Solar Design, Thermal Envelope, Daylighting, and Shading Systems

Comprehensive vocabulary flashcards covering passive solar heating systems, direct and indirect gain, daylighting physics, envelope thermography, shading design, and cool roof strategies.

Envelope-Dominated Building

A building whose indoor temperature and thermal loads are primarily governed by outdoor climatic conditions interacting with its exterior walls, roof, and windows, typically featuring a balance point temperature of approximately $60^\circ\text{F}\,(15^\circ\text{C})$.

Internally Dominated Building

A building whose indoor climate and cooling demands are predominantly dictated by heat generated within the building by occupants, electric lights, and equipment, typically having a balance point temperature around $50^\circ\text{F}\,(10^\circ\text{C})$.

Balance Point Temperature

The outdoor temperature at which total internal heat gains from people, lights, equipment, and solar radiation exactly balance the envelope heat losses escaping to the outdoors.

Sun Simulator Heliodon

A testing mechanism developed at Auburn University consisting of a domed armature of lamps and a tilting table used to simulate solar angles and shadow performance on scale architectural models.

Solar Hemicycle

The curved, semicircular passive solar plan layout devised by Frank Lloyd Wright for the Jacobs II House in Madison, Wisconsin, featuring expansive south-facing glazing protected by a $6\,\text{ft}\,(1.8\,\text{m})$ roof overhang and sheltered on the north by an earth berm.

Direct-Gain System

A passive solar heating approach where sunlight penetrates south-facing glazing directly into the living space, where the greenhouse effect traps shortwave radiation and stores heat within interior thermal mass slabs or walls.

Thermal Mass Time Lag

The delay in conductive heat transfer through dense solids; in masonry, effective diurnal heat storage is limited to the first $6\,\text{inches}\,(15\,\text{cm})$ of depth before sunset, whereas water transfers heat throughout greater depths via convection.

Night Insulation

Movable insulating shutters, curtains, or shades deployed over windows at night to inhibit thermal loss, substantially improving the solar heating load contribution of direct-gain and Trombe wall systems.

Trombe Wall

An indirect-gain passive solar heating assembly consisting of a thick ($10\text{--}16\,\text{inches}$) dark-surfaced masonry or water mass wall placed directly behind south-facing glazing, utilizing upper and lower vents to circulate convective heat.

Selective Coating

A specialized dark surface finish applied to the sun-facing side of a thermal storage wall that provides high solar absorption while drastically reducing longwave infrared radiative reradiation back toward the glazing.

Sunspace

An isolated-gain solar space (such as a solarium or greenhouse) adjacent to a building that functions as a thermal buffer and swing space, experiencing substantial temperature fluctuations from $50^\circ\text{F}\,(10^\circ\text{C})$ to $90^\circ\text{F}\,(32^\circ\text{C})$.

Stack Effect

The natural, buoyancy-driven air movement into and out of spaces resulting from indoor-to-outdoor temperature, density, and pressure differentials, widely utilized for convective venting in sunspaces and atriums.

BedZED (Beddington Zero Energy Development)

A UK zero-energy residential ecovillage employing stepped roof profiles, south-facing passive sunspaces for solar collection, and north-facing workspaces to minimize total thermal conditioning demands.

Balcomb House

A prominent passive solar home in Santa Fe, New Mexico, designed by J. Douglas Balcomb, which couples a two-story sunspace and an adobe common wall with ceiling fans and an under-floor rock storage bed.

Overcast Sky Luminance Distribution

The sky illumination pattern under full cloud cover where the zenith is approximately $3\times$ brighter than the horizon, delivering diffuse horizontal illumination ranging between $500\,\text{fc}$ and $2{,}000\,\text{fc}\,(5{,}000\text{--}20{,}000\,\text{lux})$.

Clear Sky Luminance Distribution

The daylight brightness distribution on sunny days wherein the sky region nearest the sun is approximately $10\times$ brighter than the darkest portion situated at $90^\circ$ to the sun, generating $6{,}000\,\text{fc}$ to $10{,}000\,\text{fc}\,(60{,}000\text{--}100{,}000\,\text{lux})$.

Exposure Angle (\theta)

The subtended angle through which an interior task or observer views an illuminated daylight opening, determined by the opening's dimensions, physical distance, and relative surface tilt.

Daylight Factor (DF)

The dimensionless ratio (expressed as a percentage) of indoor illuminance at a specific reference point to simultaneous outdoor horizontal illuminance under an unobstructed overcast sky.

Veiling Reflection

Specular reflections of bright daylight or artificial sources off glossy surfaces, computer monitors, or printed text that wash out contrast and impair visual performance.

Cool Daylight

The strategy of transmitting the visible spectrum ($0.4\text{--}0.7\,\mu\text{m}$) of daylight while blocking the non-illuminating solar infrared spectrum ($0.8\text{--}2.5\,\mu\text{m}$), which comprises approximately $50\%$ of incoming solar radiation.

Visible Transmittance (VT)

The optical metric quantifying the fraction of visible light passing through a glazing unit, varying between $0.9$ for ultra-clear glass and less than $0.1$ for heavily tinted or reflective glass.

Solar Heat Gain Coefficient (SHGC)

The fraction of incident solar radiation admitted through a window assembly, combining directly transmitted solar flux with absorbed radiation that is subsequently conducted and convected indoors.

Light-to-Solar-Gain (LSG) Ratio

The performance quotient calculated as $\text{LSG} = \frac{\text{VT}}{\text{SHGC}}$, where higher values represent greater luminous efficacy and cooler daylight admission.

Spectrally Selective Coating

An advanced optical low-emittance film engineered to allow high transmission of visible wavelengths while selectively reflecting shortwave solar infrared and longwave thermal infrared radiation.

Sky View Factor (SVF)

A dimensionless index from $0$ to $1$ representing the proportion of the visible sky hemisphere visible from a specific surface or window coordinate relative to an unobstructed dome.

Bilateral Daylighting

The daylighting configuration where windows are located on two separate wall planes, yielding more uniform interior illumination and significantly mitigating contrast glare compared to unilateral arrangements.

Light Shelf

A horizontal shading and redirecting blade positioned above eye level that shields occupants from direct window glare while bouncing sunlight off its top surface onto the ceiling to illuminate room depths up to $2\times$ the window height.

Roof Daylighting Forms

Top-lighting apertures integrated into the roof plane—comprising clerestories, monitors, sawteeth, and skylights—designed to illuminate building interiors beyond perimeter window depths.

Kimbell Art Museum Daylighting System

Louis I. Kahn's daylighting design in Fort Worth, Texas, featuring continuous linear roof skylights paired with suspended curved aluminum fixtures that distribute diffuse, glare-free light across cycloid concrete barrel vaults.

Diffusing Baffle

A suspended, opaque or semi-translucent vertical or angled blade (such as the ferro-cement leaves in Renzo Piano's Menil Collection) designed to block direct solar rays while diffusing natural illumination.

Infrared Thermography

An imaging technique that visualizes surface temperature differentials across building components by detecting thermal radiation in the longwave infrared spectrum.

Thermal Bridge

A localized area of high thermal conductivity puncturing an insulated building envelope (such as a continuous cantilevered concrete balcony slab) that accelerates unwanted conductive heat transfer.

Eggcrate Shading Device

A rigid exterior sun-control screen that combines horizontal overhangs with closely spaced vertical fins to block oblique sun on east and west facades, though heavily restricting external views.

Thermal Year vs. Solar Year

The seasonal phase lag of $1\text{--}2\,\text{months}$ caused by the thermal capacitance of the Earth, which makes July/August the hottest months rather than the summer solstice (June 21), and January/February the coldest rather than the winter solstice (December 21).

Overhang Outflanking

The entry of oblique morning and afternoon sunbeams past the outer edges of a horizontal overhang that matches the width of a window, requiring extensions of at least $\frac{H}{2}$ or vertical end fins.

Full Shade Line (Angle A)

The geometric profile angle drawn from the windowsill upward to the edge of an overhang that establishes full window shade during the hottest portions of the overheated period.

Full Sun Line (Angle B)

The sun ray angle drawn from the window head that limits the projection of an overhang to ensure full direct solar access during the winter underheated period.

Tempe City Hall

A civic building in Arizona designed by Rolf Osland, Michael Goodwin, and Kemper Goodwin featuring a four-story inverted pyramid massing that provides self-shading for its exterior glazing.

Heliotrope

An experimental energy-plus residence built by Rolf Disch in Freiburg, Germany, which rotates to face triple glazing toward the sun in winter for heating and turns a heavily insulated blank facade toward the sun in summer.

Parasol Roof

A raised canopy structure positioned above a flat roof plane (advocated by Le Corbusier) to shade the primary roof deck and rooftop terrace activities from direct solar heat gain.

Solar Reflectance (Albedo)

The dimensionless ratio ($0.0$ to $1.0$) of solar radiation reflected by an architectural surface, where clean white paint reflects up to $0.90$ ($90\%$) of incident sunlight.

Cool Roof

A roofing system characterized by high solar reflectivity and high infrared emittance that maintains summer surface temperatures near $120\text{--}135^\circ\text{F}\,(48\text{--}57^\circ\text{C})$, compared to conventional dark roofs exceeding $160^\circ\text{F}\,(71^\circ\text{C})$.

Bermuda Stepped Roof

A historic pitched roof system made of stepped limestone coated in white lime mortar/paint that resists hurricanes, slows torrential rainfall for cistern catchment, and reflects solar UV radiation.