation of hot water storage systems, most likely with additional electric heating to cope with higher temperature demands.

 

Air or ground source – which one is for me? 

Air source heat pumps tend to be easier to install but they offer slightly less efficiency. They also require homeowners to have the external space needed to accommodate the main pump unit, which can be up to a meter tall.

The more efficient option is a ground source heat pump, but these require the external pipes to be buried and this route can therefore involve a good deal of excavation work. If this isn’t practical, then air source is likely to be the sensible option.

It is also worth mentioning that a heat pump can both heat and cool, meaning that the same appliance can heat your home in the winter and cool it in the warmer summer.

What will it cost me?

The switch to heat pumps can be expensive, which is why the Government is offering an incentive. However, if homeowners are to ditch gas heating for heat pumps, they need to be confident that the UK climate can sustain the switch.

Historically, heat pumps have been reported as becoming less efficient and effective when the outside temperature drops below 5C. The below graph illustrates that UK temperatures in January and February regularly dip below 5C. Therefore, a back-up heating source may be needed to keep homes warm during the UKs coldest months.

 

Retrofitting to an existing heating system

If you are interested in taking the Government grant and having a heat pump retrofitted in your home, you may be worried about how it will function with the heating devices already installed, such as your radiators and hot water tanks.

Radiators have a comparatively small surface area and if used alongside a heat pump they may need to output a higher temperature than, for example, underfloor heating that has a larger surface area. Heat pumps and underfloor heating work well together, however, to avoid lots of renovation and repair work, you could investigate the practicality of having larger radiators installed, this can be a cost-effective alternative to system modifications.

Heat pumps heat water too, so if your home has a hot water cylinder you can keep it, but it will need to be checked to ensure it is compatible for use with a heat pump. Homes with a combi boiler will need to reinstall a hot water tank.

Things to be mindful of

How well your property is insulated is a considerable factor to consider when researching the viability of switching to a heat pump. Heat pumps produce heat at a much lower but more constant temperature, this means that the insulation of your home becomes incredibly important.

As a minimum your home should have:

  • Cavity/wall insulation
  • Loft insulation
  • Double glazing

Some older homes may also require floor insulation. Due to these additional requirements, it would be no surprise if symbiotic insulation grants became available for those taking advantage of the heat pumps Government grant.

 

Are heat pumps the solution to low-carbon heating in the UK?

Heat pumps have been around for many years, but historically they struggled to maintain their efficiency in extremely cold weather. Thankfully that is changing and some of the newer cold-climate heat pumps can still transfer heat effectively in sub-zero temperatures. The newer models may only require a backup heat source on the very coldest of days. The bigger issue is that currently there is no guarantee that the electricity used to power each unit comes from a renewable or truly zero-carbon source. Which makes this move feel like a compromise rather than an answer.

In the coming three decades the Government is committed to overseeing a switch from gas boilers to ground or air source heat pumps. However, in the UK there are many homes that don’t currently fit the mould, particularly his rise blocks of flats, where heat pump use is impractical due to the problems in attaching the units to the outside tall structures and protecting them from the worse of our winter weather.

We don’t argue that heat pumps can play a valuable role in achieving the UK’s climate change targets, but there is a lot more work to be done.