The process of accurate floor heating design starts long before the underfloor heating company gets involved, Architects, consultants and specifiers are the important first step in ensuring that the building has the correct floor make up and insulation levels.
The word ‘design’ indicates that something is devised for a specific function, it follows that an understanding of all aspects of that function is essential to produce an accurate design.
This can only be achieved by competent training for people involved in the various stages of the design work, and subsequently the installation procedure.
It will be reassuring for anyone responsible for a building’s performance to know that the floor heating element has been designed and controlled in the best possible way, one that takes into account any other services that may have to interact with it.
Structural Considerations
The prime consideration is that floor heating is all about contact, the pipe carrying the energy in the form of warm water must be 100% in contact with the floor structure and in turn the final floor covering must be 100% in contact with the warmed floor structure. This is not difficult to achieve, for instance when considering a standard screed floor the floor heating pipes are simply added into the floor screed without any changes to the mechanical make up.
If the pipework is installed in a manner that depends on air as a transfer medium for the heat energy, then the system will become less efficient. There are installation methods that depend on warming an air gap beneath the flooring, but remember that air is an insulator and an air gap beneath the floor could conceivably allow a flow of air, thus dissipating the benefit. The tendency here is to operate the system at a higher temperature to produce some results in the occupied space, this negates any benefit of installing floor heating. Another method is aluminium diffuser plates, this system does not utilise an air gap, but the problems arise with cheaper and thinner plates where a temperature drop of 6 deg.C can occur between the pipe groove and the edge of the plate.
Insulation
Of all the elements within a structure this plays the most important part in energy efficiency, and yet it is not given much credence at all. Building regulations for instance only recommend the minimum requirement and in general that is the standard that is applied.
Extra insulation or a much higher standard of insulating material will add very little to the total build cost, but will make a tremendous difference to the long term efficiency and running costs.
Efficient heat distribution and close control of the internal environment tends to be high tech and high cost, insulation on the other hand is low tech and low cost and that is the element that stops the expensive heat from leaking out of the building.
This issue is particularly important with floor heating, to many people insulation in the floor structure is a means of reducing heat loss from the heated area above. When the floor heating is in operation you cannot get a loss from the room ambient down through the floor as the floor is at a higher temperature than room ambient. What does happen is a downward loss from the floor heating pipes to either the substrate or in the case of a suspended floor into the ventilated void. It is therefore essential to give a little more consideration to this element of the structure.
If the building has been designed to accept a floor heating system the next step is to calculate heat losses, pipe requirements and apply a sensible and effective control system.
To achieve an accurate design and be able to indemnify the results the following information is required:-
· Scaled floor plans
· Scaled elevations
· Details of floor and wall construction
· If known, details of proposed floor coverings
At Begetube we are often asked why we need the elevations as nobody else has asked for them, the answer is quite simple—heat losses cannot be calculated on two dimensions, and until you know what the heat losses are you cannot accurately design a heating system to address those losses.
Training for Floor Heating Designers
Heat loss calculations are fairly straightforward and are usually incorporated into a computer programme, the Begetube design programme takes into account the subtle differences when calculating for floor heating. This is always the first step, but our bespoke programme also calculates pipe spacings for the floor circuits and provides a total heat input requirement for the building. The software was written by us and has served us well for ten years, changes are made as various regulations change so we are up to date at all times. Parameters can be changed to suit any scenario, such as designing for heat pumps that require lower mean water temperatures.
All this is very fast and easy to use, but we decided that simply pushing buttons and getting a result is no help to clients who phone in with questions regarding the design parameters. A more in depth knowledge of design procedure, pressure drop and flow rates would be required to give a complete technical back up, to that end all Begetube floor heating designers are now qualified by examination to be members of the Institute of Domestic Heating and Environmental Engineers. ( IDHEE )
In addition we have an ongoing product specific training programme to ensure that anyone with a problem can be talked through the sequence of operation and rectify the problem.
Training for Installers
Accuracy in the design and specification process is obviously an important issue, but this accuracy must be continued in the installation and setting up procedure.
It is not sufficient to simply show installers how to install pipe into the floor, as that is the simplest part of installation. Heating installers need to understand what it is they are dealing with, the function of all the individual components and how they fit together and provide a competent heating system. Installing a floor heating system requires care and attention to detail, it is only a heating system but it is one that is embedded in the structure of the building.
During a Begetube training course we stress that mistakes are not easily rectified, each circuit should be laid exactly as the CAD pipe drawing shows and then checked. When the installation is complete it should be checked again, it does not take long to walk round and be certain that each circuit is correct and free from kinks etc.
During the training course the following points are discussed:-
· Short history of floor heating in the UK
· Radiant theory
· Component parts
· Floor constructions
· Pipe fixing methods
· Installation, filling and testing
· Controls
· The importance of correct setting up
Controls
Any floor heating system should be accurately controlled, the water temperature flowing in the floor and the resultant room ambient temperature must be addressed.
This can be achieved by standard room stats and a blending valve, or by weather dependant control of the water temperature with predictive room sensors.
In the near future regulations regarding control of heating systems will be under the spotlight, it is likely that more emphasis will be placed on weather compensation control and possibly lowering the mean water temperature in floor heating circuits. At Begetube we have been using this level of control for ten years, and heating engineers at our training courses are instructed in all aspects of these controls.
Finally
With the correct level of technical knowledge, designing and installing an efficient floor heating system will be a straightforward operation.
Problems will only arise if there is not a complete understanding of this type of heating, it is not something that should be approximated or simply guessed.
Sensible training and a technical help line are provided by Begetube, and during the past ten years these facilities have proved to be very helpful to installers and self-builders associated with us. The technical manual is easy to understand and provides pipe and wiring diagrams, user instructions, setting up details and fault finding flow charts.
Author: Douglas Haigh FIDHEE
Begetube UK Ltd
http://www.begetube.co.uk/
