IES-VE User Forum

Hi I was wandering the best approach for testing BB101 overheating criterion B:

b) The average internal to external temperature difference should not exceed 5°C (i.e. the internal air temperature should be no more than 5°C above the external air temperature on average)

Recently I have been calculating this in Excel and filtering the results for just the occupied time. However I find with cooler weather files it is almost impossible to pass the criteria even with excellent ventilation etc.

Ross

As far as I know there is no way to do this within Vista and as you have been, you must rely on manipulating the outputs in Excel.

My understanding of BB101 Criteria B is that it was only included to enable compliance in warmer parts of the UK where it's extremely difficult to achieve Crit C (never above 32°) because the external temperature rises above this. In cooler areas it is therefore not a particularly suitable measure of building ventilation performance.

Personally, I only use Crit B when I cannot get a solution using Crit A and C. Typically, this only ever happens when working with the London DSY weather file.

Hi Ross

You're right, the BB101 difference criteria is poorly worded and ambiguous. My interpretation whenever I've needed to use it was to filter out any of the hours where the external temperature was below the heating setpoint.