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Is insulating Preheated Cold Water Main pipework a mandatory or recommended practice for WWHRS installation?
Recoup are no longer advising that preheated pipework from the Recoup WWHRS unit must be insulated.
At the time of writing, there is currently no specific Building Regulation guidance (in England) to state that it is mandatory that the preheated pipework should, or should not, be insulated.
Previously Recoup stated in our documentation that “The Preheated water supply from the Recoup WWHRS to the shower cold water inlet and water heater must be Insulated in accordance with the ‘Building Services Compliance Guide” for SAP 2012. This compliance guide has since been removed from SAP 10 and is no longer the most up to date statutory guidance.
No compliance guidance has been issued to replace it relating to the preheated pipework from a WWHRS unit. Insulation of the preheated CWM pipework, will reduce heat loss, and potentially improve System A or System B efficiency, however based on values within the SAP methodology, these losses are small whilst the shower is in operation.
Note: please do check your Country’s specific Building Regulation guidance on domestic water distribution pipework for confirmation.
Insulating the preheated pipework from the WWHRS does reduce heat loss and improve efficiency, so can be carried out if it aligns with the DHW insulation strategy for the project / property.
Note: Our legionella risk assessment was conducted with insulated preheat pipework and would remain applicable in this situation.
Preheat Pipework Insulation Guidance References
At the date of issuing this update (16/01/25) guidance was taken from NHBC and Building regulations approved document L.
- NHBC – Pipe insulation requirements for space heating and hot water systems in new dwellings.
- The Building Regulations – Conservation of fuel and power document L
Background note:
Specifying and installing effective pipe insulation is key for energy efficiency, safety and cost savings in UK buildings. Organizations like BRE, BSI and CIBSE develop the standards needed to drive insulation material and installation quality.
Most standards around insulation pipework are concerned with DHW pipe work, rather than CWM (or preheated CWM) pipework, when that CWM pipework is located within the building's heated envelope. Arguably it is best precative to insulate all hot and cold pipework to prevent heat loss / heat gain within the envelope, however, this level of insulation is not currently mandatory
The key standards are Building Regulations Part L (Conservation of
fuel and power), EN 12828, PAS 67, BS 5422, BS 5970, and HSE guidance on preventing corrosion under insulation. Part-G (Sanitation, hot water safety
and water efficiency) should also be considered, as well as any relevant HBF guidance. Compliance futureproofs buildings against tighter regulations. Workmanship certification and oversight ensure insulation performs to its potential.
Approved Document L Volume 1, 2021 edition:
With insulation being a vital tool in UK carbon reduction efforts, its standards will continue advancing. Staying current on the latest best practices, codes and standards allows industry professionals to maximize the benefits of pipe insulation.