Transmission load
Short definitionThe heat coming in through walls, ceiling and floor. It depends on panel thickness and the inside-to-outside temperature difference.
It is calculated separately for each surface: the surface area, the insulation value of the panel and the temperature difference across it are multiplied together. A wall facing outside air lets through far more heat than a wall facing a neighbouring cold room.
For walls and roofs exposed to the sun, an allowance is added to the outside temperature. Transmission load is there every hour of the day. Even when the room is empty, this heat keeps coming in.