HVAC AT THE FOREFRONT OF HEALTH AND WELLBEING
GIVEN THE HEALTH CONCERNS, STEPS TO OPTIMIZE VENTILATION AND AIRFLOW INDOORS HAVE BEEN STEPPED UP. BUT, THIS MAY ALSO BE A GOOD TIME TO THINK ABOUT IMPROVING AIR QUALITY IN BUILDINGS
Office complexes, hotels, restaurants, hospitals, and apartment buildings invest a lot of money in systems to make their spaces healthier and more comfortable for tenants and customers. But the COVID-19 crisis has completely altered the landscape. Now, HVAC systems are also at the forefront of health and wellbeing because COVID-19 is primarily transmitted through the air via respiratory droplets. In response, facility managers are exploring how to retrofit their HVAC systems to make them safer for the
Andrew Jackson, Partner, Foster +Partners stated, “There is a clear need for innovative energy recovery systems, which prevent the transfer of contaminants between incoming and outgoing air streams, and novel dehumidification technologies – such as liquid desiccant– to reach maturity quickly. The challenge for built environment engineers and designers is about to get tougher. It’s an exciting time to be in the industry.”
According to Richard Walder, Associate Director, Buro Happold UK, “We’ll see more consideration of natural ventilation in many buildings, and the enhanced fresh air rates this can bring, although it’s important that it is designed thoroughly, with properly considered controls. There is likely to be increased interest in displacement ventilation, potentially in conjunction with passive chilled beams. The fact that it can be full fresh air and gives unidirectional flow will be a significant attraction – and, of course, the supply temperatures are typically less demanding on energy than other systems. With higher primary air supply flowrates, however, consideration needs to be given to ensuring that plantrooms and ductwork distribution routes are sized sufficiently to keep pressure drops low. Appropriate design of ventilation systems will avoid the need for significant additional filtration and the energy penalty this can bring; incoming viral load is generally minimal, so adding Hepa filters onto fresh-air systems will have negligible effect, and a move away from recirculating systems will mean that internal Hepa filtration is unnecessary. As well as continuing to maintain low specific fan power, scrutiny of heat exchanger efficiency and avoiding leakage paths will become even more critical with higher fresh-air rates and increased operating hours.”
While studies are still ongoing about how the coronavirus spreads via air, evidence suggests that measures to change indoor airflow patterns could play a role in reducing transmission. Three main principles apply:
- Encourage a vertical laminar rather than turbulent airflow
- Ensure a slow, steady air speed
- Direct potentially contaminated air out of rooms and away from people
Numerous technologies can purify air. Filtration is the most common and typically the most effective method for HVAC systems). Other technologies, including irradiation and thermal sterilization, inactivate biological particles in the air without removing them. HVAC systems can also incorporate ionic purifiers, ozone generators, and other devices for cleaning air.
THE THREE KEY CONSIDERATIONS
The proactive approach provides bottom-line benefits, making properties more attractive to tenants concerned about the health issues in the current scenario. The question is, what should owners and managers be concerned about when it comes to HVAC and public health?
In the past, HVAC systems were designed to introduce enough fresh air to comprise 10%-15% of the amount of conditioned air actively being supplied to the building spaces. In the post-COVID 19 world, that may no longer be good enough. Owners and facility managers should be programming their systems to allow in as much fresh outside air as the system’s design constraints allow, and developers should consider systems that provide maximum dilution. This poses challenges though, particularly in harsher climates. Increasing ventilation requires systems to work much harder in places that experience extreme weather, particularly extreme heat or cold.
New and emerging building ventilation technologies may provide solutions to achieve building energy efficiency and saving, including advanced ventilation systems, optimized system sensing, monitoring and controlling technologies and data analytics.
A challenge with increasing filtration is the size of the filters in air-handling units. The thicker and denser the filter, the more effective it typically is. However, many systems already house the thickest filters they can handle. Additionally, passing air through a thicker filter makes the system work harder, which can lead to decreased efficiency, the need for more frequent maintenance, and ultimately, earlier replacement of the system itself. Finally, systems with thicker filters require more energy to work properly, increasing the cost associated with operating the system approach, there are other ways to clean air. A system becoming more cost-effective is UV filtration, which uses UV light rather than a physical barrier. While the up-front costs of introducing UV filtration are higher than just changing out a filter, this approach provides an affordable option for systems that can’t accommodate larger filters. Modern UV systems are more compact than in the past, and can now fit into spaces that previously could only accommodate filter-based systems.
Systems in newer buildings can typically handle higher ventilation, and the systems usually track their own efficiency so one can tell if the system is operating as it should. If it is an older system, though, you need to observe it closely to make sure it isn’t overworking. If the system has trouble keeping up with increased ventilation, you may need to upgrade or replace it.
In the highly sensitive COVID-19 environment, humidity is also a health matter. Public health experts believe that viral particles remain airborne longer in dryer air. This is significant because colder weather typically is accompanied by dryer air, and these months often align with flu season. Conversely, air that is too humid can cause mold or other issues. Ultimately, 40%-60% relative humidity seems to be the ideal range for providing both a healthy and comfortable environment. The good news about humidity is that maintaining ideal levels may not require a full upgrade of your current system. Many existing control systems have indoor humidity monitoring capability, and can even control system operation based on maintaining ideal humidity levels. These systems may simply require updates to the building controls sequences. If a building’s control system is not capable of this, building owners may consider upgrading their existing systems or just adding a separate humidifier or dehumidifier.
3-STEP UPGRADE OF HVAC HARDWARE
- Replace fixed-speed fan motors with variablespeed ones to enhance the control of airflow and allow for a minimum setting that produces lower speed airflow
- Introduce sophisticated airflow-control systems, such as those that are sensitive to pressure, to allow for smoother adjustment of airflows
- Install high-performance air-purification systems
FUTURE CHALLENGES OF HVAC CONTROL
In order to satisfy the requirement of better healthy environment and more thermal comfort performance of indoor ventilation system, prevention of indoor pollution is essential, especially considering the purpose of disease transmission resistance. Conventional HVAC systems are usually operated with excessively prescribed ventilation rates and temperature settings, without a consideration of energy efficiency. Thus, to achieve both a healthy indoor environment and building energy, efficiency would be the main challenge for designers of HVAC systems.
CFD modelling has been widely applied for the design and application of advanced ventilation systems. However, there is still a long way to go to realize online control of various types of ventilation systems using CFD since the high demand for practical design application. To realize online control of ventilation, the CFD-based Machine Learning method using artificial intelligence (AI) technology could be a potential way, which provides a high speed and accurate prediction of airflow requirements. Corresponding cross-disciplinary research on the construction of AI ventilation system should be conducted in the future. Inputs from WGI, USA, CIBSE & McKinsey & Co.
THE EXPERT VIEWS
BUILDING OWNERS AND DEVELOPERS CAN LEVERAGE A BETTER HVAC SYSTEM AS A COMPETITIVE ADVANTAGE IN THE POST-COVID 19 WORLD. REALTY+ GETS THE EXPERT’S VIEWS.
WHAT ARE THE TOP 5 CONSIDERATIONS WHILE PLANNING AN HVAC SYSTEM FOR A COMMERCIAL PROPERTY?
Rohit Korgaonkar, Founder Kromatics: The top considerations include, Location of project (city/state/ country), Ambient Conditions (DBT, Humidity), Orientations & exposure of building sides and roof, Required indoor air quality (office / Pharmaceuticals / Hospital / Sport Clubs etc) and Fresh air requirement (based on type of occupancies and type of works going on). Samir Mehta, CMD, Nishchint Engineering Consultants: Comfort with sustainability, Indoor air quality, Cleanliness are the perquisites.
WHAT ARE THE LATEST TECHNOLOGIES AVAILABLE FOR ENHANCING THE HVAC SYSTEM’S ENERGY EFFICIENCY?
Rohit Korgaonkar: Chilled water system is the most energy efficient among all the HVAC system but it has the highest capital cost and requires heavy maintenance. VRF system is also energy efficient system but less than the Chilled water system. It has single outdoor connected with the multiple indoors. It requires less maintenance as compare to chilled water system. Inverter DX system is direct expansion type of system having single ODU connected with single IDU. This is energy efficient as it has speed varying compressor as per the requirement. Fixed speed DX system is also a direct expansion type of system with single ODU connected with single IDU. This system is less energy efficient system among all the system mentioned above.
Samir Mehta: Use of alternative energy sources, Atomization in control systems, Implementation of ECBC can enhance energy efficiency.
HOW CAN THE HVAC SYSTEMS BE RE-ALIGNED TO MEET HEALTH & WELLNESS NEEDS OF AN OFFICE OR A COMMERCIAL SPACE?
Rohit Korgaonkar: It is very essential to maintain rich mixture of fresh air and return air. Previously fresh air to be introduced of 10% to 15%. Now it has to be increased for the safety purposes.For preventing infections air contaminants should be cleaned by installing filters (MERV filter, HEPA filter, UV light filters). Also, dry and cool environment is friendly for survival of viruses and bacteria’s hence humidity should be controlled between 40%and 60%. Samir Mehta: Focus should be given towards better ventilation system, Fresh air systems with pre filtration are installed. Indoor air quality to be monitored and if needed, quality should be enhanced.
WHAT ARE SOME OF THE FACTORS THAT IMPACT INDOOR AIR QUALITY AND HOW THEY CAN BE MANAGED EFFECTIVELY?
Rohit Korgaonkar: Indoor air is said to be of a good quality if its parameters are as per the comfort condition. Equipment and occupants in the area increase its temperature, humidity, dust and CO2 over O2 ratio. For improvement of Indoor air quality cooling, humidification / de-humidification, air filtration to be done in proper way. CO2 or CO sensor to be installed for checking up the CO2 over O2 ratio and fresh air to be supplied accordingly to maintain oxygen level. Samir Mehta: Type of application is important to know as ventilation plays important role in enhancing / maintaining good IAQ.
THE REASONS FOR SICK BUILDING SYNDROME AND HOW THE SAME CAN BE PREVENTED?
Rohit Korgaonkar: Sick Building Syndrome occurs due to poor air quality, toxins, poor building material, improper ventilation and improper oxygen supply. It can be prevented by regular inspections of toxin, adequate maintenance of building, planting of toxin absorption plant, increasing ACPH, maintenance of HVAC system, UV light filtration (should not be exposed), HEPA filtration and identification of harmful ingredient emitting equipment. Samir Mehta: Improper designing and lack of fresh air supply are the major reasons for sick building syndrome. Many a times while designing fresh air calculations are done, but while execution the fresh air systems are not taken in, due to costing aspects. At times, the designer and end users both do not have complete information for type of application. Designing happens in normal comfort mode, but practically requirement differ, that causes this kind of issues.