Underfloor Heating and the considerations

At the design stage there are a number of points that need to be considered:

How your floor covering will affect the performance of your underfloor heating system

You will need to choose your floor coverings carefully. A thick carpet for example my have the effect of insulating your room from the very thing that's trying to heat it. Check with suppliers that your choice of floor covering is compatible with underfloor heating. You should also be warned that some carpet shop assistants will look at you a bit strangely when you refer to TOG ratings and insulating effects. Do not accept simplistic answers (otherwise known as flannel). If the assistant can't answer you, but owns up to the fact, that's one thing, but attempts at waffle should ring alarm bells. Go somewhere else! Carpeting a floor that contains UFH is a bit like putting a duvet cover on a radiator. It will have an affect. As a rule of thumb, the thicker (or heavier) the combination of underlay and carpet - the greater the insulating effect. Heat will of course percolate through but it will take time.

 How your UFH system will affect your floor coverings

Should you choose to have a wooden floor, will the heat from your system crack or distort the wood, the varnish, or cause discolouration? Wood should be regarded as a living medium. It contains moisture. UFH will dry said moisture which can result in cracking, shrinking and/or warping. It is generally accepted that solid wood will suffer most from these problems. Engineered flooring (a laminate based on plywood construction) is considered the better option as it is the most stable.

 Where do you plan to put your UFH manifold/s in a WET system?

Each underfloor heating zone will need to terminate back at the manifold. You need to consider where you intend to site the manifold, considering you probably don't want it to be generally visible you will need to place it in a convenient hiding place. Remember, depending on the number of zones, it could take up a significant amount of space and have many pipe connections (at least two pipe ends per zone), together with a wiring centre to control zone actuators and receive room stat signals. You will also need the appropriate electrical supply. Manifolds are quite neat when the installation is complete but remember they are a necessary part of the system and will need to be accommodated. If possible, site manifolds in a fairly central location to minimise pipe run lengths.

 How many UFH zones will you create

In a multi-storey building each floor will require at least one manifold (very large projects may require multiple manifolds to cope with the large number of pipe loops). The more zones you create, the more control you have over different areas - either sectors within a large single area or from room to room. There may be practical advantages or disadvantages to creating many zones. Consider a zone as the area controlled by a single room stat. In a wet system, a single stat can control one or more loops from the manifold by simultaneously activating more than one actuator.

 Boiler/pump position and size on WET systems

Be sure to have your boiler size calculated for you so that it will cope with the demands placed upon it. Your property will have a 'heat loss' value. A 'Gas Safe' installer or competent plumber will be able to do this for you.

Check with the manufacturer whether your chosen system has it's own UFH circulating pump and/or whether you need to install a pump anywhere else in the system.

 Consider your pipework layout on WET systems

There are many way to plan your pipework layout. In short, the water flowing away from the manifold is going to be warmer than that returning. So when looking at your room, you might for example have an area that is likely to be colder than another (under a window, by an external wall or by patio doors etc). It might therefore be considered logical to direct the earlier section of your pipe run straight towards such areas - hence getting the benefit of the warmer 'flow' water. You might even wish to focus the earlier part of your layout on these areas by increasing the number of 'early or warmer' loops in areas that are prone to be cold - then working away and back to the manifold.

There are many methods and ideas when it comes to pipe layout - nothing is 'set in stone'. The good news is, that whatever your chosen layout plan it will not affect the control requirements.