Retrofitting Underfloor Heating – Installers' questions answered

With a wide range of retrofit systems now available, installing warm water UFH in a renovation project is easier than ever before. Nu-Heat helps to answer some of the most common questions asked day-to-day by installers moving into retrofitting underfloor heating. 
UHT retrospective webThese solutions are great for anyone looking to install UFH in an existing building. They have been designed to cause minimal disruption, being simply laid directly over the existing floor without the need for any timeconsuming and costly excavation work, and any competent installer will find them straightforward to work with.
Like all heating systems, there are still various factors to consider such as heat losses, heat output and some others more specific to UFH – such as height build-up.
Which retrofit system is right for the project?
The suitability of the project needs to be taken into account before choosing UFH. In a renovation, it’s likely that there are lower levels of insulation and, if this is the case, it will be necessary to check the heat output of the system versus the heat losses of the building.
A good supplier of UFH will be able to calculate the heat losses and then recommend a system that is guaranteed to perform.
For a new extension – or a property that is being refurbished to current Building Regulation standards – there is a wider range of options available because it’s likely that a system with a lower heat output will be suitable.
Providing it is known that the heat output is sufficient, it is possible to look at the various solutions that offer this output and compare how straightforward they are to install. Is it a simple system that will use boards that can go directly over the existing floor? Are the boards pre-routed to save you time? Is it a wet system that requires some drying time? Depending on the project, height build-up could be important so always check the total height of the system.
Will a retrofit system offer a good enough heat output?
Providing the property has relatively good levels of insulation and double-glazing, it is likely that a retrofit UFH system will be suitable and capable of comfortably providing enough heat all year-round. It’s important to remember that the fabric of the building can make the level of heat output critical to the success of the installation and that some projects with more insulation will require less output than others.
If the building has low levels of insulation, it could rule out most retrofit solutions that can reach approximately 80W/m². In this situation, it would be necessary to opt for a solution such as Nu-Heat’s LoPro Max that benefits from a
higher output of 120W/m².
Do all retrofit systems use pre-routed boards?
Pre-routed gypsum boards or polystyrene panels with metal heat diffuser plates are the most common type of retrofit UFH on the market. As dry systems, they are easy to work with and have very little impact on build schedules.
How long is the whole process, including design, supply and install?
UFH is often an afterthought part way through a renovation project and so timescales can be key – especially if there are other trades waiting to get started.
Working with a supplier that provides full heat loss calculation and bespoke system design, the process of initial contact, important information gathering, and supplying the finished design drawings should take around a week. Once the design and relevant criteria have been checked, the components are often shipped quickly afterwards.
For an off-the-shelf solution, where there’s no need for the design, packs can be shipped the next working day and installed in just a few hours, depending on the size of the room.
How long does it take to install a retrofit UFH system?
The install time depends on the size of the project but retrofit systems are generally quick and simple to install. An average three-bedroom home could be completed in just a couple of days and ready for floor coverings immediately afterwards. Even wet systems can be walked on after just eight hours and are ready for floor coverings after 72 hours.
In retrofit installations there should be an expectation to do some basic prep work to the existing floor, including making sure it is clean and level (if required) or tanking the room if you choose a system that uses a self-levelling compound. Aside from that, it’s a case of laying the UFH panels and installing the UFH tube to and from the manifold.
Can the system be zoned?
Retrofit UFH can be zoned in the same way as any standard UFH system. Even if the UFH is just being installed over one large open-plan area, it can still be zoned to suit the property and end-user.
Some retrofit systems are available in on-the-shelf packs, and these include everything needed to install one single zone of UFH. This is a great solution for single areas such as a kitchen or a new extension where zoning might not be needed.
How long until I can lay floor coverings?
This depends on the chosen system. Most quality dry systems can usually fit the floor covering directly over the UFH immediately without the need for any additional board or other layers beforehand.
With a wet retrofit system that uses a self-levelling compound, the end result is a perfectly level surface – ideal for tiling – that is ready for floor coverings after 72 hours.
As with all UFH, if the plan is to use tiles, it’s always recommended to use a thin decoupling layer.
Is it possible to run the UFH from an existing rad system?
A single-zone retrofit UFH system can be run off an existing radiator circuit, avoiding the need for new pipework back to the boiler.
This is a flexible option for anyone renovating and, if possible, it’s best to install the UFH so that it can be controlled independently from the radiators. This allows the homeowner to use the UFH to warm cooler floor coverings, such as tiles in a kitchen, throughout the year without having to power all of the radiators at the same time.
The reality of any installation is that there will always be specific challenges to contend with and overcome. The key to a successful retrofit project is correct planning – from a good knowledge of product options available through to a proper analysis of the property prior to commencement – because this will allow the right system to be installed to ensure the expected results are delivered.
[author image=”” ]Heather Oliver spent fifteen years working in civil engineering on both infrastructure projects and domestic housing schemes. A career change meant a move into graphic design, publishing and advertising. The combination of engineering and design experience has allowed her to further her career with Nu-Heat firstly as Publications Manager, followed by Marketing Manager and currently Development Manager.[/author]