ARE 5.0: PPD
Evaporator
low pressure cold refrigerant
SD cost estimating technique?
"Unit-rate cost estimating" We start at programming with a "rough order of magnitude" cost estimate (might be off by as much as 2X), used for a "napkin estimate" before design to determine feasibility. Used in Pre-design/programming (PA exam) As we move through design phases we get more specific and have more confidence that our estimate is close to the final construction cost; eventually, we want our estimate to be within 5%. For later, SD, DD, and CD stages: "Unit-rate cost estimating" . . . early-on in the unit-rate method (SD), we know enough about the building's size to use estimates based on cost per square foot or per cubic foot measurements Then later, as we know more about the project (CD), our estimates will tally detailed units like "number of pipe bends" and "linear feet of conduit" and "estimated cost of labor to install 50,000 sf of EPDM roofing membrane."
Roof safety railing: What height minimum?
42 inches minimum for rooftop safety railings. Permanent and temporary railing systems available. Railings required anytime work happens on the roof. May penetrate the roof or parapet. . . or may sit on top of the roof, non-penetrating, with weights (like this) Mechanical equipment screens, in most cases, are limited to no more than 18 feet above the roof surface.
How deep should the bottom of a spread footing be in a climate with a frost depth of 60″
60″ If you don't go deep enough, freeze-thaw cycles will heave your foundation. In older code versions frost depth may have measured from grade to the top of the footing. . . now the measurement is to bottom of the footing.
Design a light shelf. Draw it in section. Try to get the proportions and materials correct.
A: height of light shelf should be such that it shades room occupants from sky view B: height of top light should be as high as possible (with "A" in mind) C: extension of light shelf should be 1.4 times b if light shelf faces due south (1.7 times b if light shelf faces more than 20 degrees to the east or west of south). Figure out why that would be? (answer below). In hot climates the extension of the light shelf can be louvers to allow built-up heat to escape upward. x: to get light deep into the room (and therefore mitigate glare) sunlight should reflect off top of light shelf and then off light-colored ceiling R: because view to the sky is shaded, areas close to the window have less glare z: top of light shelf should be painted white. In cold climates, the top surface can be mirrored. Figure out why climate matters (answer below). Bottom of light shelf should also be light colored so that it doesn't contrast too heavily with the bright outdoors when viewed from within. Answer 1: the sun is lower in the sky in the east and west than in the south, especially near sunrise and sunset. To shade from the sun, we need to extend the light shelf outward farther. Answer 2: in a hot or mixed climate, a mirrored top surface would reflect unwanted heat into the occupied space.
"Horizontal footcandles" is a measure of light arriving from ______. Above or The side
Above! Horizontal footcandles is a measure of light impinging upon a horizontal surface: as if you put the light meter flat on a table, so it measures light arriving from above. Vertical footcandles measures light impinging on a vertical surface. . . so light arriving from the side.
A good barrier for preventing sound from transmitting from one room to the other is _______. Absorptive Or Airtight
Airtight Assemblies that are massive, airtight, and structurally discontinuous do the best job keeping out the neighbor's TV noise, or keeping out the bus noise, from your apartment. By contrast, sound absorption is used to reduce the sound buildup inside the same room where the sound is made, and has less impact on the neighbor's noise. In the same way that cloud cover, temperature and wind speed are each measures of weather, but not very related to one another . . . room acoustics (sound absorption), noise control (sound isolation), and impact noise control (from footfall) are each measures of acoustics but not very related to one another. A room with high or low quantities of absorption may or may not be good at keeping sound from the adjacent room out, just as a cloudy day may or may not also be windy.
When do architects use a Faraday cage?
Architects use Faraday cages as lightening protection. By creating a wire mesh on the roof, they can redirect lightening strikes around the building to the ground.
Embodied energy
By comparing "embodied energy" between building materials, we can specify with climate change in mind. A lower value translates to a smaller energy footprint (by weight). Embodied energy only accounts for the energy required to mine, extract, process, and transport the material. . . just the upstream part. To include the operation (how much energy will the insulation save? How much energy will the photovoltaic panels make? How long will the gypsum board last? Can rubber be recycled?) one must supplement an embodied energy analysis with a life-cycle analysis (LCA).
A new office building is being constructed in a seismically active locality. For greatest efficiency, where should the lateral steel bracing be inserted relative to the primary structure (columns and beams)? Outboard of the primary structure In-line with the primary structure Inboard of the primary structure
In-line with the primary structure provides the most stability.
Types of security systems. . . .
CCTV: Closed-circuit television. Cameras record the premises for security. Types of cameras: conventional, thermal (for night vision), PTZ (Pan, Tilt, and Zoom cameras so you can cover a larger area while minimizing the number of camera installations), and domes (so the retail workers at the cash registers can't see where the camera is pointing) Access control systems: Restrict entry by pin, fingerprint, or biometric pattern identification system. Motion sensors: To detect movement with infrared rays. . . Active motion sensors send out radar and let the system know when something has moved. Passive motion sensors send out nothing but monitor with a thermal camera and wait for a change in heat (because someone who shouldn't be there moved). Don't tie active sensors to lights that illuminate the suspect, because windblown bushes, small animals, and even insects can trigger a false alarm, which are very common. Passive sensors can be tuned to be more or less sensitive so that human movements can be detected above a sensitivity threshold, but those of a raccoon won't trigger the system. Fiber-optic detection systems: a fiber optic cable is woven through a fence or wall. When the intruder climbs the cable shakes and the alarm sounds. Some of these systems can only be applied to securing the property perimeter (fiber optic detection system). Others can only be applied to securing access at doors (fingerprint access control system). Some can be used for either securing the perimeter or securing access (CCTV).
Which systems are so clumsy or inefficient that you can eliminate them straight-away?
Direct expansion (DX): noisy, expensive, facade-ugly Multi-duct: use too much building volume for duct work Dual duct: inefficient-heats and cools air and then mixes the two to get to the right temperature Swamp cooler: low-energy, but brings unwanted humidity into the space
Raised access flooring system
Raised access flooring systems float floor tiles on pedestals over a 12in to 24in hollow cavity. Conduit (and ducts) can then be flexibly run-and later adjusted-under the floated floor with relative ease. Obviously raised access floors increases the required floor-to-floor height.
Displacement ventilation
Displacement ventilation: mechanical cooling, supplied near the floor, with a little-bit-cold air brought in at not-very-fast duct velocities. This displaces the warmer room air near the floor and pushes it upward. Grilles in the ceiling suck out the warmer return air (also slowly). Because our skin is warm, naturally convective plumes form where the people sit, drawing warm air up toward the ceiling grille and replacing that air with the colder pool of heavy air near the floor. Benefits: uses less energy (smaller & slower fans, 65 degree supply air instead of 55 degree supply air, more hours available for the economizer cycle "free cooling" because 65 degree outdoor air can be brought directly into the space); is quieter (slower fans); and provides superior air quality (the stalest room air is the warmest, so the stale air hovers at the ceiling near the return grille, where it can be filtered and exhausted outside). Limitations: only works in rooms with high ceilings (minimum 9′); doesn't work with heating (so you'll need radiant baseboard heating for winter); doesn't do as well in humid climates (cooling air to 55 degrees removes more of the room humidity as condensation at the cooling coil than cooling the air to only 65 degrees); with high cooling loads, occupants can feel uncomfortable (with cold feet and warm head). Used for: high-occupancy rooms (lots of people so lots of stale air to be removed); theaters (tall ceilings, need quiet); cooler climates (popular in northern Europe)
Formula for Horizontal footcandles
EH = CP(Cosθ)/D²
Formula for vertical footcandles
EV = CP(sinθ)/D²
Concentrically vs eccentrically braced frames
Each provides lateral stiffness, but the eccentrically braced frame (bottom image) better protects the building in an earthquake.
When energy-efficiency is a priority: which HVAC system should you use?
Energy-efficient systems are (1) central chiller and AHU systems with fewer compressors and fans to run, (2) renewable systems like active solar where the sun heats up hot water that, in turn, moves through a thermosyphon piped loop, (3) waste-heat-capturing systems like variable refrigerant systems (VRF) (ductless minisplits are an example of VRFs) and systems that circulate leftover heat from a hot water heater or other combustion process to a pool or radiant floor, (4) systems that leverage the temperature outside or underground like economizer cycles that allow us to use cold outside to air-condition for "free" or geothermal systems that allow us to use mild temperatures underground, (5) dedicated outdoor air systems (DOAS) that allow for fresh air in separate ducts so we can turn off the AC while still maintaining air quality, (6) all-electric heating systems (A/C is almost always all-electric anyway) in municipalities where electricity is generated with renewables, and (7) radiant and displacement ventilation systems that allow us to lower the thermostat in winter and raise it in summer while maintaining the same level of thermal comfort, like radiant floor heating, radiant ceiling cooling, old-fashioned radiators, chilled beams, and displacement cooling with from-the-floor slow air.
When thermal control is prioritized, like if each hospital room, dorm room, hotel room, or apartment needs to set its own thermostat and some rooms need heating and some need cooling and some need neither. . . at the same time: which system should you use?
Fan coil units, ducted systems with variable air volume (VAV), and variable refrigerant flow (VRF) systems like ductless minisplits Direct expansion (DX) systems (like window units or through-the-wall systems with a compressor in each room) allow for thermal control, but are unlikely to be used because they are inefficient, loud, facade-ugly, and expensive to maintain.
Fire wall vs fire barrier vs fire partition
Fire wall: most stringent-you essentially build two different buildings, structurally independent of one another. Separates two construction types or two different areas. Extends from foundation through roof. Fire barrier: more common-extends from floor to underside of structural ceiling and does not need to be structurally independent. Required for mechanical shaft walls, egress stair walls, separated uses, and incidental uses. Fire partition: least stringent-can be made out of wood and can include a dropped ceiling (doesn't have to extend to the deck above). Required for corridors.
Floor cellular raceway systems
Floor cellular raceways provide both the metal part of a concrete slab's structure, the floor pan, formwork, and the wire management in a single proprietary product.
Why does the advantage of chilled beams overwhelm the inertia of the entrenched air systems in lab buildings.
For air quality reasons, labs can't recirculate their air. If chilled beams are used in lieu of a ducted air system, we no longer have to exhaust that perfectly good 70 degree room-temperature air and replace it with 100% outside fresh air that needs to be mechanically cooled all the way from 90 degrees. Instead, when the thermostat calls out, "more cooling, boys!" we can circulate chilled water to the chilled beams (radiators in the ceiling that look like this). This is a much less wasteful regime, and there's no worry about your aerosolized lab spill being blown through all the rooms of the building because there's no recirculating ducted air needed for cooling. (Some small amount of ducted fresh air is still required, but those duct sizes are often small and they never siphon bad air from other rooms.)
What do we use geotextiles for (name every use you can)?
Geotextiles, which may look like a woven mesh or like a plastic tarp, can be buried to strengthen soil (e.g. for foundations), stabilize soil (e.g. for parking lots and roads), separate different strata of soil (fine-grain aggregate from coarse aggregate), prevent erosion (e.g. along a stream bank), keep out weeds (in a garden), keep water out, allow water to filter through, or seal soil to keep contaminants in. . . or out (e.g. for landfills).
Put these in order from highest sound transmission loss (TL and STC) to lowest sound transmission loss:
Grout: robust sound barriers are massive. Because of the mass of the grout, this barrier serves as an effective barrier to low-frequency sound, so it can, for instance separate a mechanical room from a conference room in a way that a lighter-weight stick wall (even one with the same STC value) is not able to. Perlite/Vermiculite: the puffy Perlite and Vermiculite do a bit to absorb sound as it passes through the barrier, but not much. (Puffy, fuzzy things, when they are mounted at the face of surfaces, influences room acoustics-how the person speaking sounds to the listener inside the room. That requires a different discussion than the TL/STC and airborne sound isolation.) Air: Not as good at keeping sound from the next room out (though a CMU wall, even one with only air in the cavity, is still a robust barrier relative to less massive stick-built partitions).
What is the "soft story" solution?
High first floors with slender columns doesn't always bring about a soft story first floor. The problem arises when the columns are the primary resistors of lateral force. Add columns Add bracing Add external buttresses
Shear (pin) vs Moment Connections
In steel, you can recognize a shear connection because (generally) the beam web is bolted or welded to the column, but the beam's flanges are not. Shear connections resist gravity, but don't do well in the presence of lateral forces like wind and seismic. They therefore need additional lateral resistance from cross bracing or a shear wall (rigid lateral membrane) so that a hurricane doesn't push over the pin-connected structure. The nomenclature can be confusing: shear connections need a shear wall (or cross-bracing) to resist lateral forces. Importantly, shear walls or cross-bracing are not required everywhere—only in a few of the structural bays. By contrast steel moment connections (generally) bolt/weld both the flanges and web to the column and resist both vertical gravity and lateral wind/seismic. They can handle the hurricane without the benefit of shear walls or cross-bracing. The additional cost of attaching the flanges doesn't feel like it would amount to that much extra in a building's budget, at least not relative to the extra cost of cross-bracing or building a concrete shear wall. But given the skill-level of the structural steel trades, and their location high atop steel structures exposed to the elements, the extra cost of moment connections (bolting the flanges to the beam) is surprisingly significant. Plus, code life safety requirements often dictate a concrete stair tower that can "do double-duty" as the shear walls without extra cost. So most of the connections you see in the field when a steel beam meets a steel column are shear connections. . . which means that if the neighboring column were to jump out of the way, and there was no shear wall in the bay and no cross bracing in the bay, the beam would pivot downward. If the stair tower is constructed of concrete (or concrete block with enough reinforcing bar), it can double as the shear walls for the building, resisting lateral wind and seismic loads and allowing the steel connections to be shear (pin) type.
Sketch a convective loop inside a wall cavity
In wall cavities of widths greater than 4in, a convective loop forms as air naturally rises up the warm side of the cavity and falls along the cold side. This acts as a short circuit of the thermal barrier, accelerates the transfer of heat from inside to outside, and cancels (or even reverses) the thermal benefit of the cavity. This is especially acute in tall cavities in cold climates. Note the role of radiant heat exchange across the cavity, as the warm side "sees" the cold side and transfers its heat by electromagnetic energy. Note also the role of conductive heat exchange across the solid elements of the wall The physics of a cavity wall suggest conduction, radiation, and convection are all going on simultaneously—but for simplicity, we typically measure heat transfer through the wall in equivalent conduction terms (R-value).
To quiet a mechanical system: put fibrous insulation inside the duct or outside the duct?
Inside the duct Interior duct insulation (typically 1″ thick) is remarkably successful at quieting fan noise. There's nothing as effective. Lining the outside of the duct does nothing acoustically (but will keep the air colder (or warmer) over long distances, so can help with thermal control, efficiency, and preventing condensation on the outside of a cold duct). Building scientists harbor concerns that the fibers in interior duct insulative lining may deteriorate, loosen, and be carried down the airstream to our lungs (likely carcinogen).
When given a choice on the exam, how do you decide the relative cost of design decisions if you don't have experience in this realm?
Labor is likely the deciding factor, especially if that labor is technical or specialized. That's why the screen that you are looking at now was assembled overseas. This Forbes article claims that an iPhone made entirely in the US would cost $50,000!
What building type is most associated with chilled beam technology?
Labs are most associated with chilled beam technology. Chilled beams have nothing to do with structure. Rather, chilled beams are to cooling as radiators are to heating. They are cold surfaces in the ceiling, made so with circulating water from the chiller. They cool the air through convection and cool the occupants through radiation. Common in Europe, chilled beam technology has been slow to gain widespread popularity in the US, probably because it's complicated to install and operate, or maybe just because air systems are entrenched in the minds of MEP engineers, architects, and building owners. There is, however, one building type where the advantage of chilled beams overwhelms the inertia of the entrenched air systems: Labs, especially lab buildings in warm climates. Chilled beams, because they don't rely on moving around streams of (contaminated) air for cooling, offer an energy-efficient solution.
What is an impact load?
Load of short duration, like a large tree limb falling on a roof.
A larger room has a _______ reverberation time than a smaller room. Longer or Shorter
Longer Large rooms, rooms with fewer surfaces, and rooms with harder, smoother, less-fuzzy surfaces are more reverberant (sound lingers longer after it is suddenly stopped). The more reverberant the room, the longer the reverberation time, measured in seconds. Rooms with unamplified speech, amplified speech, and amplified music generally want to be less reverberant: they want to be smaller, with fuzzier surfaces. In contrast, rooms for unamplified music, like concert halls, generally want to be more reverberant: larger, with harder and smoother surfaces.
Geothermal system
More efficient because it uses the moderate temperature of earth to heat or cool water for the refrigeration machine
You are designing a high school football stadium with an elevated drum major platform at 24″ high. Do you need a railing? (A drum major is the member of a marching band that directs the others in the band.)
No railing required for heights below 30 inches. Railings would (probably) be required for a drum major platform-or deck, walkway, or any floor-above 30 inches. Exceptions that don't need guards: the loading side of loading docks and the audience side of performance stages
Should crawl spaces be ventilated or sealed?
Old thinking: crawl spaces may be ventilated or sealed. New, evidence-based, thinking: crawl spaces should be sealed: treat them like (small) basements and think of them as part of the building's thermal enclosure. Underlay them with gravel, plastic sheeting, and a concrete slab to keep out groundwater, insulate the walls (but not the overhead plane), and heat/cool them just like the house. Before a renovation, this crawlspace had been the worst possible option. It was neither ventilated, nor part of the thermal enclosure: insulation had been on it's overhead plane, below the house floor. The room had a dirt floor, exposed to groundwater; the room required a dehumidifier all summer long. This photo captures the after-renovation crawlspace with plastic sheeting over the dirt floor, insulated walls, and an absence of overhead insulation.
The problem with lights recessed in the ceiling:
On the top floor with an unconditioned attic above, they offer an unwanted short-circuit path for infiltration (at their perimeter if unsealed) and thermal bridging (interrupts the cavity insulation). See here. Recessed lights can (rarely) be integrated with exhaust fans (see here) so that excess heat from the fixture is exhausted with the air we need to bring out of the building anyway, and because LEDs otherwise have a hard time shedding the heat they create. . . but you wouldn't want to blow supply air over your lighting anywhere you need cooling because who wants to warm air used for cooling? Unless special fixtures or construction techniques are used to box around the fixture in the cavity, recessed lights can ruin the fire rating of a ceiling. See here. On any other floor with an occupied space above, they offer an unwanted short-circuit path for noise (both airborne noise and impact noise from footfall).
What is the difference between passive and active radon mitigation?
Passive system: Caulk/sealant in foundation cracks and where the slab meets the foundation wall, and plastic sheet below the slab seals the building from the radon in the ground. Continuous, airtight plastic pipe extends from the sub-slab gravel straight up through the roof to allow an easy path for underground radon to escape without entering the house. No fan needed. Active radon mitigation: fan pulls air (and radon) through a continuous plastic pipe from below slab or crawlspace to the atmosphere, bypassing the building. We don't want the radon that is pulled out of the foundation to leak back into the building, so we seal the slab; we put the fan in the attic or anywhere else outside the enclosure; and we discharge the radon from the pipe at least 10 feet from a window, door, or other opening (including doors and openings in adjacent buildings), at least 10 feet off the ground, and above the roofline, as close to the ridge as possible. Angle the pipe discharge away from any building surface to avoid moisture discharge or mildew build up on the building wall or roof. For new homes, a passive radon system should be installed (it's cheap, and if it needs to be converted into an active system later because of high radon levels, simply add an inline fan to the existing passive pipe in the attic). In areas of the country with high radon levels, new homes should have an active system installed from the beginning.
What is automatic dimming?
When the sun emerges from behind a cloud, photosensors in the ceiling automatically dim the electric lights, especially those near the window, to save energy. Dimming is usually associated with offices because they are occupied during the daytime and have relatively constant light targets.
Put these in order from most effective insulation to least effective insulation:
Perlite/Vermiculite: most insulative. Perlite and Vermiculite are puffy rocks that have air pockets for thermal resistance, and because they are rocks, they can be exposed to moisture without significantly degrading. Air: more insulative than grout! Air molecules sit farther apart from one another than grout molecules, so air conducts heat more poorly than grout (which is a good thing when using empty cavities in cold climates). Grout: pourable and cementitious, grout serves as surprisingly poor insulation, until you remember that all dense cementitious materials serve as poor insulation.
An architect is looking to reduce the cost of ductwork in an open-plan office. Which is a viable approach? Economizer Geothermal Plenum Dual-duct
Plenum To reduce the cost and building volume associated with return air ductwork, in open-plan offices we often run a single large return air duct into the "plenum" space above the dropped ceiling and below the structural deck. If a duct is analogous to a stream, a plenum is analogous to a lake. The entirety of the plenum is then suctioned so that a return grille can be placed anywhere in the grid and suck air back to the AHU through the plenum. In "displacement ventilation" systems, we also use a plenum for supply air.
Poke-through floor boxes vs floor cellular raceways
Poke-through floor boxes: Best for retrofits and renovations because the floor slab is already poured. The fifth floor open-office wiring is run under the floor slab, in the ceiling of the fourth floor. Then holes are bored for poke-through floor boxes with electrical receptacles and data jacks for the mid-floor desk. Floor cellular raceways: Best for new construction. The fifth floor slab is poured with a floor cellular raceway system integrated into it.
How do we best reduce the build-up of low-frequency sound in a room (for instance, rumble from mechanical equipment)? Specify materials with a low Noise Reduction Coefficient (NRC) or Position sound-absorbing materials near the corners and edges of walls
Position sound-absorbing materials near the corners and edges of walls. We call this a "bass trap." Low frequency sound energy-low tones from mechanical equipment like fans, transportation noise like trucks, and amplified sound like in da club—naturally build up around the perimeter and corners of a room. Sound-absorbing materials positioned near the corners and edges of walls absorbs more of that build-up.
What is a variable refrigerant flow (VRF) HVAC system?
Pumps and manifolds move refrigerant to spaces that need heating (high-pressure refrigerant gets hot); and pumps and manifolds move refrigerant from spaces that need cooling (low-pressure refrigerant gets cold). An in-unit fan blows air over the refrigerant coil in each space. Because we can simultaneously heat the perimeter while cooling the core-just by moving refrigerant between the two-this type of system can often be your lowest-energy option. The ductless mini-split system we covered is a type of VRF.
How can the "A" and "∆T" values be reduced in a building assembly? Given Q (heat loss in BTU/hr) = U (u-value of assembly) * A (area) *∆T
Reduce the area of the building skin by designing a similar-sized building in a more compact form Reduce the wintertime inside-outside temperature differential by lowering the thermostat. This can be done with a radiant heat source, or a conversation with the owner about wearing warmer clothing.
Which type of soil is more stable to build on? Clay or Sand
Sand Clay behaves unpredictably when it gets wet. It swells. Of course most soil boring reports detail a mix of sand and clay (and silt and gravel). It is then the proportion of clay that will determine stable soil.
A surface with an absorption coefficient of 1.00 is considered _______. Sound-reflective or Sound-absorptive
Sound-absorptive. Sound absorption coefficient measured for the surface of a building material (⍺), ranges from 0.0 (fully sound reflective) to 1.0 (fully sound absorptive). Most sound absorbing materials have ⍺ values greater than 0.5 and most sound-reflecting materials have ⍺ values less than 0.2
How can we shade windows?
South facing: deciduous trees, horizontal louvers, light shelves, shade with other adjacent building masses East- and west-facing: deciduous trees, vertical louvers, light shelves, shade with other adjacent building masses North-facing: shading not required
Causes of Seismic Failure
Strong beam, weak column perforated shear wall Re-entrant corner/Irregularly-shaped building Variations of perimeter strength and stiffness. discontinuous shear wall Soft Story
When quiet is a priority: which HVAC system should you use?
Systems with far-away central compressors and far-away central fans. . . or radiant systems with no fans at all.
When is tempered glass required? When is laminated glass required?
Tempered glass: 5x stronger than untempered annealed glass. Required at storefront door (or glass panel adjacent to a door) like this where the glass extends to 18″ above finished floor. Less likely to break if you back your rolling suitcase into it, or walk into it with your body accidentally. Shards are less jagged than untempered annealed glass. Laminated glass: stronger still and when it breaks, shards generally stay glued to the laminate like this. Laminated glass is required for skylights, and hurricane-prone regions, as well as security-sensitive rooms like prisons, mental hospitals, or casino cashiers. Laminated glass can also be used instead of tempered glass in glass doors and adjacent panels.
What shape offers both the best resistance to torsion and the least resistance to wind?
The circle offers the most resistance to torsion and the least resistance to wind. circular-cross-section columns offer higher resistance to torsion (think about twisting them from above) and circular building structural forms offer the highest resistance to torsion.
Position the vertical louvers on the east or west face so that the "cut-off" angle of each fin shades direct sun.
The geometry of the fins vary relative to the position of the sun (see the next card)
Thermal Bridging
Thermal bridging happens when structure short circuits the insulation and spans clear across the assembly, touching both the inside and outside. Thermal bridging is present, but not nearly as serious a problem, in wood. Concrete or steel offer more problematic paths for heat transfer.
Underfloor raceway ducts
They're called "ducts" in this context, but they carry electrical and data wires rather than air. They can sit beneath, or flush to, the floor. Expensive, disruptive, and not very popular anymore in favor of moving power in the ceiling below, under-carpet, or cellular metal floor raceways.
Vierendeel Truss
Truss without triangles-only right angles. Useful if you don't want angled truss components to interfere with windows, but for it to function as a truss, the connections at the top and bottom chords have to resist moment forces and are often beefy and expensive.
Under-carpet wiring system
Under-carpet wiring systems: imagine laying something that looks like tape, but is actually flat insulated electrical conductors aligned edge to edge. Only 0.03 inches thick, so you can't feel it under the carpet when you walk on it. Obviously the least expensive solution and obviously the one with the least impact on floor-to-floor heights. Doesn't work as well for large, complicated floors because with higher power needs comes the need for thick electrical boxes that can't lay flat under your carpet.
Air-to-air system
fan over condenser and evaporator
Air-to-water
fan over condenser, pumped water over evaporator
Evaporative cool tower
for cooling condenser water by blowing outside air over it
In which condition does an exit (stair) need to be pressurized to keep smoke out? Buildings made of combustible construction types (wood (Type V) construction) or Underground buildings
Underground buildings have stairs that must be pressurized. The egress path (the path for getting out in an emergency) has three parts, 1.Exit access (for simplicity, think of that as the corridor from the room to the stairs) 2.Exit (the stairs) 3.Exit discharge (door from the stairs to outside) We want occupants to be safe—or at least safer and more protected from fire and smoke-when they reach the exit (stair), even if they are not yet out of the building. One of the ways we do that, is to pressurize the stair with a giant fan at the top that is activated by the building's smoke detector. With the stair pressurized, smoke is less likely to fill the stair. This type of system is required in the following building categories: 1.In tall buildings--it takes a long time to walk down 100 floors, especially if others are joining you at each floor and clogging things up, and we need you not to choke from smoke inhalation on the way down. . . We pressurize the stair so it doesn't fill with smoke. 2.In underground buildings—you need to move up to make your way outside safely, but smoke rises, so we don't want you moving up to a too-smoky-to-breathe higher floor. . . We pressurize the stair so it doesn't fill with smoke.
When there's no room for ducts. . . you're renovating a historic building and there's no dropped ceiling to hide the duct work or you're building with low floor-to-floor heights so there's no room above or below for duct work: which HVAC system should you use?
When there's no room for ducts, use either (1) a hydronic system pumping hot and cold water around the building in small pipes instead of air in large ducts or (2) a variable refrigerant system (VRF) pumping high- and low-pressure refrigerant around the building in small pipes instead of air in large ducts. Piped (ductless) systems include: fan coil units or chilled beams served by a central chiller, fan coil units served by a central boiler, in-room evaporator/condensers served by VRF (like ductless minisplits) Rooftop package units (RPU) can cool the space directly below them without running duct work, but they are noisy, ugly when visible, and inefficient (it's cold on the roof in the winter and hot up there in summer) Attic or crawlspace insulation may be added, and high-efficiency equipment may be specified, to improve energy use without tainting the historic character.
The following diagram depicts a building plumbing system. The blue arrow points to a pipe that brings hot water back to the hot water heater from the rooms with fixtures (not hot wastewater, but hot potable water). Why would we want to return hot water to the hot water heater? It's more efficient (less heat loss through pipes) It's safer (less likely to scald children or others not able to effectively work the fixture controls) It creates less stress on the water pumps Water in fixtures gets warm more quickly
Water in fixtures gets warm more quickly Hot water circulates, especially in large buildings, to keep warm water in the pipes adjacent to fixtures so occupants don't have to wait for the column of hot water to make it all the way from the hot water heater to a distant fixture. This arrow points to a hot water return pipe that brings hot water back to the basement where it is reheated and recirculated, even when no one is running a fixture in the building. In this case, the circulation is maintained (slowly) by natural convection as the hottest water rises and not-as-hot water sinks in the pipes. In some buildings, hot water circulation is instead maintained by an electric pump.
How do we bury conduit into concrete structure?
We can run steel conduit inside concrete slabs. They are placed in the bottom half of the slab (in section) to help with tension the way that rebar runs in the bottom portion of spanning horizontal concrete. The top of the conduit sits below at least ¾ inch of concrete covering and parallel conduit runs must be spaced, O.C., a distance at least three times the larger conduit outside diameter. Conduits cross at right angles. We can also pour a non-structural concrete topping over the structural slab and nestle the conduit into the topping.
When given a chance, how do you decide what is the least expensive construction technique?
What you see most often on construction sites is usually the least expensive option. OSB sheathing is more common, and less expensive, than plywood sheathing Plywood is more common as formwork, and less expensive, than insulated concrete forms (ICFs) Vinyl siding is more common, and less expensive, than wood siding Asphalt roadway is more common, and less expensive, than concrete as pavement. Brick and cobblestones are more expensive than either. . . gravel is less expensive than either. And so on. . .
We use plywood shear walls in wood construction to resist lateral forces in the two vertical dimensions (X-Z and Y-Z planes). How do we resist lateral loads in the horizontal (X-Y) plane?
Wood diaphragms, usually the kind of plywood or OSB panels over joists or rafters that we need for gravity loads anyway in our floors and roof, also double as our "resister of lateral loads" in the (X-Y) plane. Think of them as shear walls turned on their sides to be horizontal. Most wood-framed floors act as diaphragms, whether they were intentionally designed as such, or not.
Surface metal raceways
You've seen surface metal raceways on walls (they often have a metal back but a visible plastic-not metal-cover). They can be mounted on floors too. Don't specify these on floors unless you like to trip your occupants and want to ensure floors aren't cleaned properly. They are only specified when sufficiently out-of-the-way of everyday foot traffic.
Are wind loads higher at the top of tall buildings?
Yes, wind speeds increase with the height above the ground (but gustiness—circulation of wind in eddies—decreases with height). Wind is notoriously difficult to account for in tall buildings. The high pressure (windward) side takes on a "pushing" lateral load, while the low-pressure (leeward) side takes on a suction pulling load in the same direction. This can cause the building to "gallup," vibrate, and sway in ways that prove unnerving for occupants in higher floors. The downwind pattern formed by the building's disruption of wind flow, called "vortex shedding," can create a force perpendicular to the wind direction and dislodge windows. To limit the structural impact of winds on a tower, soften the corners in plan (rounded or chamfered, rather than right angles), taper or set back the building plan as it rises, twist the building as it rises, provide large apertures in the building's windward face that allow the wind to pass through at some floors, or position a heavy damper in a top floor to counteract the natural vibration of the building.
You're designing a renovation of a post-tensioned concrete building. Why is it difficult to simply drill a hole in the floor to run a new vertical pipe?
You could inadvertently core through one of the post-tensioning cables! It's not that unlikely as you might think- there are lots of hidden cables to accidentally cut
Ceiling raceways
also sold as proprietary systems called "manufactured wiring systems": run the power to the third floor open-plan desk through the ceiling of the second floor below it. Then install a poke-through fixture. Expensive because of all the drilling through the floor, and in retrofits, this might inconvenience the office tenant, below, but is a smart out-of-sight solution if you didn't install a floor cellular raceway when the building was constructed, don't like carpet, and hate the hollow thump of raised access flooring
Split system
condenser outside, evaporator inside (residential)
Room Cavity Ratio
he tall skinny room has a HIGHER room cavity ratio (2.5 x total wall area / total floor area) and a LOWER coefficient of utilization (percent of light available in the room reaching the work plane) The short wide room has a LOWER room cavity ratio (2.5 x total wall area / total floor area) and a HIGHER coefficient of utilization (percent of light available in the room reaching the work plane) We use room cavity ratio (RCR), in concert with the color (reflectivity) of the room's surfaces, to determine the coefficient of utilization (CU). We use CU to determine how many light fixtures we need in a room to sufficiently illuminate it. CU is part of a formula given in the reference material available under the electrical tab in the exam.
Condenser
high-pressure hot refrigerant
Variable vs constant cooling coil & variable vs constant ducted air speed & variable vs constant fan & variable vs constant pump
how much control over the rate of flow. Variable generally offers more comfort control and more energy-efficiency, but more complex equipment
It's wintertime, it's been a rainy month, and there's moisture inside the parapet structure. The building includes an arboretum. This can most likely be best addressed with _______. Insulation Rain barrier Vapor barrier Ventilation
insulation
Direct expansion (DX)
like a window unit; with all cooling components including refrigeration machine and fan in one box
Chilled beams
like radiators for coolth; measures are required to prevent condensation
Air-handling unit
located down the hall, cools air for delivery to the room via ductwork
Fan coil unit
located in the room, cools air by blowing it over pipes filled with chilled water from a chiller
Where should I locate a "vapor barrier?"
on the warm side of the insulation, right up against the insulation. This is a complex question and one that the ARE doesn't yet understand the nuance of, because building scientists no longer use vapor barriers in assemblies to stop all vapor out-bound migration, but instead use vapor migration as a way to dry out assemblies that have become wet. However, if you see this on the exam, assume that your goal is to keep vapor from migrating out and locate the vapor barrier on the warm side of the insulation, flush to the insulation. For a warm climate that means place the vapor barrier on the outside face of the insulation For a cold climate that means position the vapor barrier on the inside face of the insulation What if you have a mixed climate, like most of us do, with warm summers and cold winters? The ARE doesn't seem to know what to do in that scenario, so that is unlikely to be encountered on the exam. To learn more, read on. . . These enclosure questions are by far the most common questions I get from those in practice—and for good reason, because enclosure is the most labyrinthian area of building science, and among the most complex. Your building skin will need to (in order of importance) Keep out rain: rain control layers Keep out outdoor air: air control layer Keep out cold/heat: thermal control layer Dry out when the assembly gets wet (and throttle the rate of vapor migration into the cavity, but contrary to popular opinion among those in our field, providing for vapor out-migration is more important than preventing vapor in-migration): vapor control layer Sometimes more than one of these functions may be handled by a single material in an assembly, and sometimes more than one material in an assembly is responsible for a single function.
Compressor
pump that circulates refrigerant
Water-to-water
pumped water over the condenser and a different pumped water system over the evaporator
Water-to-Air
pumped water over the condenser, air over the evaporator
Minisplit
refrigerant flows through units in rooms under high pressure for heating and low pressure for cooling; can heat and cool different rooms simultaneously.
Chiller
refrigeration machine for cooling chilled water in large buildings. Includes refrigerant moving through the condenser, compressor, evaporator, and expansion valve and the water that interfaces with the evaporator (and condenser)
Swamp cooler
uses evaporation of water for cooling, with a fan, for very dry climates only
