BS EN 1264-3:2021 pdf free download – Water based surface embedded heating and cooling systems Part 3: Dimensioning.
4.2 Ceiling heating systems
4.2.1 Basic principles
4.2.1.1 Temperature difference between heating water and room
For ceiling heating systems, the specifications and Formula (1) given in 4.1.1.1 apply.
4.2.1.2 Characteristic curve
For ceiling heating systems, Formula (2) and the respective specifications given in 4.1.1.2, apply. The gradient KH is determined according to EN 1264-2 and EN 1264-5. For detailed information about the procedure, see EN 1264-5.
4.2.1.3 Field of characteristic curves
In principle, the specifications given in 4.1.1.3 also apply. With respect to the calculation method (see
EN 1264-5), the field of characteristic curves should contain the values of RAB specified in 4.1.1.3, even
though not all together are needed for practical application.
4.2.1.4 Limit curve
Physiological limitations concerning the surface temperatures of ceiling heating systems depend on geometrical conditions, i.e. in practice on the respective application. Therefore, in this document only average conditions can be taken into consideration. Consequently, it is emphasized, in practical engineering the real conditions shall be taken into account.
For rooms with a height  2,7 m, the average surface temperature (see EN 1264-1:2020, 3.4.2) should not exceed 9F,m = 33 °C. As a result, the limit curve within the field of characteristic curves is a horizontal straight line in the distance q (see below).
Using the heat transfer coefficient a = 6,5 W/(m2K) coming from EN 12 64-5, the limit of the specific output at a room temperature of 20 °C results to:
q = 85 W/m2 (rounded)
At room heights> 2,7 m the average surface temperature of the heated ceiling can be increased. If values 19F,m> 33 °C are used, the compliance with physiological limitations should be proved. In general, refer to EN ISO 7730.
4.2.2 Boundary conditions
4.2.2.1 Flow pipes to adjacent rooms
The same procedure described in 4.1.2.1 applies.
4.2.2.2 Thermal insulation
To limit the heat flow through the ceiling to rooms above, the required thermal resistance of the insulating layer RA1fl (in principle see Figure A.3) shall be at minimum in accordance with
EN 1264-4:2021, Table 1.
As for the rest, the content of 4.1.2.2 applies accordingly.
4.2.3 Design
4.2.3.1 Pressure loss
The maximum pressure loss per heating circuit should not exceed 250 mbar in order to limit the electrical power consumption of the pump, e.g. by hydronic balancing (see EN 1264-4:2021, 4.1).
4.2.3.2 Design specific thermal output
It is recommended to apply the procedure described in 4.1.3.2 accordingly.
4.2.3.3 Determination of the design flow temperature
It is recommended to apply the procedure described in 4.1.3.3 accordingly. In the case of operating with floor heating connected in parallel and using uniform flow temperature, the flow temperature of the floor heating system shall be used.
4.2.3.4 Determination of the water flow rate
It is recommended to apply the procedure described in 4.1.3.4 accordingly taking into account the reversed position of the structure shown in Figure A.3 and the changes of the transfer resistances on the surfaces as follows.