I have a room where I am trying to compare two materials on a given day using the Summer function. The issue I'm having is that beyond a certain amount of fresh air changes, the room temp is lower than the ambient temperature. The room with materials with less time lag exhibits this effect more so than the other.
Any suggestions as to why this is happening?Thanks.
Hi Tim,
I would suspect that the greater thermal mass of the material with the larger time lag means that it is taking longer to cool down the room through the air changes. On the other hand, the material with the lesser time lag would be less able to store the heat and would be more susceptible to temperature swings.
Hope this helps to clarify.
Shane Regan | Principle Building Performance Support EngineerHevacomp to OpenBuildings - A complete guide for every user | Bentley Communities
Please also note that the CIBSE calculation is an admittance method attempts to predict how a room with react over a 24 hour period. As such the ambient temperature in the UK is often cooler than the room design temp for more hours per day than it is above. This is especially the case during the night and as such the air changes you specify are cooling the room surfaces etc. This effect is smeared across the 24 hours which will reduce the room peak temperature in general.