AIR CONDITIONING
Q How much does installing an air conditioning system cost? A
Building Regulations Part O (Overheating) was introduced in June 2022. Albeit that this looks at potential overheating in new properties, there is now a lot of focus on adding cooling to our homes. Cooling is being introduced to mechanical ventilation systems and many heat pumps are now able run in reverse to cool our homes (though they don’t have the same effect as air conditioning — see page 189).
THE OPTIONS Portable models
The lowest cost air conditioning is the portable model. These units can be moved from room to room as required. A portable air conditioning unit is around the size of a laundry basket and will usually plug into a standard electric wall socket. You will need to run a duct (approximately 125mm diameter) out a window to expel the warmth. You will also need a bucket to run the condensate drain into. Portable air conditioning units start at around £250 and have no installation costs.
Installed systems
The fully installed type of air conditioning systems have an outdoor fan unit connected to indoor fan units via refrigerant pipes and have different configurations. The simplest fully installed systems are known as room air conditioners (RAC) and there is one outdoor fan unit and one indoor unit. These systems are usually for single room use and you can expect to pay from around £350 for the materials and potentially around £1,100 to £1,500 for a fully installed system.
An advancement on the RAC unit is one outdoor fan unit and two indoor units. Both indoor units serve a single room and are both either on or off. You cannot usually operate the indoor units individually and they can only be in cooling or heating mode.
The next step up is the multi-split air conditioner. These systems have one outdoor fan unit and can have up to around 10 indoor units, depending on the manufacturer. The indoor units can be located in the same room or in separate rooms and can be operated individually or in any number up to the full installed amount. The indoor units can only be in either heating or cooling mode so you can’t have some doing heating and some doing cooling. The cost of a multi-split unit is usually around £1,200 per indoor unit.
AIR CON INSTALLATION
With air conditioning units it is important to decide where the outside and indoor units are sited so that the total length of refrigerant pipe can be calculated. The two pipes each have a diameter of around 28mm including insulation. You will also need a condensate drain pipe (around 22mm diam) plumbed to each indoor unit, to take away the condensation.
There are different types of indoor units, from fan convectors that resemble a central heating radiator to wall-mounted bulkheads, slim duct systems that can be boxed in and ducts installed to distribute the air. These units are popular as the fan noise is then further away from the point of delivery but there needs to be more design detail put in to define where the ducts go. This can all add cost. Ceiling cassettes are direct fan units that are fitted into the ceiling and circulate air. The costs of multi-split systems vary according to which indoor units you have and the simplest installation will usually be the wall mounted bulkheads.
The exact specification of the different indoor units will often vary between manufacturers and it is worth getting quotes for different brands. Make sure that the installer is F-gas qualified and registered with a self-certification body. A fully installed air conditioning system must also be inspected every five years to assess its energy efficiency.
RUNNING COSTS
Air conditioning units can be hard on electricity so do take this into account. The air conditioning unit uses a refrigerant cycle to deliver cooling and the waste heat is rejected to the outside. The process allows for around 300% efficiency, so if you use 1kwh of electricity you will get an equivalent 3kw of cooling. Taking the average air conditioning indoor unit at around 2kw you will use around 600W of electricity. At around 28p/kwh it will cost around 20p per hour per indoor unit. If you also have photovoltaic (PV) panels then you have the ideal combination as you will be generating the most electricity at the time when cooling may be required and your running costs will be a lot less.