Difference between AIRAH Gain and Summer

Hi Tim

Methods used by the calculations are designed to calculate comfort conditions for occupied buildings that consider air conditioning. As you move outside of this into extreme conditions, variances in the calculation methods would be greatly exaggerated.

Regards,

Thanks Duncan.

So with this point in mind, is one of these methods more appropriate for this situation or are both exaggerated?

Cheers,

Tim

Hi Tim,

The design engineer would need to make the decision as to which calculation is most appropriate, however please note that the Summertime calculation's purpose is to find the peak temperature, while the AIRAH Gain (and CIBSE Gain) calculation is more designed to calculate Air Flow rates necessary to maintain room design conditions. With this in mind Summertime would give you more of a worst-case-scenario for peak temperature.

Thanks Shane,

Just to clarify, Our buildings are usually of typical size and construction. Much like small commercial or residential buildings (ie. I didn't consider this to be an extreme scenario)

In summary, would we best to use:

• the Summertime calculation to determine the maximum temperature with no airflow? (We note humidity doesn’t seem to affect this calculation.)
• The AIRAH (or CIBSE) Gain calculation, (changing the internal temperature until we get zero heat flow) to determine the maximum temperature with a fixed outdoor airflow / air change rate?

Hi Tim -  That sounds reasonable to me, but I should state again that the conditions of the project were extreme, and would be pushing the tolerance of the calculation.

Regards,