Getting the right size HVAC system for your home makes a massive difference in your comfort level and the cost of your energy bills. Determining what size cooling and heating system your home needs is never easy and is generally not something that you can accurately do yourself. This is especially the case if you have a larger home with more complicated cooling and heating requirements. Here are some considerations that heating and cooling technicians use to determine what size system a large home needs.
Why Proper HVAC Sizing Is So Crucial
Installing an oversized or undersized system is a huge waste of money since it won’t ever perform nearly as effectively as it should, will usually require more frequent repairs, and will almost certainly have a much shorter lifespan. If the system is too large or too small for your house, it wastes huge amounts of energy. An undersized system wastes energy because it simply produces insufficient cooling or heating. It has to run much more than it normally should and uses much more gas or electricity than a properly sized system would.
If you have an undersized cooling system, there’s also almost no chance that it will be able to cope with the extreme Las Vegas heat no matter how much it runs. With a system that’s too small, there will be many days during the summer when your home stays far hotter than you want it to be until your cooling system can finally catch up in the evening or overnight once the temperature drops. You may end up with your air conditioning running all night and your home still being too hot when you wake up.
Another issue with oversized HVAC systems is that they usually short cycle. Short cycling is when an HVAC system shuts off after less than 10 minutes and then quickly comes back on again. This happens when a system is oversized because it puts out far more heating or cooling than you need.
You may think this is a good thing since it results in your home getting fully heated or cooled faster. The issue is that the system works so fast and shuts off so quickly that the air that it produces doesn’t have time to mix with the air in each room. The result is that the temperature constantly fluctuates, so the system has to turn on again soon.
Short cycling greatly increases the amount of wear and tear on the HVAC components, which leads to a higher chance of breakdowns and a shorter lifespan. Short cycling also leads to much greater energy consumption since the HVAC system draws a huge amount of power each time it turns on. This is especially true for air conditioners and heat pumps since the starting load of their motors is often three to five times higher than their running load. Starting load refers to how much power the motor has to draw to start up while running load is how much power it takes to keep the motor running.
Factors That Play a Role in Sizing an HVAC System
The two most critical factors when sizing a central or ductless HVAC system are the size of the building and the climate zone where the building is located. Climate matters because different locations have different cooling and heating requirements based on how hot the summers are and how cold it can get in the winter. For instance, homes in Las Vegas have far greater cooling requirements than in other places because of how extremely hot our summers get.
An HVAC system always needs to produce a certain number of BTUs of heating or cooling per square foot to work effectively, and the requirements per square foot vary based on climate. In many places, all you need for a house to stay cool during the summer is around 20-30 BTUs of cooling for every square foot the home has. Homes in Las Vegas often need an HVAC system that produces 40-45 BTUs per square foot at the very least.
The largest residential heat pump or air conditioner is a 5-ton unit, and a unit this size produces 60,000 BTUs of cooling. That means larger homes in our area will almost always need to have a minimum of two units. In this case, you’ll also have two separate HVAC systems that supply cooling and heating to different parts of the house. For instance, one may supply the upper floor and the other may supply the ground level, or you could have one unit on each side of the house that supplies that side.
Let’s say that the total size of all of the living spaces in your house is 2,500 square feet. That means in our area you’d typically need 100,000 BTUs of cooling at the very least. In this case, the normal recommendation would usually be to install two 4.5-ton, 54k-BTU units as long as the two separate systems are of equal size. You’d also need two separate furnaces unless the units are heat pumps and not standard air conditioners. Nonetheless, your furnaces wouldn’t need to produce as many BTUs of heating as you’d need in places where the winters are colder than ours.
How HVAC Companies Size Cooling and Heating Systems
Much more goes into sizing an HVAC system than just looking at climate and square footage, and this is true no matter whether you have a small home or a massive mansion. That’s why most certified HVAC installers are trained to use a special formula called a Manual J load calculation that allows them to accurately determine a home’s cooling and heating requirements and what size its HVAC system needs to be.
The technicians start by calculating the square footage of the house, but they then need to determine the overall level of insulation and air sealing to get an accurate idea of how many BTUs of cooling and heating the home needs. If the house is properly insulated and its exterior structure is well sealed with little air leakage, the requirements won’t be nearly as high as they would be for a home that’s poorly insulated and has numerous air leaks.
These initial calculations allow the technician to get a baseline of the home’s HVAC requirements. They then need to factor in things like the number of occupants and the location, size, and number of all of the house’s windows and exterior doors. These factors are especially important in determining cooling requirements since people, windows, and exterior doors all contribute to heat gain and lead to the requirements being at least a bit higher.
The general rule is that cooling requirements increase by 500 BTUs for each person living in the home and for every window and exterior door. Large windows and skylights, especially those that face south and west, can increase the requirements even more because of all of the sunlight and heat they let in.
Polar Air & Heating, Inc. has been serving Las Vegas and the surrounding areas since 1998, and we’re the area’s top choice to handle all of your home’s cooling and heating needs. Our expert technicians have years of experience in HVAC installation and will always ensure that your new system is exactly the right size and type for your home. To schedule a consultation for your new HVAC system or ductless mini-split or any repair or maintenance services, contact us today.
