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Underfloor Heating: Don't let the piper call the tune

Keith Westcott of Even-Heat believes that using on-site trades can ensure vital flexibility for floor heating installations
Underfloor Heating: Don
DURING the past decade, or so, commercial underfloor heating projects have come to be handled in a slightly different way from other types of heating systems and, indeed, ventilation and air conditioning systems.

These latter are normally supplied and installed by quite separate companies. However, it has become quite common for consultants to specify floor heating systems chosen, of course, for quality and service backed up with technical knowledge based on sound design...and then last, but not least, installation.

Often a package consisting of 'design, supply and install' is specified simply to ensure the floor heating becomes a one-stop-shop all the way from initial design to final commissioning.

Now, in the complicated world of the construction contract, there can be benefits in this form of sub-sub-contract for design, supply and installation, but that desire for a single contact to be responsible for the floor heating can also lead to other factors being overlooked.

The packaged solution can give the impression of simplifying the contract, while actually overlooking the benefits that experienced on-site mechanical contractors and heating engineers can bring.

Seeking a single source of blame should things go wrong implies fear, a residue no doubt of the mistrust of underfloor heating that was common 20 years ago. Such concerns have no place in a modern context. Underfloor heating is as reliable as any other method and offers huge benefits in comfort and efficiency.

Installation in the hands of skilled mechanical contractors should present no special problems and can be programmed into the schedule with the flexibility to meet the changing circumstances that are a feature of every construction project.

Basic procedure

Installation of underfloor heating is not difficult. If a detailed pipe layout plan is provided, along with a good installation guide which includes design criteria, the installation is a basic procedure. Indeed, in the early years, a significant proportion of the systems I inspected had been installed by beginners!

However, if installation is straight forward I believe timing and allocation of responsibilities can be anything but! The route from initial material delivery and off-loading to final handover can be confusing for the site manager as responsibility swaps between trades.


Specialist personnel cost money and they need to be kept busy.

So, it is pretty much inevitable the specialist floor heating installation team will be on site to complete the laying of the pipes only at scheduled times. Once that task is finished they will be off to the next project, leaving crucial responsibilities such as the monitoring of system pressure - as the shovels spread the screed and the hammers hit the nails - to others.

Building schedules are renowned for changing - even on the day before the specialist trade is due on site! If - and it is highly likely - the floor heating installer has other installations pending, any delay can quickly become disruption.

In my experience, the most efficient and best organised installations are done by the normal on-site trades. The flexibility offered is virtually impossible for specialist installers to equal.

There are many benefits in using on-site sub-contractors but, crucially, they are mainly based on site until completion which is a prime attraction. That continuity permits vital crisis management - switching from one demand to another within the overall heating and DHW installation. Progress can be made in circumstances that would leave the specialist floor heating installer demanding compensation.

Floor heating installation is becoming as much second nature to the general heating contractor as installing radiators. This new level of experience can be of great service to the project manager.

It is a long list

Materials must be off-loaded and stored. Site staff must be familiar with health and safety requirements. Any first fix within the floor trades such as gas mains must be completed and the area inspected on the day before installation. Insulation must be laid and tanked Visqueen provided for flow screeds etc.

The area has then to be cleared for installation of floor heating pipework. Once laid, the pipes must be filled and pressure tested and the double-regulating valves at the manifold set to the design requirements. Subsequent traffic over the pipes must be monitored and protection provided before screeding and flooring.

Periodic monitoring of the pressure gauges for leaks should be carried out while screeding is in progress. Direction must also be given to the screeders in positioning floor probes within the screed.

Flow and return connections to the manifolds must then be made and the necessary liaison carried out with the electricians for the hand- over of all electronic controls.

The system can now be flushed ensuring all air is purged from both floor heating pipes and primaries then dosed with inhibitors. The flow temperature can be set to minimum and slowly raised to the set design temperature.

Finally, any small adjustments required for the system balance should be made before hand-over with advice for the user on use of the controls.

This is just a simplified version to give an insight into the range of responsibilities involved.

You can see that the laying of pipes is just one part of a much bigger picture and the packaged approach really isn't necessary.
1 May 2007


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