Exclusive UK Partner for HydroTop Works B.V.

The heat pump
that disappears
into the roof.

HydroTop™ is a roof-integrated casement system that houses an air-source heat pump within the roof void, making installation viable in millions of UK homes where a conventional external unit simply cannot go.

Get in Touch How It Works

<30 min

Typical loft installation time

150mm

Maximum projection above roof surface

10kW

Maximum heat pump output supported

The Challenge

Millions of UK homes cannot accommodate a conventional heat pump.

Terraced properties, conservation area houses, and homes with limited external space represent a substantial share of the UK housing stock, and they are precisely the properties where the Warm Homes Plan's ambitions are hardest to deliver.

Space, planning, noise, and aesthetics combine to make a conventional external installation impractical or impossible. This is the single biggest practical barrier to the UK's heat pump rollout, and until HydroTop™, the market had no adequate answer.

No external space

Terraced properties and those with limited garden or facade access have nowhere to put a conventional ground or wall-mounted external unit.

Noise objections

External heat pumps generate neighbour objection on acoustic grounds, a consistent barrier in dense urban and suburban housing.

Planning restrictions

Conservation areas and Article 4 directions prevent or complicate the placement of visible external units on many properties.

Homeowner resistance

The visible external unit is one of the most common sources of homeowner reluctance, an aesthetic barrier that delays or kills installations entirely.

The Solution

HydroTop™ puts the heat pump where it belongs, out of sight.

HydroTop™ is a prefabricated, insulated casement system installed between and across the roof rafters. The heat pump sits level within the casement regardless of pitch, with the only external element a low-profile aluminium cap projecting no more than 150mm above the roof surface.

Compatible with all major heat pump manufacturers up to 10kW, installers and programme managers retain full freedom to choose the most appropriate unit for each property.

The complete system arrives pre-assembled. Installation is typically completed within a day. All servicing is carried out from inside the loft, in any weather. Independent testing by Enertek International confirms performance at least equivalent to a conventional external installation.

Read the Full Solution Overview →

Fig. 01: Cross section view of HydroTop in a roof

The Installation

From crane to completion.

A small mobile crane is all that's needed. The pre-assembled unit arrives with the heat pump already inside, no separate placement required on site. Typically completed within a day.

Craned into place

Positioned on the roof, typically completed within a day.

Lowered into the void

Seats precisely regardless of pitch, from 30° to 60°.

Guided from the loft

Insulated housing protects the heat pump from the elements.

Sealed and connected

Invisible from outside, accessible entirely from within.

Full loft access

Complete servicing access, in any weather, from indoors.

Invisible from the street

Low-profile caps sit flush, undetectable at street level.

Why HydroTop™

Every installation challenge, solved in a single system.

Virtually invisible

Powder coated to match the roof, one would not know it's there.

Permitted Development

Designed to meet Class C and Class G of the GPDO. In most cases no formal planning application is required, including many conservation area settings.

OEM neutral

Works with all major brands up to 10kW.

Significantly quieter

Roof-void housing noticeably reduces perceived external noise.

Fast to install

Placed within a day. Serviced entirely from the loft.

Sustainable materials

Manufactured from recycled materials.

Who We Serve

Built for the people delivering the UK's heat pump transition.

Homeowners

Want a heat pump but struggling to find the space?

HydroTop™ was designed specifically to solve it.

Social Housing & Local Authorities

Unlock your hardest-to-treat stock, at scale.

Reaches mid-terraces conventional solutions cannot.

Retrofit Aggregators & ESCOs

Fewer exclusions. Better programme viability.

A standardised solution specified across a programme.

Architects & Retrofit Coordinators

Specify with confidence. Eliminate redesign risk.

PAS2035 compatible, technical support available.

Heat Pump Installers

Stop turning away the jobs you can't currently do.

A capability, not a competitor, for MCS partners.

FAQ

Common questions.

How long has HydroTop™ been available?

HydroTop™ has been available in the Netherlands and across Europe since 2015, where it has been installed thousands of times across both new build and retrofit projects. Inbox Thermal Solutions is now bringing this proven, mature technology to the UK market for the first time, backed by an exclusive distribution and representation agreement with HydroTop Works B.V.

What is the lifespan of the HydroTop™?

HydroTop™ is designed for a multi-decade service life, significantly exceeding the typical heat pump lifecycle and well beyond the lifespan of a conventional external unit.

Which heat pumps is the HydroTop™ compatible with?

HydroTop™ is compatible with an increasing range of heat pump manufacturers up to 10kW, including Panasonic, Nibe, Bosch, Mitsubishi and Daikin. Installers and programme managers are not tied to a single brand or supply chain.

What independent testing has the HydroTop™ undergone?

HydroTop™ has been independently tested by Enertek International (UK) and Kiwa, confirming no adverse effect on heat pump efficiency. Fire safety testing has been carried out by Peutz. UK-specific certification is being actively progressed by Inbox Thermal.

Does installing a HydroTop™ require planning permission?

In most cases, no. HydroTop™ is designed to meet the requirements of Class C and Class G of the Town and Country Planning (General Permitted Development) Order, meaning formal planning permission is not required for the majority of domestic properties, including many conservation area settings. We recommend confirming the position for each specific property as part of the survey process.

How long does a HydroTop™ installation take?

A HydroTop™ installation is typically completed within a day. The casement unit arrives pre-assembled and is lowered into position by a small mobile crane before the cap is fitted and finished at roof level. All subsequent servicing and maintenance is carried out from inside the loft.

Our Story

From the Netherlands to the UK's rooftops.

HydroTop™ started life in the Netherlands, where HydroTop Works B.V. spent years perfecting a simple idea: a heat pump that lives inside the roof instead of fighting for space beside it. Thousands of installations later across the Netherlands and wider Europe, it's proven, weathered and ready.

Inbox Thermal Solutions is the small, enthusiastic team bringing that idea across the North Sea. We're the exclusive UK partner for HydroTop Works B.V., and we started this business because we think it solves a real problem: too many British homes, especially the terraces and conservation-area properties that make up so much of our housing stock, have nowhere to put a conventional heat pump.

That means working closely with the people who will actually get HydroTop™ onto UK roofs: social housing providers running retrofit programmes, the aggregators and ESCOs managing delivery at scale, the architects and retrofit coordinators specifying it into their projects, and the installers who fit it.

We're a small team, but a determined one. Our job is to bring HydroTop™ to the UK properly, understood and installed one roof at a time, so more people can heat their homes without fossil fuels.

The heat pumpthat disappearsinto the roof.