Whether you’re living in a cold or hot area, you need an air conditioning system that can maintain a comfortable temperature and humidity. Heating, ventilation, and air conditioning (HVAC) systems are becoming more of a necessity rather than a luxury. And if you’re a wise investor, you would make sure to get just the right size of the HVAC unit needed for your property.
Manual J Calculation
Ultimately, you can determine what size of HVAC unit is needed for your building by hiring a contractor who can conduct a proper method of Manual J calculation.
Manual J calculation is a technique performed with computer programs designed by the Air Conditioning Contractors of America (ACCA).
Factors that affect the Manual J calculation:
- Climate zone
- Building’s year of construction
- Type of property (residential or commercial)
- Building’s space area (SQFT)
- Building’s space height (FT)
- Insulation grade system
- Amount of exposure to sunlight
- Number of windows (tightness of windows)
- Number of occupants
- Number of kitchen spaces
How to Calculate The Right HVAC Load
Step 1: Identify the area size by the square foot
If you have a blueprint of the building, you can easily refer to the total square footage of the area, including each room’s size. Otherwise, you’ll have to manually measure each room’s length and width, calculate each square footage, and add up the total square footage of the whole area in the house that requires heating or cooling. It’s important to note that the height of each room should also be precisely measured.
Alternatively, you can get the measurements from the exterior, which is a much quicker process. When you get the total measurement by the square foot, you can subtract the entire area that does not require heating or cooling.
Step 2: Calculate the number of BTUs required in HVAC units
British Thermal Unit (BTU) is a measurement unit for the energy required to increase temperature. One BTU increases the temperature of one pound of water by 1° F.
Air conditioning units have standard BTU ratings, which tells you the amount of the cooling power it can produce.
If you want to get the BTU rate of the HVAC unit with the ideal cooling capacity, one way is to multiply the total area (by square foot) by 25 BTUs. For example, a 2,000 square feet area with standard height would then require 50,000 BTUs.
Another way of getting the HVAC unit’s right size is to consider the tonnage in calculating the required BTU rate for a particular area:
- AC tons per square foot for Commercial Spaces
One ton of AC can remove 12,000 BTUs from a 500-square foot area in an hour.
- AC tons per square foot for Residential Spaces
One ton of AC can cool down an area of 400 square feet in an hour.
So, in this case, to calculate the HVAC sizing, let’s set another example for a 2,000 square foot commercial area. Get the required tonnage by dividing 2,000 sq ft by 500, which will amount to 4 tons. Multiply 4 tons by 12,000 BTUs, and it would total to 48,000 BTUs.
Calculating the required BTU rate based on the area is just the base total. You still need to add up the BTU rates of other factors.
Step 3: Take note of the insulation factors
The insulation system built in the building is the main factor that has to be considered in installing the proper HVAC unit. But along with this, you have to account for other varying factors, such as the number of persons occupying the building, the number of kitchens, the number of windows in each of the rooms, the tightness of the window seals, the number of doors attached on the exterior part, and the amount of sun exposure that enters the building.
You need to add the following on the total calculation: 100 BTUs (for residential) or 380 BTUs (for commercial) per person; each window is equivalent to 1,000 more BTUs; each exterior door is equal to 1,000 more BTUs; and another 1,200 BTUs for every kitchen.
Step 4: Get the size of the air conditioning unit you need
Based on the previous steps and examples stated above, you can get the size of the HVAC unit needed for your residential or commercial building.
Let’s make an estimated calculation of HVAC load for a commercial space with 2,000 square feet, occupied by 10 people, has 2 kitchens, 8 windows, and 3 exterior doors.
- 2,000 sq ft = 48,000 to 50,000 BTUs
- 10 pax * 380 = 3,800 BTUs
- 2 kitchens * 1,200 = 2,400 BTUs
- 8 windows * 1,000 = 8,000 BTUs
- 3 doors * 1,000 = 3,000 BTUs
Total: approx. 65,200 to 67,200 BTUs
Why is it important to determine the right size of the HVAC unit?
It’s a common misconception for HVAC customers to assume that they can simply buy a random unit for their commercial or residential building, as long as it has a large capacity to produce heating or cooling systems.
Does it really matter to have the appropriate HVAC unit size for a particular building?
Apparently, the answer to this question is a definite yes.
Naturally, a smaller HVAC unit won’t be enough to fulfill its purpose. It would also be a waste to buy a full unit that can’t function according to your expectations and requirements. On the contrary, a bigger size can be an overkill, especially in terms of the electricity it’s eating up.
Installing the right size of the HVAC unit in a particular building allows you to regulate the desired temperature inside the building without wasting any significant energy.
You can trust your HVAC contractors to determine the perfect system for your residential or commercial building. However, it’s also essential for you to know how to identify the HVAC unit’s ideal size that will fit your needs.
Texas can have mild and cool winter climates during cold seasons, but it can also get terribly hot and humid in summer. Investing in high-quality HVAC systems would be practical, as it can be utterly useful all-year-round.