![]() In comparison, flat plate radiant heating panels (typically ceiling mounted) will emit predominantly infrared radiation (radiant heat) – likely to be at least 67 per cent radiant – ie, have a high radiant factor, R, of 0.67. Typical wall mounted emitters (erroneously called ‘radiators’) will emit 80 to 90 per cent of the heat convectively and just 10 to 20 per cent by radiant heat transfer – i.e. ![]() low U values and/or relatively small external envelopes compared with the room volume) – there will significantly lower calculated heat losses due to the higher emitter radiant fraction. When high values of R and Cv are combined in large volume spaces and particularly for those with relatively small values of Σ(AU) (i.e. high air change rate), will reduce the value of the factors F 1cu and F 2cu. Similarly, a combination of a high radiant fraction, R, with high ventilation coefficient, CV (i.e. However, when examining the equations for F 1cu and F 2cu it can be seen that, as the value of R increases, both factors will get smaller. In many cases when undertaking building heat loss calculations the two factors F 1cu and F 2cu practically have a value of 1 and so the heat loss expression reverts to the time honoured simplification of: The factors F 1cu and F 2cu may be obtained from:Īnd where Σ(A) is the total area through which heat flows (m 2), and R is the radiant fraction of the heat source this will have a high value for radiant heat sources (with a maximum value of 1 for a pure radiant source) and a low value for predominantly convective sources (right down to of zero for forced air heaters). ![]() K -1), θ c is the operative temperature in the centre of the room (☌) and θao is the outside air temperature (☌).K -1), C v is the ventilation coefficient (W. ![]() Where Φ t is the total heat loss (W), F 1cu and F 2cu are factors that are related to the type of heat source, Σ(AU) is the sum of the products of the surface area and corresponding U value for each surface where there is a heat flow (W To determine the predicted heat loss using the CIBSE Simple Method the following relationship is used: Radiant heating was traditionally associated with gas-fired or steam-supplied high-temperature, high-roofed industrial applications however, ceiling-based low temperature radiant heating is now regularly applied to the healthcare, educational and secure facility sectors. The use of radiant heating panels in buildings can provide an energyefficient and space saving solution, contributing to reduced energy in a building, helping to meet the TER (Target CO 2 Emission Rate) as well as lowering its operational energy use. ![]()
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