Thermal Loads are the amount of heat energy required to add or remove from a space in order to maintain the desired room temperature. The Heating Load is the amount of heat energy added, and Cooling Load is the amount of heat energy removed. Since thermal loads are the primary cost for most building types, engineers can use them to calculate operational costs.
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Maintaining lower thermal loads are imperative to a high-performance building. Higher thermal loads are attributed to the high energy usage required to regulate them, as well as the heating and cooling requirements handled by the heavy use of air-conditioning systems. High thermal loads are also the result of a project's climate zone; irregular or extreme temperatures on the outside increase the heating/cooling demand to keep temperatures acceptable inside.

The heating and cooling loads are described by the HDD (heating degrees days) and CDD (cooling degrees days) of the climate of the project location. HDD quantifies the demand for energy needed to heat a building. CDD quantifies the demand for air conditioning to cool a building. If your location has more HDD, typically cooler climates, then heating will be your primary thermal EUI load. If your location has more CDD, typically hotter climates, then cooling will be your dominant thermal EUI load. A more detailed description is provided by the U.S. Energy Information Administration.

Thermal mass also greatly impacts thermal load, as poorly insulated wall assemblies, thermal bridging around windows, or other infiltration issues with floors, ceilings, and roofs require more active strategies to regulate temperature.

Combat high thermal loads in the early design phases by revisiting shading strategies, passive strategies, facade materials, and thermal mass.