An air source heat pump is a renewable heating system designed to replace, or in some cases complement, your home’s traditional boiler. Invented in 1856, air source heat pumps have been in use for one and a half centuries to heat homes and supply hot water doing away with the need for fossil fuels. They’re especially popular in the Nordic countries, where temperatures often plummet below zero.
Air source heat pumps take advantage of the fact that outdoor air at any temperature above absolute zero (-273° Celsius) contains energy. It simply transfers a certain amount of this energy as heat from the outside to the inside of your home.
An air source heat pump does all the things your home’s boiler does only relying on the energy found in the air and some additional electricity instead of gas or oil as its primary fuel source. This means it’s much better for the environment – and often for your wallet, too.
How does an air source heat pump work?
An air source heat pump works much like a fridge in reverse.
An air source heat pump draws outside air into the system. This air is used to turn a refrigerant inside the unit into vapour. This vapour, in turn, is then compressed and produces heat as a result. The heat is then transferred to your home’s heating system, providing your home with heat and hot water. Air source heat pumps are designed to keep indoor spaces at a steady temperature with gentle top-ups through the day to keep you and your family comfortable. Gone are the days of running to the thermostat or switching between turning the boiler on and off constantly.
The system is so efficient that heat can even be extracted from the air when temperatures fall below freezing. This ensures that even in the coldest conditions, your home’s heating won’t let you down while helping to lower your carbon footprint by up to 65% and reduce energy bills.
What does an air source heat pump sound like?
An air source heat pump is quieter than most people expect. In fact, government regulations dictate that heat pumps can only be installed if they do not exceed 42 decibels when measured from the closest habitable room (living room or bedroom). However, a heat pump will normally only operate at this level for a short time (while it is reaching the target temperature), and the volume will reduce thereafter. To put this into context, the humming of a fridge is around 40dB, and an average gas or oil boiler at home is somewhere around 50-55dB depending on model and age.
If the predicted noise level is greater than 42dB, you will need planning permission to install a heat pump at your property. Rest assured, our surveyors always conduct a sound check, prior to installation, to ensure the sound level is within the approved limit.
To put the sound levels of an air source heat pump into perspective, see below how other ambient noises compare:
Breathing - 10dB
Bird calls - 40dB
Heat pump regulations - 42dB
Conversation at home - 50dB
Vacuum cleaner - 70dB
What is hybrid heating?
Hybrid heating is a combination of your existing boiler and our highly efficient air source heat pump and smart controls. Combined, they create a heating system that uses less energy, costs less to run, and is better for the environment.
Depending on the outside temperature and your home's heating capacity, our intelligent controls decide when to engage your heat pump or use your boiler. This ensures your home is always heated in the most cost-efficient way.
As your existing boiler provides your hot water requirements, hybrid heating can be a good option if you have no space for a hot water tank but want to save money on your energy bills. Please note though that hybrid heating setups are not eligible for the Government’s Boiler Upgrade Scheme Grant.
What are the key differences between standalone and hybrids?
In a hybrid heating system, a heat pump is added to your existing heating setup to produce heat for the home. Your boiler is still used for hot water or to top-up the heat generated by your heat pump, for example on exceptionally cold days. The system makes use of the heat pump alongside your boiler to heat your home in the most efficient way. Combined, they create a heating system that uses less energy, costs less to run, and is better for the environment.
A hybrid system requires a functioning boiler but is likely to result in fewer changes to your current heating setup. Please note that hybrid systems are not supported by the Boiler Upgrade scheme, which is set to replace the Renewable Heat Incentive (RHI). Read on to find out more about funding opportunities.
In a standalone system your boiler is removed, and the heat pump powers your home’s heating and hot water. Standalone systems require a hot water tank, as the water must be stored once heated until it is ready to use. If you don’t have a hot water tank, this isn’t a problem as we can install one at the same time as your heat pump.
What are the benefits of a heat pump?
An air source heat pump offers a range of benefits:
Increased heating efficiency – Air source heat pumps are up to 4 times more efficient¹ than traditional boilers, and therefore require less energy to heat your home.
Reduced carbon footprint - Air source heat pumps don’t use fossil fuels and are better for the planet. Switching to an air source heat pump immediately reduces your carbon footprint as you’ll be using electricity. A high share of this comes from renewable sources.
Lower fuel bills – Because air source heat pumps are much more efficient, they can cost a lot less to run. Homes that rely on oil, LPG or electric heating are most likely to make savings, while those on gas can achieve the same or even lower running costs.
Smart energy control - Control your heating remotely with smart controls through your phone or computer and keep your heating system optimised to meet your heating needs as efficiently as possible.
Increased comfort - Keep your home at a steady temperature effortlessly with gentle automatic top-ups through the day to keep you and your family comfortable.
Long lifespan - The typical lifespan of an air source heat pump is up to 20 years.²
Why would I get a heat pump instead of a new boiler?
Air source heat pumps are extremely efficient at generating heat. In fact, they can produce up to four times more energy than the electricity they consume, making them 3-4 times more efficient than a standard boiler. This means you use less energy for the same amount of heat, which is better for your purse as well as the environment.
The system is so efficient that heat can even be extracted from the air when temperatures fall below freezing. This ensures that even in the coldest conditions, your home’s heating won’t let you down while helping to lower your home’s carbon footprint by up to 65% and potentially reduce your energy bills.
What grants are available to help with installing an air source heat pump?
The Boiler Upgrade Scheme (BUS)
The Boiler Upgrade Scheme (BUS) will launch in April 2022 and initially run for three years. The government has set aside £450m to provide grants of up to £5,000 to property owners to replace fossil fuel heating systems with air source heat pumps. It will replace the Renewable Heat Incentive (RHI) which will run its course at the end of March 2022.³
Contrary to the RHI, which paid owners of air source heat pumps quarterly over the course of 7 years for the renewable energy they produce after they’ve installed their heat pump, the BUS works differently. Interested parties will simply have to get a quote from an MCS-accredited installer, who in turn will apply for the voucher on behalf of the customer.
To be eligible for the BUS, the following requirements must be met:
Be a resident in England or Wales
Be a homeowner
The property must have an Energy Performance Certificate (EPC) that is not older than 10 years
The EPC must not recommend any of the following insulation measures
Cavity wall insulation
Note that there are exemptions to these requirements, for example, in the case of listed buildings or those located in a conservation area.
If you have a valid EPC that recommends loft and/or cavity insulation but the measures have already been installed, you will have to get an updated EPC which evidences this.
Similarly, if you’re planning any works on your property such as an extension, these will have an impact on the heat requirements of the property. We recommend you complete these works first so that we can determine the heat loss of the property including any recent changes, which is essential in designing an efficient air source heat pump system.
How much electricity does a heat pump generally use?
There’s no hard and fast rule for how much electricity will be used by a heat pump, as it depends on the home it is heating and how warm you like your home to be. A proposal document by us will always include the estimated annual consumption of the new air source heat pump and a comparison against your current estimated usage so you know exactly what to expect.
The good news is that heat pumps are an incredibly efficient way to heat your home. Where a traditional boiler might operate at 90% efficiency, heat pumps can operate at up to 350%, meaning they generate up to 4 times more energy than they consume.
What happens when the temperature drops below -15°C?
When designed correctly, an air source heat pump easily maintains a constant and comfortable temperature in your home all year round - even in sub-zero weather. In fact, an air source heat pump can work effectively in extreme temperatures down to -15°C. Your heat pump will be designed, fitted and configured to work to the lowest temperature recorded in your postcode area over the last 10 years, as measured by the MET Office.
More than 1.4 million households in Norway comfortably rely on air source heat pumps as their source of heating despite the freezing temperatures of the Nordics. The efficiency will be impacted by colder weather but will always be higher than that of a standard boiler.
How does radiator size affect the efficiency of the system?
The size of your radiators impacts your heating system’s ability to heat your home to the desired temperature. Larger radiators, for example, allow the system to run at a lower flow temperature and create increased efficiency.
We may suggest replacing your radiators with larger models to increase the efficiency of your heating system. The advantages of larger radiators come from the larger surface area for heat to be transmitted to your room. Our surveyors will be able to confirm this as part of our survey and these replacements will be shown in your proposal document. For many of our installations, our surveyors found the existing radiators to be sufficient for the new air source heat pump to work at the highest efficiency levels.
If a pre-install survey concludes that some radiators would need upgrading, it’s important to note that these radiators rarely double in size. Rather think of it as replacing them with models that have an additional panel. Remember, it’s the surface area that counts, not the overall size of the radiator.
What’s on the inside of a house when the heat pump has been installed?
Inside your house very little will change. You’ll still have radiators and pipework, and you will also have a hot water tank. There are often a few more components on the hot water cylinder and a few zone valves, but nothing should feel too different. The main difference will be your heat pump unit outside the property.
Do I need a new hot water cylinder with an air source heat pump?
When installing an air source heat pump, it has traditionally been standard practice to install a new 'heat pump ready’ hot water cylinder – but in many instances it’s not the most practical solution as it presents homeowners with an additional cost that can sometimes prevent them from going green. That’s why at Igloo Works we’re giving you the choice between replacing your existing hot water cylinder or keeping it.
The first thing to consider when looking at whether it is best to replace your hot water cylinder with a ‘heat pump ready’ one is the size of your existing cylinder coil. If your existing cylinder has a coil area of 2.5m² or more, it is already ‘heat pump ready’ and you do not need to replace it.
The impact of keeping your existing hot water cylinder is potentially higher running costs as it costs more to heat your hot water using the immersion than the heat pump, but on the positive side you would see an upfront saving of £2,000- £2,700 as you are no longer buying a new hot water cylinder.
Every house is different, and we will work with you to understand your existing setup and work out what the potential additional running costs and savings could be for you.
If the area of your cylinder coil is smaller than 2.5m², or if it is not possible to tell how large the cylinder coil is, we recommend you read our more detailed answer to this question.
Will an Air Source Heat Pump work in my property?
Our air source heat pump solutions are suitable for most homes, and our dedicated survey and design teams will be able to find the best option for your property.
A few things to consider:
The air source heat pump needs to sit outside the property on flat ground, ideally as close to your property as possible to increase the efficiency of the pipework. The size of the unit may vary slightly depending on the energy requirements of your properly. The smallest unit takes up a space of 0.4m³ and the largest one just 0.53m³ of space. By comparison, a standard 240 litre wheelie bin takes up 0.46m³.
It's important for an air source heat pump to sit on a flat, stable surface outside of the property and that nothing blocks the air flow. We recommend having at least 30 cm of clearance to each side of the unit, 30cm to the rear of it, and 1.5m to the front. Our survey team will help with where to best position your heat pump.
We can install in most properties. However, please note we are unable to install heat pumps in flats/maisonettes/apartments and non-domestic properties.
Listed buildings are not always restricted and many owners of listed buildings are able to install heat pumps. We’d advise you to first check with your local planning authority for their specific guidance before proceeding.
For homes in conservation areas or heritage sites, it is often still possible to install a heat pump. However, we’d advise you to first check with your local planning authority for their specific guidance before proceeding.
What if I have solar panels?
Solar panels can work well with a heat pump. The solar panels will create the electricity for the heat pump to run on, essentially providing your own cycle of renewable energy, ideal for when you’re looking to reduce your carbon footprint even further. Our surveying team will be able to discuss this with you during a survey of your property.
Will it work with my underfloor heating?
Yes, underfloor heating works well with our systems. Air source heat pumps emit a continuous flow of heat (around 40°C), which is exactly what underfloor heating needs. This makes underfloor heating and air source heat pumps a great combination.
Will the system work with electric heaters and an electric boiler?
If you’re currently on a full electric system, we would need to install an entirely new "wet" central heating system including radiators and pipework, to be able to install a heat pump. If you already have a “wet” heating system powered by a fully electric boiler, your heating can easily be converted to run on a heat pump, and you could make significant savings on your heating bills.
Can microbore pipework affect installation?
A heat pump requires higher water flow rates than a traditional gas or oil boiler, and as ‘microbore’ pipework is usually 8-10 mm in diameter (about the thickness of a ball point pen), this is simply too narrow to handle the flow rates needed. Therefore ‘microbore’ pipework isn’t compatible with a heat pump and would need replacing with larger diameter pipes (usually 15 mm and 22 mm) piping for us to install your new heat pump.
What if I plan to do other building work in my house?
Any changes made to the structure of your home are likely to impact its heat requirements and therefore the system design. If you are planning any renovations that will change the shape, size, or floor plan of your house, it is worth having the plans completed before getting a heat pump. You will also need to consider getting an update to your EPC (Energy Performance Certificate).
We will need to understand how the system will work in the new house design to ensure it’s right for your home. Having your heat pump installed before the works are completed may risk the system not functioning correctly.
Small changes, for example redecorating or installing a new bathroom suite, will not impact the heat demand of your house, so if you are only planning these sorts of changes we can proceed as normal.
Can underfloor heating be fitted after installing an air source heat pump?
Underfloor heating works well with a heat pump. However, having it fitted after your heat pump has been installed would still constitute a change to the heat demand of the system, so risks the system not working at its most efficient.
To get the most out of your underfloor heating and heat pump combination, it’s best to have this designed as a single system so it can work at maximum efficiency. We would therefore need to know all the details upfront. Let us know if you are planning a change to underfloor heating and we can ensure this considered in your heat pump system design.
Will I need to improve the insulation in my home before I get an air source heat pump?
Insulation requirements for Boiler Upgrade Scheme (BUS)
To be eligible for the BUS, the following requirements must be met:
Be a resident in England or Wales
Be a homeowner
The property must have an Energy Performance Certificate (EPC) that is not older than 10 years and which has a heat demand number stated on it
The EPC must not recommend any of the following insulation measures
Cavity wall insulation
There are exemptions to this requirement in the case of listed buildings or those located in a conservation area. In these cases, it’s best to check with your local planning authority to get specific advice for your home.
Do insulation improvements need to take place before the heat pump installation?
We always recommend having your insulation work completed prior to having your heat pump system designed. This is because we design to the current heating requirements of your home. Having insulation installed at a later point will change the heating demand (by reducing the heat loss and therefore making your home more efficient), so you may end up with an oversized (and possibly more expensive) heat pump if you haven’t completed the insulation beforehand.
EPC requirements and process for an air source heat pump installation
EPC requirements and process for an air source heat pump installation
An Energy Performance Certificate (EPC) contains information about a property’s energy use and suggestions on how to make the property more efficient.
What do we need?
An EPC must be dated within the past 10 years and accurately reflect the current layout of your home.
Why do we need an EPC?
The EPC tells us heat demand and loss within your house, so we know how much heat you will require. This allows us to design a system that is specific to the requirements of your house.
It’s also a requirement for applying for the Boiler Upgrade Scheme (BUS). If the EPC indicates insulation work is required to bring your home up to the standard needed the BUS, you’ll need to have this completed and obtain a new EPC before we can claim your voucher from the BUS.
Surveys and installations during Covid-19
We're doing everything we can to make sure we keep our staff and customers safe during the coronavirus outbreak. In addition to home visits, we also offer virtual surveys. Our experts can assess your home over a video call to determine the best solution for your home.
Home visit surveys and installations
We've taken the following measures to ensure home visits and installations can proceed safely:
All of our surveyors will wear facemasks and sanitise their hands. Where possible, and if safe to do so, we may ask you to open windows to increase ventilation.
During installation, we’ll wash or sanitise our hands regularly and follow social distancing guidelines.
After installation, we’ll thoroughly sanitise all surfaces we’ve touched using antibacterial wipes.
If you have any concerns, please get in touch.
What can you expect during installation?
Every install is different, so there’s no one-size-fits-all answer. Once you’re happy with the design for your property, and have agreed an install date with our team, we’ll provide you with a personalised timeline for your installation.
Before we carry out your installation, we’ll take care of all the preparation behind the scenes and order everything to the requirements of your design. Once our team are on site, they’ll explain the installation process and keep you updated on progress.
If we anticipate any disruption to your heating or hot water, we’ll let you know in advance so there aren’t any unexpected surprises. Our installation team are professional, highly trained and qualified – so if you have any questions while they’re working, they’ll be more than happy to answer them.
How big are the air source heat pumps?
The dimensions of our air source heat pump units are below (width x height x depth; in mm):
MHC-V4 (5.1kW): 1295 x 792 x 400
MHC-V6(5.7kW): 1295 x 792 x 400
MHC-V8 (7.25kW): 1385 x 945 x 410
MHC-V10 (8kW): 1385 x 945 x 410
MHC-V12 (11kW): 1385 x 945 x 410
MHC-V14 (13kW) 1385 x 945 x 410
MHC-V16 (13kW): 1385 x 945 x 410
Why are Igloo quoting a larger/smaller unit than another company?
If you’re getting multiple quotes, you may find that the system design varies. This is likely due to the product range available, as different manufacturers offer different sizes of heat pumps.
The heat pump selected in your system design will have been chosen to match the heating requirements of your home and ensure it produces the right amount of heat to keep you comfortable.
Once the threshold for a smaller heat pump has been exceeded, it will be necessary to jump to the next size available. For example, if your home required 5.5kW to heat, we would have to use an 8kW heat pump as we have 5kW and 8kW units. However, another provider might only have a 9kW option, so your quotes would be for different unit sizes.
Despite the differences, the designs are still correct. We design all of our systems to meet your home’s specific heat demand to ensure you are always able to heat your home as you want to.
What are the warranties on the system?
There is a 10-year manufacturer’s warranty on the heat pump and a 2-year workmanship warranty as we are a member of the consumer protection scheme HIES. HIES offers customer advice and protection following the installation of renewable energy systems.
More information on the warranty can be found in your handover pack after your install is completed.
What happens at 10 years when the warranty end?
There is no scheme to elongate the life of a warranty, but your heat pump will require yearly servicing to ensure the warranty remains valid for those 10 years, just like a regular boiler. Once the warranty ends, it is recommended to continue good maintenance and regular servicing to prolong the life of your heat pump.
Smart Heating Research Project - General
How do I set up my temperature logger on my smart device?
You can either use the instructions that came with the device or use this video. Note the video shows an older type of heat logger, however the process remains the same.
Please place your heat logger on your thermostat, or as close to it as you can. If this is not possible, then place it in the room where you spend most of your time in your home. Avoid placing your logger in direct sunlight or above a heat source such as a radiator or on a mantlepiece.
When will I get my heating report?
We will notify you by email when your report is available.
How do I know my heat logger is working?
After pairing the heat logger to your smartphone, you should be able to see the temperature and humidity figures with the SensorBlue app. If these turn green and change value, the device is successfully collecting data. If they do not turn green and change value, make sure Bluetooth is switched on and that the heat logger is within the Bluetooth range of your smartphone.
How do I send Igloo the data file from the SensorBlue app?
The video below shows you how to send the data from the SensorBlue app to Igloo, step-by-step. If you have any difficulties, the FAQs below should help.
How to withdraw from the Smart Heat Research Project
You can withdraw from the project at any time, by simply sending an email to email@example.com.
Please note if you withdraw before the 31st March 2022, you will not be entered into the £1000 prize draw.
Smart Heating Research Project - Troubleshooting
How do I change the battery?
The temperature logger uses a CR2477 coin cell.
Using a flat screwdriver, gently pry apart, starting at the notch on the side of the casing.
Push the battery out and replace with a new CR2477 battery.
Turn on the App, and then press the gold button on the PCB board. You will see the LED flash.
After you see the temperature and humidity turn green on the App. Clip the plastic case back together.
How is my heat logger being delivered?
It will be delivered by Royal Mail, it is a small package and will fit through a standard letter box, you do not need to be in when it is delivered.
I am moving to a new house, can I still take part in the research trial?
Unfortunately, moving to a new house meaning that you can no longer take part in the trial. You may keep the heat logger but please contact firstname.lastname@example.org before you move so that we can explain how to send us the temperature data collected so far.
I do not have access to my email account on the smart device where I use the SensorBlue app, how do I send you the data?
The SensorBlue app can offer a number of other ways to share the data, such as via Dropbox, Google drive or iCloud. Once you have uploaded the CSV file to one of these locations you would need to access the data from another device (with email enabled) to send the file as an email attachment to
email@example.com. (Do not forget to include your postcode in the subject
line to help us link your data to the right account.)
Note you can have the SensorBlue app on multiple devices, all connected to the same heat logger.
It takes a long time to synchronise the data to my smartphone, is that normal?
Yes, this can take a few minutes, especially if it has been a few days since you last synchronised. The synchronisation process is done via Bluetooth, so make sure your smartphone is close to the heat logger while syncing.
My heat logger arrived damaged; can I have a new one?
The synchronisation failed before it had finished, what do I do?
Don’t worry if this happens, just hit the green Retry button on the app. It may have failed because you had moved out of Bluetooth range, so you may need to move your smartphone closer to the heat logger.
Why do I need to add my postcode in the subject line of the email?
Adding your postcode to the email subject line will help us ensure we link your heat logger data to the right account.