The Cheapest Time to Air Condition a New Build Is Before You Move In

The most common objection to air conditioning in a smart house is not the unit on the wall. It is the trunking: the white plastic duct carrying pipe and cable down the outside of the building to the outdoor unit. On a rear elevation, painted to match, most people stop noticing it within a week. But it is the thing customers ask about first.

On a new build you can avoid it entirely, if you move at the right moment.

What first fix means

First fix is the stage after a house is weathertight — frame up, roof on, windows in — but before the plasterboard goes on and the walls are closed up. It is when the electricians and plumbers run everything that needs to be buried.

If refrigerant pipe, interconnecting cable and a condensate drain go in at that stage, they are inside the wall forever. Nothing is visible afterwards except the indoor unit itself and a small grille or cover where the services reach the outdoor unit. No trunking anywhere.

You do not have to fit the whole system then

This is the part people miss. The expensive, disruptive bit is the pipework, not the kit. You can have the services run and capped at first fix and leave it there — no indoor units, no outdoor unit, no commissioning, no spend on equipment.

A year later, when you have lived through a summer and know which rooms actually need it, the install becomes a couple of hours per room rather than a day. The services are already waiting behind the plasterboard.

How to get access

This is the awkward part, and it varies enormously between developers.

• Ask early. Once a plot is past first fix, the opportunity has gone. Raise it when you reserve, not when you are two weeks from completion.
• Some developers will quote it as an extra through their own contractors. Usually the simplest route even if it is not the cheapest.
• Some allow third-party trades on site under site supervision, with insurance details and a method statement. Some refuse outright, and that is their right — it is their site and their liability until you complete.
• Get whatever is agreed in writing, and check with the warranty provider that it does not affect your structural warranty. Nobody wants that argument in year four.

If you have already moved in

Then you have missed the cheapest route, and it genuinely does not matter very much. A surface install on a finished house is routine work, and a tidy one is a long way from the industrial-looking jobs that give trunking its reputation. Run on a rear or side elevation, in the right colour, following a line the eye already expects, most people never comment on it.

There is also usually a second window. If you are having a loft boarded, a garage converted or anything else that opens up a ceiling or a wall, pipework can often be run then at very little extra cost. Worth asking before the plasterboard goes back.