Consultation: MIS 3005-D: The Heat Pump Design Standard

12 February 2024

MCS has today published a four-week consultation on changes to MIS 3005-D: The Heat Pump Design Standard which aim to clarify the circumstances under which a hybrid heat pump heating system would be compliant with MCS requirements.

Currently, MIS 3005-D requires that when designing a heat pump heating system, “a heat pump should be selected that will provide at least 100% of the calculated heat loss…”. The term ‘should’ prescribes a requirement or procedure that is intended to be complied with unless reasonable justification can be given. Therefore, hybrid heating systems are allowable for MCS Certification only if there is reasonable justification as to why the heat pump cannot be sized to provide at least 100% of the calculated heat loss. What is considered reasonable justification can be subjective and open to interpretation.

In addition, where a hybrid heating system is installed, the standard currently gives no minimum sizing requirement for the portion of heating which is to be delivered by the heat pump, which risks poorly performing systems being installed.

Industry feedback suggests that this lack of clarity regarding ‘reasonable justification’ and lack of guidance on sizing hybrid heat pump systems is restricting the installation of such systems.

Hybrid heat pump systems can have several benefits, including acting a stepping stone to 100% heat pump solutions. Consequently, the updates proposed in this consultation are expected to increase the number of heat pumps being installed to support reaching the government target to install 600,000 heat pumps a year by 2028.

MCS is now consulting on the proposed changes to MIS 3005-D which include:

  • The introduction of a definition of a hybrid heat pump system
  • The removal of the requirement that a heat pump should be selected that will provide at least 100% of the calculated heat loss when installing a hybrid heat pump system
  • Introduction of the requirement for a minimum 55% peak power output contribution from the heat pump at a 55°C flow temperature and at design conditions when installing a hybrid heat pump system

This consultation also seeks feedback on whether the heat pump should always be prioritised in a hybrid heat pump system or if there should be a set minimum of heat supplied from the heat pump.

MCS would now like to invite comments from stakeholders. The deadline for submitting comments for this consultation is 10.00am on Monday 11  March 2024.

Please send consultation responses to consultations@mcscertified.com using the form provided below: