Worth its Weight in Air: How Do You Choose an HVAC System for Your Building?

When designing a new building, air quality and temperature are very important features! How are the correct systems chosen to make sure that a structure has the right heating and cooling? 

Deciding on the right HVAC (Heating, Ventilating, and Air Conditioning) system is dependent on three things; what type of building the system will be designed for, what comfort level the building owner wants, and how much the owner is willing to spend. As it tends to be, when the comfort level goes up, the price goes up, and vice versa! Here are four different system options with varying levels of comfort and price to help you decide what might be right for your building.

One of the most reasonable systems is a furnace. Often used in residential homes and light commercial buildings, it is easy to install and fairly inexpensive. To obtain a ballpark estimate of cost, figure around $4 to $8 per building square foot. The catch is the restricted level of comfort that can be controlled from a furnace. Because there is only one thermostat connected to the system, it is difficult to make sure all the spaces in the building are at the desired temperature. The room with the thermostat may be comfortable, but other outlying rooms may not have that same comfort level.  Giving a furnace system a rating based on cost and comfort (using “$” for cost and “C” for comfort level) it would have the following rating: ($, C).

A packaged rooftop unit is on the cheaper end of systems for light commercial building applications, and even for some larger commercial buildings with multiple units. It is, however, around 2 to 3 times the cost when compared to a furnace. When it comes to obtaining an estimate, figure somewhere between $12 and $18 per square foot. What elevates these systems from the average furnace is the ability to cover more building area from a single unit. If the area covered by a furnace starts to be larger than 2,000 square feet, then it will have a hard time keeping up with demands of the space. Another perk that makes this system a little better than a basic furnace is its ability to vary the amount of airflow provided. Some packaged rooftop units can even deliver a small amount of dehumidification. The catch? They still work off of a single thermostat, so rooms may have varying temperatures as with a furnace. Cost vs. Comfort Score: ($$, CC)

Leveling up to a packaged rooftop unit with VAV (Variable Air Volume) terminal boxes, prices start to climb. This system is very similar to the basic rooftop unit, but with VAV boxes throughout the building so that the airflow can vary in individual spaces. Some of these boxes can even provide ‘reheat,’ which adjusts the incoming air temperature. This type of system is around 1.5 to 2 times more expensive than a stand-alone packaged rooftop unit, and the control systems for this type of system start to become a little more sophisticated.  In terms of budgeting, figure somewhere between $20 and $30 per square foot.  Of course, this depends on the number of VAV boxes in the system and how advanced those boxes are.  Comparing this to a basic furnace system, it’s around 4 times more expensive. This system is ideal if you desire every space (or even a number of spaces grouped together) to be regulated exactly how you would like. Each box works off of its own thermostat, so the users of each space can set their own desired level of comfort.  When conditioning a variety of spaces with diverse needs (office space, hospital room, conference room, etc.), this system is very useful.  Cost vs. Comfort Score: ($$$, CCCC).

Finally, we come to the pièce de résistance; a custom air handler with VAV terminal boxes. Quite a mouthful to say, this structure is best suited for larger commercial buildings that have multiple levels served by the same system. This type of system is highly adjustable and can include a wide array of options for the preferred comfort level. Some of these options include humidifiers and/or dehumidifiers, many levels and types of air filtration, multiple types of heating/cooling media, different fan configurations, and more. These units are designed to provide the highest level of comfort throughout an entire building, from room to room. They also typically have a much more sophisticated control system which allows users a greater ability to set their desired comfort level.  Now for the big question; how much does it cost for one of these custom systems? On average, it can range anywhere from double to 4 times that of a packaged rooftop system with VAV boxes.  In terms of budget cost, figure around $40 to $80 per square foot. That’s right. It’s around 10 times more expensive than a basic furnace! But remember, these types of HVAC systems aren’t typically for your everyday residential home; large commercial buildings with many floors are the ones who tend to use this kind of machinery. Cost vs. Comfort Score: ($$$$$, CCCCC).

These HVAC system examples make it evident that the level of comfort and control you get is what you pay for. How you decide what system to have installed depends entirely on the type of building, how much comfort you want, and how much money you want to spend. Money can’t buy happiness, but it can buy you a top-of-the-line HVAC system!

Bocephus Thomas, ME

Design Collaborative