Wits University exam venue gets CESA award-winning makeover

Contributed by the Maninga Engineering team

At the 2023 CESA Aon Engineering Excellence Awards in the category of Engineering Technology and Innovation – HVAC Building Systems Design Excellence; Maninga Engineering received a commendation for the Test and Examination Centre: Part 1 – Flower Hall for the University of Witwatersrand.

The new Flower Hall. All images supplied by Maninga Engineering

The Wits Flower Hall is located in the south-western corner of the West Campus and is currently being used as a test and examination venue. The Flower Hall was built to house the flower displays of the WITS Agricultural Society. The building was commissioned in 1969.

The University’s requirement was to free-up academic and office space for various schools in anticipation for increased enrolment of post-graduate student as per Wits 2022 Strategic Vision. Therefore, building an environmentally friendly building with a low carbon footprint without compromising end user comfort was essential.

The architects created a three-storey conversion which will initially be used as an examination venue. The mechanical solution was to accommodate dual use by the end-users while adhering to the University’s Urban Design Framework. The new first floor is a full floor and the second floor a partial ‘mezzanine’ floor. A new ‘south’ lobby was inserted into the first bay of the Flower Hall with staircases leading to the new floors. The existing steel glass curtain wall to the south façade was replaced with a new glazed curtain wall.

A further phase of building will see the conversion of the building for use as Engineering Research Laboratories.

Air-cooled chiller inspection and commissioning.

Maninga Engineering, as the appointed mechanical engineers, took the task of reducing the energy consumption of the building by using unconventional methods. The objective set out was to:

• Provide thermal comfort for the occupants
• Reduce operating costs
• Ensure energy efficiency
  • Prior to choosing a method of internal air conditioning, the cooling load had to be minimised to ensure that the equipment to be installed would not draw excessive energy. The building envelope had to be analysed and assessed. The following was done to reduce the cooling load:
    • Install clear glazing to shopfronts and windows
    • Install insulation to roof structure
    • Separate the circulation areas from the occupiable spaces
    • Recess the points of window installation – ensuring sufficient shading

The active chilled beams approach was chosen for implementation. The method used allows for modular partitioning. A building management system (BMS) controls the chilled beams. When the client decides to convert to laboratories, each group of four chilled beams has hardwired controllers, allowing each room to be at its predetermined temperature.

Active chilled beams act as a radiator cooled or heated by recirculating water from a scroll heat pump chiller. In the instance of cooling, the warm air would rise to the chilled beam and the cold air would flow down to the occupants; the water flow into the chilled beam is automatic and dependent on the amount of cooling required. The fresh air required in the space is distributed to the chilled beams through duct work, from a central air handling unit.

The air handling unit (AHU) not only serves to provide fresh air but also aids in humidity control. The chilled beam has a coil in which the heat transfer is conducted. The temperature control had to be carefully considered and catered for, so the air does not reach its dew point.

The chilled beam method is new to the continent and is in its early adoption phase. There are few installations noted in South Africa and Botswana. The Flower Hall installation is the biggest installation in Africa, with 138 active chilled beams installed in one space.

This solution is unique in that it is the largest of its kind to be installed in South Africa. It is automated and can adjust itself depending on the amount of cooling required.

The University’s objective was to ensure that the solution observes the health and safety of the occupants in the building. The success will be measured by the level of comfort, making the environment conducive to end-users.

HVAC System: Flower Hall Building

The Flower Hall has an adaptable system:

• Active chilled beams
• Air cooled chiller
• Air handling units (with EC plug fans – for variable fan drive)

The chilled beam HVAC system consists of several key components working together to provide efficient cooling and heating. Below is a description of each component:

Chilled beams: Chilled beams are the primary components responsible for cooling and heating the space. They are typically suspended from the ceiling and resemble radiator-like units. Chilled beams utilise recirculating water from a chiller to cool or heat the surrounding air. The beams contain a coil through which the heat transfer occurs. The cooled or heated air is then distributed to the occupied space.

Air cooled chiller: The chiller is a crucial component of the chilled beam system. It is responsible for cooling the water that circulates through the chilled beams. The chiller uses a refrigeration cycle to remove heat from the water, lowering its temperature. This chilled water is then supplied to the chilled beams to cool the air passing over the coil. The chiller can be located outside the building, often on the roof, to dissipate the heat generated during the cooling process.

Air handling units (AHUs): Air handling units play a vital role in the chilled beam system. They are responsible for supplying fresh air to the space and controlling humidity levels. The AHUs contain filters to remove impurities from the incoming air. They also condition the air by cooling or heating it, ensuring it reaches the desired temperature before being distributed to the chilled beams. AHUs may incorporate additional components such as fans, heat exchangers, and humidifiers to optimise air quality and temperature control.

Piping: Water is moved by piping from the chiller to the chilled beams. Polypropylene (PPR) pipes were used due to their durability, corrosion resistance, and ease of installation. These pipes transport the chilled or heated water from the chiller to the chilled beams, allowing for efficient heat exchange and temperature regulation.

Ducting: While the primary cooling and heating in a chilled beam system occurs through the chilled beams, ducting is still required for distributing fresh air from the AHUs to the chilled beams. Ducts transport the air to the appropriate locations, ensuring proper air distribution and ventilation throughout the space. The ducting can be smaller in size compared to conventional HVAC systems since the chilled beams require less air supply.

Building management services: One independent control system was installed to integrate some parts of the system for better energy management. These components work in harmony to provide a comfortable and energy-efficient HVAC solution. The chiller cools the water, which is then circulated through the chilled beams. The chilled beams cool or heat the air passing over their coils, which is then distributed to the occupied space. The AHUs supply fresh air and condition it before reaching the chilled beams. The piping facilitates the circulation of water, while the ducting distributes the conditioned air. By leveraging these components, the chilled beam system offers efficient temperature control, enhanced indoor air quality, and reduced energy consumption.

Integration and control: To achieve optimal performance, the chilled beam system components must be integrated and controlled effectively. The building management system (BMS) plays a vital role in co-ordinating the operation of the chilled beams, AHUs, and other system components. The BMS monitors and adjusts the temperature, air distribution, and water flow to ensure thermal comfort while maximising energy efficiency.

The control system includes hardwired controllers for each group of chilled beams, enabling individual temperature control for different spaces. This flexibility allows for efficient operation, especially during the future conversion of the building for use as Engineering Research Laboratories.

Chilled beam cooling has a number of advantages:

• Reduced ceiling void height (decreases required space by 50%).
• The system requires 30–50% lower air flow allowing reduced plant sizes and variable.
• operation, allowing increased plant efficiency.
• The airflow from the chilled beam is lower than the conventional diffuser type; therefore reducing the feeling of draft.
• Adaptable to room orientation and usage.
• Little noise levels.

Chilled beams reduce maintenance compared to the conventional variable air volume (VAV) systems, since the chilled beam only requires an annual dusting of the filter. Low maintenance and operating cost: up to 50% savings compared to conventional VAV system can be achieved.

Controlling the internal environment of the building without using conventional air makes this project unique. An air-cooled chiller is located on roof of the building. The unit is used to heat up and cool the water which circulates in the air handling unit.

The chilled beam HVAC system offers several benefits compared to conventional variable air volume (VAV) systems. Here are the key advantages of chilled beam technology:

Energy efficiency: Chilled beams are highly energy-efficient due to their lower air supply requirements. They operate at higher cooling capacities while using significantly less fan power. This results in reduced energy consumption and lower operating costs.

Improved comfort: Chilled beams provide superior thermal comfort by distributing conditioned air at a low velocity, minimising drafts and creating a more consistent temperature throughout the space. The slow air movement also reduces noise levels, creating a quieter and more comfortable environment for occupants.

Space optimisation: Chilled beams require smaller ductwork compared to VAV systems, freeing up valuable ceiling and void spaces. This allows for better space utilisation, increased flexibility in design, and potentially reduced construction costs.

Enhanced indoor air quality: Chilled beams rely on a separate air handling unit to supply fresh air, allowing for effective filtration and improved indoor air quality. This helps remove contaminants, allergens and pollutants, promoting a healthier environment for building occupants.

Longevity and low maintenance: Chilled beams have a longer lifespan compared to VAV systems, typically lasting up to 30 years. They have fewer moving parts, resulting in minimal maintenance requirements and lower ongoing operational costs.

Environmental sustainability: Chilled beams contribute to environmental sustainability by reducing energy consumption and carbon emissions. Their energy-efficient operation and potential for utilising renewable energy sources align with green building initiatives and sustainability goals.

Design flexibility: Chilled beams offer modular partitioning, allowing for flexible and adaptable space configurations. This is particularly advantageous when repurposing or retrofitting buildings, as the system can easily accommodate changes in room layout or function.

Cost savings

While the initial capital investment may be higher than VAV systems, chilled beams offer long-term cost savings. Their energy efficiency, reduced maintenance needs, and longer lifespan result in lower operational and replacement costs over the life of the system.

Overall, chilled beam HVAC systems provide a range of benefits, including energy efficiency, improved comfort, space optimisation, indoor air quality, longevity, environmental sustainability, design flexibility and cost savings. These advantages make chilled beams an attractive option for enhancing building performance and occupant satisfaction.

The chilled beam has a life expectancy of 30 years, which is double that of the conventional variable air volume (VAV) type of installation. The chilled beams require less air input, thereby reducing the size of air handling units. Since the air volume required to be cooled has reduced, the chiller size also reduces. The reduced size of the AHU and chiller; little to no input power; and high life expectancy of chilled beams yield high savings and meaningful returns for the client.

A cost analysis was conducted to showcase the benefits to the client to justify the capital cost and view the savings on the operational, maintenance and replacement costs. The conventional VAV system faired just under two million rands lower than the chilled beam system. However, at the end of year 15 the client would need to replace the entire VAV system, in contrast to the chilled beam system which would require component replacement. Over a 30-year period, the client would have saved approximately R20-million. The internal rate of return was calculated to be approximately 17% with the chilled beam installation paying itself off in 15 years.

Energy efficiency considerations related to M&E technology

Superior equipment has been used in this project – only the chiller is used to heat the water. The efficiency comes from the radiant energy.

Energy savings with beams: When compared with a traditional HVAC system, chilled beams provide superior energy savings by reducing the reheat by 50% and reducing annual fan energy 30 to 40%.

Energy reduction can be primarily derived from reduced reheat and fan energy required to operate the system. In addition to the energy- and cost-saving benefits of a chilled beam system, there are significant space savings with chilled beams with a space reduction of 50% or more in duct area and supply and return chases, and a 30 to 40% air handling unit footprint reduction – potentially increasing the usable floor space in a building.

Passive design inclusion and design impact

The project incorporated passive design strategies to enhance the building’s energy performance. By analysing the building envelope, measures such as clear window glazing, insulation and shading were implemented to reduce cooling loads. These passive design elements work in conjunction with the active chilled beam system, optimising energy performance and occupant comfort.

The design incorporates the separation of occupied areas and circulation areas. It was important to keep the solar heat gain low, therefore glazing and roof insulation were heavily considered. The system could cater to a lower demand for cooling.

The following design criteria were applied in the design and configuration of all technical systems and services:

• Adequate capacity: load handling capabilities to meet present and future requirements.
• Reliability: under all circumstances.
• Adaptability: ability to cater for changes in future technology and expansion without infrastructure modifications.
• Flexibility: simplicity of operation and ability to cater for changes in occupancy.
• Maintainability: ease of maintenance and totally serviceable with locally available components.
• Cost-effectiveness: minimised capital and long-term operational costs.
• Energy efficiency: the systems must operate at optimum efficiency and minimum energy costs.
• Sustainability.
• Safety: the designs must be performed with due consideration given to the circumstances of the patients and the environment.
• Security: consideration must be given during the design process to potential incidents of equipment vandalism and improper use and handling.

The impact of the design choices made during the project is significant. The conversion of Wits’ Flower Hall into an Engineering Analytical Laboratory allows for space optimisation and meets the University’s requirements for increased academic and office space. The integration of an innovative HVAC system contributes to the sustainability goals of the institution while providing an efficient and comfortable environment for occupants.

Renovation work commences.

Thermal comfort and indoor air quality

Occupants’ thermal comfort is the primary objective in radiantly heated or cooled space. To provide an acceptable thermal environment for the occupants, the requirements for general thermal comfort shall be taken into account by using the index of predicted mean vote (PMV) or operative temperature (to), and local thermal comfort – for example, surface temperature, vertical air temperature differences, radiant temperature asymmetry and draft.

In laboratories and exam venues, thermal comfort is crucial for the occupants’ productivity, concentration and overall well-being. Chilled beams offer several benefits in terms of thermal comfort:

• Zoned cooling: Chilled beams provide zoned cooling, allowing different areas within the facility to be controlled independently. This feature is particularly useful in laboratories and exam venues, where maintaining different temperature requirements in different spaces is often necessary. The difference between exam venues and laboratories is the set points required for cooling. It must be noted that the ability to cater to the different heat loads and temperature set points is ideal for the design.
• Low air velocity: Chilled beams operate with low air velocities compared to traditional air conditioning systems. This reduces drafts and the sensation of moving air, creating a more comfortable environment for occupants.
• Quiet operation: Chilled beams generate minimal noise as they do not have large fans or blowers. This low noise level is advantageous in environments like exam venues where a quiet atmosphere is essential for concentration. Laboratory environments require silence as well, so the students can listen to instructions clearly as well as concentrate.
• Improved air quality: Chilled beams can be designed to work in conjunction with dedicated fresh air systems or other ventilation systems. This allows for the supply of fresh, filtered outdoor air, promoting better indoor air quality. ASHRAE standards recommend the use of ventilation systems capable of delivering an appropriate amount of fresh air per occupant and per space.

In addition to thermal comfort, indoor air quality is another crucial aspect to consider in laboratories and exam venues. Chilled beams contribute to maintaining good indoor air quality in the following ways:
Indirect air distribution: Chilled beams operate without actively recirculating room air, thereby reducing the spread of airborne contaminants. This indirect air distribution helps minimise the potential for cross contamination between spaces.

Air filtration: By integrating chilled beams with a dedicated outdoor air system or central air handling units, air can be filtered to remove particulate matter and contaminants before being supplied to the space. This filtration process helps maintain a healthier indoor environment.

Moisture control: Chilled beams can help control humidity levels in the space. When properly designed and integrated with the building’s HVAC system, they can effectively remove excess moisture from the air, reducing the risk of condensation and mould growth.

Main ductwork feeding chilled beams.

Site conditions and inside conditions required

Johannesburg has a hot summer (November–March) and a mild, drier winter (May–September). The peak travel times are March– May and October–December.

Site conditions:
Johannesburg Wits Flower Hall Building:
Altitude 1 753m
Outside Design Conditions Summer 32°C db and 21°C wb
Inside Conditions Required

Exam venue:
Temperatures Summer 22.5°C +/-1.5°C db
Relative Humidity 50% RH

Laboratory:

• Temperatures Summer 19.5°C +/-1.5°C db
• Relative Humidity 50% RH
  The plant is designed to control or maintain temperature in the individual spaces within a temperature variation +/- 1.5°C of the design. Humidity – which is not controlled beyond the prevention of condensate and mould – will vary depending upon the outside conditions, the time of day and the occupancy.