What is the difference between a typically constructed home versus a home built to Passive House standards with regards to heat gains and heat losses?
While every house loses heat, Passive Houses lose a significantly smaller amount of heat that is replenished by the planned natural and intentional heat gains.
Solar Gains (sunlight coming in windows)
Latent heat from fixtures
All homes have solar gains, internal gains, and heating gains; however, THE BIG DIFFERENCE is that Passive Houses are carefully designed to capture more sunlight heat during the winter season than a regular house. Passive Houses also lose far less heat than a code built home, so the resulting heat that needs to be supplied by the heating system is on average only about 15% of that required by a typical code built home.
Temperatures always seek equilibrium, just like a cup of coffee that cools off until it reaches the temperature of the surrounding air. Having an energy efficient home is all about having a balance within your home of heat losses and heat gains. Homes built to Passive House standards have an equal flow of heat loss (through the roof, walls, windows, ventilation) and heat gains (home heating system, solar gains, and internal gains or free heat gains), as is illustrated in this Heat Flow [kWh(m²)] graph.
In an unmodernised existing building, free heat gains are insignificant as the heat losses are very high. In contrast, in Passive House buildings they contribute significantly to the heating of the building.
IPHA – Passive House Institute, 2018/02
Below are a few images to help understand the heat loss pathways in a home built to standard building practices versus a home built to Passive House standards.