Design HVAC for Modern Office Facility

Much like office practices and workflows, modern offices are changing. They are designed to be more open than in the past, which consisted of a ring of private cabins or offices surrounding clusters of cubicles in the centre of the office floor. The open plan design calls for alternative considerations for heating, ventilation and air conditioning, or HVAC duct design.

Cubicles are increasingly replaced with workspaces created for specific activities, such as team lounges, fitness centres and large work tables for discussions and collaboration on team projects. The HVAC system consumes a significant portion of all energy needs in a building, and changes in the office layout will impact the HVAC design. Thinking and planning for HVAC design in an office space needs to begin as early as possible when considering renovation or a new project to save energy costs.

Design goals for office buildings are based on the fundamental principle of ensuring health and safety to those occupying those buildings. Ventilation, therefore, is required at all times and must eliminate or minimise pollutants. The measure of air flowing in or out of a space is cubic feet per minute or cfm. Generally, a person needs up to 30 cfm of outdoor air, and an ideal comfortable temperature is between 20 and 24ºC with 20-60% relative humidity. The efficiency of HVAC systems design makes these conditions possible.

Some of the key strategies for efficient HVAC systems design in modern offices include:

Reduction of Cooling Loads

Well insulated walls, floors and windows are a must. The use of natural light for a healthier workplace is becoming increasingly accepted as the norm and for the reduction of heating loads during the winter season. For warmer climates, tinted low-e glass can help avoid solar gain (solar heat gain or passive solar gain), which is the increase in thermal energy resulting from the absorption of solar radiation, and reduce cooling loads. Low emissivity glass, or low-e glass has a super-thin transparent coating that reflects infrared energy or heat. This glass minimises both ultraviolet and infrared light passing through it without affecting the visible light that is transmitted.
Lights that automatically switch off during sufficient daylight conditions are a useful energy-saving idea, which can work as a complement to cooler lighting options and will generate less heat, thus reducing cooling loads on the HVAC system.

HVAC System Size

It’s important not to install an HVAC system that is too big for the energy needs of the office concerned. Oversized air conditioning systems typically create discomfort during the day. Such systems generally switch on and off continuously and are not efficient in removing humidity, resulting in an office area that is predominantly humid and dotted with hot and cold spots. More than just square footage needs to be considered in calculating HVAC load requirements. Computer simulation can accurately analyse building materials, daylight, lighting design and space activities affecting HVAC loads.

Zones

Multiple zones with independent temperature controls within a large open space translates to greater efficiency and comfort. Different areas in open spaces have different temperature requirements, such as:

• Perimeter areas, which need separate controls, as they are more susceptible to weather
• Computer rooms, which have special temperature needs and controls
• Conference rooms and other areas that host large gatherings of employees, which need more cooling while in use and less when empty 

Modern offices with fewer internal walls make these design details tricky.

Sensors
Smart buildings use sensor technology, mainly with two types of sensors – light sensors and occupancy sensors. These can be incorporated with HVAC design early in the design stages. Light sensors sense the amount of daylight available and adjust lighting accordingly. They can be connected to the HVAC system to maintain heating and cooling. Occupancy sensors track the number of people in a given space at a given time. They communicate with HVAC controls to regulate temperatures. During a large meeting, for example, occupancy sensors help increase cooling for the area concerned.


A ‘Sensible’ Option
Environmental sensors lead to cleaner, healthier air. Sophisticated sensors provide real-time data on air quality, revealing the surprisingly unhealthy current conditions of most offices worldwide and a related reduction in productivity. Studies show that a 670-sq ft office with 15 employees can generate CO2 levels of 1,000 parts per million (ppm) in under 8 hours. This is equivalent to 2.5 times atmospheric carbon dioxide levels and at a level that may cause 15% decrease in cognitive performance in employees. Meeting and conference rooms, naturally, are even worse, with 3,000 ppm, significantly decreasing productivity.
Organic compounds from furniture and carpets combine with these high levels of carbon dioxide to increase fatigue in employees and decrease productivity. In some cities, windows cannot be opened due to the toxicity of the smog outside. Indoor air quality could be improved with HVAC systems that react to carbon dioxide and airborne particles. This could be achieved by pulling in fresh air and filtering out pollutants.


Under-floor Air Distribution
Typically, air conditioning cools a space using overhead air distribution. This method may not be ideal and less energy efficient in open spaces with high ceilings. Use of under-floor air distribution is a popular trend today. Diffusers are installed under a raised floor, transmitting cool, air-conditioned air throughout the space. Stratification moves warm air upwards to the ceiling and cooler air-conditioned air replaces it at ground level. This method has been found effective in providing continuously comfortable conditions and maintaining better air quality.

Ventilation
An effective HVAC design must control humidity, eliminate odours and remove dust, carbon dioxide, bacteria and viruses that may contaminate the space and spread illness. In an open-plan office, this is critically important. The correct indoor air quality must be regulated and maintained for the well-being of employees and their productivity. Sufficient intake and distribution of outside air and the controlled circulation of conditioned air is a mandatory requirement of efficient HVAC design.

Experts’ Design
Whether renovating or creating from scratch, professionals from the field, such a HVAC mechanical engineering consultants, must be taken on board right from the early stages to avoid costly errors at later stages. Consultants will utilise their professional HVAC design and drafting skills to produce high quality HVAC shop drawings, which can then be coordinated with other trades.

Open Windows
Decades ago, offices had windows that could be opened. Currently, most offices worldwide are air conditioned and air tight. Windows that can be opened help control energy consumption and give people greater control over their work environments. But skyscrapers with offices don’t have windows that open or have access to fresh air during a work day. Why? Well, some of the reasons for permanently closed windows are:

1. To prevent cooled, air-conditioned air from escaping and unfiltered air, noise, rain and insects from entering
2. That offices are wary that people may fall out or jump out, resulting in the offices and management being held responsible
3. That some employees may open windows on a hot day, making the air conditioner work harder
4. That in keeping with modern architecture, open windows are unfashionable and they disturb the lines of the building
5. That with many employees on any floor, natural ventilation is near impossible
6. That energy is saved, increasing productivity

Facts show that these concerns are no longer concerns. A naturally ventilated, intelligently designed office building can halve the energy consumption of constantly air-conditioned buildings. A naturally ventilated building need not support intense and constant HVAC system needs. Ventilation that is natural and access to fresh air contributes to an increase in productivity. A connection to the outdoors, a perception of control and better overall health are beneficial side effects of natural ventilation. The design of HVAC systems in an office facility thus has a direct bearing on the productivity of the office’s inhabitants.

With the help of qualified and experienced HVAC mechanical engineering consultants, a comfortable, safe and secure office building may be constructed with the right HVAC shop drawings. In the global environment of outsourcing MEP (mechanical, electrical, plumbing) design services, the quality, expertise and experience required can be found overseas, resulting in cost-effective, precise HVAC design and drafting.

The Challenges of Coordinating Risers

For modern buildings, risers carry the very life blood of a comfortable space. Much like an arterial system, different kinds of risers perform various necessary functions for the health of a building. They are conduits or carriers of fluids, fuel or air. Coordinating risers is critically important within the workflow of MEP coordination and clash detection, and this can be challenging at times. Challenges generally occur with hydraulic services design during renovation of older buildings. Let’s look at how that may happen.

Well, first off, what is a riser?

Also known as a vertical riser, a riser is a void that contains a duct, pipe or conduit or a combination of all services that rises through a building to carry or transport gases, fluids or electrical signals in the form of piping. In general, a dry riser is an empty, or dry, pipe used to carry water for firefighting systems, and a riser cable can deliver electricity or communications between several floors. Looking at risers in more detail, they can be:

1. Vertical Riser Ducts
As mechanical pipes and electric cables are aesthetically unappealing, typically they are hidden away in vertical riser ducts. These ducts must be strategically placed to minimise pipe lengths and cable runs, thus cutting costs. Pipes must run unhindered vertically in ducts, especially sanitary waste pipes, so that this waste water need not navigate bends in pipes. Since vertical risers cut through floors and can be vulnerable for the spread of fire, they must adhere to strict guidelines.

2. Vertical Riser Cables and Pipes
Sometimes, it is practical to have risers exposed. Servicing becomes easier. Cables connect to sockets and light fittings to riser conduits mounted on walls and columns. Cables and pipes that travel through floors are covered with fire-protected collars, to prevent the spread of fire through them. Increasingly, services pipes are becoming part of the décor.

3. Wet and Dry Risers
Vertical pipes, that are both wet and dry risers, run the full height of a building and are built near stairs to provide a direct water feed to each floor in case of fire. Dry risers have ground coupling pipes outside the building that can be connected to an external water source in case of emergency. Wet risers are connected to the building’s water supply.

4. Dry Risers in Fire Fighting
A dry riser usually includes the following:
Inlet Box

1. Made of galvanised sheet steel, for recessed mounting, with architrave
2. Has a hinged, lockable door with a panel glazed with wired glass, so that the lock can be opened after breaking the glass. 
3. Hoses can be connected to inlets without opening the door.
4. Large enough to access for maintenance and operate the drain valve

Inlet Breeching

1. A two-inlet breeching, with instantaneous male coupling, back pressure valve, blank cap and chain
2. Has a gunmetal gate valve for drain purposes, with plug and chain

Landing Valves

1. Straight or oblique gunmetal gate pattern valves, with flanged inlet, instantaneous female outlet with blank cap and chain, fixed with a leather strap and padlock
2. Lined and coated with woven synthetic fibre hose and diffuser branch pipe nozzle
3. Valve, hose and nozzle in a box, on purpose-made hangers

Air Release Valves

1. Brass automatic air release valve, with a rubber ball inside

For a tall building with the same floor layouts (e.g. apartments), the riser equipment/elements will change size as they move down or up the building. As such, a section of each riser will show slightly different sizes, especially for ductwork, which is why a drawing is created for every floor, even when the rest of the floor is the same.

With a variety of risers to deal with in the MEP (mechanical, electrical and plumbing) sector, it is crucial that the MEP systems coordination workflow, especially with regard to hydraulic design of liquid or water piping systems, is efficient. Technological advances and the innovations they enable have been a prime factor in fuelling this efficiency. In the construction industry, BIM (Building Information Modelling) has been driving immense change in the MEP coordination process and the delivery of MEP coordination drawings.

The use of BIM technology has made equipment tracking and task monitoring easier. Covering almost every aspect of a construction project, the BIM process involves project managers, subcontractors, designers, architects and other construction professionals participating in controlling individual processes and project phases, with a smooth exchange of information during the larger MEP coordination process.

Increasingly, the trend in the AEC (architecture, engineering, construction) sector is to design 3D models for 2D construction documentation and 3D trade coordination. Generally, the trade design or MEP design follows the architectural design stage. Trade professionals, such as HVAC mechanical engineering consultants and others, collaborate with architects to design mechanical, electrical, plumbing, fire prevention and fire protection services. A consultant or MEP contractor ensures that the MEP design is efficient, clash-free and installation-ready. At this point, fabricators who create ductwork or pipework components, electrical ladders or module sprinklers share their input. Thus, a fully coordinated 3D model is developed that can be used for clash detection.

Subcontractors (for the different trades) can virtually place systems as shown on detailed design drawings with individual elements, which include risers, offsets, hangers, conduits with required radius bends and cable trays. Other elements to consider include data communication lines, fire protection system controls and process piping.

At this point, challenges may arise, especially during the renovation of an existing structure. Some of the circumstances that may contribute to challenges in installation of risers include:

• Riser replacement in an existing building – opening up walls creates a mess, dust and debris throughout the premises and destroys expensive decorative finishes that were lovingly installed. In older buildings, asbestos can be destroyed, as well as lead-based paint that has peeled off.
• Existing plumbing risers may be difficult to handle after years of corrosion, because rust makes steel pipes brittle.
• As hot and cold risers behind kitchens and bathrooms are replaced, tiles, cabinets and walls must be removed.
• Risers must be replaced entirely or not at all, since new risers attached to old risers can break.
• Accessing risers takes time and money.

Signs that risers need replacement are hard to miss. Upper floors will experience low water pressure. Debris will appear in the water – bits of corroded pipe in sinks, showers and bathtubs. Time is an indicator. Galvanised steel pipes last for about 50 years, accumulating scale and rust inside, while brass lasts for nearly 70 years. Copper pipes last even longer. Coloured water is a definite indication of rust and scale accumulation. Also, excessively hot showers are a result of clogged plumbing risers that reduce the flow. The need to replace existing risers during renovation introduces different kinds of challenges for coordination.

- For example, during the renovation of an existing building, one of the chase walls was opened, and a large conduit was installed inside a duct chase against an exhaust duct riser, causing a clash in the planned duct connection. A coordinated model showed ductwork and risers in the limited space and how their placement could be manoeuvred to avoid the clash, guiding the fitting of components to meet the design requirements.

- In another building, the floor-to-floor height was 20 feet, generally enough for ductwork and piping from air handlers to central core chases. In this case, a chilled water piping that was routed only 10 feet above the floor and close to the AHUs (air handling units) and supply and return ducts, next to the shafts, made for difficult coordination. Ductwork from 2 AHUs had to pass above the chilled water piping and between hanger rods. Coordinated design drawings showed a more efficient duct placement.

- Yet another example involved duct and pipe routing between an existing main electrical room and adjacent AHUs. The electrical room had floor-mounted AHUs right outside, and the adjacent AHUs had disconnect switches and variable frequency drives (VFDs). Coordinated MEP drawings and 3D modelling showed that the chilled water piping to the electrical room AHUs had to be moved, as did the larger AHUs and VFDs, allowing the ductwork and piping to be placed with the correct amount of clearance.

Easing MEP Coordination
Forming a key part in setting up and laying out design, MEP coordination is a key means to connect building elements and make the structure functional. Earlier during MEP coordination, drawings were overlaid and compared and spatial and functionals interferences, or clashes, were dealt with by multi-trade professionals. This method needed countless revisions before the finalisation of the coordinated drawings, but BIM processes changed all that. The BIM workflow involves a 3D approach and data-based reasoning to help MEP contractors plan, design and install equipment, including risers, efficiently.

Using BIM technology, a once-prolonged and tedious process fraught with delays, insufficient data and miscommunication, is now smooth and efficient. A building’s MEP systems are seamlessly integrated and coordinated with architectural and structural systems, creating clash-free models.

The placement of elements of MEP design, such as risers, can be intelligently designed and laid out. Tools, such as Navisworks, enable clash-free designs, with multi-disciplinary integration in one work environment. Flawless MEP coordination drawings are produced.

The Revit Solution
Creating a 3D model with Revit software enables easy coordination during design, and clash detection can be performed with Navisworks. So, early on in the design process, the model can be coordinated with architectural design and MEP design that includes risers. The models of new buildings and those of existing buildings will have differing degrees of efficiency, since existing buildings contain unknown elements, spaces and conditions which may not be represented in models.

The good news is that with BIM-enabled MEP coordination, most of the challenges concerning the design, layout and clashes of risers in MEP systems is eliminated and smooth coordination results. Those firms that find it difficult to provide hydraulics and plumbing design services and MEP coordination services may consider online collaboration and outsourcing, which is efficient, accurate and cost-effective, for the delivery of precise MEP coordinated drawings as part of the hydraulics and plumbing design services and MEP coordination services. Managers can retain full control of the project, resulting in faster delivery.