A manual for designing HVAC systems :

HVAC (heating, ventilation, and air conditioning) systems are essential to a building's efficient operation. They are in charge of continuously maintaining comfortable circumstances. M.Asif Shahid

A manual for designing HVAC systems

For four key reasons, HVAC systems are crucial to architectural design efforts.

  • First, during the design phase, it is important to account for the fact that these systems frequently need a significant amount of floor space and/or building volume for equipment and distribution components.
  • Second, for many popular building styles, HVAC systems are a significant budget factor.
  • Third, the effectiveness of thermal comfort initiatives is frequently directly correlated with the efficiency of a building's HVAC systems.
  • The operation of HVAC systems, which maintains proper thermal conditions, is the final key factor in building energy usage.


Evolution of the HVAC system :


The first stage in choosing an HVAC system is to identify and record the restrictions imposed by project-specific performance, capacity, space requirements, budgets, and other essential criteria. This typically begins with a formal consultation with an architect or owner to ascertain their needs.


Owners' Needs


If the client is a king and the architect is a creator, then the client's needs and demands must be fulfilled.


The building and its HVAC needs must be planned in accordance with the customer's objectives. Consider a multistory office building as an example. Either a single owner or several owners may be associated with the entire structure. A central plant is typically preferred by a single owner because the air conditioning is of a higher calibre and has a longer lifespan. In comparison to a floor-by-floor system, the expenses of operation and maintenance are also reduced. Additionally, owners have the option of choosing an intelligent structure by integrating a building management system (BMS).


This will make it possible for the owner to benefit from the air conditioning plant's optimal utilisation. A floor-by-floor air conditioning system using packaged units or split units is best suited for a property with many owners because it enables individual ownership and energy billing, subject to aesthetics and space considerations.

The user(s)' regular business hours are another crucial necessity. Some users might work different shifts or at different times. Some spaces, like computer rooms, can require air conditioning around-the-clock. There can be unique design specifications for other places. Many engineers choose a "hybrid system," which combines a central plant with packaged units/split units, due to the numerous requirements. For instance, a hotel might use rooftop units for meeting spaces and restaurants, packaged unitary air conditioners (or fan coil units served with an air-water central system) for the individual guest rooms, and a central plant system for the lobby, hallways, and other common areas. Such systems provide a great degree of flexibility in order to accommodate varying working hours and unique design requirements.

While the architect is in charge of the overall building design, the HVAC engineer is in charge of the system design. The HVAC designer's understanding of systems determines the sort of system used. The role of important system components, the types of systems that are available, and what these systems can and cannot do are all things that architects must be aware of. The majority of clients might not be aware of the advantages and limitations of HVAC design elements, thus it is the architect's and HVAC engineer's duty to advise on the best course of action. The building owner may be the architect's client, who may be the client of the HVAC engineer.


What factors affect HVAC design?


Over the course of the project's economic life, investment in a building project requires a substantial capital outlay and related expenses. The idea that building expenses only need to be incurred once is false. Buildings, like any other enterprise, have operating costs because they use a lot of energy and need water and disposal facilities, which adds up to a lot of ongoing spending. The HVAC systems are frequently very large and are accountable for a sizable amount of the construction and maintenance costs of a building.

Every structure is different. For instance, functional needs, occupancy patterns, and usage criteria vary between residential flats, shopping centres, office buildings, hospitals, hotels, airports, and industries. It is important to carefully consider the building's geographic location, ambient circumstances, internal requirements, building materials, dimensional dimensions, aesthetic requirements, noise levels, and environmental considerations. All of these needs must be taken into account while designing and choosing the HVAC system.


Each solution starts with an evaluation of the owner's company HVAC demands, the architect's vision, the facilities manager's requirements, as well as an examination of the HVAC system itself, whether it is already in place or is being developed.


Aspects of HVAC System Design


An important portion of a building's construction budget goes toward HVAC systems, which also consume a significant amount of the building's annual energy use, frequently require large amounts of space, and contribute to the interior environment that users and occupants of the building evaluate highly. Cost is a concern for everyone! However, the savvy client first establishes a list of prerequisites before entering into negotiations. Most of the time, customers merely consider price and ignore proper equipment and design specifications. The design of HVAC systems is primarily influenced by a number of elements, including but not limited to the factors listed below. The selection process may involve a chilled water system or a direct expansion system.


architectural specifics


Structure, direction, place in the world, altitude, shape, size, and height of the modules

  • The building's use, the area's classification, occupant numbers, and usage trends
  • Ratio of interior to outside zones, glazing, plant room seating, and distribution space for services
  • Climate, shading, thermal insulation, passive climate management, and relationships with neighbouring structures
  • Plant and system design to match the characteristics of the building and the necessity to satisfy 
  • the needs (known and unknown) of the eventual tenants. 
  • New or existing building, renovation or extension project, retrofitting or new equipment

building construction information

  • Materials and thickness of walls, roofs, ceilings, floors, and partitions, as well as their relative locations within the structure, as well as thermal and vapour transmittance coefficients, areas and types of glazing, exterior building finishes and colours, which have an impact on solar radiation, shading devices at windows, overhangs, etc., which lessen solar radiation and light transmission, and building mass, especially as it has an impact on thermal capacity
  • The need for sound and vibration control, and the proximity of air-conditioning equipment to sensitive regions
  • Coordination with other services (such as electrical and plumbing work), optimal utilisation of equipment rooms, ducts, and service shafts.

rules for buildings

Regulations of Public Utilities on electrical wiring, power usage, water supply, and drainage; Government and local regulations on occupancy and safety classification; Regulations of Health and Safety on Indoor Air Quality, Ventilation Air Quantities, Noise Control, Electrical, Fuel, Insulation, and Other Hazardous Materials
Regulations and smoke-removal systems from the local fire authority. Regulations from the insurance industry.

Additional Requirements

Location of fresh air intakes and exhausts (to prevent short-circuiting and pollution); Location of fire zones and fire walls (position of fire dampers); Accessibility for equipment installation and space for maintenance;
Indoor or outdoor equipment preferences - Acceptable noise level - Space available to store equipment and its location in relation to the conditioned environment - Acceptability of components obtruding into the conditioned space.

Construction aesthetics

architectural features of a space,
-Reflected ceiling plans: Integration of air distribution devices in the ceiling to complement the arrangement of the lighting, fire sprinklers, detectors, communication systems, and ceiling design. -Size and look of terminal devices.

System-related issues

Thermal Influence: Heat Gain from People, Artificial Lighting, Equipment and Machinery, Ventilation Air Load, Ambient Conditions (Dry Bulb/Wet Bulb Temperatures), Indoor Conditions (Dry Bulb/Relative Humidity) Requirements
Thermal comfort, indoor air quality, peak cooling/heating loads, partial loads, average load conditions, pattern of change, and system capacity are all examples of system behaviour.
The consequences of thermal capacity storage on load behaviour include sensible/latent heat balancing, load diversity, and system response.
Engineers often prefer to perform their calculations using psychrometric charts, which include the real vapour pressure, relative humidity, moisture content, specific enthalpy, specific volume (or humid volume), and dew point.
Hours that the system is operational;
Zone or individual control, system response and lags, allowable tolerances and time system, direct digital controls, operation sequences, and control logic are all examples of control systems.
Energy availability, level and pattern of energy use, system type, peak load and part load energy performance, variable speed drive, energy-efficient equipment, building management systems, economizer controls, and zoning restrictions are all factors that affect energy efficiency.
-Control and operational requirements, such as those for supervision, records, adjustments, and regulations, as well as for hours of operation, transitions between the summer and winter seasons, daytime and nighttime operations, high/low limit protection, frost protection, flammability protection, and special control areas (such as computer rooms and executive offices);
Equipment setup, spare and standby requirements, and redundancy Humidification/dehumidification requirements, air purity, special acoustic treatment, fire protection, and smoke management are examples of technological aspects. Water service: capacity, pressure, maximum temperature, chemical analysis (material selection), and water treatment; commissioning, testing, and fine-tuning of the finished plant to verify that it operates in every way according to plan. As components become more complex, packed, and thus less vulnerable to any kind of repair, it becomes an issue of increasing concern.


Budgetary Considerations

Cost of capital and operating expenses (fuel, power & water)
-Consumables and maintenance costs
cost of replacement
-The expense of upgrades
cost of equipment failure
Labor expenses
– Insurance fees
-Capital interest and depreciation
-Life cycle analysis -Return on investment (ROI) analysis


Conclusion

The risk managers and insurers of the owner/company frequently have an impact on costs. The secret to successful buildings is successful HVAC systems. The most important application factor is making the best pick of air conditioning services and system. This includes the architect's principal influence. It's critical to comprehend the functional needs, building envelope features, and ideal environmental conditions. Each solution starts with an examination of the HVAC system itself, whether it is current or planned, as well as an evaluation of the owner's business goals, the architect's vision, and the requirements of the end user.