VAT on energy saving materials as Mixed Supply

Hi, As part of a house refurbishment we will be adding external and internal wall insulation, floor insulation and underfloor heating, together with an air source heat pump, solar PV and batteries. The wall insulation and underfloor heating will be installed by the main building contractor, who will also be doing the loft conversion and internal reconfiguration of the ground floor (note - there is no extension). A separate contractor will be installing the heat pump, new radiators and solar PV and battery. Would the wall insulation and underfloor heating works qualify for zero-rated VAT under the Guidance Note below if they are priced and invoiced separately by the main contractor? They are not dependent on the rest of the work, as they could be done separately and are not required under Building Regulations (as we are not extending the property or otherwise changing the walls). https://www.gov.uk/guidance/vat-on-energy-saving-materials-and-heating-equipment-notice-7086

Hi,
We can not provide a definitive reply to the liability of works carried out.The guidance in 708/6 sates:
There are mixed (or multiple) supplies where one or more element is distinct and independent.
Indicators of more than one supply taking place include when:
separate pricing or invoicing
the items are available separately
there is a time differential between parts of the supply
elements of the supply are not inter-dependent or connected

Where you’re undertaking more than one job at the same premises, the VAT liability will depend upon the circumstances.
For example, if you’re contracted to build an extension and, as part of the same contract required to fit thermostatic valves to all the radiators in the house, this is a single standard-rated supply of construction services.
However, if you have a contract to build an extension and sometime after the work has commenced, the homeowner separately asks you to install thermostatic valves, this is a supply that qualifies for relief.
It will therefore be a case of  the contractors judging whether the supplies of energy saving materials are provided as a single supply or a mixed supply by consulting this guidance.
Thank you.