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Air source heat pumps are one of the major future heating technologies. With the government on track to ban the installation of gas boilers in new builds, and for replacements, by 2035, many people are now looking to air source heat pumps as a future-proof alternative method. Installing them in a new build is no problem at all, but are they a feasible option for older houses?
Older houses do present more of a challenge for air source heat pumps, for a variety of reasons. They weren't designed with this type of heating system in mind. Many of these challenges can be overcome, however, with a knowledgeable and experienced installer.
Let's briefly look at how air source heat pump systems work. These are electricity-powered heat pumps that are designed to absorb heat from the ambient outside air and transfer it into the property's heating system.
Air source heat pumps will have an outside unit that is usually placed at ground level against a house wall. They can sometimes instead be wall-mounted or placed on a flat roof.
Within the outdoor unit is a coil that extracts heat from the air. This will still work in very cold temperatures. The heat from the air heats a refrigerant liquid so that it evaporates into a gas.
The heated gas is compressed by a compressor to raise the temperature even further and is then transferred to the property to heat it.
Gain insights: How Does An Air Source Heat Pump Work
There are two main types of air source heat pumps: air-to-air and air-to-water. They both extract heat from the external air in the same way, but the way that the heat is used in the property differs.
An air-to-air heat pump system blows the heat directly into the air of the property. This can be achieved through a series of fans and coils or a network of ducts. Air-to-air heat pumps can replace or support the central heating system, but they can't be used for hot water.
This type of system is cheaper to install but it does mean that you will need a separate heating method for the hot water system.
An air-to-water heat pump system connects directly to the wet heating system. It heats the home either through radiators or underfloor heating. It can also be used for hot water.
This is a more expensive system to install, but it does meet all of your heating needs.
New-built houses are perfectly suited for an air source heat pump, but installing a heat pump in an older home can be more of a challenge.
Take a look: Can Air Source Heat Pumps Be Installed In Flats
The main issue with installing a heat pump in an older property is the home's insulation levels. Older homes, especially those built before WW2, do not generally have high levels of insulation. Poor insulation means that there is a higher level of heat loss. While this can be a problem for any heating system, it is even more so for air source heat pumps.
This is because heat pumps operate at much lower temperatures. They are designed to produce heat at a low temperature, constantly. A gas boiler, on the other hand, is designed to produce cycles of higher flow temperatures, which turn on and off.
Heat pumps need to maintain a consistent temperature if they are to work efficiently for space heating. If the temperature drops because heat is lost, then the heat pump will need to work harder than its optimal efficiency level. This will lead to higher energy usage and higher running costs.
Improving the energy efficiency of your home is a good idea for all heating systems and especially for air source heat pumps. Reducing heat loss in older homes can be done, but it may require some work.
The first step is to thoroughly assess the current insulation levels. This may include checking walls, ceilings, the loft, and the floors. Checking for gaps in windows and doors that could be causing draughts is also important.
Older homes will often have little to no insulation, or the insulation that is in place may perform poorly or have gaps. To make the home energy efficient, much of the insulation may need to be replaced.
To fully insulate a home, you should focus on:
The process of installing insulation in old houses can be difficult because of access issues, the materials already in place, and potential asbestos.
Standard radiators are designed to be used with traditional heating systems that run at high temperatures. Air source heat pumps, however, run at lower temperatures, which isn't as well suited to smaller radiators.
Because standard radiators have a small surface area, the lower heat produced by an air source heat pump can't efficiently help the room reach the desired temperature. This means that the heat pump will need to work harder and generate more heat. It will have to work less efficiently, which will increase its carbon footprint and the cost to run it.
Dig deeper: Can Air Source Heat Pumps Work With Existing Radiators
For the heat pump to work efficiently, you should install a heat distribution system with a greater surface area. Simply replacing smaller standard radiators with larger ones can make a big difference, but if you truly want to improve the efficiency as much as possible, underfloor heating will be the most effective.
Underfloor heating systems can connect directly to an air-to-water heat pump. These are the most energy-efficient methods of heating a home using an air source heat pump. A network of pipes carrying hot water is laid beneath the floor. The hot water created by an air source heat pump flows through the pipes, heating the room above.
This type of system works at a lower flow temperature which aligns almost perfectly with the temperature level of the heat output from an air source heat pump. This lower temperature difference means that the air pump can work at its most efficient level to maintain the desired room temperature.
Air source heat pumps do make noise, but the newer models are designed to be much quieter than the older ones. The noise level is around the same as a dishwasher or microwave. With that being said, they certainly are not silent. This can sometimes be more of a problem for older houses than for newer ones.
Some older houses may have thin walls and single glazing. Since the outdoor unit of an air source heat pump is placed against a wall of the property, having a thinner wall will make it more likely that it can be heard inside.
Replacing single-glazed windows with either double- or triple-glazed windows won't only help with noise reduction, but it will also help to improve the insulation and energy efficiency of the property.
Heat pump installations will include careful consideration of where the outdoor unit should be placed, and noise disruption is an element that is taken seriously. The outdoor unit will be placed in a location where it is least likely to cause noise disturbance either to you or to neighbouring properties.
The available space needs to be taken into account when installing heat pumps in an older property. An existing heating system will often take up less room than an air source heat pump. The indoor units will often fit in the same amount of space as a gas boiler as they are smaller, but there is also the outdoor unit and hot water cylinder to consider.
The outdoor unit will require ground-level space against a wall of the property or mounted on the wall of the property. The closer to the house the better because reducing the pipework from the external components to the internal ones will improve the energy efficiency. The unit is relatively small, however, around the size of a washing machine, so you can usually find the room if you have any sort of garden area.
It will, however, require some space to its front and sides. A lot of air needs to flow through the air pump for it to extract heat efficiently, so it needs enough clearance for good air flow.
Of bigger concern is the hot water cylinder. This is needed for an air-to-water air source heat pump to heat your hot water system. These are often quite large. The average height ranges from 0.8 metres to 2.2 metres and the diameter from 0.45 metres to 0.7 metres.
Depending on the construction and design of an older home, these elements can sometimes be difficult to fit in comfortably.
In the majority of cases, space will be found to install heat pumps even in unusually designed homes. Of all the heat pump options, air source heat pumps are the most space-saving. Ground source heat pumps and water source heat pumps both require much larger pieces of land outside in which to operate.
They don't, however, require the heat pump to be placed outside because they don't need any air flow. If your issue is with your outdoor space, then a ground source heat pump system could work better.
If you truly do not have space to fit a hot water cylinder, you could consider an air-to-air heat pump, rather than an air-to-water model. You could then use traditional heating methods for heating your hot water. An air-to-air heat pump does not require a hot water cylinder. It only needs the internal unit and external unit of the heat pump itself.
Many older homes have a unique character, and some of this character will come from period features that increase the attractiveness of the property. An air source heat pump will look like a modern, industrial addition to the external property, and many people worry that it will take something away from the design of the home.
It is not advisable to box in your air source heat pump in an attempt to hide it. The outdoor unit requires a large amount of air flow for it to work efficiently.
Instead, your heat pump installer can help you find a discreet location that will still allow the heat pump to transfer heat well. You could consider erecting a dividing fence or growing some larger plants a little further away from the heat pump but in such a way that it becomes less visible from certain angles.
Heat pump technologies and other renewable energy technologies do not usually require planning permission. Instead, they come under permitted development rules. There are some exceptions to this, however, which include some categories that could be relevant to old houses.
If your property is a listed building or is located in a World Heritage Site, Conservation Area, or Monument Site, you may need planning permission before you can install an air source heat pump.
Your first step is to contact your local planning authority. They will have all of the information about your property's status and location. If you do require planning permission, you can get help from local experts, organisations such as Planning Aid England (PAE), or your heat pump engineer.
We are passionate about helping people reduce their carbon emissions and energy consumption through the use of low-carbon heat pump technologies. We understand that heat pump installation can be more challenging in older homes, but our highly trained team of installation engineers has the knowledge and experience required to thoroughly understand the needs and complexities of old houses.
We will visit your home to assess its insulation level, condition, available space, and heating demand. We can then advise you on the type of heat pump that would be best suited to replacing your fossil fuel boiler. We will work with you on the best course of action if any modifications need to be made to improve the energy efficiency of your home or the heat pump's performance.
We will also keep you informed throughout the project if we come across any unexpected issues that need to be addressed or that might slow us down.
Check out: Can You Put An Air Source Heat Pump In Garage
Contrary to popular belief, air source heat pumps work in older properties. There may be some challenges due to the original construction that could impact the heat pump's efficiency, but most of these can be overcome. Your home may need some internal modifications to allow the heat pump to produce enough heat energy to power your hot water and heating systems and to reduce heat losses, but once these are in place, you can relax and let your heat pump keep your home at a comfortable temperature, in an environmentally friendly way.
