HVAC Sizing 101 – How To Determine The Size Of The HVAC System You Nee…

An HVAC system is a large investment on your part. We’re not just speaking in reference to the initial costs of purchasing and installing the equipment, but we’re also referencing the amount of money you will use on energy bills over the years. Statistics say that you will use well over $2,000 this year on energy bills alone. Your HVAC system accounts for almost half of the energy your home consumes within that time period. Your home, no matter how old or new, is an energy hog. Whether you’re choosing to upgrade your existing HVAC system or installing a new one in your new home, here are some tips you should to pay attention to in order to choose the proper-sized system that will ensure energy-efficiency.

So what does one do to prevent your home from sucking up so much energy? First, understand that if your equipment is old, it’s time to replace it. Equipment that is 10 years or older is extremely inefficient and should be replaced, preferably with an energy-efficient form (i.e. Energy Star qualified). When purchasing any kind of HVAC equipment, it’s smart to go with an energy-efficient form. It will save you a ton of money over the years.

You’re probably wondering, “So if I choose energy-efficient equipment, why does sizing matter?” It matters! Choosing the proper-sized equipment (i.e. proper heating/cooling output) directly affects your comfort, your HVAC system’s efficiency and its maintenance and operating costs. You can see how important and underestimated this topic is. In fact, it has been estimated that over half of the HVAC industry does not size your HVAC systems properly.

“Oversizing” tends to be the biggest mistake that is made. When you oversize an HVAC system, it can affect a number of areas within the time of action. For example, the installation will be more expensive. Typically oversized systems tend to cost more to function, break down often, run inefficiently and require more maintenance. Oversized air conditioners tend to shut off before they’ve had a chance to dehumidify the air properly. This results in a clammy ecosystem that may be inclined to mold. Oversized furnaces create uncomfortable temperature swings.

When your HVAC technician attempts to size your system, they should not be reading a label or simple by-the-book standards. Instead, the calculation should be multi-variable and include factors that are rare to your situation. For example, what is the climate like in your area? How many windows do you have and what size are they? How much insulation is there and what kind of insulation is it? How big is the house? Is the house two-story or one-story? How much outside are is sneaking in? How many occupants are there?

There are two industry standards that should be used to help determine the proper size for your system. These are “Manual J” and “Manual D”, produced by the Air Conditioning Contractors of America. Manual J, also called “Residential Load Calculation”, is chiefly used to determine HVAC size calculations. A reputable HVAC company will tell you that they use Manual J to determine sizing. Manual D, also called “Residential Duct Design”, is used to determine duct sizing. When looking for a company to help install your new HVAC system, always be sure to inquire whether or not they use Manual J and D in their sizing and installation course of action.

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