Acoustics from ALS Chapter Six

Acoustics

from ALS Chapter Six

Velocity of sound through air depends on the barometric pressure and altitude.

sound can be transmitted through water.

Sound frequency = (the pitch) is the number of cycles per second (cps), more commonly known as Herz thus 60 cps = 60 Hz

Square wave = sounds much like a buzzer or even an outboard motor

Acoustics uses logarithmic scales

Sound Intensity level = the decibel

Sound power level = measures the power at the source in watts/cm(squared)

Sound pressure level = pressure exerted by the sound wave on a surface at a given location.

IL and SPL have the same value.

two sound sources at 60 dB total IL of 63 dB not 120

Double distance from a sound source to receiver cuts the intensity to one quarter, change in only 6 dB

Sound - Isolation

Sound - Isolation

from Ching Viz Dictionary of Architecture

transmission loss = a measure of the performance of a building material or construction assembly in preventing the transmission of airborne sound, equal to the reduction in sound intensity as it passes through the material or assembly when test at all one-third octave band center frequencies from 125 to 4000 Hz: Expressed in decibels, abbr.: TL

average transmission loss = a single number rating of the performance of a building material or construction assembly in preventing the transmission of airborne sound, equal to the average of its TL values at nine test frequencies.

Sound transmission class = a single number rating of the performance of a building material or construction assembly in preventing the transmission of airborne sound, derived by comparing the material or assembly to a standard frequency curve, abbr.: STC

The higher the STC rating, the greater the sound isolating value of the material or construction. An open doorway has an STC rating of 10; normal construction has STC ratings from 30 to 60; special construction is required for STC ratings above 60.

Impact noise = structure borne sound generated by physical impact, as buy footsteps or the moving of furniture.

impact insulation class = a single number rating of the performance of a floor-ceiling construction in preventing the transmission of impact noise, abbr.: IIC

Sound - Acoustics and Noise

Sound - Acoustics and Noise

from Ching Viz Dictionary of Architecture

reflecting surface = a non absorptive surface from which incident sound is reflected, used esp. to redirect sound in a space. to be effective, a reflecting surface should have a least dimension equal to or greater than the wavelength of the lowest frequency of the sound being reflected

attenuation = a decrease in energy or pressure per unit area of a sound wave, occurring as the distance from the source increases as a result of absorption, scattering, or spreading in three dimensions.

acoustical treatment = the application of absorbent or reflecting materials to the walls, ceiling and floor of an enclosed space to alter or improve its acoustic properties.

diffracted sound = airborne sound waves bent by diffraction around an obstacle in their path.

reflected sound = the return of unabsorbed airborne sound after striking a surface, at an angle equal to the angle of incidence.

live = highly reverberant or resonant, as an auditorium or concert hall

dead = without resonance, as a room free from echoes and reverberations.

soundproof = impervious to audible sound.

resonance = the intensification and prolongation of sound produced by sympathetic vibration.

sympathetic vibration = the vibration induced in one body by the vibrations of exactly the same period in a neighboring body.

reverberation = the persistence of a sound within an enclosed space, caused by multiple reflection of the sound after its source has stopped.

decay rate = the rate of decrease of sound pressure level after its source has stopped, usually expressed in decibels per second.

reverberation time = the time in seconds required for a sound made in an enclosed space to diminish by 60 decibels.

echo = the repetition of a sound produced by the reflection of sound waves from an obstructing surface, loud enough and received late enough to be perceived as distinct from the source

flutter = a rapid succession of echoes caused by the reflection of sound waves back and forth between two parallel surfaces, with sufficient time between each reflection to cause the listener to be aware of separate, discrete signals.

focusing = the convergence of sound waves reflected from a concave surface

noise reduction = the perceived difference in sound pressure levels between two enclosed spaces, due to the sound isolating qualities of the separating barrier as well as the absorption present in the receiving room: expressed in decibels

absorption = the interception and conversion of sound energy into heat or other form of energy by the structure of a material, measured in sabins or absorption units.

sabin = a unit of sound absorption, equal to one sq. ft. of a perfectly absorptive surface

metric sabin = a unit of sound absorption, equal to 1 square meter of perfectly absorptive surface, also called absorption unit.

absorption coefficient = a measure of the efficiency of a material in absorbing sound at a specified frequency, equal to the fractional part of the incident sound energy at that frequency absorbed by the material

noise reduction coefficient = a measure of the sound absorbing efficiency of a material, equal to the average of the absorption coefficients of the material, computed to the nearest 0.05 at four frequencies: 250, 500, 1000 & 2000 Hz.

Sound - General

Sound - General

from Ching Viz Dictionary of Architecture

Hearing = the sense by which sound is perceived involving the entire mechanism of the internal, middle and external ear and including the nearvous and cerebral operations that translate the physical operations into meaningful signs.

Decibel = A unit for expressing the relative pressure or intensity of sounds on a uniform scale from 0 for the least perceptible sound to about 130 for the average threshold of pain. abbr. dB

Decibel levels of two sound sources cannot be added mathematically

loudness = a subjective response to sound indicating the magnitude of the auditory sensation produced by the amplitude of a sound wave.

phon = a unit for measuring the apparent loudness of a sound, equal in number to the decibels of a 1000-hz reference sound judged by a group of listeners to be equal in loudness to the given sound.

sone = a unit for measuring the apparent loudness of a sound, judged by a group of listeners to be equal to the loudness of a 1000-hz reference sound having an intensity of 40 decibels

Audio frequency = a range of frequencies from 15 Hz to 20,000 Hz audible to the normal human ear.

auditory fatigue = physical or mental weariness caused by prolonged exposure to loud noises.

sound power = the amount of acoustic energy radiated by a source per unit time, expressed in watts.

sound power level = teh acoustic power of a source measured on the decibel scale, equal to 10 times the common logarithm of the ratio of the acoustic power to a reference power, usually 10 to the negative 12th power watts.

sound pressure = the difference between the actual pressure at any point in the field of a sound wave and the static pressure at that point, expressed in pascals.

sound pressure level = sound pressure measured on the decibel scale, equal to 10 times the common logarithm of the ratio of the sound pressure to a reference pressure, usually 20 micropascals

sound intensity = the rate at which acoustic energy flows through a medium, expressed in watts per square meter.

sound intensity level = sound intensity measured on the decibel scale, equal to 10 times the common logarithm of the ratio of the sound intensity to a reference intensity, usually 10 to the negative 12th power watts per square meter.

logarithm = the exponent indicating the power to which a base number must be raised to arrive at a given number.

common logarithm = a logarithm having a base of 10.

Light - Distribution

Light - Distribution

from Ching Viz Dictionary of Architecture

Beam spread = the angle of a light beam that intersects the candlepower distribution curve at points where the luminous intensity equals a stated percent of a maximum reference intensity.

beam = a group of nearly parallel rays of light.

throw = the effective length of a beam of light.

Spacing criteria = A formula for determining how far apart luminaires may be installed for uniform lighting of a surface or area, based on mounting height.

spacing criteria(sc) = spacing(s) / mounting height(mh)

point method = a procedure for calculating the illumination produced on a surface by a point source from any angle, based on the inverse square and cosine laws.

lumen method = a procedure for determining the number and types of lamps, luminaires, or windows required to provide a uniform level of illumination on a work plane, taking into account both direct and reflected luminous flux. Also called Zonal cavity method.

work plane = the horizontal plane at which work is done and on which illumination is specified and measured, usually assumed to be 30 inches above the floor

ceiling cavity = the cavity formed by the ceiling, a plane of suspended luminaires, and the wall surfaces between these two planes.

room cavity = cavity formed by a plane of luminaires, the work plane and the wall surfaces between these two planes.

floor cavity = the cavity formed by the work plane, the floor and the wall surfaces between these two planes.

room cavity ratio = a single number derived from the dimensions of a room cavity for use in determining the coefficient of utilization.

coefficient of utilization (CU)= the ratio of the luminous flux reaching a specified work plane to the total lumen output of a luminaire, taking into account the proportions of a room and the reflectance of its surfaces.

light loss factor = any of several factors used in calculating the effective illumination provided by a lighting system after a given period of time and under given conditions. formerly called maintenance factor.

recoverable light loss factor (RLLF)= a light loss factor that may be recovered by relamping or maintenance, as lamp lumen depreciation, luminaire dirt depreciation and room surface dirt depreciation.

lamp lumen depreciation = a light loss factor representing the decrease in luminous output of a lamp during its operating life, expressed as a percentage of initial lamp lumens.

Luminaire dirt depreciation = a light loss factor representing the decrease in luminous output of a luminaire resulting from the accumulation of dirt on its surfaces, expressed as a percentage of the illumination from the luminaire when new or clean.

Room surface dirt depreciation = a light loss factor representing the decrease in reflected light resulting from the accumulation of dirt on a room's surfaces, expressed as a percentage of the light reflected from the surfaces when clean.

nonrecoverable light loss factor (NRLLF) = any of several permanent light loss factors that take in to account the effects of temp., voltage drops or surges, ballast variations, and partition heights.

Average maintained illuminance = (initial lamp lumens x CU x RLLF x NRLLF) / work area

initial lamp lumens = lumens per lamp X lamps per muminaire

Light - Incandescent Lamps

Light - IncandescentLamps

from Ching Viz Dictionary of Architecture

Lamp = any of various device for producing light or heat as by electricity or gas.

incandescent lamp = a lamp in which a filament gives off light when heated to incandescence by an electric current. Also called a light bulb.

bulb = the glass housing of an incandescent lamp, filled with an inert gas mixture, usually of argon and nitrogen, to retard evaporation of the filament. Its shape is designated bu a letter, followed by a number that indicates the lamp diameter.

lamp diameter = the max. diameter of a lamp bulb, measured in eighths of an inch.

filament = the threadlike conductor of an electric lamp that is heated to incandescence by the passage of an electric current.

incandescence = the emission of visible light by a body when heated to a high temp.

extended service lamp = a lamp designed for reduced energy consumption and a life longer than the conventionally set value for its general class. (aka. long life lamp)

efficacy - a measure of the effectiveness with which a lamp converts electric power into luminous flux, equal to the ratio of flux emitted to power input and expressed in lumens per watt.

rated life = the average life in hours of a given type of lamp, based on lab tests of a representative group under controlled conditions.

three way lamp = an incandescent lamp having two filaments so that it can be switched to three successive degrees of illumination.

Bulb types

A = standard rounded shape of general service incandescent lamps

B = a flame shaped bulb for low wattage, decorative incandescent lamps

C = a cone shaped bulb for low wattage decorative incandescent lamps

CA = a candle shaped bulb, low watt incandescent

R = Reflector bulb of blown glass for incandescent and High-intensity-discharge lamps, having an internal reflective coating and either a clear or frosted glass front to provide the desired beam spread.

PAR = parabolic aluminized reflector bulb of cast glass for incandescent and HID lamps having precisely formed internal reflector and a lense front to provide the desired beam spread.

ER = An ellipsoidal reflector bulb for incandescent lamps, having a precisely formed internal reflector that collects light and redirect it into a desired pattern at some distance in front of the light source.

A/SB = A bulb having a hemispherical, reflective silver bowl opposite the lamp base to decrease glare

G = a globe shaped bulb, incandescent, low brightness for exposed use.

PS = pear shaped bulb, large incandescent

S = straight sided bulb for low watt, decorative incan. lamps

MR = multifaceted reflector bulb, tungsten halogen lamps, highly polished reflectors arranged to provide desired beam spread.

TB = quartz bulb for tungsten halogen lamps, similar to standard A bulb but with angular profiles

tungsten lamp = incandescent lamp having a tungsten filament

tungsten-halogen lamp = tungsten lamp having a quartz bulb containing a small among of halogen that vaporizes on heating and redeposits any evaporated tungsten particles back onto the filament.

IR lamp = a tungsten-halogen lamp having an infrared dichroic coating for reflecting infrared energy back to the filament, raising lamp efficiency, and reducing radiant heat in the emitted light beam.

infrared lamp = an incandescent lamp having a higher percentage of its radiant power in the infrared region than a standard incan. lamp, often having a red glass bulb to reduce the radiated visible light.

Light - Reflection

Light - Reflection

from Ching Viz Dictionary of Architecture

law of reflection = the principle that when light or sound is reflected from a smooth surface, the angle of incidence is equal to the angle of reflection, and the incident ray, the reflected ray and the normal to the surface all lie in the same plane.

angle of reflection = the angle that a reflected ray makes with a normal to a reflecting surface at the point of incidence

angle of incidence = the angle that a straight line, as a ray of light falling on a surface, makes with a normal to the surface at the point of incidence.

reflection = the return of light, sound, or radiant heat after striking a surface.

incidence = the striking of a ray of light or sound wave on a surface.

refraction = the change of direction of a ray of light as it passes obliquely from one medium into another in which its velocity is different

specular = directed from a smooth, polished surface. (like a mirror)

diffusion = a scattered reflection of light from an irregular surface or an erratic dispersion through a translucent material.

diffuse = Dispersed from an irregular surface.

Reflectance = the ration of the radiation reflected by a surface to the total incident on the surface.

absorptance = the ratio of the radiation absorbed by a surface to the total incident on the surface.

transmittance = the ratio of the radiation transmitted through and emerging from a body to the total incident on it, equivalent to one mines the absorptance.

diffraction = the modulation of light or sound waves as they bend around the edges of an obstacle in their path.

angle of refraction = the angle that a refracted ray makes with a normal to the interface between two media at the point of incidence.

Opaque = impenetrable to light

translucent = transmitting and diffusing light so that bodies on the opposite side are not clearly visible.

transparent = capable of transmitting light so that bodies situated beyond or behind can be distinctly seen.

Light

Light

from Ching Viz Dictionary of Architecture

Light = Electromagnetic radiation that the unaided human eye can perceive, having a wavelength in the range from about 370 - 800 nm and propagating at a speed of 186,281 mi./sec

nanometer = A unit of length equal to one billionth of a meter, used esp. to express the wavelengths of light in or near the visible spectrum. Abbr. = nm

Angstrom = A unit of length equal to one ten-billionth of a meter, used esp. to express the wavelengths of radiation. Symbol: A

Ultraviolet = <>

Violet = ~370 nm (visible)

Blue

Green

Yellow

Orange

Red = ~800 nm (visible)

infrared = > 800 nm (non-visible)

luminous intensity = the luminous flux emitted per unit solid angle by a light source expressed in candelas

candlepower = Luminous intensity expressed in candelas

candle = a unit of luminous intensity used prior to 1948, equal to the luminous intensity of a wax candle of standard specification.

candela (Cd) = the basic SI (Systeme International) unit of luminous intensity, equal to the luminous intensity of a source that emits monochromatic radiation of frequency 540 x 10 to the 12th hertz and that has a radiant intensity of 1/683 watt per steradian. Also called a standard candle.

solid angle = an angle formed by three or more planes intersecting at a common point.

steradian (sr) = a solid angle at the center of a sphere subtending an area on the surface equal to the square of the radius of the sphere.

luminous flux = the rate of flow of visible light per unit time, expressed in lumens.

lumen (lm) = the SI unit of luminous flux, equal to the light emitted in a solid angle of one steradian by a uniform point source having an intensity of one candela.

cosine law / Lamberts law = the law that the illumination produced on a surface by a point source is proportional to the cosine of the angle of incidence.

inverse square law = One of several laws relating two quantities such that one quantity varies inversely as the square of the other, as the law that illumination produced on a surface by a point source varies inversely as the square of the distance of the surface from the source.

illumination / illuminance = the intensity of light falling at any given place on a lighted surface, equal to the luminous flux incident per unit area and expressed in lumens per unit of area.

lux (lx) = the SI unit of illumination, equal to one lumen per square meter.

foot-candle (FC)= A unit of illumination on a surface that is everywhere one foot from a uniform point source of one candela and equal to one lumen incident per square foot.

Luminance = The quantitative measure of brightness of a light source or an illuminated surface, equal to the luminous intensity per unit projected area of the source or surface viewed from a given direction.

Lambert (L) = A unit of luminance or brightness equal to 0.32 candela per square centimeter.

Foot-lambert (fL) = A unit of luminance or brightness equal to 0.32 candela per square foot.

Lighting Fundamentals: Design Considerations

Lighting Fundamentals: Design Considerations

from Ch. 18 MEEB 9th ed.

Lighting Design Considerations

Quantitative lighting design considerations:

1. Daylight - its introduction and integration with electric light.

2. The interrelationship between the enregy aspect of electric and natural lighting, heating, and cooling.

3. The effect of lighting on interior space arrangement and vice versa.

4. The characteristics, means of generation, and utilization techniques of electric lighting.

5. Visual needs of specific occupants and of specific tasks.

6. The effects of brightness patterns on visual acuity.

Qualitative lighting design considerations:

7. The location, interrelationship, and psychological effects of light and shadow, that is, brightness patterns.

8. The use of color, both of light and of surfaces, and the effect of illumanant source on object color and sometimes the reverse.

9. The artistic effects possible with patterns of light and shadow including the changes inherent in daylighting, and so on.

10. Physiological and psychological effects of the lighting design, particularly in spaces occupied for extended periods.

Balance point

Balance point = Represents the beginning of the need for space heating equipment when the heat lost through the building's skin and infiltration matches the heat gained through solar plus internal loads.

Common HVAC Fan Types

Common HVAC Fan Types

from MEEB 9th ed.

Panel:

Most simple

For high efficiency air delivery, motor is generally mounted in the center of the propellers.

Likely the most noisy.

Not designed for much static pressure from ductwork, filters, etc.

Fixed Pitch vaneaxial:

Capable of working against somewhat more static pressure than the panel fan

More common in industrial applications.

Centrifugal:

With an airfoil bladed wheel

Has high efficiency over a wide operating range

Quieter than previous two.

Major changes in pressure result in only minor changes in volume of air delivered.

Vane axial adjustable pitch:

Takes less space than centrifugal fans

Can work against more static pressure.

The pitch is adjustable occasionally, not continuously

For system balancing or seasonal changes in air volume

Vane axial controllable pitch:

The automatically controlled pitch responds to changes in temp., humidity, air flow, etc., depending on the sensors used.

Commonly used in VAV systems.

Heating, Ventilating, Air-Conditioning (HVAC) System Types: All Water Systems

Heating, Ventilating, Air-Conditioning (HVAC) System Types: All Water Systems

from MEEB 9th ed.

All Water Systems

General:

Typically deal only with temp. control, air quality is left to separate systems.

Only heat and cool, distribution trees are slim.

Air quality is dealt with elsewhere, either locally, by means of infiltration or windows, or by a separate fresh air supply system, or simply by fresh air from an adjacent system, such as a ventilated interior zone.

Familiar all water application is the simple fan coil unit.(Because units with the same name are used in air and water systems, this further blurs the distinction between these two HVAC families)

The units may be found above ceilings, below windows or in corners, simply control the temp. (and to a limited extent, the relative humidity) of the air already in the room, which is blown through the coils.

Condensation on the coils occurs requiring a drain pan and drain line.

Common in motels, hotels and apartments.

Inherently noisy due to fan coil unit.

Heating, Ventilating, Air-Conditioning (HVAC) System Types: Air and Water Systems

Heating, Ventilating, Air-Conditioning (HVAC) System Types: Air and Water Systems

from MEEB 9th ed.

air and water systems

General:

Several variations, most heating and cooling of each zone is accomplished via the water distribution tree

water distribution tree = Much thinner than tree needed by air.

Air quality = filtering, humidity, freshness achieved by small, centrally located conditioned airstream, equal to the total fresh air required, is provided.

Several distribution trees are involved, yet total space the require is still less than required for all air systems.

Exhaust air = may be gathered in a return air duct system, making heat recovery possible. OR, (cheaper alternative) air can be exhausted locally, to avoid the construction of yet another distribution tree.

Two-pipe system = Water distribution provides either heating OR cooling ONLY.

Four-pipe system = Provides simultaneous heating AND cooling.

air and water Induction systems:

Air terminals found below windows throughout the U.S., high velocity and high pressure, constant volume fresh air supply is brought to each terminal, where it is forced through an opening in such a way that air already within the room("bypass" or secondary, air) is induced to join the incoming jet of air.

Circulation = fairly thorough circulation of room air is accomplished with only a little centrally treated air.

Finned tubes = air passes over them for heating or cooling.

Thermostat = controls the unit's output by controlling either the flow of the water or the flow of secondary air.

air and water Fan-coil with supplementary air systems:

Fan-coil located below a window is typical, it moves the room air as it provides either heating or cooling.

Centrally conditioned, tempered fresh air is brought to the space in a constant-volume stream;the fan moves both fresh air room air across a coil that either heats or cools the air, as required.

Air and water Radiant panels with supplementary air systems:

Either ceiling or wall panels contain the heated or cooled water to provide a large surface for radiant heat exchange.

Centrally conditioned, tempered fresh air is brought to the space in a constant volume stream.

Equipment in the space consists of a large surface, which must be kept clear of obstructions to radiant heat exchange.

air and water, Water loop heat pump systems:

Variation on two-pipe distribution system.

Heat pumps (water-air) either draw heat from the loop (heating mode) or discharge heat to it (cooling mode).

For a large building in cold weather, excess heat of the interior zones is used to warm the perimeter zones.

Loop temp. ranges between 65-90 deg F.

In hot weather, a central cooling tower disposes of the loop's excess heat, whereas in cold weather a central boiler adds the loop's needed heat.

Due to use of individual heat pumps, this system is closely related to direct refrigerant systems.

Often considered an all water system.

Heating, Ventilating, Air-Conditioning (HVAC) System Types: Direct Refrigerant & All-Air Systems

Heating, Ventilating, Air-Conditioning (HVAC) System Types: Direct Refrigerant and All-Air Systems

from MEEB 9th ed.

Way to classify HVAC systems = by the media used to transfer heat.

Thousands of liquids and gases can be used, three must common in building applications are air, water and refrigerant.

Four main system classifications:

Direct refrigerant systems

All air systems

air and water systems (see separate post)

all water systems (see separate post)

(last three, the heating/cooling production equipment is typically located centrally in a large building.) (in direct refrigerant system, the machine is usually located adjacent to the zone(s) it serves.)

The air handling components = served centrally or floor by floor

Direct refrigerant systems = These nearly eliminate the distribution trees of air or water, relying instead on a heating/cooling device adjacent to or within the space to be served. Prevalent in skin dominated buildings with extensive perimeter zones. tending to be in smaller buildings.

All air systems = Air is the only heat transfer media used between the mechanical room (central station) and the zones it serves, and because air holds much less heat per unit volume than water, the distribution trees for this class are quite thick.

Higher velocities = can be used to reduce duct sizes, but this generates more noise and higher friction resulting in more energy used by fans. Should be used sparingly where space limitations are extreme.

All air systems provide Overall best comfort = Quantities of air moved through the central station(s) are heated or cooled, humidity controlled, filtered, and freshened with outdoor air, all under controlled conditions.

All air, single zone system = The common, small building forced air system, controlled by a single thermostat.

All air, single duct, variable air volume (VAV) system = Most popular large building system of the 1990s. Its single duct requires less building volume for distribution than multi duct systems, and the variation of air volume flow rate (rather than of air temp.) saves energy relative to the single duct with reheat.

Central station = Supplies at normal velocity either a heated or a cooled stream of air.

Automatic volume controls = linked to each zone's thermostat, adjust the volume admitted to that zone, within an air terminal diffuser, often located above a suspended ceiling.

All air Fan powered VAV system = This variation allows individual units to heat when the main supply system is cooling, it might serve perimeter zones. In such a case, the cool air is reduced to a minimum for IAQ and the unit's fan draws additional air from a ceiling (or floor) plenum, heating it as required.

All air multi zone system = Each zone has an individual, centrally conditioned air-stream, the total distribution tree volume grows to astonishing size with only a few zones.

Central station = produces both warm and cool air streams, which are mixed at the central location to suit each zone.

Application = More likely to be found on medium size buildings, or on larger building in which smaller central stations are located on each floor.

Return = The single return air stream collects air from all zones.

All air Single duct with reheat system = This system, along with VAV, has the smallest distribution tree of this class. because at each zone the only object added to the duct is a small reheat coil (heat provided by steam, hot water, or electric resistance.

central station = provides a single stream of cold air that must be cold enough to meet the maximum cooling demand of any one zone, all other zones reheat this air as needed.

Cold weather = outdoor air at temp's as low as 38 deg F can be used, the colder the single central airstream, the less air need be circulated.

Not ideal for buildings with large interior zones in the U.S., central airstream needs cooling most of the time, then much energy is spent to reheat the airstream at most zones.

All air Double duct, constant volume systems = Two complete distribution trees are required, at the height of summer the cooling airstream does all the work, whereas in the coldest winter conditions the heating airstream carries the load. Air from these two streams are mixed at each zone's air terminals to meet heating/cooling requirements.

Temperature and volume can be controlled, thus this system offers better comfort under reduced load conditions than does the single-duct, variable volume system.

Cost = Much more expensive to install, consumes much building volume for the two distribution trees and is usually more energy consuming than the single duct, variable volume system that has largely replaced it.

Heating Systems from Ching Visual Dictionary of Architecture

Heating Systems from Ching Visual Dictionary of Architecture

All-water system = an air conditioning system in which either hot or chilled water is piped to fan-coil units in the served spaces, where air is circulated locally.

two pipe system = All water system in which one pipe supplies the hot or chilled water to fan coil units, and the other pipe returns it to the boiler or chilled water plant.

Four pipe system = all water system in which separate hot water and chilled water piping circuits provide for simultaneous heating and cooling as needed in various zones of a building.

supply pipe = a pipe for conveying hot or chilled water from the boiler or chilled water plant to a can coil unit.

return pipe = a pipe for conveying water from a fan coil unit to the boiler or chilled water plant

terminal unit = any of various devices for delivering a heating or cooling medium to a space.

fan coil unit = A terminal unit containing an air filter, heating or cooling coils, and a centrifugal fan for drawing in a mixture of room air and outside air.

coil = a connected series of pipes or tubing in rows or layers, often having fins attached to dissipate heat.

All air system = an air conditioning system in which central fans distribute conditioned air to the served spaces by means of ductwork.

single duct system = an all air system in which a single duct conveys conditioned air to the served spaces

constant air volume system = an all air system in which a master thermostat automatically regulates the quantity of conditioned air supplied to each zone.

variable air volume system = an all air system in which a thermostatically controlled variable volume box regulates the quantity of conditioned air supplied to each zone.

terminal reheat system = an all air system in which a reheat coil regulates the temp. of the air being furnished to each individually controlled zone.

multizone system = a central air handling unit capable of serving up to eight zones simultaneously.

zone = a space or group of spaces in a building whose temp. and air quality is regulated by a single control.

mixing box = a chamber for proportioning and blending cold and warm air under thermostatic control to reach the desired temp..

reheat coil = an electric or hot water coil for raising the temp. of the air in the supply duct of an air conditioning system.

air water system = an air conditioning system in which high velocity ducts supply conditioned air from a central plant to each zone where it mixes with room air and is further heated or cooled in an induction or fan coil unit.

induction unit = a terminal unit in which primary air draws in room air through a filter and the mixture passes over coils that are either heated or chilled by secondary water from a boiler or chilled water plant.

high velocity duct = a small duct capable of conveying primary air at a velocity of 2,4oo fpm or higher.

primary air = the conditioned air supplied at a high pressure and high velocity by a central air handling unit.

Forced Warm-Air Heating from Ching Visual Dictionary of Architecture

Forced Warm-Air Heating from Ching Visual Dictionary of Architecture

Forced Warm-Air Heating = a system of heating a building by means of air heated in a furnace and distributed bya a fan through ductwork to registers or diffusers

extended plenum system = A perimeter heating system in which a main duct conveys warm air to a number of branch ducts, each serving a single floor register.

Bonnet = A chamber at the top of a hot air furnace from which the leaders emerge. also called plenum.

Leader = a duct for conveying warm air from a furnace to a stack or branch duct. Also called main, trunk.

Manifold = a pipe or duct fitting having several outlets for making multiple connections.

gathering = a tapered section of a duct or flue forming a transition between two sections, one of which has a greater area than the other.

boot = a duct fitting forming a transition between two sections which vary in cross sectional shape.

duct = a pipe or conduit of sheet metal or fiberglass for conducting heated or conditioned air. also called air duct.

ductwork = a system of ducts, connectors, and dampers for conveying air in a heating, ventilating or air conditioning system. also called ducting.

stack = a vertical duct for conveying warm air from a leader to a register on an upper floor.

chase = a continuous space or recess built into a wall or through a floor for pipes or ducts.

grille = a grating or perforated screen for covering, concealing, or protecting a wall, floor or ceiling opening.

register = a device for controlling the flow of warm or conditioned air from an outlet, composed of a grill with a number of parallel blades that may be adjusted so as to overlap and close the opening.

perimeter heating = a heating system that distributes warm air to registers placed in or near the floor along exterior walls.

perimeter loop system = a perimeter heating system in which a loop of ductwork, usually embedded in a concrete ground slab, distributes warm air to each floor register.

perimeter radial system = a perimeter heating system in which a leader from a centrally located furnace carries warm air directly to each floor register.

flexible duct = a pliable, airtight fitting installed between two ducts, or between a fan and a duct, to prevent the transmission of noise and vibrations along the ductwork.

duct liner = a fiberglass blanket for lining the inside of a duct to reduce noise and serve as thermal insulation.

diffuser = a device having slats at different angles for deflection warm or conditioned air from an outlet in various directions.

throw = the distance a projected airstream travels from an outlet to a point where its velocity is reduced to a specified value.

terminal velocity = the average velocity of a projected airstream at the end of the throw.

drop = the vertical distance a horizontally projected airstream falls from the elevation of its outlet, measure at the end of the throw.

spread = the extent to which a projected airstream diffuses at the end of the throw.

Mechanical Heat from Ching Visual Dictionary of Architecture

Mechanical Heat from Ching Visual Dictionary of Architecture

Mechanical System = Any of the systems that provide essential services to a building, as water supply, sewage disposal, electric power, heating, ventilation, air-conditioning, vertical transportation or fire fighting

Space heating = the heating of a limited area, as a room, esp. by means of a heat source located within the space.

Franklin stove = A cast-iron stove resembling an open fireplace but having enclosed sides, back, top and bottom, with a front completely open or able to be closed with doors.

Stovepipe = a pipe, usually of sheet metal, serving as a stove chimney or connecting a stove with a chimney flue.

Thimble = A protective sleeve of sheet metal passing through the wall of a chimney, for holding the end of a stovepipe.

Central heating = A mechanical system that supplies heat to an entire building from a single source through a network of ducts or pipes.

Thermostat = device that automatically responds to changes in temp. and activates switches controlling such equipment as furnaces, refrigerators, and air conditioners.

thermocouple = device for measuring temp. in which a pair of dissimilar metals, as copper and iron are joined so that a potential difference generated between the points of contact is a measure of the temp. difference between the points.

bimatellic element = a material made by bonding two metallic strips having different coefficients of expansion, used in temperature indicating and temp. controlling devices.

Combustion air = Air required for combustion of fuel in a furnace

Furnace = apparatus in which heat is produced, as for heating a house or producing steam.

horizontal furnace = a furnace designed for installation in a low attic or crawl space.

wall furnace, recessed in or amounted on a wall and supplying heated air directly to a space without the use of ducts.

Heating load = The hourly rate of net heat loss in an enclosed space, expressed in Btu per hour and used as the basis for selecting a heating unit or system.

Heating degree day = A degree day below the standard temp. of 65 deg F, used in estimating fuel or power consumption by a heating system.

Degree day = A unit that represents on degree of departure in the mean daily outdoor temp. from a give standard temp..

Ching Dictionary of Architecture: Heat - Thermal Comfort

Ching Dictionary of Architecture: Heat - Thermal Comfort

Thermal Comfort = Human comfort as determined by the ability of the body to dissipate the heat and moisture it produces by metabolic action.

Psychrometric chart = A chart relating the wet-bulb and dry-bulb readings from a psychrometer to relative humidity, absolute humidity, and dew point.

dry-bulb temperature = the temp. recorded by the dry-bulb thermometer in a psychrometer. Indicated as vertical lines on the psychrometric chart

psychrometer = an instrument for measuring atmospheric humidity, consisting of two thermometers, the bulb of one being dry and the bulb of the other being kept moist and ventilated so that the cooling that results from evaporation makes it register a lower temp. than the dry one, with the difference between the readings being a measure of atmospheric humidity.

wet-bulb temperature = The temp recorded by the wet-bulb thermometer in a psychrometer. Indicated as diagonal lines on the psychrometric chart

Comfort zone = Range of dry-bulb temperature, relative humidity, mean radiant temp, and air movement judged to be comfortable by a majority of Americans and Canadians tested. This comfort zone varies with climate, the season of the year, type of clothing worn and the activity level of the individual. Also called Comfort envelope. Plotted location on the psychrometric chart.

dew point = the temp. at which air becomes saturated with water vapor. Also called dew-point temp.

Effective temp. = A temp. representing the combined effect of ambient temp, relative humidity and air movement on the sensation of warmth or cold felt by the human body, equivalent to the dry-bulb temp. of still air at 50% relative humidity which induces an identical sensation.

Humidity ratio = the ratio of the mass of water vapor to the mass of dry air in a mixture of air and water vapor. Also called "mixing ratio".

Relative humidity (rh) = The ratio of the amount of water vapor actually present in the air to the max. amount that the air could hold at the same temp., expressed as a percentage.

Absolute humidity = The mass of water vapor present in a unit volume of air.

Specific humidity = The ratio of the mass of water vapor in air to the total mass of the mixture of air and water vapor.

Hygrometer = Any of various instruments for measuring the humidity of the atmosphere

Enthalpy = A measure of the total heat contained in a substance, equal to the internal energy of the substance plus the product of its volume and pressure. The enthalpy of air is equal to the sensible heat of the air and the water vapor present in the air plus the latent heat of the water vapor, expressed in Btu per pound (kilojoules per kilogram) of dry air. Also called heat content.

Adiabatic heating = A rise in temp. occurring without the addition or removal of heat, as when excess water vapor in the air condenses and the latent heat of vaporization of the water vapor is converted to sensible heat in the air.

Mean Radiant Temperature (MRT) = The sum of the temperatures of the surrounding walls, floor and ceiling of a room, weighted according to the solid angle subtended by each at the4 point of measurement. Mean radiant temp. is important to thermal comfort since the human body receives radiant heat from or loses heat by radiation to the surrounding surfaces if their mean radiant temp. is significantly higher or lower than the air temp.

Radian heat = Heat energy transmitted by the radiation of electromagnetic waves in contrast to heat transmitted by conduction or convection.

Evaporative cooling = A drop in temp. occurring without the addition or removal of heat, as when water evaporates and the sensible heat of the liquid is converted to latent heat in the vapor. also called adiabatic cooling.

Ching Dictionary of Architecture: Heat Transfer

Ching Dictionary of Architecture: Heat Transfer

Convection = The transfer of heat by the circulatory motion of the heated parts of a liquid or gas owing to a variation in density and the action of gravity.

Conduction = The transfer of heat from the warmer to the cooler particles of a medium or of two bodies in direct contact, occurring without perceptible displacement of particles themselves.

Radiation = the process in which energy in the form of waves or particles is emitted by one body, passed through an intervening medium or space, and absorbed by another body.

Thermal conductivity = The time rate of heat flow through a unit area of a given material of unit thickness when the temp. difference across the thickness is one unit of temp.

Thermal conductance = the time rate of heat flow through a unit area of a given material when the temp. difference across the specified thickness of the material is one unit of temp.

Thermal resistance = the reciprocal of thermal conductance, expressed as the temp. difference require to cause heat flow through a unit area of material of given thickness at the rate of one heat unit per unit time.

R-value = A measure of thermal resistance of a given material, used esp. to specify the performance of thermal insulation. The total R-value for a building component or assembly is the sum of the R-values for each layer in the component or assembly.

Thermal transmittance = the time rate of heat flow through a unit area of a building component or assembly when the difference between the air temp's on the two sides of the component or assembly is one unit of temp. Also called the coefficient of heat transfer.

U-value = A measure of the thermal transmittance of a building component or assembly, equal to the reciprocal of the total R-value of the component or assembly.

1/R(total) = U, IE. 1/R+R+R+... = U

Thermal break = An element of low thermal conductivity placed in an assembly to reduce the flow of heat between highly conductive materials. Also called thermal barrier.

Infiltration = the flow of outside air into an interior space through cracks around windows and doors or other openings in the envelope of a building

Ching Dictionary of Architecture: Heat Basics

Ching Dictionary of Architecture: Heat Basics

British thermal unit (BTU) = The quantity of heat required to raise the temperature of one pound (0.4 kg) of water 1 deg F.

Calorie (cal) = A unit of heat equal to the quantity of heat required to raise the temp. of one gram of water 1 deg C at a pressure of one atmosphere, equivalent to 4.186 joules. Also called gram calorie, small calorie

Kilocalorie (Cal) = A unit of heat equal to the quantity of heat required to raise the temp. of one kilogram of water 1 deg C at a pressure of one atmosphere, equivalent to 1000 small calories. Also called kilogram calorie, large calorie. (note the capitalized C in the abbreviation)

Fahrenheit scale (F) = A temp. scale in which 32 deg F represents the freezing point and 212 deg F the boiling point of water under standard atmospheric pressure.

Convert Fahrenheit to Celsius = Subtract 32 from Fahrenheit number then multiply by 5/9 to find degrees Celsius.

C = (F-32) x 5/9 OR C = (F-32) x .5555555555...

Celsius scale (C) = A temp scale divided into 100 degrees, in which 0 deg C represents the freezing point of water under standard atmospheric pressure. Also called the Centigrade scale.

Convert Celsius to Fahrenheit = Multiply Celsius number by 9/5 an then add 32 to find degrees Fahrenheit.

F = (C(9/5)) + 32 OR F = (C x 1.8) +32

Kelvin scale = An absolute scale of temp. having a zero point of -273.16 deg C

Absolute scale = A temp. scale based on absolute zero with scale units equal in magnitude to centigrade degrees.

Absolute zero = The hypothetical lowest limit of physical temp. characterized by complete absence of heat, equal to -273.16 deg C or -459.67 deg F.

Absolute temperature = Temperature as measure on absolute scale

Kelvin (K) =The base SI unit of temp. equal to 1/273.16 of the triple point of water.

Triple point = The particular temp. and pressure at which the liquid, gaseous and solid phases of a substance can exist in equilibrium.

Heat capacity = the quantity of heat required to raise the temp. of a substance by one degree.

Specific heat = Heat capacity per unit mass of substance: the number of Btu required to raise the temp. of one pound of a substance 1 deg F, or the number of calories per gram per degree centigrade.

Latent heat = The quantity of heat absorbed or released by a substance during a change in phase at constant temp. and pressure.

Phase change = point at which a substance changes from a gas to liquid, liquid to gas, liquid to solid, also applies in reverse (caused by temp., no change in chemical composition)

Sensible heat = The quantity of heat absorbed or released by a substance during a change in temp. without a change in phase.

MEEB: Heating / Cooling Systems: Hydronic and Coils

MEEB: Heating / Cooling Systems: Hydronic and Coils

Combines a perimeter hot water heating pipe with an overhead air handling system.

Boiler with tankless coil supplies domestic hot water.

Boilers heat output supplies both the perimeter loop and a coil in the air handling unit of the duct system.

Cooling coil if implemented is connected to and adjacent outdoor condensing unit.

Winter indoor temp's remain more constant.

MEEB: Heating / Cooling Systems: Cooling Coils Added to Warm Air Furnaces

MEEB: Heating / Cooling Systems: Cooling Coils Added to Warm Air Furnaces

Commons system utilizing a rather simple arrangement of the refrigeration cycle.

Air to Air refrigeration device is used (in contrast to water to water, not applicable here)

- Air is directly passed over the evaporator coil in which the refrigerant is expanding from a liquid to a gas

- Heat is moved from the indoor air to the outdoor air by the step up action or heat pumping nature of the refrigeration cycle.

- Indoor air cooled in this manner by the expanding refrigerant is usually know as "direct expansion.

- The cooling coils are therefore often referred to as DX coils.

- Compressor-condenser unit is placed outdoors on a concrete slab or on the roof, causing noise and heat, must be taken into account for planning.

MEEB: Warm Air Heating Systems

MEEB: Warm Air Heating Systems

Began to supersede the fireplace about 1900

- Originally iron furnace stood in middle of a basement hand fired by coal

- Sheet metal enclosure surrounding it.

- Opening in side admitted combustion air.

- Short duct from top of enclosure delivered warm air to a large grille in the middle of the floor of the parlor

- other rooms were heated by communication with this room

Modern Warm Air Furnaces

- Automatic firing of oil or gas

- Operational and safety controls

- ducted air to and from each room

- Blowers / fans to move air

- Filters for Indoor Air Quality

- Adjustable registers

Uniform conditions and reasonably equal temp's in all parts of a building

Building can be quickly warmed

Cleans the recirculated and outdoor air with filters

Air can be circulated without heat introducing fresh air

Central cooling can be incorporated if ducts are sized to handle the greater rate of air flow required.

Humidifier can be added if needed.

Dehumidification can be accomplished if cooling is included in the design

Supply registers in floor below areas of glass is common, minimizing heat loss at the windows.

High return grills pick up warmer air for reheating

Furnace located reasonably close to middle of building.

MEEB: Hot Water Baseboard Radiator Systems

MEEB: Hot Water Baseboard Radiator Systems

Four arrangements:

Series Loop System = water flows to and through each baseboard or fintube in turn

- water at the end of a run will be cooler but temp. drop seldom exceeds 20 deg in residences

- Valves at each baseboard are not possible, they would shut off the other units too.

- Adjustment by damper at each baseboard reducing natural convection of air over the fins

- known as a "one-zone" system

One Pipe System = Connect from the main pipe connect to each baseboard through a branch and fitting, water is returned to the main pipe in direction of flow through another connection branch.

- Valve can be used at each one to reduce heat or complete shutoff

- Uses more piping

- Water temp. will be lower at end run

Two Pipe Reverse-Return System = Separate branch from main supply to each baseboard but return is connected to a separate return line which follows the flow of the supply back to the boiler.

- Provides the same supply water temp. to each baseboard or radiator

- More pipe required

- Equal distribution

- Preferred option

Two Pipe Direct Return = Similar to Reverse return except the return water pipe flows in the opposite direction of the supply pipe

- Causes unequal distribution, water from first radiator returns to boiler first

- end of line radiators are "short circuited" by conflicting loops running through the previous radiators.

- Not preferred option