In 2012, only about 63% of commercial buildings attempted to heat 100% of their floorspace while about 91% of commercial buildings attempted to cool 100% of their floorspace, according to the EIA. In order to effectively do this, your HVAC unit has to be just the right size – not too big and not too small.
When shopping for a new HVAC unit, the common misconception is that “bigger is better.” It should be common knowledge that an air conditioner or furnace that is too small won't keep your employees, guests, and/or tenants comfortable, but many people find it hard to believe that a unit that is too big will have adverse effects as well.
Poor Air Quality
Air-conditioners work to cool the air; that's a no-brainer. It may come as a surprise though that they also have a second job description: to remove moisture from the room. When the A/C takes in warm, moist air it passes over an evaporator coil that condenses the moisture. This moisture then collects on the coil before it is evacuated from the system (and ultimately your building) via a drain. If an HVAC system is too big, it will cycle too quickly, thus not allowing enough time for the air to process and evaporate, leaving you with cool but uncomfortably humid rooms.
Increased Wear and Tear
Because an HVAC system that is too big won't adequately remove moisture from the rooms, the obvious remedy is to go with a unit on the smaller side. Unfortunately, an air conditioner or heater that is too small for your building will have longer cycle times which means all the components that are used to handle the air and deliver it through each floor will be working more frequently.
Just like an automobile that generally lasts longer the less you drive it, those HVAC components under the stress of a heavy workload will start to fail earlier. This, unfortunately, has a ripple down effect as other parts start to overcompensate for those that are going bad. In the end, you're lucky to see half of the expected 15-20 year lifespan and will quickly realize this system is more expensive than any other building maintenance cost simply because of a poor installation.
Higher Utility Bills
Along the same lines of increased wear and tear from frequent cycling, an HVAC system that runs longer is using more energy. This results in higher utility bills or increased fuel consumption which puts another huge dent in your wallet. Generally an HVAC system that’s too small only offers two options: either pay more to be comfortable, or dress accordingly and have meetings off-site.
Finding the Right Size Unit
There will always be some guesswork involved in finding the perfect sized unit, but it's not rocket science. Generally, a 1 ton HVAC unit can heat or cool anywhere between 500-800 square feet. By doing the math, you can measure your square footage and find the associated sized unit that you need. Commercial HVAC systems have such a wide range of sizes available. Accurately estimating the size of the unit has to take into account dozens of factors, such as:
- How many buildings do you have?
- How large are the rooms?
- How insulated is your building?
- Each room?
- What materials were used?
- What kind of floors do you use?
- Are your windows/doors open a lot?
These are just a few of the factors. An HVAC company almost always has someone who specifically does load calculations. In order to receive the most accurate size, you’ll want to talk with them and provide all of the information they need. The more accurate the sizing, the more efficient (both for cost and comfort) your unit will be.
You can also use this method to find out if your unit is too small or too big now. If it is, it could explain other unexplained symptoms, like high energy bills, that you’ve been experiencing since installation.
How You Can Help Yourself
Even if you find what you think is the properly sized HVAC unit, there are still some important pieces of the puzzle to put together for perfect energy utilization. For example, it's imperative that all window and door gaps are properly sealed and that outside walls have adequate insulation. Upgrades such as adding or upgrading building insulation to the latest codes and standards represent costs at first, but pay themselves off in lower utility bills and less wear and tear on the A/C and furnace, ultimately saving you money.
Carl Taylor is an associate of Comfort Pro.
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