Class O – Flue for a micro combined heat and power on commercial

Whilst you do not need planning permission for a micro combined heat and power system, you will need an external flue for the boiler. 

Micro combined heat and power (micro-CHP) is a technology that generates heat and electricity simultaneously, from the same energy source, in individual homes or buildings. The main output of a micro-CHP system is heat, with some electricity generation, at a typical ratio of about 6:1 for domestic appliances.

For commercial properties, this is covered under Class O of Part 14.  You will not need planning permission. 

As long as the flue does not extend more than 1 metre above the highest point of the roof or in the case of a conservation area or world heritage site isn’t on a wall or roof slope facing a highway you are fine. This height can be exceed if replacing a higher flue.

Apart from these two minor restrictions on a flue for a micro combined heat and power heating system you can crack on. 

If you are in a listed building, you will need listed building consent and planning permission. 

For the residential version of this, please see Class F of Part 14

Legislation

Class O – installation etc of flue for combined heat and power on non-domestic premises

Permitted development

O. The installation, alteration or replacement of a flue, forming part of a microgeneration combined heat and power system, on a building other than—

(a) a dwellinghouse or a block of flats; or
(b) a building situated within the curtilage of a dwellinghouse or a block of flats.

Development not permitted

O.1 Development is not permitted by Class O if—

(a) the capacity of the system that the flue would serve exceeds 45 kilowatts thermal;

(b) the height of the flue would exceed either—
(i) the highest part of the roof by 1 metre or more, or
(ii) the height of an existing flue which is being replaced,
whichever is the highest;

(c) the installation of the flue would result in the installation on the same building of more than 1 flue forming part of either a biomass heating system or a combined heat and power system;

(d) the flue would be installed on a listed building, within the curtilage of a listed building, or on a site designated as a scheduled monument; or

(e) in the case of a building on article 2(3) land, the flue would be installed on a wall or roof slope which fronts a highway.

Page Updated:  4th March 2023