TRVs can be recorded in a current EPC assessment, but they are only one part of the heating-controls input. Learn when controls may help a D-to-C route.
Thermostatic radiator valves can be a sensible low-cost improvement, but a landlord should not install them on the assumption that they will automatically move an EPC from D to C. The commercial question is whether the existing heating controls are holding back this particular property, and whether a complete, correctly recorded control arrangement closes enough of the rating gap.
Start with the certificate and the property model before buying hardware. A free EPC assessment can compare TRVs, a programmer, a room thermostat, qualifying smart controls and other credible measures against the current score. The result is a spending decision based on the whole dwelling, not a promise attached to one valve.
The short answer: TRVs can matter, but only as part of the assessed controls
Yes, TRVs can affect the heating-controls input in a current RdSAP EPC for an existing home. They are not a fixed number of EPC points, however. The effect depends on the main heating system, the controls already installed, the dwelling's standardised energy costs and how close the score is to the next band.
Installing controls also does not edit an existing certificate. An accredited assessor must inspect the property, record the accepted inputs and lodge a new EPC before the register changes.
How RdSAP records TRVs and heating controls
The current RdSAP 10 conventions, version 12.2, apply from 6 August 2026. Convention 4.13 says TRVs are included when they are present on at least 50% of the radiators. The count includes every radiator, including one in a hallway or another non-habitable room.
The June 2026 RdSAP 10 specification treats the control arrangement as a combination. For a boiler with radiators, its improvement table distinguishes no controls, a programmer only, a room thermostat only, TRVs without a room thermostat, a programmer with a room thermostat but no TRVs, and the fuller programmer, room-thermostat-and-TRV arrangement.
That distinction matters. Adding a few TRVs may leave the recorded arrangement unchanged if the 50% threshold is not met. Adding TRVs to a system that lacks an effective programmer or room thermostat may still leave a different control gap. Conversely, replacing controls already recorded correctly is unlikely to create a new EPC input.
TRVs, thermostats, programmers and zoning are not the same thing
Landlords often use 'thermostat' as a catch-all term. For an assessment, the functions and physical equipment are more important than the sales name.
- TRVs regulate individual radiators in response to local temperature. RdSAP applies the 50%-of-all-radiators convention before recording their presence.
- A room thermostat controls the heating system against the temperature at its location. It is a separate control from a TRV.
- A programmer or time switch controls when the system operates. A timer alone does not provide room-temperature control.
- Time and temperature zone control lets at least two zones have independently programmed heating times and independent temperature control. The RdSAP conventions allow wired, wireless, remote or mobile systems that provide those functions.
- A smart thermostat is not accepted merely because an app exists. RdSAP requires the appropriate product database entry, while app-only control needs a fixed receiver and evidence of the time, temperature or zoning functions.
A smart meter is different again: it measures supplied energy rather than controlling the heating. See the smart-meter EPC guide if the current certificate or product description is causing confusion.
When heating controls may help a D-to-C route
Controls deserve modelling when the EPC records a weaker arrangement than the one installed, when the system genuinely lacks one part of the recommended package, or when the score is close enough to C that a proportionate measure could contribute to the final route. They can be attractive because the work is usually less disruptive than major fabric or heating-system replacement.
They should still be considered alongside the full D-to-C evidence-first plan. A one-point property and an eight-point property do not have the same answer, and the same control package can have a different modelled effect in two apparently similar terraces.
Cucumber Eco may identify controls as part of a credible route, but the controls must be installed as specified, present at the assessment and accepted in the complete model. No product or isolated measure can be promised to produce EPC C before the property is assessed.
When TRVs are unlikely to be the decisive measure
- The current EPC already records the relevant TRV and thermostat arrangement correctly.
- TRVs would remain below the 50% threshold once every radiator, including hallway radiators, is counted.
- The main heating system uses a different control category, so a boiler-and-radiator recommendation is not the right comparison.
- The property has a material fabric, hot-water or heating-efficiency gap that a small control change cannot bridge.
- The proposed smart product cannot be identified in the approved database or its fixed receiver and functions cannot be evidenced.
A five-step decision process before you buy controls
- Read the current EPC. Note the score, heating-system description, recorded controls and recommendations rather than looking only at the letter band.
- Count every radiator and identify which have working TRVs. Record the programmer, room thermostat, zone controls, fixed receivers and product model details.
- Compare the site facts with the certificate. If the controls are already present but missing from the EPC description, ask the assessor what can be verified on a new inspection.
- Model the likely route before authorising work. Compare the complete control package with other small measures and any evidence gaps that may have more influence.
- If controls are selected, use a competent installer where required and retain model details, invoices and commissioning information. Make sure the equipment is accessible and operating for the assessment.
What the assessor needs to verify
The government's EPC guide explains that EPCs assess the building and its services using standardised assumptions. For heating controls, the assessor needs to identify what is fixed to the property, how it controls the relevant main system and which RdSAP option applies.
Clear access is usually more useful than a staged folder of product leaflets. The assessor may need to see the radiator valves, controller, thermostat, receiver and boiler connection. Model numbers and installation records can help where a smart control must be matched, but the assessor remains responsible for the final input.
Keep the legal standard separate from the improvement decision
The current domestic MEES guidance says covered private rentals in England and Wales must presently reach EPC E unless a valid exemption applies. Future landlord requirements are a separate policy and legislative question; use the maintained MEES 2030 guide for that wider timeline.
This article is assessment guidance, not legal advice. A TRV recommendation does not by itself establish compliance, and a landlord should not rely on a modelled scenario as though it were a lodged certificate.
The landlord verdict: model the package, not the product
TRVs can be a useful, proportionate part of a D-to-C route when they complete a stronger heating-control arrangement and the property model shows that the change matters. They are not an automatic score boost, not a substitute for a room thermostat or programmer, and not a reason to skip the rest of the assessment.
Find out whether heating controls are worth buying
Cucumber Eco can review the current certificate, compare the controls with the specialist EPC route and identify the lowest-cost credible next step before you commit to work. Start your free EPC assessment.
Frequently asked questions
How many radiators need TRVs for an EPC?
Under the current RdSAP 10 convention, TRVs are included when they are present on at least 50% of all radiators. Radiators outside habitable rooms, such as a hallway radiator, count in the total.
Will fitting TRVs move an EPC from D to C?
Not necessarily. TRVs can affect the heating-controls input, but the result depends on the controls already recorded and the complete dwelling model. The change may contribute to a route, make no difference to the recorded category or be insufficient to cross the band boundary.
Is a smart thermostat better than TRVs for an EPC?
They perform different functions and can form part of the same control arrangement. A smart thermostat must meet the applicable RdSAP and product-database rules, while TRVs are subject to the radiator-coverage convention. The better option is the package the property model supports.
Can an old EPC be changed after controls are fitted?
No. Fitting controls does not edit a lodged EPC. An accredited assessor must complete a new assessment, use the accepted controls in the full property model and lodge the resulting certificate.
