Self-build barn kept warm by Grant renewable heating system

A complete Grant heating system has been installed at a custom build barn set in the rural Wiltshire countryside. The property is being heated by a highly efficient Aerona 290 air source heat pump which has been installed alongside a hot water cylinder, underfloor heating system and aluminium radiators all supplied by Grant UK.

The Project
Property: self-build 
Heat source: air source heat pump
Products installed: Aerona 290 9kw air source heat pump, Quick Recovery 2 Smart Pre-Plumbed 250L cylinder, Uflex underfloor heating system and Afinia aluminium radiators

In December 2025, the project of building a 200m² self-build home in Marshfield, Wiltshire, was completed. Comprising of three bedrooms, this two-storey detached barn has been built with efficiency in mind with high levels of insulation throughout and a renewable heating system meeting its space heating and hot water requirements. The homeowners not only wanted a heating system which was effective and reliable, they also wanted the products installed to sympathetically complement the property’s aesthetics. Here, we learn how Grant UK’s products provided the solution for the homeowner, their builder and the installer.

Insulating the property for a low-temperature heating system

From the offset of this build, the homeowners wanted their new home to be as thermally efficient as possible. Not only did they need to minimise the heat loss from the property which is situated in an exposed rural location, but high levels of insulation would also support the efficient operation of the low-temperature air source heat pump heating the property. Consequently, a number of energy-efficient measures were installed in the barn, including:

• Window insulation: triple glazed windows have been installed throughout the property
• Roof insulation: the roof is covered with a 150mm bonded covering with a further 150mm of Rockwool sound insulation laid beneath, which also serves to reduce the noise of rain
• Wall insulation: cavity wall insulation has been installed featuring 125mm Celotex and 40mm insulation bonded to the cladding
• Floor insulation: throughout the ground floor of the property, 150mm of Celotext has been laid. 

You can learn more about how improved insulation levels can make your home more energy efficient here. 

Choosing the right heat pump for the self-build barn

The homeowners turned to their local heating engineer, Dave Croker from Howard Croker Partnerships Ltd, for advice and guidance on which air source heat pump would be best for their new home. Howard Croker Partnerships Ltd are G1 Heat Pump Installers based in Corsham who have also worked on a number of projects with the builders of the barn, CG Goodchild Ltd, so both the builders and the installer were familiar with Grant products. 

“Dave Croker recommended the Aerona 290 because it is Grant’s latest model of heat pump and more efficient,” commented the homeowner. “Another important factor for us was the look of the heat pump – the Aerona 290’s black casing and design matched the black cladding on the barn so we felt this heat pump ticked the right boxes for both aesthetics and performance.” 

For selecting the correct size of heat pump for the barn, Dave Croker shared the plans of the property with Grant UK’s in-house Design Team who carried out a heat loss calculation for each of the rooms and produced the estimated heat loss of the total property. With a heat loss of 6.740kW, the 9kW Aerona 290 air-to-water heat pump model was chosen to meet the heating demand of the barn operating on the system with a design flow temperature of 45ºC with an external air temperature of -2.64ºC.  

Features of the Grant Aerona 290 ASHP

The Aerona 290 is Grant UK’s R290 heat pump which uses the more environmentally friendly R290 refrigerant. With five models available ranging in heating output from 4kW up to 15.5kW, the Aerona 290 heat pump range is designed to suit the heating demand of large range of properties, from smaller homes through to properties with higher space heating requirements. Here are some of the features of this R290 heat pump:

• Incredibly low noise levels with all models awarded the Quiet Mark
• Highly efficient heat pumps with excellent SCOPs and A+++ ErP energy rating
• MCS accredited and eligible for Government funding and grants
• Available with a 7 year guarantee when installed by a G1 Heat Pump Installer (Terms and Conditions apply).

Interested in reading more about advantages of 290 heat pumps? Visit our Knowledge Hub for more information. 

Heat pump cylinder

Alongside the Aerona 290 heat pump, one of Grant UK’s latest generation of hot water cylinders was also installed – a Quick Recovery 2 (QR2) Smart pre-plumbed single coil 250L cylinder. As well as featuring factory-fitted primary system pipework, this cylinder model has factory-fitted pre-wired controls including the Aerona Smart Controller and wiring centre to ease installation and set-up. With its large internal coil, this cylinder is specifically designed to work alongside low-temperature heat pumps to support their efficient operation. 

Specifying the heat emitters

As with any heat pump system, the choice of heat emitters is just as important as the correct sizing of the heat pump unit itself. With this barn spanning across two floors, two types of heat emitter were selected:

• Grant Uflex Underfloor Heating (UFH) installed throughout the downstairs of the property
• Grant Afinia aluminium radiators installed in all the rooms upstairs. 

The Uflex UFH system is a screeded underfloor heating system using 16mm pipework and this was laid throughout the entrance hall, dining room, kitchen, living room, office and utility room. The underfloor heating system was installed during the early stages of the build, in Summer 2025, allowing for the floor screed to dry while other building works took place. This underfloor heating system provides a large surface area through which the heat from the heat pump system can be effectively transferred into the living spaces downstairs, achieving the desired temperature set for each room.

Meanwhile, upstairs in the barn, twelve Afinia aluminum radiators have been fitted. Like underfloor heating, the Afinia radiators are ideally suited for low temperature heating systems because they have low water content and are highly responsive to changes in temperature demand. The radiators vary in size from smaller 6 panel radiators through to larger 12 and 14 panel options. 

How can Grant UK help with specifying heating systems for self-build homes?

Grant UK’s Design Team can provide a range of services to help homeowners, developers and installers with specifying renewable heating systems for custom and self-build homes. Upon receipt of a property’s plans, Grant UK’s Designers can produce basic heat loss calculations as well in-depth system quotations, providing customers with a list of the Grant products required for their heating system installation. The team can also supply underfloor heating system designs and drawings (for confirmed orders) to further support the installation of Grant heat pump systems. 

If you are planning a self-build project and you are researching suitable heating systems, please contact our Design Team with your plans. 

Claiming Boiler Upgrade Scheme funding for self-build

The Boiler Upgrade Scheme (BUS) is a Government funding initiative which is available to eligible households in England and Wales. Through the BUS, homeowners can claim up to £7,500 towards the cost of an air source heat pump installation when they replace an existing fossil fuel boiler. New build developments are not eligible for BUS grants however self-build and custom homes may be eligible provided:

• You (or the original owner) built the property or you paid a builder to build it
• The property has never been owned by a business or organisation.

For this self-build barn in Wiltshire, the homeowners were able to claim BUS funding to financially support the installation of the heat pump. Howard Croker Partnerships Ltd completed the installation through Grant UK’s MCS Partnership Scheme with the installation achieving MCS certification for BUS eligibility. 

Please read our Home Heating Blog to learn more about the Boiler Upgrade Scheme.

Customer feedback from the homeowners and installer

The installation of the air source heat pump and cylinder was completed in November 2025 with the system commissioned in early December which allowed the homeowners to move into their new home in time for Christmas. In addition to the Grant renewable heating system installed, the property also features a solar PV system which generates electricity for the heat pump and the wider home. With landscaping the only element of the project still underway, the homeowners and their installer have reflected on the installation and both are pleased with how the Grant products are working. 

“Moving into our new‑build home with the Grant heat pump combined with the Grant hot water cylinder has been a really positive experience” comments the homeowner. “Coming from gas central heating in our previous home, we weren’t sure what to expect, but the Aerona 290 has genuinely exceeded our expectations. The heat is steady, comfortable, and far more consistent than what we were used to with gas. It runs quietly in the background, and it’s reassuring to know that our new home is starting off with an efficient, low‑carbon system that’s built for the future.

“If anyone is considering a heat pump for a new build, we’d definitely recommend the Aerona 290. It’s been easy to live with, cost‑effective to run alongside our solar panels, and a great match for a modern, well‑insulated home. We’re really pleased with the switch and wouldn’t hesitate to recommend it to others.”

Meanwhile, the installer Dave Crocker writes, “It was our first time installing an Aerona 290 unit and the installation went really well. We’ve previously been fitting the Grant Aerona³ heat pumps which we’ve always liked. The new black R290 unit looks great though and it was straightforward to fit. The Aerona Smart Controller was also easy to set up and use. It was also our first time fitting one of the new Grant QR2 pre-plumbed cylinders – the controller came factory-fitted and pre-wired to the cylinder which reduced the installation time for us and made set-up and commissioning easier. 

Read more about Grant renewable heating technologies

Whether you are building your new home or you are interested in upgrading your existing heating system for a more sustainable option, as this case study has shown, here at Grant UK, we supply complete renewable heating package solutions. To learn more about our products and services, please follow the links below:

• Explore Grant’s air-to-water heat pumps
• Read more about Grant’s complete renewables heating range
• Contact our Design Team for specification support.