Wet Underfloor Heating for new build properties

Underfloor heating systems are unobtrusive in design and are a popular heat emitter choice for new build properties. Wet underfloor heating systems use a series of pipework laid beneath the floor through which warm system water flows and heat is transferred through the floor into a room. Underfloor heating systems installed in new build homes need to be designed during the early phases of a build so architects, specifiers and developers need to be planning their heating system installations well before the first brick is laid on site.

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In this blog, we will explain:

• What is wet underfloor heating?

• Why wet underfloor heating works well in new builds

• How wet underfloor heating fits into the overall heating system

• Design considerations for wet underfloor heating in new builds

• Wet underfloor heating and air source heat pumps

• Choosing floor finishes for wet underfloor heating

• Installation stages for wet underfloor heating in a new build

• Pros and cons of wet underfloor heating in new builds

• Wet underfloor heating systems from Grant UK

What is wet underfloor heating?

In a wet underfloor heating (UFH) system, warm water flows through plastic pipework which in new builds is usually laid within the floor construction. The heat source, an air source heat pump for example, warms up the system water which then flows through the UFH pipework and the heat is radiated evenly upwards from the floor into the rooms. An underfloor heating system transforms the entire floor surface area into a heat emitter, delivering even heat distribution and maximum comfort. Unlike traditional steel radiators, there are no cold spots or draughts with underfloor heating and wall space is left completely free to maximise a home’s aesthetics.

Learn more about wet underfloor heating systems:

• Read our ultimate guide to efficient and comfortable heating with wet underfloor heating systems

• Compare underfloor heating versus radiators

• Discover more about low profile wet underfloor heating systems.

Why wet underfloor heating works well in new builds

Wet underfloor heating is perfectly matched for new build homes because:

• a screeded underfloor heating system is simpler to install as part of the floor construction and can be laid without impacting or delaying a build

• underfloor heating complements low-carbon heat pumps, maximising efficiency for homeowners

• an underfloor heating system transforms the entire floor surface area into a heat emitter, providing even warmth and ultimate comfort for homeowners.

A wet underfloor heating system is easier to design and can be planned well in advance of the first brick being laid on site. Developers can submit their plans to Grant UK’s Design Team, sharing room layouts and building specifications so that detailed line drawings for the underfloor heating pipework layout can be supplied. Developers can therefore be equipped with a bill of materials, including UFH pipe length, manifolds and actuators, as well as clear UFH system arrangement drawings to make installation simpler.

Wet underfloor heating works incredibly well with modern, well-insulated new build homes. Furthermore, underfloor heating systems work exceptionally well with renewable heating systems such as air-to-water heat pumps. With more and more developers specifying heat pumps for their properties as the Future Homes Standard comes into force, underfloor heating systems provide the large heat emitter surface area to support the efficient operation of low-temperature heating systems.

Developers and self-builders who install wet underfloor heating in their new build homes can therefore integrate a choice of heat emitter which partners heat pumps efficiently, delivers comfort effectively and is a desirable feature that prospective homebuyers look for.

How wet underfloor heating fits into the overall heating system

A wet underfloor heating system is one part of the wider central heating system for a new build. A low-carbon heating system will comprise of an air-to-water heat pump, suitable heat emitter(s) and a separate hot water cylinder which work together to fulfil the space heating and domestic hot water requirements for a home. Underfloor heating can either be laid throughout both the downstairs and upstairs of a property or developers may opt for underfloor heating on the ground floor combined with radiators on the first floor.

The design of the underfloor heating system should be completed alongside the design of the wider heating system. The accurate system design during the early stages of a build will inform developers and their contractors of the size of heat pump needed for each style of home, the size of hot water cylinder required and a clear plan for positioning the wet underfloor heating circuits, manifolds and controls within a property. Grant UK’s Design Team can help with both the heat pump system specification and underfloor heating system design, supporting developers with the installation of underfloor heating paired with an air source heat pump for low-temperature heating for their properties.

Design considerations for wet underfloor heating in new builds

A wet underfloor heating system design must factor in floor construction, room layouts and zoning, and insulation and heat loss.

Floor construction and build-up

There are different types of wet underfloor heating systems, some of which require a thicker layer of screed to be laid and others which either require little or no screed. The type of underfloor heating system installed will influence the amount of screed required. For example, the Uflex UFH system uses 16mm pipe and a traditional screed which is typically laid to a thickness of 60-70mm. Developers therefore need to factor in this build-up in floor height when planning door thresholds and other fixtures within a property.

Low profile wet underfloor heating systems which have a finished floor height of just 15mm and non-screeded wet underfloor heating systems are alternative UFH solutions for new build properties, both of which are supplied by Grant UK as well.

Room layouts and zoning

The pipework arrangement for a wet underfloor heating in new build homes will be determined by room types and heating zones. Rooms with a higher heat loss, such as a conservatory or a bathroom where there is limited floor area, will require the spacing between the pipe runs to be reduced so that a higher heat output can be achieved.

The configuration of one or more heating zones within a home will influence the positioning of manifolds, controls and pipework layout. Properties with open-plan living will likely use a single heating zone to serve the heating requirements for that space. Alternatively, developers may choose to group several rooms together in a single heating zone for example one zone downstairs and a separate heating zone upstairs. With the heating zone(s) determined, it is then possible to confirm practical pipe runs, the positioning of controls/room thermostats and the suitable location for fitting manifolds and the wiring centre.

Insulation and heat loss

Minimising heat loss from a property can be achieved through installing double or triple glazed windows, adding wall insulation and laying roof insulation. Floor insulation levels are another part of a build which must meet minimum standards. With wet underfloor heating systems, a layer of insulation should be applied beneath the pipework to prevent downward heat loss and to maximise heat output into the room above. Furthermore, the heat loss calculation for the property will determine the correct sizing of the underfloor heating system ensuring rooms with higher heat loss have adequate additional pipe to ensure design temperatures are achieved.

Wet underfloor heating and air source heat pumps

Air source heat pumps operating on lower flow temperatures are more efficient. Heat emitters which have a larger surface area to transfer heat from the system into rooms are ideally suited to heat pumps. Wet underfloor heating transforms the entire floor area into a surface area for emitting heat and this is why UFH works so well with lower water flow temperatures. Learn more about air source heat pumps and underfloor heating systems in our Knowledge Hub.

Traditional radiators are typically designed to operate with higher temperature heating systems such as boilers. Steel radiators installed with a heat pump will often need to be oversized in order to fulfil the desired design temperatures. Developers are therefore presented with the choice of larger, bulkier radiators versus seamless wet underfloor heating which delivers comfortable heat at lower temperatures.

Visit some of our case studies to read more about Grant heat pumps and underfloor heating systems in new builds and self-build homes:

• Grant heat pumps installed at luxury barn conversions in Norfolk

• R290 heat pump renewable heating system for self-build in Wiltshire

• Complete home heating system for self-build home in Cornwall

Choosing floor finishes for wet underfloor heating

The type of floor covering laid on top of a wet underfloor heating system must not impair the transfer of heat from the system into a room. Floor finishes such as tiles, stone and polished screed have excellent heat transfer and work best with wet underfloor heating. Carpet has poor thermal conductivity, low heat transfer and can only be laid on top of underfloor heating when the carpet tog and underlay do not exceed 1.5. Developers therefore need to ensure that when their customers are choosing the floor finishes for their new home, they need to select a floor covering which is compatible with wet underfloor heating.

Installation stages for wet underfloor heating in a new build

Installing a wet underfloor heating system splits into four key stages: planning and design, first-fix preparation, installation and testing, and commissioning and final system checks. Here is an outline summary of how to install wet underfloor heating in new builds:

• Planning and design: an accurate heat loss calculation and system design should be drawn up as soon as a property’s plans are finalised. This will determine the size of heat pump needed as well as the UFH system design to specify a system that will effectively and efficiently fulfil a home’s heating requirements.

• First-fix preparation: before an underfloor heating system is installed, the floor area must be prepared. Floor insulation must comply with Building Standards and suitable membranes and floor primers should also be in place.

• Installation and testing: using the drawings supplied, the layout of the UFH pipe should be measured and marked out before the UFH pipe is then positioned and clipped into place. The manifolds can then be installed, the pipework connected and the system filled and tested – it is important this is done before the screed is laid in case there are any issues within the system. The screed can then be laid and left to dry – the drying time will be determined by the amount of screed which has been poured but this will typically be approximately 4 weeks.

• Commissioning and final system checks: in a new build, this step may happen some time after the UFH installation because other trades and services may need to be completed first. When ready, the UFH controller and actuators can be fitted and the heat pump connected so that heat can be introduced to the system, the complete central heating system can be commissioned and final checks can be carried out to ensure all is working correctly.

Pros and Cons of wet underfloor heating in new builds

Wet underfloor heating systems deliver multiple benefits to new build homes including comfort, efficiency and seamless aesthetics. Some of the pros of underfloor heating include:

• underfloor heating achieves even, comfortable heat throughout a home and there are no cold spots as the UFH pipework is laid evenly throughout an entire room

• underfloor heating can be fitted as part of the floor construction, integrated during the early phases of a new build development

• non-screeded underfloor heating systems or low profile UFH are incredibly quick to install as there is no drying time

Some of the disadvantages of underfloor heating include:

• installation costs can be higher compared to installing new radiators

• system design can be more complex but support from Grant UK can make this stage straightforward for developers and their installers

• not all floor finishes are compatible with UFH, such as thicker floor coverings.

Wet underfloor heating systems from Grant UK

Grant UK’s Uflex wet underfloor heating range includes different solutions for developers and their properties which work alongside the Grant Aerona³ and Aerona 290 heat pumps. From traditional screeded UFH systems which are ideal for ground floor rooms through to low profile and overlay board UFH systems which require minimal or no screed and can be fitted in all rooms within a property. With new build homes making the transition to low carbon, sustainable air source heat pump heating systems, partner with Grant UK for your whole house heating solutions.