Written by: Briain Kelly
Reading time: 5mins
Getting a heat pump can be one of the best ways to make your home more energy efficient by stopping the use of fossil fuels for your heating and hot water needs.
But while heat pumps are becoming more common, it isn’t as simple as just slotting one where your boiler currently is. Getting a heat pump is usually the end stage of retrofitting a home.
Depending on how old your home is, there may be a lot you need to do to make it suitable for a heat pump. On top of this, the specifics of your home, and the outside area, will affect what type of heat pump it is suitable for.
Why You Can’t Just Install a Heat Pump
Heat pumps operate very differently from boilers, with one of the main distinctions being their lower flow temperature. Some of the key distinctions are:
High Heat Loss Leads to Higher Costs
Heat pumps are thermostat controlled systems. This means that they want to either raise your whole house to a specific temperature, or individual rooms if you have thermostatic valves installed.
If your house has a high level of heat loss, on top of the lower flow temperature, then the heat pump is really going to struggle to reach and maintain those temperatures. To do this it will work harder, and substantially reduce its COP.
To be financially worthwhile, a heat pump needs a high efficiency due to the higher price of electricity per kWh compared to oil and gas.
Delivering Heat at Lower Temperatures
The lower flow temperature of a heat pump can also mean that you need to upgrade your central heating system to effectively heat up a room.
Older narrow radiators are fine for a boiler. But the lower water temperatures of a heat pump need large panel radiators with a greater surface to deliver heat from.
It should be noted that this is far from a guarantee, and you may be just fine without your current radiators. This will vary from home to home.
Most Important Areas to Tackle in Your Home
The most important areas in your home that need to be improved on in order to get a heat pump are the walls and the roof. Between them, up to 65% of a home’s heat loss can be through the roof and external walls.
The best order to tackle the most important home insulation upgrades is:
- 1
Attic Insulation: Add at least 200mm of loft roll insulation to your attic. Ideally you would like a total of 300mm attic insulation.
- 2
Cavity Wall Insulation: The simplest and most affordable way to improve your wall’s performance. Add bonded bead insulation up to a thickness of 100mm.
- 3
Doors & Windows: Replace older single or double glazed windows with modern triple glazing. External doors might also need replacing.
- 4
Draught Proofing: Take steps to seal any locations where air is getting in such as around doors and under skirting boards.
If you do not have a cavity wall, then you will have to get internal or external insulation instead. These are significantly more expensive than cavity insulation, and it will likely be more cost effective to get your windows done first.
Can your home receive heat pump grants?
There are a number of eligibility criteria to receive the SEAI’s heat pump grant bundle. Some of them you can’t do anything about, such as the year it was built. You can however, tackle the heat loss from the building.
This is important because not getting the heat pump grant if you can meet the eligibility requirements means leaving up to €12,500 on the table.
Heat Pump Grant Requirements (SEAI)
There are two ways of determining if your home has a sufficiently low Heat Loss Indicator (HLI).
Surveying Your Home
Once you have your home ready for a heat pump, you still need to know exactly what heat pump to install. This is determined by both your heat needs, including space heating and hot water, and how effectively that heat can be delivered.
Based on the size of your home, its BER, and how much hot water you typically use, a qualified technician should be able to create an estimate of what your expected heat demand is.
This information is used to correctly size the heat pump that your home needs. Your space heating requirements will also be used to determine if you need to replace any radiators.
Heat Demand Elements
There are two main elements that need to be kept in mind when quantifying your home heat demand. A heat pump must be suitable to meet both of these requirements.
Split vs Monobloc Heat Pump
If you are getting an air-to-water heat pump, as the vast majority of homes do, you will also need to consider whether to get a split or monobloc style system.
The difference between them is quite simple:
Insight:
Space is a key consideration in choosing between the two. A monobloc system has a larger outdoor unit, since it has to house both heat exchangers. However, it has no indoor unit, which can be a boon for apartments and small houses where space is limited.
This choice also relates to whether the outdoor space of your home can meet the legal requirements for a heat.
Outdoor Space Requirements for a Heat Pump
While you are unlikely to need planning permission for a heat pump in Ireland, there are still legal regulations that an outdoor unit must meet. There are also conditions that need to be met for them to operate properly.
Separate from the above legal requirements, the outdoor unit of a heat pump needs sufficient clearance to allow a steady flow of air into and out from the fan unit. It also needs to be placed in a location where there is access for maintenance.
Hybrid System or Hot Water Cylinder?
Another question about space is whether or not you intend to use your heat pump for domestic hot water as well as space heating.
If you are going to do so then you will need a hot water cylinder, as the lower temperature of a heat pump means that it cannot make hot water on demand the way a combi boiler does.
If space is limited, a hybrid system may be a practical alternative. In this setup:
