Home trends come and go, but one movement seems to be gaining strength. More and more homeowners are renovating their houses to be more energy efficient, saving them money on utility bills each month. While most home remodeling projects swap out old appliances for energy-efficient models, one design campaign is changing the way in which homeowners view energy consumption entirely. Passive houses are so efficient, they barely need heating or air conditioning.
Passive home design relies on placement of home features and the use of specific materials to generate heating or cooling inside of a house. Through the implementation of orientation, controls, airtightness and thermal mass, a passive house can store and redistribute the energy in a home to avoid the need for expensive heating systems.
The sun provides enough energy to allow life to form on planet Earth. That power can be harnessed to warm a home. The orientation of the house – the way the windows face – is one key principle that makes passive housing possible. The windows of a living room space should face within 30 degrees of true south – the closer to zero degrees, the better. This ensures that the right amount of light gets inside the home during certain times of year. The windows of the bedrooms should face within 30 degrees of true north.
A control is a feature that allows the homeowner to determine when and where light will enter the house. These can be built-in overhangs, awnings, retractable screens and more. Controls work together with the orientation of windows to determine how much sunlight makes it inside. For example, a built-in overhang will extend over the windows of the house. The sun reaches a high zenith during summer. However, the overhang blocks that light from getting through the window at peak times of day. This prevents the house from getting too warm. However, during winter, the lower angle of the sun allows rays to make it past the overhang and heat the house.
A passive home must be airtight to operate correctly. Most of the heating or cooling of the building is generated through light or movement (people walking around inside) and if there are leaks in the structure, that heat or cool air will be lost. Passive homes rely on a delicate balance of shading and sunlight, and a leaky window or door frame will disrupt that. Eco-friendly homeowners must purchase and install windows that are Energy Star certified.
Proper insulation is another way to prevent energy loss. The highest quality of insulation should always be used in a passive home.
Thermal mass and absorbers
Both thermal mass and absorbers refer to certain building materials that trap heat, including concrete, brick, stone and tile. These materials are often dark in color, as deep shades absorb more of the sun’s energy than light shades. The difference between the two is that thermal mass is generally laid between the interior and exterior walls, while absorbers are exposed to the elements.
The energy trapped by thermal mass and absorbers is released in the home using the simple principles of convection, conduction and radiation, creating a system of indoor climate control.
- Convection: Convection occurs when hot air lifts, cools and falls back down, then is reheated to rise once more. This is the process that occurs when water boils.
- Conduction: You experience conduction when you touch a warm radiator. The heat is transferred through contact.
- Radiation: When radiation occurs, an area is warmed by an object. For example, you feel the heat of the sun on your face without touching it.