Try mini-duct system for central air

Q: After the heat wave we have had recently, I think we need to add central air-conditioning. We have electric baseboard heating, so there are no ducts. What are the simplest central system options available?

A: Your situation with no heating duct system is not uncommon in older homes throughout the country, especially in hot or cold climates.

In hot climates, one or two small space heaters or floor furnaces are all that is needed for heating. In cold climates, boilers and other non-ducted heating systems are common.

You have basically two options to cool your entire house: a mini-duct system and a mini-split system. A mini-duct system has cooling air outlets (registers) in every room, whereas a mini-split system has cooling air circulators in just a few rooms. The cool, dehumidified air from the circulators will flow throughout your home, but there may be uneven temperatures and the noise level is higher than with a mini-duct system.

A mini-duct system is easy to install inside the walls with minimal remodeling. The small ducts fit inside a typical framed wall without having to disturb the drywall. Trying to install standard metal ducts with an outlet in every room is difficult, especially in two-story homes. Unico's mini-duct blower is modular so it also installs easily in the attic.

The mini-duct system has some comfort and overall efficiency advantages over a standard ducted air-conditioning system. Both systems use a high-efficiency outdoor compressor unit, but the mini-duct system operates at a much higher air pressure. This high pressure is needed to force the cooling air through the small insulated ducts.

Since the blower operates at a high pressure, dense cooling coils, which would create too much air flow resistance for a standard ducted blower system, can be used. These dense coils keep the room air in contact with them longer to increase the amount of dehumidification by up to 30 percent. If your house is dehumidified, you can feel comfortable at a higher temperature, therefore saving energy.

There are generally several mini-ducts run to each room. These terminate at 2-inch diameter outlets typically mounted up near or in the ceiling. With several outlets in each room, the cool air is distributed well throughout each room. Long, but narrow, outlet registers are also available for mounting under cabinets or where there are other space constraints.

The cool air blows out of the outlets at a high velocity. This creates a vortex effect that draws room air into the flow for excellent mixing.

Even though the cool air blows out at a high velocity, the system operates very quietly. The main blower and heat exchanger unit is often mounted in the attic with a larger insulated truck duct running almost the length of the attic. The insulated room ducts run off this trunk duct or from other secondary smaller trunk ducts to the room outlets.

Send inquiries to James Dulley, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com.