Passive Building Design Glossary

Net Zero: A net zero building is a building that generates as much energy on-site as it uses. The area aims to completely negate the amount of greenhouse gases produced by human activity, achieved by reducing emissions and implementing methods of absorbing carbon dioxide from the atmosphere.

Passive Design: Passive design is a type of building design and site orientation that prioritizes reducing energy use. It minimizes a building’s reliance on mechanical systems, such as heating, cooling, and lighting, while focusing on utilizing natural elements like sunlight, wind, and vegetation.

Solar Exposure: Solar exposure is the amount of solar radiation that is directed at a certain place.

Vegetation: Trees and shrubs create different air flow patterns, provide shading and keep the surroundings cooler in warm weather. Vegetation can be used for energy conservation in buildings by shading buildings, the use of roof gardens, acting as buffers against cold and hot winds, and changing the direction of wind. The green cover lowers ambient temperatures through evapotranspiration.

Deciduous Trees: Deciduous trees are trees that seasonally shed their leaves, typically in the autumn, and then regrow in the spring. Examples are oaks and maple which provide shade in summer and allow solar gain in winter.

Coniferous Trees: Coniferous trees, also known as conifers, are cone-bearing seed plants, typically evergreen trees or shrubs with needle-like or scale-like leaves.

Thermal Insulation: Thermal insulation is the process of reducing heat transfer between objects or spaces by using materials that resist the flow of heat.

Orientation: Orientation is the relative position of a building to the sun. Building orientation has significant impacts on the building’s energy efficiency, by harnessing the sun for solar gain for heating.

Ventilation: Ventilation is how the wind flows through a house. Ventilation also brings fresh, clean air into a house.

Wind Rose: A wind rose shows how many hours per year the wind blows from the indicated direction. This wind rose for Framingham, MA shows the wind comes from the west.

Urban Heat Island: Urban heat islands are urbanized areas that experience higher temperatures than outlying areas. Structures such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies.

Thermal Envelope: The thermal envelope of a building is the physical barrier that separates the conditioned (heated or cooled) interior from the unconditioned exterior or other unconditioned spaces, like an attic or garage.

Thermal Bridging: Thermal bridging occurs when the walls are more conductive than the insulation. Thermal bridging is a main cause of heat lost in poorly insulated homes. It happens around doors and windows as well as studs.

Energy Efficiency: Energy efficiency is the term used for reducing the amount of energy used.

Green Roofs: A green roof is a roofing system where the roof surface is partially or completely covered with vegetation and a growing medium (plants, soil, rocks), installed over a traditional roof.

Electric Charging Station: An electric charging station is used to charge an electric vehicle. Charging stations produce much less greenhouse gases than a regular car. For 100% clean energy, the charging stations used will be powered by solar energy.

Electric Bus: Electric buses use a battery to power the bus, not fossil fuels, making it clean transportation.

Flat Roof: A flat roof is one where there is no slant or gable on top of a building.

Shed Roof: A shed roof is a roof where there is only one slant. Shed roofs are good for solar panels as the roof can be angled though it also has to be angled to the south.

Passive Building Design System Components