Air treats your building like a slow journey through a series of tunnels and holes. Right now, air is passing through the walls, between the floor joists, and through the loft hatches of homes all over the place. You may not have even noticed that Air is there at all.
The air pressure inside a building is always trying to equalize with the outside air pressure. The way air moves through the walls, floor joints, and loft hatches of homes is determined by the stack effect. Warm air is lighter than cold air, so it rises up through the building. As it gets to the top of the building it leaks out through any gaps around light fittings, loft hatches and joints in the roof. As it escapes it creates a slight vacuum which pulls in more air from the lower part of the building. This fresh air enters through the floor, along the skirting boards, and any cracks in the walls near the ground. So the building is slowly breathing in and out.
There is a point somewhere in the middle of the building where the air pressure is roughly equivalent to that outside the building. This is often referred to by building scientists as the neutral pressure plane (NPP). Air is trying to leave a building above the NPP and trying to get into the building below the NPP. For HVAC Williamsport PA, see //qualityairmechanical.com/hvac/.
But there is more to this issue than just the way that air moves up through a building in winter and down through it in summer. Most buildings that are air-conditioned are cooled to a temperature that is lower than the temperature outside. In such cases the warm interior air actually moves down through the building and enters at the lowest points while the cooler air drains out of the upper parts of the building. So in a building that is air-conditioned the neutral pressure plane can actually move down through the building in the summer so that warm air enters at the lowest points and cooler air leaves from the upper parts of the building. This is just one of the many reasons why some rooms are always too cold in the winter and too hot in the summer even when the same setting is selected on the thermostat for all of the rooms in the house. Understanding how pressure and heat move through a building envelope can help to explain why this is the case.
However, in older homes, typical gaps in a home’s building envelope could cause increased pressure in the building due to the stack effect. Therefore, an understanding of the building’s pressure behaviour is also important when managing heating or cooling in a home.
