Colglo Blog

Under floor heating that goes over the floor. [Really?] Yes!

Posted by Collister & Glover on Sep 14, 2018 3:07:45 PM
Collister & Glover

There seems to be a lot of confusion about underfloor heating. We are asked everyday "how can we make this work for us?"  "Do we fit it under the floor, in the floor, on top of the floor?" "Do we go electric or water?" This may surprise a lot of people, but actually, your home will usually will tell you what can be done.


Electric underfloor heating - what choice have I got?

There are four types of electric systems. Simply put, they all use a network of wires underneath your floor that heat up. The individual wires are laid in such a way to cover the whole floor and sit on top of a layer of insulation. You can use different floor coverings, vinyl, wood, even carpet if you avoid high tog ones.

In an electric wire system, the electric wires themselves are thin so add very little height to your floor.  You really only need insulation, a power supply and a floor thermostat. This makes them easier to install compared to a water-based system, but over the long term they are dearer to run. 

You do have to ensure that all electrical works conform to Part ‘P’ of the Building Regulations and current IEE Wiring Regulations. The system should be protected by a suitable RCD device. You may also need to check your main distribution board to make sure you have the correct fuses, RCDs etc.

Water underfloor heating - what about that?

Water-based systems are a network of pipes linked to your existing boiler that pump hot water around your room or rooms.

Water based underfloor heating systems distribute heat more evenly than electric, and they use water at a lower heat than a radiator, making your boiler more efficient.

Installation can be more expensive than electric wires but because the heating pipes are more efficient, the long-term costs are less.

A quick explanation of floor & flooring

  • Floor is your existing floor type floorboards, concrete etc.
  • Flooring (floor covering) means carpets, wood block, tiles etc. 

Electric underfloor - The 4 Types

Electric heating mats


Underfloor heating mats are supplied on a roll and they are fitted over your floor. The cables within the mat can be removed and the remainder shaped to fit awkward spaces. It can be supplied in different power outputs depending on the brand. The size of your floor can also dictate the power required. They only need a thermostat and a power source.

Aluminium foil electric heating mats

Electric-FoilThese are usually installed under carpet and vinyl floors.

The foil heating mats are fully earthed so they can be installed in wet areas such as bathrooms & kitchens, you should make sure they comply with electrical & building regulations.They can be a bit trickier to install than heating mats but they also only need a thermostat and a power source for installation.


Loose electric wire systems


Loose wire systems are really only for smaller areas such as bathrooms. Again they only need a thermostat and a power source. The cable is supplied in a continuous roll and has to be spaced out evenly over the floor and then secured  in place with pipe clips or ties.

In-screed electric wire systems
Good when installed in new extensions & conservatories. They generally take longer to heat up than the other electric systems here.

The cables are designed to be fixed to the re-bar under a minimum screed height. Obviously takes a bit of skill to lay screed.

Electrical wire systems on their own tend to be suited to heating small areas but if in doubt you can use the electric heating mats as above. It can be bought with the wires embedded in the mat, making it suitable to cover larger areas. Generally installing heating mats is cheaper than wires.


Water based under floor heating - The 4 types

There are several methods of installing wet systems into a home that do not require the removal or alteration of your existing floors. They use insulated panels with channels routed out, or pipes stapled in. Although there are only four basic types there is a lot more choice with how it is fitted. In general they only need a thermostat and a pumped water supply instead of electric.

Systems are generally installed to cover a whole floor.  Water systems integrate well with your existing boiler. The water from your boiler goes to a manifold that can split the flow into several circuits. Each of these circuits can be one room or more.

A question we get asked is "If it is underfloor heating, how does it go over the floor?"  Well it comes in different forms, you choose the type of heating to match the type of floor you have. The key thing to understand here as explained above, the words floor and flooring mean different things.

Descriptions of the different floor types can vary depending on the brand but in general, they are described by the fitting type.

A 'solid' floor system is fitted over a solid floor. (Duh!) Concrete or screed floors usually.


'Suspended' systems are those that can be fitted between the joists of a floor. Flat wooden boards nailed onto timber joists (floors or ceiling) are a good example of where you would fit these.

Suspended Floor System fitting from below

'Floating' floor systems can be fitted onto a concrete or  onto floors that are not nailed down, e.g. where the floor planks are either glued or snapped together. Laminate floors are usually termed floating floors. 


A 'modular' system is similar to a suspended system but are particularly good in tight spaces or when the panels are fitted from above or below into a space. Fitting from above involves taking up your floor boards. Fitting below involves taking down your ceiling. (Something you always wanted to do and were always putting it off.) The panels in this system are manufactured with the water pipes in place. Makes things a little bit easier.

This type is also designed for use in applications where a solid floor installation is not suitable due to structural weight limitations or where a ‘dry screed or dry fill’ floor option is required.



How your house chooses the underfloor heating type

Your house will have, or is about to have, a particular type of floor.

  • A structural floor such as concrete or cement screed.
  • A floor that is fitted, wooden boards, hardboard etc
  • A floor with joists.


1. Within the floor - when modifying your home


Underfloor heating whether electric or water can be installed within the concrete or screed floor easily if you are modifying your house, building an extension or renovating a building. And it requires little change to the floor design or construction. A Solid Floor System needed

2. Over the floor


When a floor is already in place e.g. floorboards and there is no requirement to disturb its construction, underfloor heating can be laid over the top of the existing floor. 
The panels add minimal height and the choice of systems means they can be used with any type of floor covering. An Overlay System is used here

3. In between joists 


Between the joist heating is normally installed in upper floors or the ground floor of a building that has a cellar. Even if your floors are already in place you can install the heating system from below, without disturbing the floor above. A Suspended or Modular System can be fitted


There are different packs for these different floor types.

The installation is the same whether you are working on a room or the whole house. Depending on what you intend to install, (in the floor, between the joists etc.) you simply choose the best method of fixing for you.


Connecting floor pipes to your boiler? Use a Manifold

All the pipes in the underfloor system connect to a manifold. They usually attach to a wall using a secure fixing bracket making installation quick and easy. The manifold (controlled by a wiring centre) keeps precise control of water flow through the system giving even energy efficient heating. 

Manifolds can have up to twelve ports, giving control of twelve rooms or zones. The word 'zone' just describes the merging of two or more rooms into one. The image below shows a three port manifold that can have up to three under floor heating zones


Hot water passes through the underfloor heating system and is returned back to the manifold. 

It is connected to the boiler via pipework and a pump circulates the hot water through the circuit back to the boiler.


A bigger view

And they fit into your existing system like this....  A ground floor and a second floor could be above or below. 


In this system all the rooms are heated using individual pipe circuits. Individual room zones give you maximum control over heating times and temperatures.Each part of the home will be at optimum levels.

A full manifold and blending valve assembly is used together with a dedicated wiring centre for each floor of the house. This enables flow temperatures to be accurately controlled. Hot water from the boiler is pumped round each of the four circuits of this system.

There are four pumps in total, two circulation pumps for radiator circuits and two pump packs for the under floor heating. 

Each pump pack will contain 

  • An EEI compliant pump 
  • A mixer valve 
  • And a bend and adaptor kit

Nearly all systems are easily upgraded to smart internet control systems by adding options that include: room thermostats, wet room thermostats, master control units and Ethernet based remote controls. Each system can be built to individual requirements. An internet connection is required for initial setup and ongoing use.

Thermostats connect via wiring centres to the manifolds and thermostatic radiator valves. All of the temperature controls are in turn controlled by a multi zone programmer. The programmer determines the flow of hot water throughout the system.

There are several thermostat control options, either  wired or remote control (RF) systems can be used. They vary from simple dial options to smart controls such as 'Hive' and 'Nest'


Choosing an underfloor heating control option

All systems come with a choice of temperature control including the new Smart Internet Controls which can be regulated remotely using smartphone apps.

A smart control platform is designed to give homeowners precise control of their Underfloor Heating system when they’re away from home using a smartphone or tablet.

Along with a range of features, the remote-control system can be used to set the temperature of any room in the house at any time. It’s fully programmable, so it can conserve energy and cut heating costs.


You can connect or upgrade a wired system to other systems, upgrading to a Smart Internet Control platform is as simple as switching thermostats.

Many systems are easy to install using a two-wire connection into the wiring centres.

  • Programming is straightforward with a simple timer via a web page dashboard
  • Every day of the week can be individually programmed to suit
  • Energy use can be easily monitored online
  • Temperature can also be adjusted manually on a simple three-button thermostat
  • Temperature can be temporarily boosted in a selected part of the house
  • It operates even if the internet is temporarily down, since data is stored on the thermostat


Smart Control products

Dial Room Thermostat

Simple Dial Room Thermostat

This thermostat can be installed in every standard room of the house where temperature control is required. 


Wet Room Thermostat

This thermostat is installed with a wet room sensor to provide temperature control in bathrooms and other wet areas and is connected to the other thermostats in dry areas of the home. 


TFT Master Thermostat

This device connects to a broadband router via an Ethernet connection to make the entire control system internet based. The unit operates up to ten thermostats.

WiFi-HubWi-fi Module

Installed, near the manifold, this wall mounted device allows wireless connection to the broadband router, allowing system owners to view statistics and make changes to the preset temperature log and schedules.


Smart Settings for the system

Although the Smart Internet Control range is compatible with both radiators and underfloor heating, it is optimised for use with underfloor systems. The system comes with the following pre-set values but they can be changed as required.


That covers this particular blog ....

There is an interactive graphic here that demonstrates some smart control functions available.

If you have any questions related to our underfloor service, or would like to speak to one of our sales & advice team you can contact us on 01244 288 000.

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Topics: underfloor heating