What Changed
On 10 December 2025, MCS published a standards update that signals air-to-air heat pumps will be brought into the MCS framework. This isn't a "maybe" or "someday"—it's a clear step toward full implementation, likely by Q3 2026 based on typical MCS timelines.
This represents a significant expansion of the MCS certification scheme, bringing air-to-air heat pumps into the formal framework alongside air-to-water and ground-source systems.
- Official standards update: MCS announced a heat pump standards update as a first step toward bringing air-to-air systems into MCS. Source (MCS)
- Installer impact ahead: when air-to-air enters the formal scheme, survey evidence will need to demonstrate system suitability, room-by-room requirements, and compliance with standards.
- Documentation readiness: installers should expect tighter alignment between site evidence and the declared system design, even for smaller domestic jobs.
Why this matters: Air-to-air installations are already growing (up significantly year-on-year in some markets), but without MCS certification, installers cannot access BUS grants or provide MCS-certified installations. Once MCS certification is available, air-to-air systems will be eligible for grant support and will benefit from the consumer trust associated with MCS certification.
Why Installers Care
Air-to-air systems can expand your install offering, but they also introduce different evidence questions. Where air-to-water often hinges on emitter upgrades and pipework, air-to-air must demonstrate that the system is matched to room usage and heat demand.
If you are working in tighter properties or mixed-use spaces, the evidence trail becomes even more important. Room use patterns, zoning intent, and the relationship between indoor units and outdoor placement all need to be defensible if questions arise later.
That means installers need to protect against the same two risks that show up across MCS work:
- Survey evidence requirements: if the evidence does not match the design, the job can be delayed or challenged in compliance checks.
- Callbacks and rework risk: missing room data or unclear siting details can trigger return visits just to fill gaps.
- Customer expectations: air-to-air is often sold on comfort and speed; evidence gaps translate into delays that customers notice.
Installers who capture consistent room-by-room evidence early can add air-to-air jobs without increasing admin overhead, and keep MCS audits smooth when the standards land.
Think of the survey pack as insurance: if standards tighten, a thorough pack can still pass because it already contains the information a reviewer is likely to request.
It also reduces internal friction. When your designers and installers trust the survey data, you can move from quote to install without debates about missing room context.
What to Capture on Site
Until the standard is fully implemented, the safest approach is to capture evidence that proves the system was specified for the actual building and room conditions.
That means capturing both the physical layout and the assumptions behind zoning. A quick set of wide shots is rarely enough when the decision hinges on airflow, door positions, or internal obstructions.
- Room-by-room photos: room layout, heat emitter presence, glazing, and any obstructions to airflow.
- Unit siting evidence: indoor and outdoor unit positions, clearances, and access routes for maintenance.
- Electrical supply details: consumer unit position, spare capacity, and visible cable routes.
- Fabric and insulation context: loft insulation depth, construction type, and obvious thermal weak points.
- Existing heating context: current system type and controls, especially where zoning or occupancy patterns are relevant.
- Documents on the day: EPC (if available), proof of insulation, and any previous survey reports.
RdSAP evidence documents should be photographed on the day when applicable. That removes the most common source of evidence gaps later in the process.
If you need to model or justify room loads later, these photos and notes help maintain alignment with the original survey, even if the customer delays the install decision.
Evidence Requirements
For air-to-air heat pump installations, survey evidence typically includes:
- Room-by-room documentation: photos and measurements for each room
- Unit siting evidence: indoor and outdoor unit positions, clearances, access routes
- Electrical supply details: consumer unit position, spare capacity, cable routes
- Fabric and insulation context: loft insulation depth, construction type, thermal weak points
- Existing heating context: current system type and controls, especially where zoning or occupancy patterns are relevant
Complete evidence capture helps ensure smooth compliance checks when MCS certification becomes available for air-to-air systems.
Timeline & Market Impact
Based on typical MCS standards timelines (initial announcement → consultation → implementation), air-to-air is likely to be MCS-certifiable by Q3 2026. That gives installers 6-9 months to prepare.
What to expect:
- Q1-Q2 2026: MCS consultation and standards refinement (installers can influence outcomes by submitting feedback)
- Q3 2026: Full implementation likely (air-to-air becomes MCS-certifiable, eligible for BUS grants)
- Q4 2026 onward: Market acceleration as MCS certification enables grant access and consumer trust
The expansion of MCS certification to include air-to-air heat pumps will make these systems eligible for BUS grants and provide consumers with the assurance of MCS certification. This is expected to accelerate adoption of air-to-air systems in the UK market.