Adding Onto Your Home Affects Your AC

adding onto your home effects your AC

Adding a new room to your house is an exciting venture, but are you aware of how adding onto your home affects your AC? Here are a few things to consider while you’re planning for that new addition. 

Will My Existing AC Unit be Enough

You need to make sure that the AC unit you have will be efficient enough to cool the addition to the house. 

Air conditioners are sized by the number of BTUs they put out. BTUs stand for British Thermal Units and refer to the amount of energy your air conditioner is using per hour.

To figure out what size air conditioner you require, you first need to determine the amount of BTUs you require. This is done by calculating your square footage.

Use the following equation: ((House sq.ft. x 25) / 12,000) – 0.5) = required tons

For example: your house is 2,350 sq.ft. Plug it into the formula: ((2,350 x 25) / 12,000) – 0.5) = 4.39

This means that your house requires a central unit of 4 to 4.5 tons.

However, if you live in a hot climate, where temperatures are high most months out of the year, you will need to change the formula slightly, because otherwise your unit will be undersized. Instead of subtracting 0.5, you will need to ADD it.

So the new formula looks like this: ((2,350 x 25) / 12,000) + 0.5) = 5.39

This means that your house requires a central air conditioning unit of 5 to 5.5 tons.

Keep in mind that this is just an estimate for you to use. HVAC contractors use a Manual J calculation to determine the heating and cooling loads of a home or building, and recommend the capacity of HVAC equipment needed. 

How is Ductwork Effected? 

Duct systems are sized to provide just the right amount of airflow from the furnace to each of the ducts in the system. A duct run may start at the air handler with a 10-inch-diameter duct, then step down to 8 inches and then to 6 inches as the duct run branches off and gets further away from the air handler. Depending on the size of the area you’re trying to heat and the distance away from the furnace, you may be able to extend right off the end of the 6-inch duct, or you may need to go further back and tap into one of the larger ducts. 

A single small duct run won’t have as much effect on the system as larger ones will. When airflow is rerouted, the rooms farthest from the air handler are affected the most. Sometimes airflow will be reduced to the point of being ineffective for cooling that space. Setting up and balancing a duct system is a matter of knowing the amount of airflow being produced, the size of the spaces being heated, the diameter of all the ducts, and the total length of each duct run. Under- or oversizing the duct runs can result in poor performance throughout the entire system. This is a big factor for how adding onto your home effects your AC.

Dealing with hard to cool additions

So what happens if your current system isn’t adequate to handle a new addition to a home?  Typically, one of three things can occur. First, you can buy a new whole-home system. We only recommend this if your current AC needs to be replaced, or is over 10 years old. Next, you can buy a dedicated unit for the addition. This can sometimes ease the burden of your other AC unit and add some extra life to it. And last, you could opt for a ductless split system.

A ductless mini split air conditioner delivers heated, cooled or ventilated air directly to the target room, without running through ventilation ducts. Ductless AC and heat systems, just like ducted ones, have two main components: a compressor outdoors and one or more air handler units indoors. Indoor units can be placed almost anywhere in the room, as long as they can be reached by a thin conduit. They normally each have their own remote control, for easy access.

If you have and questions about how adding onto your home affects your AC, give us a call at 813-929-HAWK.


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