Pros and Cons of VAV Systems

As a building owner, you understand how important it is to have a comfortable and energy-efficient environment for your occupants and guests. The system choices available today are broader and more diverse than they have ever been.  You may have been considering investing in Variable Air Volume (VAV) systems, but aren’t sure if it is the right option for you.

In this blog post, we will explore the pros and cons of VAV systems so that you can decide whether or not they are the best choice for your buildings mechanical system. From improved air quality to reliable system operation, discover all of the advantages and disadvantages associated with installing or transitioning to a variable air volume system.

What is a VAV System?

VAV stands for Variable Air Volume.  A VAV system is a type of heating and cooling system that building owners employ to provide a high level of comfort control to the occupants of a building.  A VAV system varies both the volume and temperature of the air delivered to the occupied spaces, in order to closely match the instantaneous heating or cooling demands of the space.  These systems offer building owners an efficient and cost-effective way to control the climate of their property by providing a higher level of precision than many constant volume or single zone types of systems.

This type of system offers improved environmental control by providing precise temperature regulation, as well as improved energy efficiency through its ability to handle extreme temperature swings with ease. It also let’s building owners take advantage of computational technology for improved air handling, allowing for greater precision in the operation of their climate control systems.

Ultimately, building owners who implement variable air volume systems in their buildings can see improvements in both cost and comfort levels due to the precise, efficient regulation of the indoor environment.

How Does a VAV System Work?

A Variable Air Volume system is able to adjust both the volume and temperature of air that flows through buildings via the heating and cooling systems.  Commercial property managers can use VAV technology to better manage their energy resources, while creating a more comfortable environment for the occupants.

The exact workings of a Variable Air Volume system vary depending on the type of system employed; however, they all typically involve the use of electronically controlled air volume dampers for each space or control zone, adjustable speed drives to modulate the fans and compressors on the units providing the cooling/heating, and digital temperature sensors in each control zone to gauge and manage the airflows and temperatures to each space based on the heating or cooling needs of the space on a real-time basis.   

As the temperature in the space approaches its set point, the dampers are able to automatically reduce airflow to closely match the actual load in the space.  The result is precise temperature control and energy efficiency, because airflows are never higher than is actually required to keep the space comfortable. The equipment supplying the cooling and heating is also modulated to deliver only what is necessary to meet the building demands at that moment, saving energy by not over delivering capacity.

Although many buildings have long used split systems or rooftop units configured to various temperature settings for each area or zone within a facility, VAV systems enable building owners to maintain an ideal environment in a much more efficient manner.  Rather than on-off or even multi-stage operation, as is common with constant volume systems, VAV systems are able to react and adjust to the actual demand continuously.

Typical Uses of VAV Systems

Office Buildings

Building owners increasingly rely on VAV systems to control the climate inside their office buildings. These systems allow for the cost-effective regulation of temperature and comfort in all occupied spaces. The systems change the quantity of air that is delivered, allowing heating or cooling needs to easily scale as people enter or leave a space. This has been proven especially useful in areas where occupancy can vary significantly throughout the day due to office hours, meetings, and other events.  

Variable Air Volume systems are also beneficial because they reduce the hot and cold spots, which are common in traditional commercial HVAC systems, providing an energy-efficient way to maintain a comfortable temperature throughout the entire building.

VAV systems are usually quieter than most other systems.  This is partially due to the fact that the air volume remains moderated the majority of the time, while peak flows only occur during the highest loading conditions.  Constant volume systems, by contrast, deliver the full air volume at all times, regardless of the local space’s load profile. VAV systems are also quieter than most decentralized systems, like water source heat pumps, because the refrigeration compressors and fans are typically located far from the occupied spaces.  The only noise from the VAV system is the movement of air, and even that is moderated due to the VAV dampers reaction to the loads in each space.

Schools

Schools often turn to Variable Air Volume systems for many of the same reasons as office buildings, including quiet operation and room-to-room control capabilities that single zone systems can’t provide. In addition, the energy saving features of a VAV system ease budgetary constraints and allow for more resources to be allocated for educational purposes, rather than utility costs and facility expenses. These systems provide an all-in-one solution that can cool or heat any learning environment, making them a popular choice for schools.

Furthermore, VAV systems use advanced technology that offers superior temperature regulation capabilities. This smart technology can maintain comfortable indoor temperature settings, while also conserving energy use, giving school administrators more control than ever over the energy efficiency and comfort levels in their buildings. The inherent variability of the loading of a space in an educational environment lends itself well to the use of a VAV system for energy conservation and precise temperature control.

Large Commercial Spaces

VAV systems are an essential component of HVAC systems in large-scale commercial properties like malls, department stores, and mixed use facilities. These systems allow for the optimal delivery of air, temperature, humidity control, and energy efficiency support to large buildings and areas.

By enabling the creation of individual zones within a single building, VAV systems are particularly useful for multi-occupancy structures with varying populations and internal temperature requirements, like those found in malls and mixed use facilities.

Through regulation of both space temperatures and energy consumption via customizable solutions, investing in a Variable Air Volume system is an option worth considering for any business looking to improve its facility’s performance, sustainability, and efficiency.

Benefits of VAV Systems

Installing a variable air volume system in a building is one of the best decisions for businesses and property owners looking for the ultimate in temperature control and efficient operation.  VAV systems allow for flexible zoning, which means heating and cooling can be adjusted based on the needs of each area of the building. This helps reduce energy costs, and has resulted in significant savings for businesses that have implemented these systems.

Another advantage is that buildings are quieter since a VAV system only distributes the amount of air necessary to meet the current demands of the space.  This results in a reduced air volume moving throughout the building, creating less air noise in the occupied areas. 

A third advantage is that the air, and therefore temperatures, are controlled more evenly throughout the building.

VAV systems also centralize most of the maintenance, including routine maintenance, because there are no filters to change or motors or belts above the ceiling. Most of the routine maintenance on a VAV system occurs at the central air handling units, resulting in less disruption to the occupants and easier maintenance access than systems that rely on fan coil units or water source heat pumps in the ceiling space. In addition, a VAV system takes up less space, inside buildings, than most traditional HVAC systems. This benefit makes it easier to install without large-scale remodeling and improving the amount and quality of the leasable area.   As such, installing a VAV system makes sense — not just financially, but also from an environmental sustainability perspective.

Cons of VAV Systems

Variable Air Volume (VAV) systems have long been seen as a remedy for inefficient operation in a building’s HVAC system. While VAV systems have many benefits, there are also some cons.

VAV systems are one of the more costly types of commercial HVAC systems.  The complexity of the controls and quantity of automatic dampers required, to achieve the improved temperature uniformity, comes at a cost premium relative to constant volume systems.

Because VAVs are an “all air system”, the amount of ceiling space consumed by the system ductwork is greater than it would be for a hydronic or refrigerant based fan coil system.  However, this is at least partially offset by the smaller vertical height of the typical VAV box, relative to an in-ceiling fan coil of equivalent capacity.   

The control systems involved in a VAV system are more complex than with most other constant volume or water based HVAC systems.  This means that specialized control technicians are required to diagnose system failures when they occur. In conclusion, while Variable Air Volume systems offer improved efficiency, temperature uniformity, and acoustics for HVAC systems within a building, it also has a few downsides.

Looking to Install a Variable Air Volume System?

Despite their innate complexity, HVAC systems of all types are essential to buildings, and must be carefully designed to function both efficiently and effectively. These systems often represent a large investment for building owners, so partnering with an experienced MEP Engineering firm is critical to ensure that the owner’s money is well spent.

Here at Schnackel Engineers, we have decades of experience in assisting with decision-making, engineering design, cost estimation, construction administration, and documentation of the establishment of cost effective building management systems.  With such a broad range of services available under one roof, not to mention our very talented and experienced team of engineers, you can rest assured that your investment will be in good hands when you partner with us.

Contact Schnackel Engineers today if you’re looking to install a Variable Air Volume system in your building!