Passive design strategies seek to achieve comfortable indoor temperatures without relying on mechanical heating and cooling systems. These are achieved through a combination of building orientation, insulation, shading and daylighting.
Large glass openings on the southern and northern facades of a building are used to collect solar energy, which is then stored by thermal mass materials. The absorbed heat is released slowly into the occupied space to warm it in winter.
Transparent Materials
The use of transparent materials is a key element in passive design to promote energy efficiency. These materials allow sunlight to enter the building, minimizing the need for artificial lighting during daylight hours and creating a comfortable, visually appealing environment for occupants. In addition, they promote a sustainable, eco-friendly construction process and reduce the use of fossil fuels.
The role of building materials in passive design extends beyond energy efficiency to include thermal comfort, natural ventilation and aesthetics. Building materials should provide the appropriate level of insulation to achieve an efficient design, and they should be selected according to the climate. For example, a building in a cold climate requires an extensive use of glass to maximize solar heat gain and minimize the need for active heating.
Insulation can be achieved using natural or man-made products such as wool, recycled denim and sheep’s wool or Aerogel (a material that contains more than 90 percent air). The best type of insulation is continuous, avoiding gaps or leakage that can result in heat loss. Prefabricated structural insulated panels offer superior and more uniform insulation than conventional stud construction.
Passive design strategies reduce the need for artificial cooling and heating, resulting in lower utility bills. This approach minimizes carbon emissions, improves indoor air quality and provides a resilient shelter against climate change.
Thermal Insulation
One of the main principles ensuring a high level of quality and comfort in Passive Houses is effective insulation. It prevents heat loss through roof and wall surfaces, thus reducing heating costs in winter and cooling costs in summer. Insulation materials must also provide moisture control and fire resistance. They can be made of natural and recycled materials, such as hemp wool and cellulose. They are nontoxic and have a low environmental impact.
The choice of insulation depends on the climate zone in which the building is located. Generally, passive buildings require thicker insulation than conventional ones to achieve an optimal thermal balance and reduce energy consumption. It is important to choose a material with a good U-value and a selectively high solar heat gain coefficient (SHGC), as well as a high visible light transmittance.
Efficient insulation is essential in any type of construction, but it becomes especially important when combined with other passive design strategies. The most effective solutions are those which are tailored to the particular climate in which the building will be located. For example, in extremely cold climates, the use of high thermal mass and insulated external walls helps to even out extreme temperature differences between day and night, as well as to protect against harsh summer sunlight. These solutions work thanks to a property of certain materials known as thermal lag.
Natural Ventilation
In some climate zones, natural ventilation can be used to maintain indoor air quality in winter without relying on mechanical cooling systems. However, achieving this requires careful design to take advantage of local weather conditions.
A building’s occupants can control natural ventilation by opening and closing windows, depending on the time of year and local wind conditions. The position and size of windows, together with external shading, are important factors in directing wind-induced ventilation. A sloping roof, with overhangs to reduce direct sunlight penetration in summer and restrict air and water leakage in winter, can also help. In addition, thermal mass—such as clay brick or concrete floors—helps to retain the heat energy that radiates from a building’s interior during the night and morning. Natural buoyancy also plays a role; if a room’s exhaust opening is located high above the inlet, the stack effect encourages warm air to rise and exit the building, drawing in cooler, fresher air from below.
To maximize the effectiveness of natural ventilation, buildings are best sited to take advantage of the prevailing summer winds. This can be determined by consulting seasonal “wind rose” diagrams, which show wind direction and speed across the skyline. Buildings should be positioned with windows on the north and south sides to facilitate cross-ventilation. In coastal climates, for example, seaside buildings are often designed with openable windows on the ocean-facing side to take advantage of cooling sea breezes.
Daylight Harvesting
The building construction industry is responsible for a significant portion of the global energy consumption and pollution, contributing to depletion of natural resources and affecting human health. To counteract these negative effects, the AEC industry is focusing on passive design strategies that minimize the impact of buildings on the environment by using natural resources and environmental conditions to provide heating, ventilation, and lighting for occupants without the need for active mechanical systems.
Passive elements allow daylight to penetrate deeper into the building, connecting occupants with the outdoors and elevating their sense of well-being. These include transparent materials with a high visible light transmittance to maximize the amount of natural sunlight available and light-redirecting devices such as skylights, prism diffusers, and reflective surfaces. Zoning and controls also play a crucial role in daylight harvesting, as they can be used to reduce artificial lighting usage and improve energy efficiency.
The selection of insulating materials is also important, as they prevent heat loss through roof and wall surfaces, helping to lower heating costs in winter and cooling costs in summer. These can be made from a variety of natural or man-made insulation, including recycled denim and sheep’s wool, cellulose, Aerogel, or Structural Insulated Panels (SIP), which are prefabricated structural elements that reduce construction time and offer greater insulation value than traditional stud walls.