In his building-science presentations, John Straube often talks about how skyscrapers co-evolved with revolving doors. This is because of the stack effect: Warm air rising in a tall building creates a pressure difference that makes opening a ground-level swinging door very difficult. The taller the building, the greater the pressure difference and, as a result, the harder it is to open the door. A similar relationship exists with temperature: The greater the temperature difference, the faster the heat flows to the cooler space.

When you make changes to one part of a house, you may create problems elsewhere. Rising energy costs and federal subsidies have encouraged homeowners to swap conventional furnaces for high-efficiency, direct-vent models. Unfortunately, the atmospherically vented water heater is often left behind. These orphaned water heaters are now venting into an oversize flue that was once shared by two appliances. Half of these orphaned heaters won’t have enough draft to get flue gases outside the house.

Because water runs downhill, roofing components should be installed “shingle style” by starting at the bottom of the building and overlapping lower courses with subsequent courses. Any holes should be repaired, and the water-resistive barrier (WRB) should be lapped over (not behind) window head flashing and step flashing on abutting roofs.

Air-permeable insulation such as fiberglass and blown cellulose does little to stop air moving through it, which is why you need an air barrier. An air barrier is an air-impermeable layer that prevents conditioned air from mixing with outdoor air. Insulation such as closed-cell spray foam and rigid foam is its own air barrier.

Rooms over attached garages, which can be uncomfortably hot or cold depending on the season, are a perfect example of how heat moves from warmer spaces to colder spaces, by taking the path of least resistance. Typically, the problem is that poor insulation and air-sealing details allow unconditioned outside air to mix with conditioned interior air. This makes these rooms difficult to heat and cool.

There are four primary factors that affect human comfort: air temperature, relative humidity, radiant temperature, and air movement. People are often most comfortable when the air temperature is between 70 and 80 degrees Fahrenheit and when the relative humidity is between 30% and 70%. A slight breeze on a hot sunny day can make you feel comfortable, but a draft in your living room on a cold day can be uncomfortable.

Building an eco friendly home can help you save energy, save money, and save the environment. A net zero home is capable of generating as much energy as it consumes. Here are some best practices to keep in mind when building your eco friendly home.