Integration Of Buidling Materials & Systems Flashcards
HVAC system sizing
Sometimes the cooling equipment chosen will be slightly undersized in order to keep initial costs low, knowing that some occasional minor extremes will be tolerated
active systems are often used in combo with passive systems; can often possibly reduce the size of the active equipment
Mechanical spaces, variables affecting space requirements
Scope of the system (local, centralized, or district)
Type of HVAC system
Building size
Building type
Passive systems use
Scope of the system, local
local system serves one zone and used for small building or for specific areas of a building
-Several local systems can be used if more than one zone is required in small or moderate sized buildings (ex. Commercial gas-fired heaters)
-ex. Residential furnace, window mounted air conditioner
-least space needed
Scope of the system, centralized
Centralized system serves several zones from one location
-common in commercial a and institutional buildings of moderate to large size
-there can be several centralized systems in one building if the building is very large or for reasons of efficiency
-most space needed
Scope of the system, district
district system serves several buildings by a single plant
-ex. Central steam plant on a college campus
Type of HVAC system
-all-air system; needs the most space
-all-water system; needs the least amount of space
-air-water system; no return ducts needed
-electric systems and direct expansion systems
Building size
affects the volume of heating and cooling needed
Building type
consider the individual control needs and provisions for ventilation and positive pressure on the building types
Passive system use
passive systems influence the size of equipment needed because it can reduce or eliminate the capacity needed from the equipment
Mechanical Spaces, Preliminary sizing, medium to large building with all-air or air-water system
mechanical room should be 3-10% of the total building area being served
-includes space for boilers, chillers, fans, fuel (if needed), and related pumps and piping
Mechanical Spaces, Preliminary sizing, medium to large building with all-water system
mechanical room should be 1-3% of the total area
Mechanical Spaces, Preliminary sizing, cooling towers
when needed are .2-1% of the building area served and located on the roof or outside the building
Mechanical Spaces, Preliminary Sizing, Boilers and Chillers
-usually at least 2 boilers so one can operate while the other is being serviced
-chillers usually located in the same room as boilers
Air Handling Units
-AHUs included in all-air and air-water systems
-AHU uses water from the boilers and chillers to heat or cool the air
-AHU located in the fan room
Fan Rooms
-fan room ideally located next to an exterior wall, but can be placed further inside the building as long as fresh air and exhaust air can be carried in and out by ductwork
-fan room equipment includes fans, filters, humidifiers, preheat coils for cold climates, return air ducts, outside air intakes, and exhaust ports, as well as dampers and a mixing box to control the mixing of fresh or, return air, and exhaust air
—equipment is heavy, noisy, and causes vibration
-multiple fan rooms can accommodate multiple building uses, seasonal changes, or zoning requirements
Location of equipment in small or low-rise building
mechanical equipment is usually best located in the basement or on the ground floor
Best location for boilers and chillers
located on lower levels due to structural requirements; best located away from sensitive areas due to noise
High-rise building mechanical equipment location
mechanical equipment rooms may be located in the basement along with a primary fan room that distributes air upward
-boilers and chillers may be located in the basement with smaller fan rooms located on each floor; allows greater smoke control in case of fire
Best location for mechanical rooms in general
mechanical room located next to an outside wall to allow for the intake of combustion air and near a service door or removable panel for the replacement of boilers and other equipment; located near the chimney
Round ducts
more efficient and maintain air pressure better
Rectangular ducts
make better use of the space available above ceiling and in vertical duct chases
Vertical ducts
can be centrally located and feed horizontally out, or can be located along the perimeter, and feed horizontally in
Horizontal trunk ducts
should follow the paths of building circulation systems
static head (or static pressure)
the amount of pressure that must be applied to overcome frictional resistance and cause air to flow through the system; measure in inches of water
fan rooms should be located to minimize the length of ductwork needed
-the longer the ductwork the more friction there is
-larger ducts keeps the pressure lower but means more space is needed for the ducts
-increasing the size of the can raise pressure but results in higher initial costs, higher operating costs, and more noise
Low pressure duct space sizing
allow a cross-sectional area of 10-20 SF for every 10,000 SF of floor space served
Coordination of mechanical systems with project design details
the clear space between the ceiling and the structure can be tight, sometimes coordinating the placement of ducts and recessed light fixtures is difficult or not possible in the space provided; low-voltage or low-clearance light fixture may be specified
Mixing box
controls the air that flows into a space from the main air supply line; also located in the plenum; mixing box reacts to thermostat, adjusts the air’s velocity and the noise it makes
Mixing box, terminal reheat system
cool air enters the mixing box at a fixed temperature, the mixing box contains a hot water coil that can add heat as needed
-identified easily but the air ducts and copper pipes leading into the mixing boxes
Mixing box, dual duct system
the mixing box receives cool air and hot air from 2 separate ducts; it mixes and distributes the air to ducts that service individual rooms or spaces
Mixing box, variable air volume system
the control device is called a VAV box; VAV box receives air at a constant temperature and varied the airflow rate as needed to maintain the desired temperature
Relocating mixing boxes
can be expensive due to their size and connection with ductwork and thermostats
Access flooring
a false floor of individual panels raised above the structural floor with pedestals
-more commonly covers electrical, communication, and computer wiring, but can sometime be used to house some types of HVAC ductwork that serve individual workstations
Residential construction ducts and plumbing
small ducts and plumbing pipes are typically run within the walls and between floor joists or in crawl spaces or attics; large horizontal ducts may be run below the floor joists and a dropped ceiling or furred-down space must be built to conceal them
Square air diffusers
common in suspended ceilings because their inexpensive and easy to install
slot air diffusers
used when the appearance of the device needs to be minimized or when space available is limited; provides uniform air supply along a window line
Plenum
the space between a suspended ceiling and the structural floor or roof
used as a space for ductwork, sprinkler piping, plumbing piping, wiring, signal systems, speakers, and recessed lighting
Mid- and high-rise building plenums
it make more economic sense to minimize the plenum height to reduce the floor-to-floor height
Plenum levels
-uppermost level is the structure of the building
-next level is mechanical ducts, mixing boxes, and other HVAC equipment; smaller branch ducts may need 12-16” of space
-next level down is the plumbing and sprinkler piping; usually 4-6” of space needed
-lowest level is for recessed luminaires; ranges from 9-12” for compact fluorescent downlights, to 4-5” for standard fluorescent fixtures; LED and compact fluorescent fixtures can reduce the depth further
-depth of suspended ceiling is usually about 2”
plenum can be used as return air space
in this case use of exposed combustible material within the plenum is prohibited
-electrical wiring would need to be in steel conduit
access doors
small, steel doors with frames that are opened through use of a thumb latch or key to provide access in a ceiling to equipment
Thermostats
-placed away from exterior walls, heat sources, or other areas that may adversely affect their operation
-48” aff, but coordinate location with light switches and other nearby wall-mounted control devices
Coordination with ceiling items
air supply register should be placed near windows and other sources of heat loss or heat gain, while return air grilles should be placed away from the supply points to provide good heat and air circulation throughout
Window coverings and air supply
-can interfere with supply air diffusers or other heating units near the window
-window could crack if heat buildup is excessive
Acoustic separation
special detailing or construction may be needed to create a continuous sound seal around the floor and ceiling, above the ceiling, and along the perimeter wall
Water pressure from a city main
is 50 psi; must be reduced by the friction if the system and still be high enough to operate fixtures
Flush valve psi needed
10-20 psi
Shower psi needed
12 psi
Pressure in a column of water
Increases in proportion to depth
Static head
express water pressure in terms of the height of a column of water; ex. A column of water 1’ height exerts a pressure of .433 psi at its base, so a pressure of .433 psi is equivalent to 1’ of static head; 1 psi is equivalent to 2.3’ of static head
2 primary types of water supply systems
Upfeed and downfeed
the choice is usually based on the height of the building and the pressure needed to operate the fixtures
Upfeed system
uses pressure in the water main to directly supply the fixtures
there is always some friction in the system and some pressure must be available to work the highest fixture, so the practical limit on building height is 40-60’
Downfeed system
water from the main is pumped to storage tanks near the top of the building and flows to the fixtures by gravity; more often used where the building is too tall for an upfeed system; maximum height of a zone is from 60 psi or about 138’
Upfeed and downfeed systems
sometimes the lower floors of a high-rise building are served by an upfeed system and the upper floors are served by a downfeed system
Direct Upfeed system (tankless system)
several pumps are used together and controlled by a pressure sensor, when demand is light, only one pump operated to supply the needed pressure, when the demand increases, the pressure drop is detected by the pressure sensor and other pump is signaled to start
medium sized buildings can use it
Water supply system components
consists of piping, fittings, valves, and other specialized components
Piping material
piping can be made of copper, steel, plastic, or brass
Union
a special fitting that connects 2 rigid sections of pipe and that can be easily unscrewed to allow for repairs or addition to the piping system
gate valve
seals a metal wedge against 2 metal parts of the valve; used where control is either completely on or off; no turns so has low friction loss
globe valve
used where water flow is variably and frequently controlled, such as with faucets or hose bibs; a handle operated a stem that compresses a washer against a metal seat; water must make 2 90 degree turns so the friction loss is high
check valve
works automatically and allows water flor in only one direction where, for example, back flow might contaminate a potable water supply
angle valve
where water control in sinks and lavatories is needed a single-handle faucet is used
water hammer
the noise caused when a valve or faucet is closed too quickly, causing the water moving in the system to stop abruptly and the pipes to rattle; prevented by air chambers and shock absorbers
air chamber
a length of pipe installed above the connection to the faucet that cushions the surge of water
shock absorber
performs the same function as an air chamber with a manufactured expansion device
pressure reducers/ pressure regulators
needed on fixtures if the supply pressure is too high, over about 60 psi; too high water pressure can cause wear on a fixture
pressure relief valves
safety devices designed to open when pressure exceeds a predetermined max; used on water heaters and similar equipment where excessively high pressures could cause damage or explosion
flow restrictor
a device to reduce the amount of water that comes out of. Tap or other fixture; used on showe heads and sinks to limit water use
Most r emote fixtures
After the various pressure losses are deducted from the available pressure at the water main, there. Must still be adequate pressure at the most remote fixture
Pressure loss in pipes
depends on the diameter of the pipe and on the flow rate, which is typically measured in gallons per minute; pressure loss due to friction within the pipe and friction is greater for smaller diameters and for greater flow rates
demand load
aka maximum possible flow; the flow rate that would be needed if every fixture in the system were in use at the same time; found by adding up the load values for all the fixtures
water supply fixture units
how the load value for a fixture is measured
fixture unit
a unit flow rate approximately equal to 1 CF/min
probable demand
aka peak demand, maximum probable flow, or maximum expected flow; the maximum flow rate that can be expected under typical conditions
used to design the water supply system
Finding probable demand
tables and graphs are available that relate the demand load (in fixture units) to the probable demand (in gallons per minute)
Once probable demand is known
this value can be used with a chart that shows how flow rate, pipe size, pressure loss due to friction, and velocity are related
used to choose the smallest diameter that will handle the needed flow rate without losing the pressure needed to operate
Using the table of estimated demand
find the probable demand in gallons per minute, and then read across to the intersection with one of the pipe diameter lines; if total friction loss is too great, select a larger pipe size and perform the calculation again
Flow rate for sound sensitivity
velocity at more than 10 ft/sec is too noisy; for sound sensitive areas don’t go above 6 ft/sec
Thermal expansion in piping
-allow for expansion of piping, especially for long lengths of piping
-there are also in-line expansion fittings
most efficient way to reduce the need for irrigation
use plants that can grow with the climate’s natural precipitation
Irrigation design
should be designed as efficiently as possible; timers, rain sensors, and tensiometer (measures the moisture content of the soil at the plant’s roof zone)
Two-pipe circulating system
can be used to reduce the need to run water until the hot water makes it to the pipe
all fixture are connected to both a supply pipe and a return pipe; the natural convection in the system keeps the water slowly circulating; hot water rises to the uppermost fixtures and cools as it falls down to the water heater to be reheated; pumps may be needed if there isn’t enough room for circulation
Size of the water heater
based on the total daily and peak hourly hot water demands of the building
Larger building water heaters
for larger buildings a separate storage tank is needed in order to meet demand, while a smaller boiler actually heats the water
recovery rate
the number of gallons per hour of cold water that can be heated to the desired temperature
demand load calculated
only from those fixtures that use hot water
Pipe size minimums
in no case can the pipe size be less than the minimum size given in the plumbing codes
Water heater temperature setting
water heaters are set to keep the water at the highest temperature that is needed at the point of use
Water temperature comfort
water above 110 degrees becomes uncomfortable to the touch
direct heating
brings the water into contact with surfaces heated directly by flame, hot gases, electricity, or solar radiation
Indirect heating water heater
uses another medium to transfer the heat from its source to the surfaces that are in contact with the water
3 basic types of heating systems
Storage tank
Tankless
Circulating
storage tank system
the same tank is used both to heat the water and to store it for use
tankless system
water is quickly heated as it is needed and immediately sent to where it is needed
circulating system
the water is heated in one place and then moved to a separate tank for storage until needed
2 types of drainage
Sanitary drainage
Storm drainage
sanitary drainage
includes any drainage that may include food or human waste
storm drainage
involves only runoff from roof drains, landscaped areas, and the like
storm drainage does not need to be treated
Drainage Systems
designed to safely carry away sewage to a private or municipal disposal system
Drainage systems consist of the following parts
Trap
Drainage piping
Vent
Air gap
Vacuum breaker
Stack
Drain
Sewer
Trap
-located at every fixture and designed to catch and hold a quantity of water, which forms a seal that prevents sewage system gases from entering the building
-usually installed within 2’ of the fixture but may be installed at slightly greater distances depending on the size of the pipe
-connected to the drainage piping, but also connected to vents
Vent
-pipes that lead from the drainage system to the outside air, typically through an opening in the roof
-allow built-up sewage gases to escape instead of bubbling through the water in the traps
-allow pressure in the system to equalize so that waste being discharged does not create a siphon that drains the water out of the traps
Air gap
-used as a safety feature
-faucets are always mounted with their outlets at least 2” above the highest possible level of wastewater
Vacuum breaker
prevents siphonage on fixtures where the water supply is below the rim of the fixture by closing when backward water pressure is present
Stack
-a vertical pipe that carries wastewater down to the bottom of the building
-if wastewater includes human waste it is called soil stack
-stack must extend through the rood and be open to the outside ai; called a stack vent
-vents must also be open to an exterior; vents on lower floors connected to a vent stack that runs parallel to the soil or waste stack
Drain
-All stacks are connected to a horizontal drain at the bottom of the building
-from within the building to a point 3’ outside the building, this is called the house drain or building drain
-From 3’ outside the building to a main sewer line or private disposal system , the horizontal pipe is called the house sewer/building sewer
-cleanouts provided where stack connect with the house drain to allow for maintenance; also required outside the building for maintenance of the house sewer
Drain, waste, and vent (DWV) pipe
piping designed for drainage systems
-available in copper, cast iron, and plastic
backflow preventers
such as backwater valves; keep wastewater from reversing flow and backing up into fixtures, which could contaminate the water supply of cause the basement to flood
sump pit and sump pump
installed when plumbing fixtures must be below the level of the house drain and house sewer; collects the sewage and pumps it to a higher level when’re it can flow by gravity to a sewer
floor drains
collect water in shower rooms or in places where overflow is likely
interceptors
collect foreign matter at the source instead of allowing it to enter the sewer system; common types are grease traps, plaster traps, and lubricating oil traps
sizing of drainage pipes
based on flow rate expressed in fixture units
drainage flow rate
expressed in drainage fixture units (dfu)
Plumbing fixture location
fixtures should be located as close to main plumbing lines as possible
Drains slopes
drains must slope at least ¼ in/ft, but ⅛ in/ft is allowed for pipes larger than 3”
max distance from a trap to the nearest vent
Plumbing code limits it
Island fixture venting
connects directly above the waste line where the trap arm discharges; the vent is carried up above the. Bottom of the sink and then looped horizontally and downward below the floor line; below the floor line the vent pipe runs horizontally to the nearest vent stack
air admittance valve placement
can be placed above the vertical waste line in the island to vent the sink
wet columns
areas where hot and cold supply and drainage risers are located
chase wall
consists of 2 rows of studs separated by several inches, the exact dimension being determined by the largest pipe or duct that has to be concealed
sink carrier
steel framework inside a chase wall that carried the weight of wall mounted sinks
toilet carrier
similar to sink carrier and supports wall mounted toilets
Chase wall thickness
chase wall with fixture on 1 side should be 12” thick and a chase wall with fixtures on both sides should be 16” thick
private disposal system components
consists of a septic tank, and a leaching field