Is My House Suitable for a Heat Pump

This is perhaps the most important part of determining whether or not your home is suitable for a heat pump system.

Most heat Pumps operate at a lower temperature than boilers, with a typical top operating flow temperature of 55℃. However, they are at their most efficient when operating in the range of 35-40℃.

Relying on this constant flow of low level heat makes them more susceptible to heat loss from a poorly insulated home. If your home is leaking like a sieve, a heat pump won’t be able to keep it warm.

For homeowners who live in an older building, there are multiple upgrades which can be carried out first to make your home heat pump ready.

Which of these is necessary will depend on the specifics of individual homes. A house may have attic insulation, but no cavity wall insulation. Or the insulation in place could be older, and not up to current standards.

The thermal transmittance of an area such as a wall, floor, or ceiling is expressed as its U-value. This is the rate at which heat passes through that structure when the unit temperature difference is maintained between the ambient air temperatures on each side.

The lower the U-value, the better the thermal performance of the structure in question.

The SEAI has set guidelines for what U-values buildings should achieve for different areas after the installation of new insulation.

If they are not already present, then insulation should be installed on water pipes and the domestic hot water tank which make up the central heating and water supply systems as well to prevent heat loss there.

Another area of a home which is relevant to whether a heat pump would work is the heating system currently in place. 

A home with traditional radiators which are designed to work with water flow temperatures of 60-80℃ might not be suitable for many heat pump systems. In this case, it would be an option to install a high-temperature heat pump model. While more expensive, these are still far more efficient than fossil fuel boilers.

Another option would be to replace the radiators as part of any renovations to the property. If replacing the floor to install insulation, this would also be an ideal time to think about getting underfloor heating.

More modern homes with larger radiators or underfloor heating systems are already well suited to all heat pump models.

We’ve mentioned above that there are basic targets which people should set out to hit if installing insulation in their homes. 

Meeting those requirements can be dependent on the quality and thickness of the insulation installed. This along with new doors and windows could potentially be cost prohibitive.

One thing which must be kept in mind if carrying out home energy efficiency upgrades before getting a heat pump installed is that once you start altering the fabric of the building there are thermal efficiency requirements which must be met.

Building Regulations also determine what U-values are permitted whenever an extension or material alteration to the fabric of an existing home.

These are the maximum U-Values permitted when renovations have been carried out to any of these elements, and ideally, you should be exceeding them.

There are also exceptions to these rules. The Cavity Wall U-Value only applies if it is suitable for cavity wall insulation.

The SEAI has its own set of requirements for homes to meet before being eligible for heat pump grants. 

Up to €6,500 is available to help homeowners with the cost of installing a heat pump, but if your home was built prior to 2007 it must first undergo a Technical Assessment. 

This assessment will measure the Heat Loss Indicator (HLI) of your home, which is a measurement of the total heat loss per m² of the property.

𝐻𝐿𝐼 = 𝐹𝑎𝑏𝑟𝑖𝑐 𝐻𝑒𝑎𝑡 𝐿𝑜𝑠𝑠 + 𝑉𝑒𝑛𝑡𝑖𝑙𝑎𝑡𝑖𝑜𝑛 𝐻𝑒𝑎𝑡 𝐿𝑜𝑠𝑠 𝐹𝑙𝑜𝑜𝑟 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑑𝑤𝑒𝑙𝑙𝑖𝑛𝑔 [ 𝑊/𝐾 ∙ 𝑚2 ]

In order to qualify for the grant your home must have an HLI of 2 or less. 𝐻𝐿𝐼 ≤ 2 𝑊/𝐾 𝑚2 

If you do not meet this standard, the assessment will recommend upgrades which can be carried out to meet the standard.

If these are not cost feasible to carry out, then an HLI of ≤ 2.3 𝑊/𝐾 𝑚2 can be accepted if other qualifications are met.

Issues can arise if the property in question is a Protected Structure or located in an Architectural Conservation Area. These are likely to be older buildings which have poor thermal performance.

Traditional buildings which make up the core of most towns and cities were often built prior to 1940. They will typically have solid masonry walls, single glazed windows, and timber framed roofs. 

Census data shows that such buildings could comprise as much as 18% of Ireland’s housing stock. The biggest areas of heat loss in traditional buildings are:

It’s not impossible to carry out renovations on these buildings, but such works are always assessed for their material and visual impact on the structure.

This can cause issues if someone wants to carry out the kind of renovations which would bring them up to a standard where a heat pump would be usable.

Government guidance on retrofitting traditional buildings outlines how work such as insulation should be done without negatively affecting the original fabric.

If working with a protected building or within an ACA it would be advisable to consult with your local authority on how work should be carried out.