Understanding zones : solar gains and zoning
Let’s try to understand zoning in buildings having HVAC system. For that we first need to know what solar gain is. The heating and cooling of the building depends on the heat from the sun. The change in the thermal loads due to the changes in the position of the sun is known as the solar gain.
To understand how solar gain leads to zoning lets take an example.
Suppose that we have a house with an HVAC system. The rooms or zones in the houses have been given the names as shown in the figure. We will try to understand the zoning on the basis of the heating pattern and the movement of the sun.
The sun rises in the east. In the morning hours, the easterly walls will be directly heated by the sun. Thus the NE and SE zones will be at a higher temperature than the rest of the building and thus will need more cooling to keep the whole temperature of the building at one constant temperature.
Now as the early hours progresses to midday, the thermal load on NE and SE will reduce and internal part of the building will also be experiencing equal thermal load as NE, SE, NW and SW .Thus the whole building will be requiring almost same amount of cooling capacity.
Now as the sun moves towards the west in the evening, the NW and the SW zones will be under direct solar gain and thus will need more cooling than the rest of the zones.
In this way, depending on the solar gain, the temperatures of the zones are controlled and maintained.