Choosing the right AC size can be a very daunting task considering that this is a long-term investment for your home and family. In most purchasing decisions, people tend to think that the bigger item offers greater value. However, when it comes to an AC, a bigger unit isn’t always better.
An oversized AC will quickly cool your house and then shut off. Since it doesn’t go through the entire cycle, heat will soon infiltrate your home once again, and the AC will kick on. The short cycles strain your AC, and it’s more likely to wear out quicker than expected. This will also drive your energy bills up, and the AC won’t adequately draw moisture from the house.
A smaller unit is equally problematic. An undersized AC will work harder, but it won’t adequately cool a larger space. It runs longer, which increases energy use and the chances of a breakdown. A correctly sized AC, on the other hand, provides comfort, humidity control, durability, good air quality, and quiet operation. The following factors will guide you in picking the right AC size for your home.
1. The Square Footage
Begin by calculating your home size to determine the required cooling capacity. Get the square footage of your house by first dividing it into sections to calculate the area accurately. For the rectangular-shaped rooms, multiply the width and length. If you have circular spaces, measure the distance from one end to the center and calculate the area.
For triangular rooms, multiply the length with the width and divide by two. Repeat the process for all the rooms you intend to cool, but exclude the garage, sunroom, and any other spaces that don’t have vents in them. Count rooms that open up to one another as a single space. Next, get the total square footage of the rooms by adding your calculations together.
2. British Thermal Units (BTUs)
BTU is a standard unit of measurement that represents the cooling effect that an AC can provide. To calculate the required BTUs to cool your house, multiply the square footage by 20. As a general rule of thumb, you need 20 BTUs for each square foot of space. Let’s say a rectangular room is 35 feet long and 20 feet wide. That means that it has a square footage of 700 square feet. So, you would multiply 700 by 20 to get the minimum cooling capacity needed, which is 14,000 BTUs.
The AC’s cooling capacity can either be in wattage, BTUs, or tons. Keep in mind that 1 AC ton is equal to 12,000 BTUs per hour, which is equal to 3,500 watts of cooling. Considering the example above, you will need 14,000 BTUs, 1.67 tons, or 4,000 watts of energy to cool such a room.
3. The Number and Type of Windows
Although big windows allow ample lighting, give stunning views, and create an illusion of bigger spaces, they affect the temperature of a house. Windows allow heat entry into the home, which increases the volume of air that your AC needs to cool. If you have more than one big window in a room, you should add 10% to the number of BTUs needed.
However, if you have well-insulated windows and always keep the shutters, curtains, and blinds shut for most days, they help keep out the summer heat. You can thus reduce your cooling capacity by 10%.
4. The Quality and Amount of Insulation
You will need fewer BTUs to cool a well-insulated house than an uninsulated one since it loses conditioned air through the gaps and allows heat entry. Consider the nature of the construction materials and the quality of insulation around doors and windows and in walls, floors, and the attic.
Today, most states have building codes that indicate the quality of insulation that a house should have. Some older homes have inadequate insulation, so they will need a more powerful AC.
5. The Number of People Living in the House
Every human body dissipates a certain amount of heat. The BTU calculation of 20 per square foot works on the assumption that every space in your house has two people. Add 600 BTUs per hour per person if more than two people occupy one room at a particular time. If you have a gym at home, the activities increase the amount of heat in the room as well. Add 380 BTUs for every person working out in the gym at a specific time.
6. Your Climate Zone
If you reside in a warm region, your AC will work harder to produce the desired cooling effect. Choose a unit with a higher number of BTUs if you live in a hot, humid region. Likewise, you can go with fewer BTUs if you live in a colder and drier area.
7. Heat-Generating Equipment
The oven, microwave, and stove emit heat while in operation. If you intend to cool the kitchen or any other room with heat-generating equipment, add 4,000 BTUs to your calculated amount.
8. The Home’s Design
A home with a more compact design, like a multi-story townhome, requires less energy to heat than a ranch-style house. The upper floor of a building acts as a layer of insulation for the rooms beneath.
The BTU calculations work for rooms with 8-foot ceilings. Add more BTUs for a ceiling height above this range. East- and west-facing rooms also tend to get a bit hot during summer, and they require higher cooling capacity than the north- and south-facing rooms. Also, consider the floor plan. It will take less energy to cool an open floor plan than multiple separate rooms.
9. The Age and Quality of the Ductwork
If you have poorly installed, leaky, or damaged ductwork, it can let the conditioned air escape. Your AC will thus require more cooling capacity to maintain a desirable temperature. You should call a professional to assess the nature of your ductwork before installing a new AC. They can fix leaks or advise you to install new ductwork that delivers the correct air volume at the desired temperature. A technician will also ensure that the ductwork size matches the AC’s capacity.
Do You Need Professional AC Sizing Services?
It can be difficult to figure out the size of AC that you need for your home. If you find it complex to calculate the required cooling capacity for your space, consult a professional HVAC technician. They will thoroughly assess your house considering the above factors. With their expertise and experience, they can help you pick a suitable AC.
Once you buy a right-sized system, you should also maintain it regularly. Plan for preventive maintenance so that a professional can assess and inspect all the AC components, fix minor issues, and clean and lubricate parts to ensure that the AC works at optimum efficiency.
If you need assistance, don’t hesitate to call Holbrook Heating & Air Conditioning. Our company specializes in AC and furnace repair, installation, and maintenance services. We also offer indoor air quality and commercial HVAC services in Syracuse, NY, and the surrounding areas. Reach out to us today to schedule an appointment.
