The principal sources of noise in an air system are the fans, the duct distribution system itself, and terminal devices. Most fan manufacturers can readily provide a sound power spectrum for a particular fan operat- ing under a specific set of conditions.
With this information, the designer can select an acoustical treatment to reduce this sound energy to an acceptable level. The fan noises most difficult to remove are those in the lower octave bands.
Thus, sound attenua- tion in those bands is an important objective for acoustical treat- ment of fans with low-frequency characteristics such as centrifugal fans. Sounds in the higher octave bands will normally be absorbed in the duct distribution system, particularly if the ducts are lined. For quiet operation, fans should be selected for maximum static or total efficiency. In variable-air-volume systems, sound pressure levels should also be checked at minimum system flow condition if dampers, inlet vanes, or blade pitch fan control schemes are used.
In general, large fans at high static pressure conditions produce the highest noise levels. Noise and vibration can also be generated within and when exit- ing the distribution system by the movement of air or water.
These problems can be controlled by velocity limitations, appropriate dis- tribution layout, use of attenuators, and equipment selection. For piping design, see Section 5.
Several noise sources can exist within an air distribution system. In general, components with higher pressure drops will produce higher sound levels. A pres- sure-reducing device, damper, or pressure regulator located in a ter- minal unit may generate noise as the energy expended in pressure reduction is converted to sound. This is why oversizing of terminal air devices is undesirable. Pressure-reducing devices should be installed in the duct system with sufficient downstream ductwork to absorb the sound generated by the device.
Large terminal units with pres- sure-reducing devices should not be installed in occupied spaces without considering acoustical treatment downstream and in the radiated sound path from the terminal to the room.
Sound can travel through ductwork from one room to another. For example, an air-conditioning system that serves a series of music practice rooms will require ductwork with sound baffles between rooms, lined ducts, or ample duct turns to attenuate noise.
Noise control will influence duct configuration, size, and system static pressure. The sound produced by room terminal equipment cannot be easily reduced. Control of this potential problem starts with system selection and entails careful equipment selection and sizing to achieve the noise criteria for a given conditioned space.
The more moving parts in a terminal, the noisier it will be. Air-cooled unitary terminal equipment is likely to be near the high end of the noise scale.
Water-cooled terminals, including water-source unitary ter- minals, can be significantly quieter. Air terminal equipment, in ascending order of noisiness, include air diffusers, variable-air-vol- ume boxes, fan-coil units, high-induction-ratio terminals, and pack- aged terminal air conditioners. Continuous terminal noise is usually less annoying than intermittent or alternating noise. Terminal equipment, because of its location, provides the few- est options for acoustical mitigation.
The solution is essentially in the selection of the equipment itself. Greater opportunities for noise control through attenuation e. Air ducts passing through adjacent rooms can be transmission channels for cross-talk, as can unsealed openings around ducts or pipes. Cross-talk through such paths can be controlled through building design. Occasionally, partitioning will be located so as to divide a room terminal or outlet.
This creates a virtually uncontrollable path for sound transmission between rooms. Different prod- ucts vary in their acoustical performance. Often such equipment is not acoustically rated, at least not on a basis that permits compari- son with other equipment using catalog data. When in doubt, con- sider visiting operating installations or arranging for prototype testing to ensure that the design objectives can be met.
Vibration from fans, pumps, refrigeration compressors, and other moving equipment must be kept within tolerable levels. As in the case of sound, degrees of satisfaction vary depending upon the function of an occupied space. Extraordinary precautions must be taken to protect sensitive areas, such as those housing electron microscopes or research animal colonies.
Vibration from imbalanced forces produced by a fan wheel and drive, unless suitably isolated, will pass undiminished into the structure and be transmitted to occupied spaces, where less stiff building members centerpoints of structural spans, windowpanes, a chandelier in a ballroom may respond with noticeable secondary vibrations. Every member of the building design team must contribute toward achieving a satisfactory acoustical including sound and vibration environment.
Local systems include window air conditioners, packaged heat pumps, and unitary or water-cooled packaged units without central source equipment. Centralized equipment requires a few large spaces, while decentralized equipment requires smaller spaces per equip- ment unit but more of them.
Central boiler and chiller plants use industrial or large com- mercial-grade equipment. Such larger equipment is usually more efficient than smaller local equipment units. Major maintenance can be done in one location, away from occupied areas. The integration of heat recovery from one system to another is facilitated. A central system provides better opportunities for vibration and noise control since the major equip- ment need not be located in or near occupied areas.
Zone control is provided by terminal units, VAV or mixing boxes, control valves, or dampers, depending upon system design. Local systems can provide room or zone control without any central equipment, but this approach may be noisier, present more equipment service problems, and interfere with occupant activities in the spaces. Local stand-alone equipment is generally of lower quality, has a more limited useful life, and, in the case of room air conditioners and other unitary equipment, is often deficient in humidification and outdoor air control capabilities.
In some cases, it may be difficult or impossible to provide outdoor air for ventilation to stand-alone units because they are located remote from an out- door air source. Local cooling units require either air- or water-cooled condens- ers. They can be readily moved from one location to another if changes in building use require it. It is often simpler to relocate stand-alone units than to modify extensive duct and piping systems.
Stand-alone units, however, may have a great impact on the build- ing facade via numerous louvers connecting the condenser elements to the ambient air heat sink.
Nevertheless, local systems are com- monly used with a number of building types where fully indepen- dent control, low cost, and limited distribution networks are desirable and access to outdoor air is not a problem. A closed-loop water-to-air heat pump system see Chapter 7 involves individual refrigeration compressors, wherein heat is trans- ferred from units in the cooling mode to the water loop, making the heat available to units that may be operating in the heating mode.
While the coefficient of performance COP of an individual heat pump may not be as high as that of central equipment, a closed-loop heat pump system can be more efficient as a system on a seasonal basis.
These systems often require a supplemental boiler to supply heat when heating demand exceeds coincidental heat rejection from units in the cooling mode, and a cooling tower to reject heat when most units are in cooling mode.
A ground-source heat pump system Chapter 9 takes this interconnected looping concept a step further. Facility with computer- aided drafting software is becoming a prerequisite for many entry- level engineering positions. Familiarity with simulation packages is usually a plus when applying for entry or more advanced positions. The most common virtually universal use of computers in most design offices is for the production of drawings and specifi- cations.
In most offices, software programs are also routinely used to calculate design heating and cooling loads. Such programs are an important analysis tool and, for maximum utility, must have the capacity to handle a large number of thermal zones. Other multiparameter calculations, such as the sizing of ductwork and piping networks and the analysis of sprinkler loops, can also be handled by specialized software.
Many HVAC systems are selected based upon the past experience of the designer and the lowest first cost, not upon detailed energy studies combined with life-cycle cost analyses of alternative systems. This is not an acceptable practice for high-performance buildings. Codes are laws or ordinances or other types of regulations that specify government-mandated minimum requirements for certain aspects of the design and construction of buildings.
All states in the United States and all Canadian provinces have building codes. Many large US municipalities have promul- gated local building codes, which are generally stricter than or dif- fer in some respect from the state codes over which they take precedence.
The model code picture has changed recently with the promulgation of the International Building Code series of model codes, which is a collaborative effort of the afore- mentioned code bodies ICC.
It is becoming increasingly common for clients to require green building certification for selected projects, which will require the design team to address the U. Federal government buildings are not subject to state or local codes, but the designer must follow applicable regulations issued by the General Services Administration often referred to simply as GSA or the responsible federal department or agency. If state or local codes do not provide appropriate guidance, use ASHRAE or other suitable standards or guidelines to establish a good design practice benchmark.
Standard In its current form Standard Under the prescrip- tive approach, a designer follows a clearly defined methodology using explicitly stated performance targets for mechanical equip- ment, lighting, and building envelope assemblies.
If a designer wants more flexibility to employ innovative design strategies or make trade-offs between systems and strategies, the energy cost budget approach is available. Using this option, a designer simu- lates the energy performance of a proposed building design and compares it to the performance of a comparable building meeting the requirements of the prescriptive method.
Actual energy costs or utility rates in force at the location of the proposed building must be used in the calculations. If the annual energy cost of the proposed building design is no greater than that of the building as designed by the prescriptive approach, the building is deemed to comply with the standard.
The performance approach allows for greater design flexibility; this, however, requires much more design and analysis effort than the prescriptive method. Although originally written as a standard for good design and not as a legal document, Standard Since the standard is often updated more frequently than state adopting legislation, verify for each project whether a particular state energy code refers to the latest version of Standard As with building codes in general, several states notably California and Florida have developed their own energy codes that differ to some extent from Standard These codes take precedence over Standard Likewise, Canadian building and energy codes will generally apply in the Canadian provinces.
This standard has not been as widely adopted as Standard Standard provides energy efficiency guidance for design work involving existing buildings. An interesting recent trend has been an attempt to design to bet- ter-than-minimum energy standards often to obtain green build- ing certification.
It is good practice to follow the provisions of these model codes when local requirements are less stringent or do not exist. The developer of a speculative building is primarily concerned with first cost, and concern with operating costs may vary from minor to none.
On the other hand, an institutional client who expects to own and occupy a building over its entire useful life is frequently willing to accept additional first costs if these result in operating cost savings.
On many projects, the United States govern- ment requires a life-cycle cost analysis covering capital, operating, and maintenance costs and including the effects of interest and cost escalation. Industrial or commercial clients may want to know the rate of return on investment termed ROI. Using the methods and data generally assumed by the client for financial projections makes an economic analysis more applicable and avoids subsequent criticisms and objections relative to such necessary assumptions.
Regardless of the method of financial analysis used, annual costs for each air-conditioning system under consideration must be determined. For a realistic analysis, the costs of maintenance and repairs, which may be difficult to obtain, should be included in the economic analysis—especially if they are expected to differ substantially between alternative systems or equipment.
Frequently, manufacturers either do not have such information or are reluctant to divulge it. The Hartford Steam Boiler Inspection and Insurance Company has also collected much useful data related to equipment failure.
This indicator is sometimes used to determine whether a particular additional first cost is warranted by projected savings in operating costs. While the method is very straightforward, it ignores the time value of money interest or discount rate. It should be used only for periods not exceeding three to five years. It can be modified by discounting savings occurring in future years see below. Discounted Cash Flow. Revenues or savings and costs are calculated separately for each year over the assumed lifetime of a building, piece of equipment, or strategy.
They are then discounted and summed to a specified year, usually either the first or the last year of the analysis period. The discount factor takes into account the time value of money. The NPV is the difference between the present value of revenues and the present value of costs. It is the sum of all annual discounted cash flows referred to the first year of the analysis. The higher the NPV the more desirable a project, sub- ject to the initial cash limitations of the investor.
This is the discounted cash flow, including first cost, operating costs, maintenance costs, and any sal- vage value, usually referenced to the last year of the analysis.
Life-cycle costing is required on many federal government projects. Profitability Index. The profitability index is defined as the ratio of the net benefit to the net cost. This index normalizes the total benefits to a single unit of invested capital.
It is a useful concept for making choices among different projects when the amount of available capital for investment is limited. It is obtained by iterative calcu- lations once the cash flow stream has been identified. If the IRR is higher than that, the project will be undertaken; if it is not, the investor will balk.
After-Tax Analysis. An after-tax analysis includes the effects of taxes, particularly income taxes, on the financial aspects of the project. Levelized Cost. This method is generally used only by public utilities, since their rates are set based upon an allowable return on investment.
It does not usually apply to private sector analyses. Economic analyses may be performed either in current nomi- nal dollars or in constant dollars where the effects of inflation are removed. Constant dollar analyses are generally easier to use and, for that reason, are often preferred.
Many economists also believe that they yield a more accurate picture of the financial viability of a project. However, since certain tax items, such as depreciation, are always given in current dollars, after-tax financial analyses must be conducted in current dollars.
This rate may be increased to account for technological uncertain- ties or perceived risks. Full-service leases, including utility costs, are based upon this parameter. The rentable area may be defined in the lease, sometimes by reference to a standard, such as that of BOMA. Strangely, many leases fail to define the term, and it becomes defined by the established practice in an individual build- ing by default.
Significant disparity can occur among buildings in the same region. For an office building, the definition will vary somewhat depending upon whether a floor is leased to single or to multiple tenants. Toilet rooms, mechanical equipment rooms serving the floor, janitorial closets, electrical closets, and column spaces are included in the rentable area.
For multiple ten- ants on one floor, the term usually excludes public corridors, lob- bies, toilet rooms, mechanical equipment rooms, etc. Building construction costs are related to the gross area, whereas income potential relates to the rentable area. This ratio can be significant in the economic evaluation of air-conditioning alternatives. The air-conditioned area—which relates most closely to mechanical equipment initial and operating costs—may be similar to the single-tenant rentable area defined previously.
Construction costs, including mechanical costs, how- ever, are reported on the basis of gross building area. Therefore, if such cost information is to be used for budgeting of initial cost, gross area should be used to create a total construction cost model.
On the other hand, operating costs may be more realistically based upon rentable area. To some degree, a building's air-conditioning system can influ- ence the ratio of rentable area to gross area. While equipment located on the floor under windows may occupy otherwise usable space, this space is almost always included in the rentable area. Thus, no reduction in income results from the use of underwindow units. If air-conditioning equipment to serve each floor is located in a mechanical equipment room on that floor, such space may also be included in the net rentable area.
Compare this concept to a central system serving an entire building from a rooftop penthouse through supply and return duct shaftways. Due to the method by which rent- able area is defined, the penthouse and the shaftway space may be considered non-revenue-producing. Thus, paradoxically, even though more total building area and perceptually more valuable space may be used by locating equipment on the tenant floor than by putting it in a rooftop penthouse and using duct risers, the decen- tralized arrangement could result in more revenue and a better net return for the construction cost investment.
This is necessary for a detailed analysis of operating costs, and it enables the designer to look for ways to take advantage of the utility rate structure to decrease these costs. Sometimes advantageous rates can be negotiated with the local utility if special conditions exist such as off-peak loading resulting from thermal storage or an agreement to shed loads during times of peak demand. Most utility tariffs for nonresidential buildings consist of a cus- tomer charge, a demand charge, and an energy charge.
Few resi- dential tariffs include demand charges, primarily because of the relatively high cost of demand meters. The energy charge is an overall con- sumption charge per kilowatt-hour or Btu or cubic foot of gas used. It may be a flat charge or a decreasing block charge in which the cost per unit of energy decreases as monthly use increases or an increasing block charge in which the opposite occurs.
Some tariffs make the energy charge a function, among other variables, of the monthly demand. Some utili- ties calculate their monthly charges on a billing demand that is never less than a certain fraction of the highest demand during the previous 12 months called a ratchet clause.
Thus, a high air-condi- tioning demand during a particularly hot summer day may raise utility costs for a customer for an entire year. It is thus beneficial to investigate methods of avoiding simultaneous operation of high- demand equipment, if that is feasible.
Thermal storage see Section 9. Some utilities have even introduced them for their residential customers. Generally, rates are higher during periods of heavy use on-peak, daytime and lower during periods of light use off-peak, nighttime.
Some utilities reduce or waive their demand charges during off-peak periods. Thus, time-of-use or other charges may differ from summer to winter. Bauman, F. International Building Code. International Energy Conservation Code. Klote, J. Principles of Smoke Management. Washington, DC: U. Government Printing Office. Green Building Council. Such criteria should include space temperature and humidity, air speed surrounding occupants, mean radiant tempera- ture MRT , indoor air quality requirements, and sound and vibra- tion levels.
The selection of appropriate design criteria will be influenced by a number of conditions: the ages and activities of the occupants, the occupant density, and the contaminants likely to be present in the spaces. The physical character of the space can have some bearing on occupant comfort.
For example, surface temperatures of walls and floors can affect thermal comfort and influence the design space temperature. Assumptions regarding occupant clothing will influence comfort criteria. The designer must also consider economic parameters. A bal- ance frequently must be sought between optimum environmental conditions and system performance capabilities on the one hand and first and life-cycle cost targets on the other. Also, carefully consider the construction and operating com- plexity of the system concepts.
Design objectives will have but a slim chance of being realized if system design features reach beyond the capabilities or understanding of operating and mainte- nance staff assuming there is such staff. This point cannot be overemphasized and deserves serious discussion with both client and contractor at an early stage. The design, construction, and use of an occupied space, as well as the design, construction, and operation of its HVAC systems, will determine the extent of satisfaction with the thermal environment.
Not all individuals perceive a given thermal environment with the same degree of acceptability. It is important to remember that thermal comfort is more than just a response to temperature.
The standard establishes a comfort zone Figure for people in winter and summer clothing engaged in primarily seden- tary activities 1.
At the fringes, careful attention must be paid to the effects of the other comfort variables lest discomfort result from draft or MRT. As the comfort chart Figure indicates, RH does not have a significant bearing on thermal comfort in most situations as long as the space dry-bulb temperature is within the comfort range. RH, though, does affect odor perceptibility and respiratory health.
Maintaining humidity within this range during winter, however, is complicated by 1 energy use considerations, 2 the risk of condensation on windows and window frames during cold weather, 3 the risk of condensation within the exterior building envelope, and 4 the need to provide and maintain humidifying equipment within the air-conditioning system. The economic value of winter humidity control for occupant well-being is not always appreciated by designers.
Significantly reduced absenteeism among children, office workers, and army recruits as a result of winter humidification has been reported Green , If a higher humidity is acceptable under summer conditions, considerable energy savings can be realized, as shown in Figure Repeating this pro- cedure for a different value of RH yields the energy savings obtain- able by raising RH.
Be cautious, however, about choosing excessively high humidities. Air speed and MRT are environmental variables that will affect thermal comfort and can be used to enhance comfort potential while reducing energy use.
See Section 3. MRT can be thought of as the weighted average surface temperature of the surroundings. Summer energy requirements for dehumidification Dubin and Long Furthermore, the larger the control zone and the distance from occupant to controller and the more diverse the ther- mal load characteristics within the zone, the more the selected parameters affecting occupant comfort will vary.
The obvious desirability of individual occupant control of ther- mal conditions is usually compromised by the physical arrange- ment of a space, the mobility of the occupants, the inherent system capabilities, and the high cost of providing a temperature control zone for each person. The degree of compromise is an important design concern. A single zone one thermostat to control space tem- perature throughout a commercial building is not appropriate and will guarantee low occupant satisfaction.
This is especially true if the building is compartmented, as in an office building. The last alternative is often used in office buildings. For exam- ple, supply air terminals may be provided for each office module, but the perimeter heating system for an entire building or for sepa- rate exposures of a building may be controlled from a common point.
Attempting to both cool and heat a number of perimeter rooms with different solar exposures and potentially diverse thermal characteristics from a single control device is not recommended. This simplifies the system design and makes it less costly to install and operate. On the other hand, interior and perimeter spaces should almost always be on separate systems or control zones because of the disparity of their thermal loads.
Decisions regarding zoning requirements and the related cost implications must be resolved through the collaboration of the design team, the owners, and, if feasible, the prospective tenants. Appropriate zoning is critical to occupant comfort and HVAC sys- tem success. In addition to defining the size of temperature control zones, the degree of control desired has considerable impact on the selection of the air-conditioning system. These standards focus upon ventilation but also deal with filtration.
They do not expressly consider reduction of pollutants at the source. The term ventilation is often used to refer specifically to out- door air introduced into a conditioned space, not to the total amount of air supplied to the space. The definition of ventilation from Stan- dard When a quantity of ventilation air is specified, it typically refers to the outdoor air portion only—except in special cases defined in Standard The total amount of air supplied to a par- ticular space is generally determined by the cooling load require- ments of the space, subject to the minimum ventilation airflow specified in applicable codes or standards for that type of space.
Buildings are usually ventilated by supplying filtered out- door air through the HVAC system. Different HVAC systems pos- sess different capabilities to meet ventilation requirements. Natural airflow through open windows or through infiltration is the ventilation method of choice for many residences and other small buildings.
Such airflow is variable, however, and to a large measure hard to quantify and control. Cooling and indoor air quality systems designed to utilize natural ventilation are common in Europe, but they are rare in the United States. Mechanical venti- lation dominates design in the United States.
Local and general exhaust systems usually complement a ven- tilation system by containing and removing selected contaminants at the source, as is the case with a bathroom exhaust. It is common practice to supply sufficient outdoor air through an air-conditioning system to make up for air that is exhausted plus an additional amount of air to provide building pressurization to offset infiltra- tion. Energy considerations generally suggest that the ventilation air supply not be increased above the amount needed for dilution of contaminants, except to balance exhaust airflow and provide nomi- nal pressurization.
Large-scale infiltration is more effectively lim- ited by ensuring reasonable tightness of the building envelope. Ventilation is not the only means of limiting contaminant lev- els, and it should not be considered a cure-all. Filtration, for exam- ple, is discussed in Section 3. Source control, where practicable, is most effective. Building materials, such as carpet and wall cover- ings, should be selected for low emission of volatile organic com- pounds.
Physical containment or segregation of emission sources may be appropriate. Indeed, control of some sources may be beyond the capabilities of even a well-designed ventilation system. The objectives and capabilities of a proposed ventilation system should be understood by all who are concerned with the construc- tion and operation of the building.
Indoor air contaminants can be solids, liquids, or gases vapors. Some can be irritants or odiferous, thus affecting occupant comfort. People vary in their sensitivity to contaminants. Minute concentrations of certain fungi and other impurities can cause serious discomfort and impairment in sensitive individuals while not affecting most occupants. Standards for vapors specify a quantity of pollutant per unit volume of air, in parts per million ppm. The standards typically include all particle sizes—the total suspended particulate concentration TSP.
Large particles are filtered by the nasal passages and generally cause no adverse physiological response unless they are allergenic or pathogenic. Smaller, respira- ble suspended particles RSP are important because they can lodge in the lungs. Other contaminants found in outdoor air, such as nitrogen oxides and carbon monoxide, may have indoor sources as well. Most indoor pollutants, however, emanate from inside sources.
It also sets forth acceptable quality parameters for outdoor air used for building ventilation. If the outdoor air source exceeds the allowable contaminant parameters, it must be cleaned or purified prior to introduction into occupied spaces. An additional complicating factor in the buildup of contaminants is the variation in dilution rates and effectiveness of the ventilation deliv- ery systems often found in buildings.
Contaminant concentrations vary spatially as well as over time. These variations add further nonuniformity to pollutant concentrations. The standard offers the designer two procedures for determining the required ventilation rate—the ventilation rate procedure and the indoor air quality procedure. Unless unusual pollutants are present, these rates are intended to produce acceptable indoor air quality.
The basis for the occupancy ventilation rates is an underlying minimum outdoor airflow per occupant as a means of controlling CO2 to a concentration of ppm. Although CO2 per se is not a contaminant of concern at this low concentration, it is an easily measurable surrogate for other contaminants, such as body odors. The indoor air quality procedure offers an analytical alterna- tive, allowing the designer to determine the ventilation rate based upon knowledge of the contaminants being generated within the space and the capability of the ventilation air supply to limit them to acceptable levels.
Frequently, local building and occupational codes prescribe threshold limit values and ventilation rates. When high-efficiency air filters are installed in an air-handling unit, the total supply airflow helps control particulate concentra- tions within a space. Consequently, all-air constant-volume systems and, to a lesser extent, variable-volume systems , if equipped with such filters, can produce respirable particulate concentrations in the building environment that are lower than those achievable by sys- tems in which the supply airflow rate is solely limited to the ventila- tion rate typical of air-and-water systems.
Certain applications demand removal of gaseous contaminants present in the outdoor air or produced within the conditioned space. Harmful gases and vapors can be removed by adsorption or oxi- dization. Activated carbon is the adsorptive material most com- monly used in HVAC systems. Potassium permanganate impregnated into the carbon or an alumina base is used to oxidize certain chemicals for which carbon has limited effectiveness.
Air washers see Section 5. But such scrubbers need contin- uous maintenance to keep the recirculated water from becoming highly corrosive and the reservoir a breeding ground for biological contaminants. Rare-book rooms and valuable artifact display or storage areas in museums and archival depositories are candidates for gas removal provisions, but the operations and maintenance staff should understand that careful maintenance is required for effective performance.
Notwithstanding such gas removal provi- sions, the ventilation rate in these types of spaces should be main- tained at no less than 15 cfm [7. The standard further prescribes a maximum rate of air movement air speed of 30 fpm [0. That chapter of the Handbook describes different methods of room air distribution. It also presents a space air distribution perfor- mance index ADPI , which permits prediction of the comfort potential that can be achieved with a given supply air distribution design.
The higher the index, the more uniform the conditions of comfort as determined by temperature variation from a control value and air velocities at various locations in the occupied zone. Using the guidance of that chapter, a designer can develop air distri- bution layouts that are likely to maintain a high probability of ther- mal comfort. Therefore, ADPI predictions apply only if the average space temperature is close to that value.
Occupant comfort has been reported to suffer as a consequence of low total supply airflow in a space, even when the space tempera- ture is well inside the comfort envelope. Because of this, many designers have adopted a minimum total supply airflow benchmark of 0. These values are based upon an all-air system with conventional supply outlets. The standard provides dry-bulb, dew-point and wet-bulb temperatures; enthalpy; humidity ration; wind conditions; solar irradiation; latitude; longitude; and elevation for locations worldwide.
Standard also includes statistical data, such as mean temperatures; daily ranges; degree hours; and seasonal percentages within ranges of temperatures. Data and tables have been completely revised for the edition. The standard now includes climatic data for locations throughout the world, an increase of , as well as climate zone maps for major global regions. Data licensing information. Home Technical Resources Bookstore.
Mission: To serve humanity by advancing the arts and sciences of heating, ventilation, air conditioning, refrigeration and their allied fields. Vision: A healthy and sustainable built environment for all. The celebration included a ribbon cutting and remarks from special guests, donors, and President Schwedler. For a recording of the event and access to approved photos for download and use Click Here.
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