Debunking 8 common underfloor heating myths

by UFH1

The following information aims to debunk 8 of the most common myths that surround the installation and running of underfloor heating systems.

Myth: There’s a cost per m²

Fact: Underfloor heating isn’t priced like flooring etc. There’s a vast range in price and the cost of a system depends on the floor construction, heat source, installation type i.e new build/retrofit, controls specified etc. The difference in equipment can range from £5-£30+vat per m² for new builds (typically £8-£12+vat per m²) and retrofit systems start at £20+vat per m². For more information on pricing a project, please see this post.

Myth: 1 port/circuit per room

Fact: The amount of circuits in an underfloor heating system depends on pipe spacing, size of pipe used and the connection lengths to the manifold. For example, a 30m² room would require at least 2 circuits (at 200mm spacing with 16mm pipe) and would require 4 circuits (100mm spacing with 11.6mm pipe) using our Premium retrofit system.

The maximum length of a circuit is 100m (16mm pipe) and 80m (11.6/12mm pipe).

Myth: Each manifold port is a ‘zone’

Fact: A zone is an area/room(s) to be controlled. With reference to the above explanation, a zone can have multiple circuits/ports from a manifold. A zone is usually defined by the thermostat controlling circuit(s).

Myth: Underfloor Heating is left on all the time

Fact: All heating systems should be used by correct use of the controls. Vast ‘peaks and troughs’ in temperatures are what make heating systems inefficient. The best way to use UFH (and any other system) is to use the setback on the controls. In other words, set the minimum temperature at around 16°-18° in Spring/Summer and 18°-21° in Autumn/Winter outside of any programmed or manual temperature settings.

The UFH will only be on when it is required, when the thermostats are calling for heat to get to a set temperature. Good UFH systems can give hours of residual heat so it can feel like the system is on when it’s actually off. The setback temperatures will enable a quick heat up time to a higher required temperature and prevent large peaks and troughs. Check out this post for more information on selecting the right controls.

Myth: Underfloor Heating takes hours to heat up

Fact: The initial heating up of a concrete floor can take hours. However, in reality this should only be from the first commissioning. Correct use of the controls as described above in normal use will prevent this. The thicker the concrete the longer the heat up time, however, the better residual heat given off.

As a guide, most in screed systems take 1-2 hours to get to room temperature although can dissipate heat for several hours. Therefore setting the controls to come on and go off before they are required is advised. Retrofit systems can heat up within an hour.

Myth: You can’t have UFH in an existing house

Fact: Our retrofit systems (or commonly known as ‘overlay’ or ‘overfloor’ systems) are designed to go over the existing floor and some produce the output of a ‘conventional’ UFH system without the need to excavate the floors.Obviously there will be some examples where it’s impossible to have UFH, although there are now retrofit wall and ceiling heating systems available instead.

Myth: You can’t have UFH with joisted floors

Fact: There are multiple types of joists used in building but there is a system for each type. UFH installations will require either fitting above the flooring/joists, fitting from below or fitting in between the joists. If you require more information relating to this, you will find this post useful.

Myth: You can’t have UFH with carpet

Fact: YES you can! The Carpet Foundation carried out some research in conjunction with the Underfloor Heating Manufacturers Association (UHMA) and this proved conclusively that most carpet can be used over underfloor heating systems without impairing the performance of the system.

The research showed that a carpet/underlay with a combined thermal resistance of less than 2.5 tog allows underfloor systems to operate efficiently. We recommend consumers going for the thinnest combination of carpet/underlay they’re happy with up to a maximum of 2.5 tog. Check out this post if you want more information on installing underfloor heating when you have a carpet.


Free CAD
Full Installation
Industry Leading
Best UK
Trade Rates
We Will Beat
Any Quote