Question-and-Answer Resource for the Building Energy Modeling Community
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Hi, I have done these studies before, it is important not to autosize anything in the Radiant object, not only that but EnergyPlus thinks that the capacity of your radiant slab should be calculated considering a delta T of 10K from surface to room. Usually the capacity of your radiant slab is provided at around a delta T of 4-5K so you need to increase the capacity in your model to accommodate the delta T 10K programing, in other words the design capacity you put into energyplus is the capacity at a delta T of 10K. The way we check then to make sure our ceilings are reaching the correct surface temperatures is by plotting against capacity of the ceiling. Also you need to make sure your water temperatures going into your ceilings is correct. I have done 4 or 5 different studies on surface temperature of radiant slabs in EnergyPlus and they have matched fairly well once I have hard sized everything and understood that design capacity is at a delta T of 10K.
I hope this is helpful!
