Whole House Cooling

Central air conditioning is installed in many new homes that lie in areas that see intense heat and or humidity. Stepping into an air conditioned home from a muggy 90-degree day is indeed a relief. If you have an older home and have been using window units, a central A/C unit would be big improvement, for both convenience and efficiency.

Central air conditioners are often more economical to run than many separate units installed in many rooms. The convenience comes with avoiding the seasonal installation and removal of these window units. If your home has a central forced air heating system, the installation of central air is a relatively easy task because the duct work and air handling fans that distribute the air are already in place. Adding a cooling coil into the existing air handling system saves the expense of a new or secondary air handler. Homes that have baseboard, radiant and other ductless systems will require a more involved A/C installation. If your home falls into this latter category, there are other options available that may prove less costly or intrusive to install.

Air Conditioning Basics

Conditioned air is air that has been “conditioned” this usually means that it has been cooled down. When air is cooled it also loses a lot of its humidity or moisture by the process of condensation. Lower levels of humidity in conditioned air allow our bodies natural cooling process of perspiration / evaporation to be more effective, and therefore make us feel cooler. Basic laws of physics and thermodynamics control how this whole process happens.

Some people wrongly believe that air conditioners and refrigerators “make cold”, while in fact, they move heat from one place to another. In a refrigerator you can feel the heat that is removed from the inside by placing your hand near the outlet vent. In air conditioning, an evaporator coil removes the heat from the air that flows through it, this heat is then released somewhere else by a condensing coil. In split systems this condensing coil is usually located outside the home. Locating the condensing coil outside also minimizes the noise that accompanies the compressors and fans that these systems require.

New Ducts and Air Handlers

If your home is one that lacks a central forced air heating system, A/C can still be installed, it is just going to entail more work and expense. These costs will vary by the configuration of your home. Single story homes can be readily equipped from the attic, basement or crawlspace if present. Multi-story homes may need more complex ductwork to span the different levels or have redundant systems installed to be served from multiple areas. Obviously the more intrusive the work the greater the cost. The backs of closets often provide a “chase” that is used for running ductwork from a basement to a second floor. A large portion of the expense of these installations comes from new air-handling systems that are already present in existing forced air-heating systems.

Costs and Alternatives to Central Air

Retrofitting an older home can be complex. One alternative to a central system may be installing fixed wall units in just a few rooms. These work much like a window unit but do not need to be installed and removed each season.

Cost for these systems run about $2500 per room, a central system can run $7000 to $8000 for a typical 3-bedroom home. Costs can vary by region so check with your local installers for your location. Designing your project based on costs, and impact to your home is something to do first. Ceiling fans by comparison are quite economical, with costs around $50 to $200. Home design can also play a role in heating and cooling, in the desert South West, adobe homes, which have been around for centuries, are naturally cool compared to other buildings. Super-insulated homes, earth sheltered and earth-bermed homes also have lower cooling requirements and may be completely passive in their cooling design. Evaporative coolers and whole house fans are other low cost options.

Should you retrofit this fall?

Ancient Romans ran cool water from aqueducts through the walls of some buildings to keep them cool. In more modern times people sat in front of fans and sipped iced lemonade to stay cool. When I was a kid growing up in the Midwest, we used to hide out in the basement in our home that lacked A/C to stay cool. Here in Colorado, at 8500 feet, it rarely gets so hot that AC is needed, so we get by with a few open windows and ceiling fans. The cooling choices you make should reflect your home, your budget, and your lifestyle.