Adding a Central Air Conditioning System in Your Home

Whether or not you have ductwork installed in your home, adding a central AC system is actually more cost-effective and less troublesome than you might initially think. And cost is probably the main impediment to finally shifting to a central air cooling system.

However, there are many reasons to justify your decision to replace your dripping, noisy window-type air conditioning units with a quiet and efficient central AC system that can cool your entire home. These include the hotter summers, and growing older that causes you to be less tolerant to heat, among others.

conditioners and replace them with quiet, efficient whole-house central-air-conditioning systems. But we don’t take the idea any further.

Central Air Conditioning

If you have existing forced-air furnace ducts, as a homeowner, it is just natural to worry that altering your heating system will be expensive, and may ultimately result in inefficiency. The truth is, installing a central AC system is actually easier and would cost less.

When you add central air to your forced-air heating system, you can expect to spend around $3,500 to $4,000 if you have a 2,0002 ft. home. Two technicians can complete the job in two or three days, usually without changing the ducting.

Now, if your house will require ducts, you may need to spend twice as much. If you work with a contractor with enough experience in retrofitting, the ductwork can be cleverly hidden behind walls or closets, and in the attic. The job will only result to a little mess, and cuts into walls and ceilings will be minimal.

The first step involves selecting the right unit. It is likewise the most important decision to make before installing a central AC in your home.

Another important factor is heat-gain calculation. All HVAC contractors begin their home evaluation by performing a J load calculation as prescribed by the Air Con Contractors of America’s manual. This will determine the heat gain in your home.

The J load is easy to compute, and it will determine the size of the unit you will need. If a prospective contractor recommends a particular unit for your home solely based on experience, then it should raise a red flag. Cross the contractor out of your shortlist and move on to the next.

Although your location is a consideration, other factors come into play when determining the right size of the unit. These include the amount of attic and wall insulation installed, the placement and types of doors and windows you have, as well as your home’s orientation in relation to the sun.

The calculation will also tell you the benefits you stand to gain by upgrading your home insulation. By converting your home into a more energy efficient unit, it may be possible to reduce your required air con unit’s size.

The split-system condenser is installed outside, with no obstructions to the airflow. The condenser will then vent the heat that is absorbed from the refrigerant while it pushes cool refrigerant to the indoor fan and coil system.

Getting the Right Unit Size

Based on the heat-gain calculation for your home, the contractor will come up with the recommended AC size. This is expressed in either Btu per hour or tonnage. A ton is equal to 12,000 Btu/hr.

Now, why is it important to get the proper unit size for your home’s AC? If you have an undersized unit, it cannot completely cool your rooms on very hot days. The unit will likewise be more expensive to operate since it will be forced to run longer compared to a unit of the right size.

On the other hand, an oversized compressor will also cost more money to run since it will require more power to run a bigger-sized unit. An oversized unit likewise doesn’t necessarily pull humidity down in a more effective manner. This is because it quickly cools the air, but shuts off before properly circulating the air volume past the coils, and get the necessary moisture.

This will only result to a room feeling damp and clammy. The actual temperature will likewise not match the AC unit’s indicated temperature.

Unit Efficiency

Once the proper unit size is determined, your contractor would next discuss the unit’s efficiency. This is expressed by the SEER (seasonal energy-energy efficiency rating). It indicates the Btu rating an air con will remove pre wattage of electricity consumed.

The higher SEER you get, the lower the cost to operate. According to Federal law, new AC units must have a minimum rating of 13 SEER. This ensures lower operating cost, higher quality performance, better sound shields, more safety features, as well as lower voltage requirements. The higher the SEER, in general, the bigger initial cost for the equipment.

Central Air Conditioning

Unit Types

You next need to decide which system type to purchase. There are two main types:

Package System – This involves ganging the condenser that cools the refrigerant as it emits warm air to the unit’s fan and coil system that, in turn, cools down and blows the cooled air. The ducting system directly connects to the unit. Essentially, it is a massive wall air con with ducts. Package systems, however, are rare.

Usually, the fan and coil system is mounted on the floor of the attic. It uses piped in refrigerant for cooling air from the condenser installed outside. The fan blows the cooled air to the rooms below through the ducting system.


Split System – A split system involves a condenser installed outdoors and a fan and coil system indoors. Pipes that carry the refrigerant connect the two units. If you have an existing forced-air furnace installation, the pipes are attached to an attached cooling oil system in your furnace air handler.

Sometimes, it directly goes to the existing plenum. But, if it doesn’t work due to space constraints, the contractor will make a new sheet metal plenum. If there’s no existing forced-air installation, the new fan and coil installation is usually done in the attic, where cool air can be delivered through a duct system. The 20’ to 30’-long pipes carrying the refrigerant can be disguised as a downspout.


Proper Placement – There’s no such thing as a 100% noise-free condenser, regardless of what the manufacturer claims. It is therefore a good idea to discuss with your contractor on a suitable location far from a home-office window or bedroom.

Never enclose the condenser completely or install it under a deck as the exhaust will warm the air on top. Bear in mind that any restriction to the airflow will negatively affect the unit’s efficiency. However, you can conceal the condenser in the landscaping. Just make sure the air can circulate freely around it.

No Ducts? No Worries

Majority of central ACs are split-type models. The condenser is installed outdoors, while the fan and coil installation is indoors. The two are connected by pipes running outside the house. The piping is often disguised as a part of the home’s gutter and spout system. Ducts accommodate rooms in the second floor through ceiling registers. The ductwork usually runs through closets going down to rooms in the ground floor.

Maintaining the balance is a return duct that lets air back to the fan and coil, and a filter is installed inside the duct to keep the cool air free from dirt and airborne dust.

Delivering Cool Air

The furnace ducts use to blow hot air during cold months are also used for the air conditioning system.

If Ducts Are Installed

Have your ductwork inspected. Modifications are often necessary to accommodate a larger volume of cool air coming from the AC system. Older duct systems, unfortunately, are often bigger. Thus, they work better when trying to retrofit the central AC system. Today, ductwork tends to be smaller as the HVAC industry learns more and more about airflow dynamics, as well as the sizing of delivery systems and furnaces.

Following are the usual modifications necessary for existing ducts:

Upsizing the Furnace Blower – The blower size is rated in cfm or cubic feet/minute. By upsizing the blower, you adjust the cubic footage of cool air necessary for your home. An undersized blower will move insufficient air through the coils. The can then freeze.

Sealing the Ducts to Improve Efficiency – The sealing job is best left to pros. This is because an imbalance in the system can trigger hazardous back-drafting during heating season or warm air pockets during the colder months.

Replacing Old Supply Registers – Swapping the older registers for new ones will allow a bigger air volume to pass. Grilles of old registers with only ¼” wide slits offer extreme resistance to airflow. On the other hand, new grilles can help improve the flow of air by around 15% to 25%.

Ducts that feed cooled air from the attic-installed fan and coil system often wind up in the ceilings of rooms in the first and second floors.

If New Ducts Are Necessary

Because the HVAC’s fan and coil system is attic-mounted in many retrofit AC systems, it can be difficult for supply and return ductwork to reach ceiling registers in the rooms below (first and second floor). Ducts feeding the rooms in the second floor often run through the attic floor then dive in-between the floor joists. This is where they are linked to the ceiling registers. Ducts feeding the rooms in the first floor usually run down through the closets in the second floor.

Your contractor will first determine the ducts’ position to come up with the floor plan for the second floor. It will then be laid over the first floor’s floor plan. Second floor closets often provide access to the locations of the ceiling registers in the first floor.

Ductwork that run in closets doesn’t take up a lot of space. Since ducts are often either 12×6” or 10×8” even in a cramped 2×4’ closet, they use up only 4 out of the total 64 cu. ft.

There are cooling contractors who will recommend using an inexpensive and small flexible hose called a flex duct. However, you should avoid using the material in active closet spaces. This is because it can’t handle normal wear and tear, and it is prone to getting punctured.

How messy can duct installation be? In general, ceiling and wall surfaces are barely touched. No holes in the ceilings in the first and second floors are necessary to accommodate the registers, although some closet floors in the second floor may require a bit of work for the installation of new ducts. However, these holes are small, and will barely create some mess.

With or without ductwork installed in your home, you need to contact a reliable HVAC contractor if you think a central AC system will make your home more pleasant to stay in during summer. The contractor will then assess the cost of installing a central air conditioning system as well as the methods to use.

By selecting the right contractor and equipment, you will help ensure comfortable conditions in your home for years to come.

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