Where to put your air source heat pump

Planning where you install your air source heat pump carefully is very important in order for it to run at maximum efficiency. Clearly, a good installer will guide you on this, but we have compiled a few things you should be aware of:

Ground-level or suspended?

Where possible, the ASHP unit should be placed on the floor beside the property. This is best because firstly, it is easier to reach for servicing or maintenance. Secondly, pipework should be kept to to a minimum. Where it is not possible to fit a unit on the ground, it is possible to install it on brackets on the wall. In this case, just make sure it is not at head-height and that you can ensure access when needed.

Don’t cover up your ASHP

There’s no arguing with the fact that air source heat pumps are not the most beautiful of sights. As such, it might be tempting to try to hide it – but that’s not a good idea. We’ve seen plenty of ASHPs enclosed in their own little shed-like wooden structures, but the experts always say they should be out in the open. Air source heat pumps draw air through their sides and back, and kick cold air back out the front, once all the ambient heat has been extracted. If there’s something in front of it, this cold air can bounce off it and get sucked back in through the back and sides. An air source heat pump running on cold air isn’t going to do much! The manual of your individual unit will specify the minimum distance that must be kept clear in front of the unit.

Don’t put your ASHP indoors!

You can’t put an air source heat pump inside the house because it will effectively turn the room into a fridge. It will keep cooling the same air around it, until it can no longer extract any heat.

Planning permission for ASHP

In most cases, installing an air source heat pump is considered a small enough change to make it a ‘permitted development’ in domestic properties. The restrictions are as follows:

  • The heat pump must comply with the Microgeneration Certification Scheme (MCS) Planning Standards (or equivalent).
  • No other air source heat pump or a wind turbine has been installed on the
    building (additional installations require planning permission).
  • The outdoor unit should be no bigger than 0.6 cubic metres and at least 1 metre
    away from the site boundary.
  • Air source heat pumps installed on a flat roof should be within 1 metre of the roof
    edge. Air source heat pumps installed on a pitched roof would require planning
  • In conservation areas and World Heritage Sites, heat pumps should be installed
    at ground level and should not be fitted on a wall or roof which fronts a highway.
  • If your home is a listed building or on a site of a designed scheduled monument,
    planning permission, and in some cases listed building consent, may be required.

Put your ASHP next to the house

There are a couple of reasons why air source heat pumps are normally placed next to the property. It reduces the length of pipework required between the unit and the house. As well as looking better and reducing trip hazards, this keeps efficiency at a maximum as it minimises heat loss through the pipes. To further reduce heat loss, pipes should be insulated with specialist external pipe lagging. Internal lagging will not be suitably weatherproof!

Be aware of noise

Air source heat pumps have a reputation for being a bit noisy. Although they’re normally not very loud, it might be worth not putting them right the other side of your neighbour’s wall, for the sake of conflict. You also might want to avoid putting it next to a bedroom – you would probably be able to hear a faint humming (like from a fridge) in an otherwise quiet house at night!

Siting your ASHP

For all the reasons above, where you put your ASHP will affect its efficiency, so its worth thinking about. Always use an MCS-certified installer and be sure they are happy with where you have chosen to place your unit.

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