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Contractors who design
HVAC and M&E contractors need professional indemnity insurance whenever they design: sizing plant, calculating loads, laying out ventilation and air conditioning, modelling overheating or taking over a consultant’s design. Install-only work carries less professional risk, though site changes and commissioning still count. Your public liability policy deals with accidents; it is unlikely to respond when a building runs too hot, too stuffy or too noisy because of a design decision.
Part of: Professional indemnity for design and build contractors
In short
M&E contractors who design take on liability for whether a building performs. In England, Approved Document F says mechanical ventilation must be commissioned, with a notice to building control, and sets office fresh air rates, and Part O allows mechanical cooling in new homes only where heat can’t otherwise be removed. Air conditioning above 12 kW must be inspected at least every five years, and the report comments on sizing. PI covers negligent design and advice, but fitness for purpose terms and performance guarantees in subcontracts often go beyond what it will pay.
Last reviewed 5 October 2026 by the Apex professional indemnity team.
An HVAC or M&E contractor that only installs to a consultant’s design carries mostly accident and workmanship risk. Most firms do more than that. You size plant, select equipment, calculate heating and cooling loads, lay out ventilation, write controls strategies and take over consultants’ designs on design and build projects. Each of those is a professional judgement, and when one is wrong the client’s loss is usually financial: rooms that overheat, air quality that fails, plant that has to be replaced.
Public liability (PL) is for accidental injury and accidental damage to other people’s property. It doesn’t pay because an office won’t stay cool in July, and most PL wordings exclude claims that work failed to perform. Professional indemnity (PI) insurance usually covers your liability for negligent design, specification and advice, which is where the expensive M&E disputes sit.
The professional element grows with your role:
The following are illustrative examples, not real claims. They show the kinds of allegation M&E and HVAC contractors meet.
None of these involves an accident. Each says your design, specification or commissioning fell below what a competent M&E contractor would have done, and each asks for money rather than repairs to damaged property.
These are the rules and standards an expert will hold your design against. The Building Regulations guidance listed is for England.
| Rule or standard | What it says | Why it matters to you |
|---|---|---|
| Approved Document F, volume 2 (buildings other than dwellings) | Mechanical ventilation must be commissioned and a commissioning notice given to building control, following CIBSE Commissioning Code M. Offices need outdoor air at the higher of 10 litres per second per person or 1 litre per second per m², and new offices and some other rooms need a way of monitoring indoor air quality. | Air rates and commissioning records are the first things checked when occupants complain. |
| Building Regulations, Part O, and Approved Document O | New residential buildings must limit unwanted solar gain and remove excess heat. Mechanical cooling may only be used where heat can’t be removed adequately without it. Compliance is shown by a simplified method or dynamic modelling to CIBSE TM59 within set limits. | Cooling and ventilation design in flats is now a compliance matter, not just comfort. |
| Workplace (Health, Safety and Welfare) Regulations 1992, regs 6 and 7 | Enclosed workplaces must be ventilated with a sufficient quantity of fresh or purified air, plant needs a failure warning where health or safety requires it, and indoor temperatures during working hours must be reasonable. | Your client’s legal duties depend on your systems working. |
| Energy Performance of Buildings (England and Wales) Regulations 2012, Part 4 | Air conditioning systems with an effective rated output above 12 kW must have accessible parts inspected by an energy assessor at intervals of no more than five years. The report assesses efficiency and how the system’s sizing compares with the cooling requirement. | An inspection report can be the first document to say your system is oversized or inefficient. |
| F-gas rules in Great Britain | People who install, service, leak check or decommission refrigeration, air conditioning and heat pump equipment need F-gas qualifications, and companies doing that work for others need company certification. Operators must have equipment of 5 tonnes CO2 equivalent or more leak checked, with leak detection at 500 tonnes or more. | Certification is a legal condition of the work, and maintenance contracts put leak checks in your hands. |
Most expensive M&E disputes start with a performance specification. The employer doesn’t tell you what to install; it tells you what the building must achieve: temperatures in summer and winter, fresh air rates, noise levels, resilience. Your design is then judged on whether it delivers those outcomes, and the contract may promise more than PI will pay for.
The gap is between two standards. PI insures your liability for failing to use reasonable skill and care. A contract that says the installation will be fit for its purpose, or will achieve stated conditions whatever happens, imposes a stricter duty: you can be liable even if every calculation was competent. Most PI wordings exclude or limit liability that exists only because of a guarantee or fitness for purpose term. Read the design liability clause and push for reasonable skill and care, or at least know where you are uninsured.
Four habits make performance claims easier to defend:
If you work on smoke control or ventilation systems with a fire safety function, check whether your PI policy restricts fire safety work before you take the job on.
| Usually covered by PI | Often excluded or limited | Needs a different policy |
|---|---|---|
| Negligent load calculations, plant sizing and system design | Fitness for purpose terms and performance guarantees | Accidental water or fire damage on site (public liability) |
| Errors in overheating modelling, ventilation design and controls strategies | Liquidated damages for delay, unless the policy extends to them | Injury to your own operatives (employers’ liability) |
| Design you adopt through novation, where the policy covers it | Fire safety work, including smoke control, unless expressly covered | Damage to the works or plant before handover (contract works) |
| Negligent advice and value engineering proposals | The cost of correcting your own faulty installation | Breakdown of plant you maintain (engineering or breakdown cover) |
| Defence costs and expert evidence | Claims you were aware of when the policy began | Injury or damage caused by equipment you supply (products liability) |
The business description matters: a policy written for “mechanical and electrical installation” may not extend to design, modelling or novated design. What is covered always depends on the insurer accepting the risk and on the terms it offers.
The PI limit for an M&E contractor is almost always set by contract. Main contractors and employers put a figure in the subcontract or appointment, often with a fixed period after practical completion during which it must be kept up, and funders and tenants may ask for collateral warranties. Check whether the figure must apply to each and every claim, or whether an aggregate limit is acceptable: aggregate vs each and every claim.
PI is claims-made, so the policy that pays is the one in force when the claim is first made. Performance problems often take a full year of seasons to show, and residential claims can arrive many years later, so keep cover continuous and arrange run-off if you stop trading. If a new subcontract asks for more than your current limit, see what to do when a contract requires a higher PI limit.
A complete proposal gets better terms than a bare one, and a broker can only present what you tell us. Have these ready:
Speak to a broker
PI for HVAC and M&E contractors, placed by a named broker
Start the online proposal and save it as you go, or leave your number and a named broker will call you back, usually the same working day.
Apex Insurance Brokers is an independent insurance broker based in Bristol, established in 2009 and authorised and regulated by the Financial Conduct Authority. We are not tied to one insurer: we work with over 30 markets, including Lloyd’s syndicates through wholesale brokers, and every client has a named broker who handles the placement, mid-term changes, certificates for clients and the renewal.
Yes, if you size plant, calculate loads, design ventilation or cooling, model overheating or take on a consultant’s design. Public liability is for accidental injury and damage and usually excludes claims that a system underperformed. PI covers negligent design and advice, subject to the policy terms.
No. F-gas qualifications and company certification are legal requirements for working on refrigeration, air conditioning and heat pump equipment, but they are not insurance. PI requirements come from contracts: main contractors, employers, funders and tenants set limits and periods in subcontracts and warranties.
It can, if the problem comes from negligent design, such as wrong load assumptions or undersized plant. If your contract guarantees conditions regardless of negligence, PI may not cover the extra liability that the guarantee creates. Check the design liability clause before you sign.
Usually you take on responsibility for a design that is novated to you, so review it before you accept it and record any concerns. Tell your insurer you take on novated design and make sure the policy covers design you have adopted, not only design you produced.
It can, where a claim alleges negligent advice or a failure to identify and report a problem, subject to the policy terms. Breakdown of the plant itself and accidental damage are matters for other policies. Describe your maintenance work to the insurer.
Not usually on its own. Many PI policies exclude liquidated damages or cover them only where they flow from a negligent act. Delay caused by a design error may be part of a covered claim, subject to the policy terms.
Apex arranges professional indemnity insurance for HVAC and M&E contractors across the UK. Tell us about your work and we’ll find cover that fits. Or call 0117 325 0027.
Start your PI proposal Call 0117 325 0027Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Registered in England and Wales, company number 07014570. This page is general information, not advice on your individual circumstances. Cover is always subject to the insurer’s acceptance and the policy terms, and this page does not guarantee that cover will be available or on what terms.
