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How Do I Size My HVAC System? Building For Tomorrow
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How Do I Size My HVAC System?

The last thing you want to face in your Las Vegas home or office between May and September is air conditioning malfunction. That’s not to say that an absentee heating unit on a cold December night is any more welcome. Vegas’ desert climate definitely runs to extremes, which is why it’s critical to have a properly sized HVAC unit installed.

An inaccurately sized HVAC unit has consequences that can quickly become much more than just an inconvenience. It leads to health issues and costly energy bills. Take some time at the outset to investigate the basics of proper HVAC selection and sizing, and you’ll save yourself considerable problems down the road.


The first rule of thumb in estimating the HVAC system size you need is to remember that there is no simplified one-size-fits-all square footage answer. The result of using a standard formula based solely on square footage is that you tend to end up with a system that’s too large for your space. That means you’re paying more to purchase and install the larger unit. While it may seem counter-intuitive, a larger unit fails to accurately maintain the temperature at which you’d like your home set. Consequently, you pay more in energy bills.


When you hire a knowledgeable HVAC professional, some of the many areas of your home that will be considered for proper HVAC sizing include the following:


If you have an older home or office, it may not have adequate ventilation or ductwork to accommodate the needs of a new system. An HVAC retrofit might be necessary in order to get the maximum efficiency out of your unit.

Another consideration with older homes is the condition of the electrical system. It needs to be up to code to be able to handle your new system.


The number and condition of windows definitely have an effect on the size of unit you select. However, that’s only part of the window information you need. Where they’re placed in your home is also a contributing factor. If your windows receive a great deal of sunshine throughout the day, that means more heat enters your home. The cooling system will have to work harder during our Las Vegas summers to maintain a comfortable temperature, but the furnace produces less energy during the winter.

Window type also factors into the energy your HVAC expends. Single pane windows aren’t as efficient at insulating as are double or triple paned windows. While we’re on the topic, window treatments also figure into the calculations.


The placement of your home has a major impact on the amount of work your HVAC system is forced to do. For instance, you may be able to keep your home cooler in the summer if you do have some shade that blocks some of the desert sun.

A difference of 90 degrees in your home’s placement can have a profound effect on both your HVAC’s size and its ability to function efficiently.  Thoughtful landscaping with the inclusion of some carefully placed indigenous shade trees may improve your system’s efficiency by as much as 20%.


All air leaks should be addressed and remedied in order to get the maximum efficiency out of an HVAC unit. That includes adding weatherstripping around windows and doors to effectively seal them.


The amount and type of insulation you have in your home is a major factor in maintaining a consistent and comfortable temperature. Your home’s R-value should also be included in the load calculations.  If additional insulation is required, that can be added when the ductwork is installed.


When your HVAC is insufficient to manage the space, you’ll notice that it doesn’t seem to run consistently. It will either go nonstop or operate in short bursts throughout the day.

You will also notice more moisture in your space because the unit isn’t powerful enough to adequately maintain the temperature and remove moisture. Added moisture can ultimately lead to mold growth, which contributes to an unhealthy environment.

As mentioned above, oversized HVAC systems also create problems in your space. It may seem like a larger unit will work even better, but the opposite is true. One of the problems is that a system that’s too large doesn’t run long enough to condense the air that accumulates on the coils, so it doesn’t dehumidify the air effectively. Here again, you end up with more moisture.

You may also hear a noisy unit because it’s not running efficiently. Not only are you faced with an uncomfortable physical environment and nuisance noise levels, but you also end up paying much higher energy bills because of all the extra effort your unit has to exert.


There are so many variables that can have a profound effect on calculating the appropriately-sized unit for your home or office. One of them is the fact that you are in a desert climate, which requires you to run the air conditioner at a much higher volume and for longer periods of time than you need your furnace.

Other factors include not only the number of windows, but their size, design, and placement. Once again, the desert heat has an effect on the direction your windows face. A professional will also consider the age and construction of your home and analyze the type and amount of insulation as well as the duct work.

A professional HVAC tech will use the Manual J Method of calculating the most cost-effective and energy-efficient model and size of the unit that’s designed specifically for your environment.


Legacy Air’s experienced team of HVAC technicians takes the time to thoroughly inspect your home or business to ensure you receive the very best quality product and installation services we have available. We take every aspect of your home’s placement and condition into account in order to guarantee maximum efficiency and money savings.

If you’re looking for a reputable HVAC service to answer your questions regarding brands, equipment type, installation, coverage, and warranties, seek out the professionals at Legacy Air, and give us a call at (702) 453-4229. We pride ourselves on putting our customers’ best interests first.


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