Hi LanceP.
The installation of energy saving materials on their own can be zero rated.
However if the installation of the energy saving materials are completed as a single supply with another service/constuction taking place then the installation can be seen as being ancillary to the main supply of construction services.
If this is the case all the work will be 20%
You can find more information in the link below to establish with the supplier(s) whether single or multiple supplies are taking place.
2. Installations of energy-saving materials
Thank you.