Thermal Modelling – Heating and Cooling Load Calculations

A thermal model of the building or development is created using specialised software.
This model takes into account all of the building’s construction properties:

• Wall, floor, and ceiling composition and insulation;
• Glazing properties such as single, double or triple-glazed, whether or not the framing has a thermal break, overhangs, and whether or not the glazing is internally or externally shaded and if so, to what degree and by what manner;
• The general construction quality of the building; and even
• The colour of the exterior surfaces.

This model further implements information regarding:

• Ventilation, whether it be from natural infiltration or via heat-recovery ventilators (HRVs)
• Internal heat-gain from items such as comms rooms, cooking equipment, and computer equipment.
• Peak occupancy levels, activity, and associated supplemental ventilation requirements.

The model of the building or development is then located virtually in its final location, and in its final orientation. 

Design criteria, which designates the target indoor and outdoor conditions that the heating and cooling system will need to maintain and operate within, is then determined.

Interior design conditions are either as recommended by CWL Group based upon internationally recognised optimum targets/standards such as ASHRAE 55 and ISO 7730, those required by specialised spaces (wine cellars, indoor pools/natatoriums, museums), or those specified by the client to meet their own particular comfort preferences. External design criteria is based upon the AIRAH Critical/Comfort data sets (which themselves are based upon BoM climatic data from 1990 to 2013), the ASHRAE worldwide data set, or again, tailored to client preferences.

The model then simulates the amount of heating and cooling energy required to maintain the indoor design criteria at worst-case outdoor design criteria (the peak heating and cooling loads), or the amount of heating and cooling energy required to maintain interior design criteria on an annual, or even hour-by-hour basis. 

On most projects, an AED (Adequate Exposure Diversity) analysis is also performed, which provides insight as to the importance of airflow balancing, zoning, and distribution within the building. This also illustrates the cooling-load profile of a zone over the course of a day, which assists in estimating how the cooling system (and even hydronic radiant heating systems) will respond to the building’s glazing and ever-changing sun-angles.

The result of all of the above is assurance that the bespoke mechanical system that is specified, fully engineered and installed upon the foundation of the aforementioned modelling work, is fully tailored to each client and their building/development’s distinct comfort requirements.