PHAM NEWS | MAY 2025 36 Underfl oorHeating
Essential elements for proper calculation and design
A well-designed underfl oor heating system can contribute signifi cantly to the creation of sustainable indoor climate comfort, provided it’s carefully planned fi rst, says Myson’s Julian Clegg, who explains the data required to calculate and plan an optimally functioning heating system.
F
irst of all, it’s important to note that there is a diff erence between underfl oor heating calculations for a
new building compared to an existing building. In the latter case, you can, if necessary, just calculate the ideal system temperature and values for the hydronic balancing of the underfl oor heating system. In that case an estimate based on the year of construction usually also suffi ces. For new buildings, however, regulations stipulate that you need more detailed calculations to meet current regulations and NHBC and CIBSE guidance. A proper calculation is
absolutely essential for the optimal functioning of an underfl oor heating system in a new building. Because buildings today are much better insulated, they have a lower heat demand. This means you can heat the rooms more easily, but on the other hand you can also quickly overheat them if the underfl oor heating system isn’t balanced. This is detrimental to both indoor climate comfort and energy consumption.
Heating calculation For a detailed calculation, the following elements are at least required to properly design and plan the underfl oor heating system: • A heat load calculation in
accordance with DIN EN 12831: as this is building-specifi c, you will need a detailed fl oor plan, a cross-section of the building, U-values of the exterior components, information about the fl oor construction, and the size and type of the windows. • Confi rmation of which
type of heat generator will be
installed. This aff ects the system temperatures of the underfl oor heating system, and therefore its design. • A decision on the right
underfl oor heating system for the building. There are various diff erent underfl oor heating fi xing systems available, to cover almost every application. It’s therefore important to defi ne the requirements for the underfl oor heating system at the earliest possible stage. Factors to consider are: • Is it a new building with
Julian Clegg Technical manager for underfl oor heating at Myson
suffi cient installation height? Or a renovation project where every millimetre counts? • What type of screed will be
laid? • What heating capacity (and
therefore amount of water) is required? • What type of pipe is
required? • How quickly should the
system react? • What is the desired room
temperature? • What type of fl oor covering will be installed?
Smooth operation Based on all these values and specifi cations, you can fi rst determine the building’s heat load. This can then be used for the calculation and design of the system, including the installation distance of the heating pipes, the position of the heating circuits, the length of the heating circuits, and so on. All the data required for smooth
operation of the system, such as pressure losses, water quantities, settings, etc, can then be taken from this layout. The more precise the data and specifi cations for such a calculation are, the more accurate the results will be, and
KEY ELEMENTS
Conduct a heat load calculation in accordance with DIN EN 12831
Gather U-values of exterior components and fl oor type
Identify the type of heat generator to be installed
Choose the appropriate UFH system based on building requirements
Determine heating capacity and water amount
Select the type of pipe needed for the system
Establish the desired room temperature and system response time
the more effi ciently such a system can be set up and operated.
Getting support At Myson, we know from experience that all these calculations take time and require detailed product knowledge. We therefore off er an in-house heating design and calculation service to support our customers. Our internal experts can help in every step of the process, ranging from a preliminary calculation for the price and bill of materials, to a detailed calculation with all the values for correct hydronic balancing. Every project gets the support it needs. For example, in areas with a very high heat demand, our specialists can help you determine if the underfl oor heating system delivers suffi cient power, or if additional radiators might be required. ◼
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