Commercial HVAC Systems

Start here: what problem are you solving?

Most people arrive at a system type before they have settled the question it is meant to answer, and that is where projects go wrong. Four briefs sound similar and lead to completely different plant: "our staff are uncomfortable in summer", "this stock has to stay below a stated temperature", "our heating is on gas and we want that to change", and "we need to stop the comms room going down".

The second useful question is what constrains the building — where plant may go, whether the electrical supply has headroom, whether the building is listed or in a conservation area, and whether work has to happen outside trading hours. Those constraints frequently narrow the options more than the load does.

Air conditioning

The largest group, and the one most buyers actually mean when they say HVAC. Our commercial air conditioning overview covers the four system families, how duty is genuinely calculated, the 2026 refrigerant position and the two legal duties that attach to AC and nothing else — F-Gas leak checking and TM44 inspections.

The specific services: installation — survey, load calculation, electrical capacity, commissioning and handover; repair — faults by symptom, and why a regas is not a repair; servicing, F-Gas and TM44; and replacement, which covers R22 and R410A upgrades and the A2L charge limits that can turn a like-for-like swap into a redesign.

Refrigerant-based systems

VRF and VRV

One outdoor unit serving many indoor units on a shared refrigerant circuit, each modulating independently. The workhorse of the mid-size UK commercial building. The genuinely valuable feature is three-pipe heat recovery, which moves heat from a zone that is too warm into one that is too cold rather than rejecting it outside — worth real money in any building with more than one aspect. See VRF and VRV systems.

Close control for IT spaces

Server and comms rooms are the one space in a commercial building that needs full cooling at 3am in February, and standard comfort air conditioning is not built for it — the usual failure is a unit that trips out in the first hard frost. See server and comms room cooling.

Cellar cooling

A refrigeration problem rather than a comfort one, running continuously all year, and usually the largest single electrical load in a licensed premises. See cellar cooling.

Water-based systems

Chillers and chilled water

A central chiller makes cold water and pumps it to terminals around the building. It comes into its own above roughly 200–300 kW — and sooner in two other cases: where the refrigerant volume of a direct-expansion system becomes a problem in its own right, and in buildings with many small rooms, where A2L charge limits constrain a refrigerant-based design. Confining refrigerant to the plant room also makes chilled water the usual answer in heritage buildings where external plant is restricted. See commercial chillers.

Air-based systems

Air handling units

Central plant conditioning and distributing air through ductwork, usually with heat recovery. Construction specification matters as much as duty — an office AHU, a corrosion-resistant pool unit and a hygienic food-industry unit are genuinely different machines. See air handling units and, for the specialist case, swimming pool AHUs.

Ventilation and MVHR

Fresh air, indoor air quality and heat recovery. Frequently the system with obligations that have nothing to do with comfort — kitchen extract, process extract, and hazardous-substance ventilation all sit here. See ventilation and MVHR.

Heating and electrification

Modern commercial air conditioning is already a reversible heat pump, so in many buildings the cooling replacement is most of the heating solution. Whether electrifying heat reduces running cost depends on the gap between your electricity and gas tariffs and on the system's SCOP, which is why it has to be modelled on your actual figures. See commercial heat pumps and the heat pump versus gas boiler comparison.

Keeping it working

Whatever is installed, the same things determine whether it still performs in year eight: planned maintenance, honest commissioning records, and controls that match how the building is actually occupied. See maintenance and PPM for whole-building contracts and the SFG20 explainer for how a defensible regime is built — including which tasks are genuinely statutory and which are discretionary spending.

Ranges are for scoping only; the cost guides break down what moves each figure.

By building type

The same system behaves differently depending on what the building does. Offices need zoning by aspect; retail is dominated by open-shopfront infiltration; warehousing usually needs targeted rather than whole-volume cooling; and restaurants and kitchens are governed by the balance between extract and make-up air. The sectors index compares them.

Frequently asked questions

How do I know which HVAC system I need?

Start from the problem rather than the technology — staff comfort, a stated stock temperature, electrifying heat and protecting a comms room are four different briefs with different answers. Then have the load calculated per zone from occupancy, lighting, equipment and solar gain. The system type follows from that; it cannot be chosen from floor area.

What is the difference between VRF and chilled water?

VRF distributes refrigerant around the building to indoor units; chilled water keeps refrigerant in the plant room and pumps cold water to terminals instead. VRF is usually better for mid-size multi-zone buildings, chilled water above roughly 200–300 kW — or sooner where refrigerant volume, A2L charge limits in small rooms, or restrictions on external plant make a refrigerant-based system awkward.

Do all these systems carry the same legal duties?

The refrigerant-bearing ones do — F-Gas leak checking at intervals set by charge, plus record-keeping, applies to air conditioning, VRF, chillers, heat pumps and cellar cooling alike. The TM44 inspection duty applies specifically to air conditioning above 12 kW effective rated output. Wet systems with cooling towers add ACOP L8 Legionella control.

For indicative pricing across every system type see the cost guides, for funding see grants and capital allowances, and for the areas we cover see locations. Or request a quote.