The answer is because they loose heat. And what if we could build a house much like a thermos and prevent the heat from escaping through the building? That is exactly the winning formula on which the Passive House Science is based. The results are amazing: 90% savings in space conditioning energy (heating and cooling).
What is left is amount of energy so minuscule that you could theoretically heat your home with a hair dryer.
Here are the 6 most important principles:
Super-insulated building envelope with insulation levels 3-5 times greater than conventional.
Eliminating thermal bridging through special detailing.
Triple glazed windows with insulated frames and thermal bridge free installation.
Eliminating air infiltration losses through installing a continuous air barrier. Air- tightness verified through blower door test.
Whole House Ventilation
Maximizing the free passive solar gains.
Rigorous energy modeling to verify specific performance targets. and design the mechanical systems.
Have you ever heard the saying “The cheapest gallon of fuel is the one you don’t need”?