Passive Environmental Systems

These flashcards summarize key vocabulary terms from the lecture on passive environmental systems, specifically relating to building systems, solar geometry, insolation, shading devices, and thermal performance.

Passive System

A building system that operates using the building's design and natural elements without consuming external resources.

Active System

A building system that uses an external energy resource or mechanical devices to operate, consuming resources such as electricity or fuel.

Solar Constant

The amount of the sun's radiation reaching the Earth's outer atmosphere, approximately 1.37 kW/m².

Insolation

The amount of solar radiation received by a surface, typically measured in kWh/m²/day or kWh/m²/year.

Altitude Angle

The angle between the horizon and the sun's position above the horizon.

Azimuth Angle

The angle along the horizon between the projected position of the sun and true south.

Effective Shading Device

A device used to reduce solar heat gain, particularly effective during hot months for south-facing windows.

Gnomonic Projection

A sun path projection method mainly used for shadow studies and showing sun penetration.

Thermal Mass

The ability of a material to absorb and store heat. It is crucial in passive solar heating.

U-Factor

The overall coefficient of thermal transmittance that expresses the steady-state rate at which heat flows through a building envelope.

Conductance (C)

The number of Btus per hour that flow through 1 ft² of material per hour per degree temperature difference.

Resistance (R)

A measure of how effective a material is as an insulator, measured in hours needed for 1 Btu to flow through 1 ft².

Evaporative Cooling

A cooling process that involves using water to lower the temperature of the air.

Downdraft Cooltower

A passive cooling system that utilizes evaporative cooling to lower indoor air temperatures without mechanical assistance.

Cross-Ventilation

A passive cooling strategy that enhances indoor air flow by positioning windows on opposite sides of a building.

Stack Ventilation

A passive cooling strategy that relies on hot air rising to exhaust warm air from the building.

Passive System

A building system that operates using the building's design and natural elements without consuming external resources.

Active System

A building system that uses an external energy resource or mechanical devices to operate, consuming resources such as electricity or fuel.

Solar Constant

The amount of the sun's radiation reaching the Earth's outer atmosphere, approximately 1.37 \text{ kW/m}^2.

Insolation

The amount of solar radiation received by a surface, typically measured in kWh/m²/day or kWh/m²/year.

Altitude Angle

The angle between the horizon and the sun's position above the horizon.

Azimuth Angle

The angle along the horizon between the projected position of the sun and true south.

Effective Shading Device

A device used to reduce solar heat gain, particularly effective during hot months for south-facing windows.

Gnomonic Projection

A sun path projection method mainly used for shadow studies and showing sun penetration.

Thermal Mass

The ability of a material to absorb and store heat. It is crucial in passive solar heating.

U-Factor

The overall coefficient of thermal transmittance that expresses the steady-state rate at which heat flows through a building envelope.

Conductance (C)

The number of Btus per hour that flow through 1 \text{ ft}^2 of material per hour per degree temperature difference.

Resistance (R)

A measure of how effective a material is as an insulator, measured in hours needed for 1 \text{ Btu} to flow through 1 \text{ ft}^2.

Evaporative Cooling

A cooling process that involves using water to lower the temperature of the air.

Downdraft Cooltower

A passive cooling system that utilizes evaporative cooling to lower indoor air temperatures without mechanical assistance.

Cross-Ventilation

A passive cooling strategy that enhances indoor air flow by positioning windows on opposite sides of a building.

Stack Ventilation

A passive cooling strategy that relies on hot air rising to exhaust warm air from the building.

Passive System

A building system that operates using the building's design and natural elements without consuming external resources.

Active System

A building system that uses an external energy resource or mechanical devices to operate, consuming resources such as electricity or fuel.

Solar Constant

The amount of the sun's radiation reaching the Earth's outer atmosphere, approximately 1.37 \text{ kW/m}^2.

Insolation

The amount of solar radiation received by a surface, typically measured in kWh/m²/day or kWh/m²/year.

Altitude Angle

The angle between the horizon and the sun's position above the horizon.

Azimuth Angle

The angle along the horizon between the projected position of the sun and true south.

Effective Shading Device

A device used to reduce solar heat gain, particularly effective during hot months for south-facing windows.

Gnomonic Projection

A sun path projection method mainly used for shadow studies and showing sun penetration.

Thermal Mass

The ability of a material to absorb and store heat. It is crucial in passive solar heating.

U-Factor

The overall coefficient of thermal transmittance that expresses the steady-state rate at which heat flows through a building envelope.

Conductance (C)

The number of Btus per hour that flow through 1 \text{ ft}^2 of material per hour per degree temperature difference.

Resistance (R)

A measure of how effective a material is as an insulator, measured in hours needed for 1 \text{ Btu} to flow through 1 \text{ ft}^2.

Evaporative Cooling

A cooling process that involves using water to lower the temperature of the air.

Downdraft Cooltower

A passive cooling system that utilizes evaporative cooling to lower indoor air temperatures without mechanical assistance.

Cross-Ventilation

A passive cooling strategy that enhances indoor air flow by positioning windows on opposite sides of a building.

Stack Ventilation

A passive cooling strategy that relies on hot air rising to exhaust warm air from the building.

Conduction

The transfer of heat energy through direct contact between particles of a substance, from a warmer region to a cooler region.

Convection

The transfer of heat energy in a fluid (liquid or gas) by the movement of the heated particles from one place to another, often forming currents.

Radiation (Thermal)

The transfer of heat energy through electromagnetic waves, which can travel through a vacuum and do not require a medium.

U-Factor and R-value Relationship

The U-factor is the inverse of the total R-value (U = 1/R), where R is the total thermal resistance of a component.

Direct Gain Passive Solar System

A passive solar heating strategy where sunlight directly enters the conditioned space through south-facing windows, heating the space and thermal mass.