Whole-home cooling where there has never been ductwork
Adding an air conditioner to a house that already has a forced-air furnace is a replacement job. Adding central air to a house heated by a boiler, electric baseboard or radiators is a design project. There is no blower, no supply trunk and no return path, so all three have to be created in a way that fits the structure, delivers air to every room and does not turn the house into a construction site for weeks.
The usual approach is a dedicated air handler in the attic, a basement or a large closet, connected to an outdoor condenser. From there, supply ducts branch to each room through attic space, closets, soffits or floor cavities, and a return path brings air back to the air handler. In a two-story home, an attic air handler serving the upstairs and a second small system or ceiling-mounted supplies for the first floor is a common layout.
Where running conventional ducts would mean opening too many finished walls, we look at alternatives. Small-diameter high-velocity duct systems fit through tight spaces, and ductless systems avoid ducts altogether. Our Heat Pump Installation page explains how a ductless or ducted heat pump can deliver both cooling and supplemental heat, which is often the better investment in a home that currently relies on a boiler alone.
How a central air addition comes together
The planning phase is longer than on a replacement job, and it pays for itself in a cleaner installation.
Walk-through and measurements
We survey the attic, basement, closets and wall cavities, measure every room and calculate the cooling load for each one.
Duct layout proposal
You see a plan showing where the air handler, condenser, supply outlets and return grilles will go, with any visible soffits or chases marked.
Electrical and condensate planning
The route for the condenser circuit, the condensate drain and, for attic units, a secondary drain pan and float switch are specified.
Rough-in
Ducts, refrigerant lines, wiring and drains are installed, with openings cut neatly and dust controlled in occupied rooms.
Equipment set and connection
The air handler and condenser are set, connected, brazed, evacuated and charged.
Balancing and walkthrough
Airflow at each supply is measured and dampers are adjusted so every room gets its share, then we show you the controls.
Good reasons to add central air
Window units work, up to a point. These are the situations where whole-home cooling earns its keep.
- Upstairs rooms become unusable in summerHeat rises and gathers under the roof. A properly designed ducted system can deliver the extra cooling upper floors need.
- Window units block light and viewsThey also leak air around their frames and are a security weak point on ground-floor windows.
- Humidity lingers even when it is coolCentral systems with adequate run time remove moisture evenly throughout the house, not just in one room.
- Someone in the home is sensitive to heat or allergensFiltered, conditioned air in every room is easier on people with respiratory issues or heat sensitivity.
- You are planning to sellBuyers increasingly expect central air, and the lack of it can narrow the pool of interested buyers in some markets.
What influences a central air project
The biggest variable is the path the ducts can take. A home with a full walk-in attic above the bedrooms and an unfinished basement below the main floor is relatively simple. A home with finished attic rooms, plaster walls and no basement takes more creative routing, and possibly a different system type. Attic installations also call for well insulated ducts and an air handler with a secondary drain pan, because condensate and summer attic heat are both hard on equipment.
Electrical capacity is the next question. The condenser needs a dedicated circuit, and older homes with small panels may need a service upgrade. We check the panel during the first visit so there are no surprises. Finally, patching and painting where openings are made is usually handled by the homeowner's preferred painter or carpenter, and we discuss who does what before work begins.
Wondering whether your house can take ducts?
Almost every house can. The question is where, and a site visit answers it quickly.
Keeping the boiler and adding the cooling
Homes heated by a hot water boiler often have the most comfortable winter heat there is, and adding central air does not mean giving that up. The new air handler can be cooling-only, leaving the boiler to heat exactly as before. Some homeowners add a hydronic coil to the air handler so the boiler can also supply warm air through the new ducts, which helps rooms that radiators never quite reached.
If you are considering replacing the boiler within a few years anyway, a heat pump air handler is worth pricing alongside a straight air conditioner. It cools in summer and handles milder heating days efficiently, reducing the load on the boiler.
Filtration and fresh air while the walls are open
A new duct system is the ideal moment to plan for air quality. A filter cabinet sized for a deep media filter, a return layout that pulls from central hallways rather than a single grille and, where appropriate, a fresh air intake are all far easier to include now than to retrofit later. If allergies are a concern, our Air Cleaning And Humidifiers page covers the options.
Adding central air: common questions
How much of my house will be torn up during installation?
Less than most people expect. Most duct runs go through attics, basements and closets. Where a wall or ceiling has to be opened, the openings are cut cleanly and kept to what is necessary, and dust barriers go up in occupied rooms.
Where does the indoor unit go in a house without a furnace?
Common locations are the attic, a basement, a utility room or a large closet. The best spot is central to the rooms it serves, has room for service access and has a practical route for the condensate drain.
Will central air work with my radiators?
Yes. The cooling system is separate from the boiler and radiators, so heating continues exactly as it does now. You simply gain a second system for summer, and optionally for warm-air heating as well.
Is ductless better than ducted for an older home?
It depends on the layout and your priorities. Ductless heads avoid duct work entirely and allow room-by-room control, while ducted systems hide the equipment and treat the whole house through a single filter. Many older homes use a mix of both.
How long does a central air addition take?
Most projects take several days to a week of on-site work, depending on house size and how complex the duct routing is. The timeline is spelled out in the proposal.
Related services for homes adding cooling
These pages cover the equipment and airflow choices that come up during a central air project.