Building Systems Design II Vocabulary Flashcards

Comprehensive vocabulary flashcards covering site geometry, atmospheric radiation, thermodynamics, daylighting, building codes, egress limits, fire protection assemblies, and accessibility standards.

Summer Solstice

Occurs on June 21st when the Northern Hemisphere is tilted at its maximum angle toward the Sun, with direct solar rays hitting perpendicular ($90^\circ$) at the Tropic of Cancer ($23.5^\circ\,\text{N}$ latitude).

Winter Solstice

Occurs on December 21st / 22nd when the Northern Hemisphere is tilted at its maximum angle away from the Sun, with direct solar rays hitting perpendicular ($90^\circ$) at the Tropic of Capricorn ($23.5^\circ\,\text{S}$ latitude).

Equinoxes

The Spring / Vernal Equinox (March 21st) and Fall / Autumnal Equinox (September 23rd), during which neither pole is tilted toward the Sun and direct solar rays align over the Equator ($0^\circ$ latitude), resulting in equal day and night durations globally.

Radiance

Emitted radiation coming directly at the solar source.

Irradiance

Incident radiation striking a receiver surface.

Direct Normal Irradiance (DNI)

Unobstructed solar rays striking perpendicular ($90^\circ$) to parallel rays.

Diffuse Irradiance

Solar radiation scattered or absorbed by clouds, water vapor, dust, and smog.

Global Horizontal Irradiance (GHI)

Total incident radiation hitting a flat horizontal surface ($0^\circ$), calculated as $\text{GHI} = \text{Direct} + \text{Diffuse}$.

Global Tilt Irradiance (GTI)

Radiation incident on a fixed tilted surface, used to estimate photovoltaic system output.

Hadley Cell

An atmospheric circulation cell operating between the Equator ($0^\circ$) and $30^\circ\,\text{N/S}$, where equatorial solar heating causes warm air to rise at the ITCZ, flow poleward, cool, and sink at $30^\circ\,\text{N/S}$ (Subtropical High).

Ferrel Cell

A mid-latitude atmospheric circulation cell operating between $30^\circ - 60^\circ\,\text{N/S}$, characterized by prevailing Westerly winds.

Polar Cell

A high-latitude atmospheric circulation cell operating between $60^\circ - 90^\circ\,\text{N/S}$, where sinking cold air at the poles creates Polar Easterlies.

Urban Heat Island Effect (UHIE)

A localized microclimate phenomenon where built-up materials absorb solar heat and re-radiate it, altering local microclimates and increasing building cooling loads.

Stack Effect

A thermal mechanism where warm internal air rises and exhausts through upper envelope openings, creating negative pressure at low levels that draws cool outside air inside.

First Law of Thermodynamics

A fundamental law stating energy cannot be created or destroyed, only transformed or transferred across system boundaries, keeping total energy in an isolated system constant.

Second Law of Thermodynamics

A fundamental law stating spontaneous processes increase global entropy ($\Delta S \ge 0$), degrading useful work capacity as heat cascades down temperature gradients into ambient surroundings.

Isolated System

A thermodynamic system boundary permitting NO exchange of matter and NO exchange of energy (heat or work), such as a theoretical ideal thermos flask.

Closed System

A thermodynamic system boundary permitting exchange of energy (heat/work) but PROHIBITING exchange of matter, such as a sealed double-glazed window unit.

Open System

A thermodynamic system boundary permitting free exchange of BOTH matter and energy, such as an open room, building envelope, or urban ecosystem.

Exergy

The maximum theoretical useful work obtainable from a system as it comes into equilibrium with its surrounding reference environment ($T_0$).

Exergy Matching

The strategy of reserving high-grade energy sources for high-grade work and using low-exergy sources (e.g., $150^\circ\text{F}$ hydronic loops or $95^\circ\text{F}$ radiant panels) to satisfy low-grade heating requirements (e.g., $70^\circ\text{F}$ indoor air).

Energy Use Intensity (EUI)

A building energy measurement metric expressed in $\text{kBtu/sf/yr}$, quantifying energy consumption per unit of floor area.

Site EUI vs. Source EUI

Site EUI measures energy consumption directly at the utility meter, whereas Source EUI accounts for total energy including extraction, generation, transmission, and distribution losses.

Visible Light Transmittance (VLT)

The percentage of visible electromagnetic radiation admitted through glazing, directly impacting interior illuminance levels and daylighting autonomy.

Window-to-Wall Ratio (WWR)

The ratio of fenestration area to gross exterior wall area, prescriptively regulated under IECC §C402.4 to cap envelope thermal losses and gains.

North Glazing

Building fenestration facing North that delivers consistent, diffuse sky radiation without direct glare or thermal overheating.

South Glazing

Building fenestration facing South that is easily shaded in summer with horizontal overhangs and admits winter passive heat gains when solar altitude angles are low.

Daylight Glazing (Upper)

Apertures placed above eye level ($7'\!-0'' - 9'\!-0''\,\text{AFF}$) with high VLT ($0.60 - 0.80$), paired with interior light shelves to bounce light deep onto ceilings.

View Glazing (Lower)

Apertures placed at vision level ($3'\!-0'' - 7'\!-0''\,\text{AFF}$) with moderate VLT ($0.40 - 0.60$) and lower SHGC to control occupant glare and thermal comfort.

Spatial Daylight Autonomy (sDA)

A daylight performance metric measuring the percentage of work area receiving sufficient daylight ($\ge 300\,\text{lux}$) for at least $50\%$ of operating hours.

Annual Sun Exposure (ASE)

A daylight performance metric measuring potential visual discomfort or glare from excessive direct sunlight ($> 1000\,\text{lux}$ for $> 250\,\text{hours/year}$).

Prescriptive Path

A code compliance approach requiring strict adherence to individual component performance thresholds, such as minimum R-values and maximum U-factors.

Performance-Based Path

A code compliance approach utilizing computer energy modeling to prove proposed design energy cost/use is equal to or lower than code baseline (IECC C407).

Accessory Occupancy

A mixed occupancy legal condition under IBC §508.2 where an accessory space comprises $\le 10\%$ of a story floor area, requiring no fire separation.

Separated Occupancies

A mixed occupancy legal condition under IBC §508.4 where fire barriers or horizontal assemblies separate occupancies and the sum of area ratios is $\le 1.0$.

Fire Area

Defined under IBC §202 as the aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls, or rated horizontal assemblies.

Fire Wall

An IBC §706 wall assembly with a $3\text{-hour}$ or $4\text{-hour}$ fire-resistance rating that divides a structure into legally independent buildings, extending continuously from foundation through roof with structural independence.

Fire Barrier

An IBC §707 wall assembly with a $1\text{-hour}$ or $2\text{-hour}$ fire-resistance rating that encloses exit stairways, shafts, separated occupancies, and fire area boundaries continuously slab-to-deck.

Fire Partition

An IBC §708 wall assembly with a $0.5\text{-hour}$ or $1\text{-hour}$ fire-resistance rating used for corridor walls, tenant separations, and dwelling unit walls.

Smoke Barrier

An IBC §709 wall assembly with a $1\text{-hour}$ fire-resistance rating that restricts the movement of smoke into compartments, extending continuously slab-to-deck.

Fire-Protection Glazing vs. Fire-Resistance Glazing

Fire-protection glazing is tested for flame/smoke passage with limited surface area in rated walls, whereas fire-resistance glazing is tested under ASTM E119 to block radiant heat transmission and maintain structural integrity.

Exit Access

The portion of a means of egress system that leads from any occupiable point in a building to an exit.

Exit

The protected, fire-resistance-rated portion of a means of egress system that leads directly to the exit discharge or public way, such as interior exit stairways or exit passageways.

Exit Discharge

The portion of a means of egress system between the termination of an exit and a public way.

Diagonal Rule

An IBC §1007.1.1 requirement stating two exits must be separated by at least $\frac{1}{2}$ the maximum diagonal dimension of the area served (reduced to $\frac{1}{3}$ in sprinklered buildings).

Common Path of Egress Travel

The maximum distance an occupant must travel before two distinct and independent exit access paths become available ($75\,\text{ft}$ unsprinklered; $100\,\text{ft}$ sprinklered Group B).

Exit Access Travel Distance

The maximum overall distance from the most remote occupiable point to an exit door ($200\,\text{ft}$ unsprinklered Group B; $300\,\text{ft}$ sprinklered Group B).

Dead-End Corridor Limit

The maximum allowable corridor pocket length beyond an exit ($20\,\text{ft}$ max unsprinklered; $50\,\text{ft}$ max sprinklered for Group B/E/F/M/R/S).

Smokeproof Enclosure

An IBC §1023.11 exit stairway requirement for floors $> 75\,\text{ft}$ above fire access or $> 30\,\text{ft}$ below grade, achieved via vestibule ventilation or mechanical shaft pressurization.

Area of Refuge

An IBC §1009.6 space providing at least one $30\,\text{in} \times 48\,\text{in}$ wheelchair space per $200$ occupants served, separated by a smoke barrier and equipped with two-way communication.

Accessible Turning Space

An ADA and ICC A117.1 required floor space consisting of a $60\,\text{in}$ diameter turning circle or T-shaped turning space for wheelchair maneuverability.

Accessible Water Closet Clearance

A clear floor space measuring $60\,\text{in}$ wide by $56\,\text{in}$ deep around a water closet, with centerline $16\,\text{in} - 18\,\text{in}$ from side wall and seat height $17\,\text{in} - 19\,\text{in}\,\text{AFF}$.