IES-VE User Forum

Hi IES users,

I'm modelling an office building and want to compare BER/TER pass margin under both the 2010 and 2013 Part L requirements.

The actual model stays exactly the same in both cases.

I would expect the BER to stay the same, since I don't change anything in the model, but the TER to decrease when I'm using 2013 Regs, since it's harder to comply with Part L 2013.

However, results show that TER is decreased (as expected) and BER is increased, reducing a 2010 17% margin to only 3% under 2013.

Do you believe this is reasonable? Shouldn't only the TER change?

The underlying methodology governing how both the actual and notional buildings are modelled changed moderately between the 2010 and 2013 regs. Therefore it is completely unsurprising that the BER has changed in your model. In fact it would be quite remarkable if it had stayed the same.

If you want the details, check out the NCM Modelling Guides and compare the differences.

Also, it's worth pointing out that there are some additional inputs that are needed for 2013 and so simply switching a 2010 model to 2013 sometimes isn't enough.

CP

Hi CP,

Thank you for your answer. I'll check the modelling guide to find out these differences.

Regards,
George

Also, don't forget that the 2010 and 2013 regulations use different CO2 emission fuel factors. That alone would cause your BER to change between runs.