Heat pump mythbusters commentary - part 4: Will I need to spend a lot insulating my home to get a heat pump?

Domestic heat pump in back garden, with pots and fence in the background

In parallel with the Guardian's mini-series Heat Pump Mythbusters, we’ll be sharing a running commentary on each article and our additional thoughts on the opportunities and challenges of electrifying heat in the UK. 


Article 4: will I need to spend a lot insulating my home to get a heat pump?

Article summary

  1. Heat pumps can be the single biggest intervention a household can make to reduce their carbon emissions.

  2. In comparison to boilers which can input large quantities of heat in short bursts, heat pumps are generally set up to run “low and slow” for longer periods of time.

  3. As heat pumps work at a lower temperature than boilers, a greater volume of water needs to be circulated to deliver the same amount of energy. However, in most cases, existing pipework should be suitable for this greater volume of water.

  4. The UK has some of the least well-insulated houses in Europe, however this does not make them unsuitable for heat pumps. It is more important to design the system correctly and size radiators appropriately than it is to insulate.

  5. A quick, easy and cheap win for many houses is to insulate lofts. Insulating solid walls can be more costly and disruptive.

  6. Radiator upgrades and installation of a hot water storage tank will likely be required as part of a heat pump installation. Pipework upgrades may be required.

  7. For those on low incomes, various government grants are available for improving insulation at no cost.

Read the full article here. 

Additional commentary

1. Insulating lofts should be done whether or not a heat pump is planned as it will reduce a home’s energy consumption and associated carbon emissions regardless. From experience, this can be quite an unpleasant job working in cramped conditions, removing decades of dust and rubble, but is achievable with little expenditure. This was the only insulation installed in my terraced house prior to the installation of a heat pump.

2. As part of my installation, a hot water tank and radiator upgrades were required – the cupboard for the hot water tank cupboard is approx. 1m2. Existing pipework which was easily accessible below floorboards was replaced, but pipework which was harder to access was left in place.

3. From the Guardian's graphic developed from Nesta/Energy Savings Trust data, draught proofing and loft insulation are the cheapest measures per carbon saving, however, they have a limited maximum carbon saving. When including the Boiler Upgrade Scheme, installing a heat pump is not only cheap per kilogram of carbon saved, but also offers the greatest total carbon savings over the next best intervention (internal wall insulation) by a factor of three.

Bar chart showing relative costs of carbon savings

4. Although double glazing is relatively expensive and offers a comparatively modest carbon saving, installing it in properties which are single-glazed will likely offer a significant increase in occupant comfort. This is because the surface temperature of the internal face of double glazing is significantly higher than single glazing, reducing both cold draughts and radiant heat losses from a person to the window. Triple glazing is even better than double glazing and only 5-10% more expensive. For external temperatures of 0oC and an internal temperature of 20oC, the internal face of the glazing will be roughly the following temperatures.

Simple chart showing glazing types and relative surface temperatures.

5. Sealing up a home to reduce heat losses from draughts is a good way to reduce heat losses, however consideration needs to be given to maintaining ventilation levels to remove moisture and reduce mould growth. In new builds, Mechanical Ventilation with Heat Recovery can provide controlled ventilation very efficiently, however these systems can be difficult to retrofit in existing properties.

6. Likewise, care should be taken if installing internal wall insulation, to avoid the build-up of interstitial condensation, resulting in damp and mould growth.

7. Fuel poverty is a real issue in the UK, which the government must address as part of any energy transformation in the UK. Heat pumps and warm homes cannot solely be for the affluent.