My interest in DIY heat pump installations began when I converted my old garage into a workshop. As a keen and experienced ‘DIYer,’ I wanted the satisfaction of doing the entire project myself—including heating this previously damp and dark space. I chose to install a mini-split air conditioner in heating mode because I could keep it completely separate from the house, it was relatively cheap, and I have previous experience with these systems.
The practical side of the installation was straightforward, especially compared to understanding the permitted development and planning application aspects! In this article, I’ll share what I learned about the legal and regulatory aspects of installing my own system. It should be applicable to both dedicated air source heat pumps (ASHPs) and split-system air conditioners being used to heat spaces such as workshops, home offices, etc.
Permitted Development
Many professional air-conditioning and heat pump contractors state that any installation can be done under ‘Permitted Development’ (PD). In many situations that may well be the case, but it should be noted that the PD route has many restrictions. The following is a summary of the legislation, which is slightly different for England, Northern Ireland, Scotland and Wales. You should check the full details depending on where you live – there are links are at the bottom of the page.
The restrictions are typically:
- Compliance with MCS Planning Standards or equivalent standards.
- Only one ASHP permitted per property. (A block of flats usually counts as one property.)
- The ASHP unit must be more than 1m from property boundaries. It must be more than 1m from the edge of a flat roof and not on a pitched roof.
- There mustn’t be a wind turbine at the property.
- THE ASHP mustn’t face a highway if installed above ground storey.
- The ASHP must not be on, or on the land of, a listed building.
- The ASHP must not be in an Area of Natural Beauty (AONB), National Park, Conservation Area or World Heritage Site.
Apart from the first in the list, the requirements are clear. The first one, the MCS Planning Standards. is somewhat contentious, and has been discussed in several posts on the Renewable Heating Hub Forums. In summary:
- The standard was written by MCS, and requires that both products and installation contractors be certified by MCS.
- The cost of MCS certification is high, so much so that there are now umbrella schemes so that non-MCS contractors can work via an MCS certified company to avoid the certification expense.
- The quality of work of MCS installers is being questioned. See https://renewableheatinghub.co.uk/why-your-mcs-certified-installer-might-not-be-as-competent-as-you-think.
Fortunately, the Permitted Development legislation specifies ‘MCS Planning Standards or equivalent standards’. Unfortunately, there isn’t guidance on what is considered an ‘equivalent standard’, but it could be argued that the following would be valid as an ‘equivalent standard’.
- Selecting an MCS approved heat pump
- Working within the recommendations of MIS 3005 except for the MCS certification requirement
- Meeting the noise calculation requirements of MCS 020 (see below)
In my opinion, this part of the legislation lacks clarity. That MCS wrote the standard that has been included in the legislation appears dubious, especially since it requires installers have MCS certification (a process from which MCS itself financially benefits). A more open approach would be to either detail the requirements in the legislation itself, or to have several organisations offering acceptable certification routes, which would create a competitive market.
The MCS 020 Noise Calculation
It is perfectly possible to do the equivalent of the MCS 020 noise assessment yourself. The guidelines look confusing, but have been made more user-friendly by Heat Geek in their video.
Can you DIY install under Permitted Development?
Given the above, yes, I believe it possible to do a DIY installation of an ASHP, working within the PD rules, and fulfilling ‘equivalent standards’ to the MCS Planning Standards requirement. Indeed, MCS themselves, say that ‘an MCS certificate is not a mandatory or legal requirement for system installation’. See https://mcscertified.com/consumers-communities/certificate-queries.
However, there are a couple of other things that should be considered:
The system must be for heating purposes only.
PD excludes systems that are capable of cooling – i.e. air-conditioners. However, many Local Planning Authority departments are happy to take a sensible approach as they realise that people are using air-conditioners as heat pumps. Also see the conclusion below.
Permitted Development may be restricted by the Local Planning Authority (LPA)
Some LPAs restrict the installation of ASHPs under PD by imposing an ‘Article 4 direction’. This is typically invoked by inner city LPAs where they think noise could an issue in densely populated areas, or it could detract from the unique architecture of an area. See https://commonslibrary.parliament.uk/when-is-planning-permission-not-needed-permitted-development-in-england/
Planning Permission
If your proposed installation doesn’t meet the PD requirements, it doesn’t necessarily mean you cannot have an ASHP. Instead you must obtain Planning Permission.
Even if you intend to go down the PD route, an email to check the position with your LPA is a good idea. In my experience, LPAs vary, ranging from unresponsive to disinterested to pragmatic to obstructive, but I think it is good to establish where you stand before committing time and money.
While LPAs are under pressure to permit renewable heat systems, they do have the power to make you remove a system if they consider it in breach of Planning Permission. It can be better in the long run to have some evidence showing you approached them prior to installation.
Other regulatory considerations
As well as Permitted Development and Planning Permission, you should also consider the following regulatory requirements prior to undertaking a DIY ASHP installation:
District Network Operators
Your electricity is supplied by the District Network Operator (DNO). They need to be notified prior to installing a heat pump (or electric vehicle charging point) so they can use the data for infrastructure planning. Note that
- the DNO is not necessarily the company you pay your bill to, and
- you are not seeking permission, it is simply a requirement to inform them.
In my experience, DNOs can be slow to respond and are only interested in dedicated heat pumps, rather than small air-conditioners acting as ASHPs. Nevertheless, they should be consulted as a matter of diligence. The process for notification them is currently changing, which will hopefully improve response times. See https://www.energynetworks.org/industry/connecting-to-the-networks/connecting-electric-vehicles-and-heat-pumps
F-gas
Heat pumps utilise refrigerant gases. If it’s an F-gas (fluorinated gas) you are required by law to use a F-gas qualified professional to do anything involving the refrigerant connections. This shouldn’t stop you doing the rest of the installation yourself, it’s just any F-gas connections or lines that must not be touched. When purchasing your system will need to inform the merchant which F-gas installer you will be using.
Note that some refrigerants such as R290 (propane) are not F-gases. This removes the requirement for an F-gas registered installer. However, R290 propane is highly flammable which introduces a significant risk that some sellers and manufacturers are playing down. In reality it is blow-torch gas, without the added odour, being pumped at pressure around a system whose joints are continually stressed through thermal expansion and contraction! There have been suggestions that it could invalidate house insurance, but I haven’t yet seen it specifically mentioned in conditions or exclusions. That is to say, I wouldn’t be installing an R290 system in my own home!
Building regulations
Building regulations are separate from Planning Permission or Permitted Development. They are concerned with the standards of the work rather than the permission to do it.
Heat pump installations usually require Building Regulation approval, whereas mini-split air conditioners typically do not. However, as with Permitted Development and Planning Permission, I recommend checking with your local Building Control department.
Your installation should meet all Building Regulation requirements, including Part P for electrical work and equivalent regulations for plumbing, especially if there are components under pressure. The relevant Government documents are listed at the bottom of the page.
Conclusion
In summary; yes, you can do a DIY heat pump installation. Knowing that you have researched and are meeting all the legal and regulatory requirements will give you confidence going forward. Especially when you know that some professional installers don’t pay as much attention to the finer details surrounding PD and Planning Permission.
Unfortunately, if you want (and are eligible) to claim a government grant you almost always have to go down the MCS certified installer route. The process was designed to ensure the government wasn’t giving grant money to rogue installers, but it has introduced its own issues as detailed above.
Finally, the rules around PD are likely to change. From February to April 2024 there was a Government consultation proposing the relaxation of some requirements (including removing the ‘heating only’ condition that excludes air conditioners from PD). The outcome is awaited – see https://www.gov.uk/government/consultations/changes-to-various-permitted-development-rights-consultation for full details.
Good luck if you decide to DIY! It’s very rewarding and can save a lot of money too – especially if you aren’t eligible for a Government grant.
Written by Justin Macklin from Checkmark: https://check-mark.co.uk
Checkmark provides an F-gas commissioning service for DIY installations. Their website provides lots of information about DIY installation of ASHPs and air-conditioners.
Links: Permitted Development
Northern Ireland: https://www.legislation.gov.uk/nisr/2015/70/schedule/part/2 and amended by https://www.legislation.gov.uk/nisr/2023/95
Wales: https://www.gov.wales/planning-permission-heat-pumps
Links: Building Regulations
Part L – Conservation of Fuel and Power: https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l
Part F – Ventilation: https://www.gov.uk/government/publications/ventilation-approved-document-f
Part O – Overheating (new residential building only) https://www.gov.uk/government/publications/overheating-approved-document-o
Part P – Electrical Safety: https://www.gov.uk/government/publications/electrical-safety-approved-document-p
