When you were younger did one of your parents tell you to keep the doors closed in the winter because you were letting the cold air in?
Did they also tell you to shut the doors in the summer so the cold air couldn’t get out?
They were sort of right. Here’s what was really happening. Warmth is naturally drawn to cold (first law of thermal dynamics). That means warm air is going to find it’s way to cold air in one way or another. So in the winter, the door was open, or the windows were not sealed or the wall cavity wasn’t insulated correctly, so the warm air was seeking the path of least resistance to leave the house.
When the warm air escaped, the void was filled with cold air. So when we left the door open, we were letting OUT the heat and it was replaced with cold air drawn into the house thru leaky windows and poorly insulated walls, not just thru the open door.
The opposite is true in the summer time. We are letting in the hot air thru the door, poorly sealed windows and an inferior wall insulation package.
This is why we must make sure we insulate our cavities with a product/system that closes virtually all of the gaps and voids in the wall and other cavities and make sure the house has an upgraded seal package helping our windows, doors and attic spaced to not leak conditioned air.