Traditional ‘steady state’ calculations for heat load tend to oversize the heating plant requirement as they are limited in their assumed internal and external parameters. These simple calculations also cannot take account the previous operating periods.

In simpler terms, the building might retain some heat from the previous day instead of assuming it starts completely cold each day. It could also absorb heat from solar energy during the day and gradually release it into the rooms overnight.

Utilizing the IES model we were able to produce comprehensive calculations culminated in the determination of both the annual net thermal demand and the design day heat load.

With climate change, overheat risk in modern buildings is on the rise and is likely to become a more significant concern. You can assess the likelihood of high internal temperatures during hot weather using the SAP method. In Scotland, if the building can be cross-ventilated (with windows open at least 50% of the time at either end of the building) on hot days/nights, the overheat risk is considered “not significant.” If windows cannot be opened, you should consider mitigation measures such as screens, blinds, and/or air conditioning.