From 1 October 2030, every privately rented home in England and Wales will need an EPC rating of C or above. For landlords with a D-rated property, that deadline often comes with a worrying figure attached: up to £10,000 per property in upgrades. But many D-rated homes are not as inefficient as their certificate suggests. An EPC can only record what the assessor can see or prove on the day. Anything they cannot verify gets a cautious default value, and air tightness is one of the most important of those defaults. Since June 2025, a measured air test can replace that assumption on a domestic EPC. For a rental sitting just below the C boundary, that can be the difference between a D and a C, with no building work at all. This guide explains what the EPC C rules require, why your rating may be lower than it should be, how air testing works, and when it is (and is not) worth doing.
EPC C for landlords: what the 2030 rules say
Under the Minimum Energy Efficiency Standards (MEES), the minimum EPC rating for a rental property is currently E. On 21 January 2026, the government confirmed it will raise the standard to the equivalent of EPC C, with the new regulations expected to come into force in 2027, subject to Parliament's approval. Here is what landlords need to know:
| Rule | What it means for you |
|---|---|
| Deadline | All tenancies must meet the standard by 1 October 2030. There is no earlier date for new tenancies. |
| Cost cap | You will not be required to spend more than £10,000 per property. Eligible work installed since 1 October 2025 counts towards it. |
| Grants | Most third-party funding, including government grants, counts towards the cap. Boiler Upgrade Scheme money does not. |
| Low-value homes | For properties worth less than £100,000, the cap is 10% of the property's value. |
| Exemptions | If you spend up to the cap and still fall short, you can register an exemption that lasts 10 years. |
| Penalties | Councils will be able to fine up to £30,000 per breach, per property. |
Why an accurate EPC C now is worth having
EPCs themselves are changing. New-style certificates will add ratings for fabric performance, heating system and smart readiness, and the 2030 standard will be measured against them. Their launch was planned for October 2026 but has been moved to the second half of 2027. There is a useful transition rule. A home rated C or above on today's scale, on an EPC issued before 1 October 2029, counts as compliant until that EPC expires or is replaced. EPCs last 10 years, so an accurate C lodged now could cover a rental well beyond 2030. Miss that window and the path is longer. Landlords below C will need a new-style EPC before carrying out works, then a post-works EPC by 1 October 2030 (Elmhurst Energy).
Why is my EPC rating low? The problem with assumed values
An EPC for an existing home is produced using RdSAP, a reduced version of the government's energy rating method. The assessor records what they can see and evidence. Where they cannot confirm something, such as hidden wall insulation or how much air leaks out of the building, the software fills the gap with a default. Those defaults are deliberately cautious. Without a test, RdSAP assumes an air permeability of 15 m³/(h·m²) at 50 Pa, which Elmhurst Energy describes as a worst-case result. A very good result would be around 3 or 4. If your property is tighter than the default, your EPC is understating it.
How to spot assumed values on your EPC
- Look up your certificate on the government's Find an energy certificate service.
- Note your score, not just the band. Band D runs from 55 to 68, and C starts at 69.
- Check the breakdown of the property's energy performance for the word "assumed". It marks every place where the assessor used a default instead of evidence.
Assumed wall or loft insulation can often be corrected with paperwork, such as installation certificates or photos. Air tightness can only be corrected with a measured air test.
What is air tightness testing?
Air tightness testing, also called an air permeability test or air leakage test, measures how much air escapes through unintended gaps in a building. Think gaps around windows and doors, between floorboards, at loft hatches and where pipes and cables pass through walls.
The result is given in cubic metres of air per hour, per square metre of the building's outer surface: m³/(h·m²). The lower the number, the tighter the home and the less heat it loses to draughts.
Pulse air test vs blower door test
There are two accepted ways to measure air tightness. Both are recognised under the industry testing standard (CIBSE TM23) and for Building Regulations. Our guide to Pulse air tightness testing explains how the test works in more detail.
| Pulse air test | Blower door test | |
|---|---|---|
| How it works | A unit inside the home releases a short, controlled burst of air and measures how it leaks away | A large fan is sealed into an external doorway to pressurise or depressurise the home |
| Test pressure | Low pressure (result reported at 4 Pa) | 50 Pa |
| Test time | Minutes | Longer set-up and test |
| Impact on the home | Nothing fitted to doors, no drilling | Fan and frame fitted to a door during the test |
Who can carry out an air test for an EPC
For the result to count on an EPC, the test must be carried out by a qualified Level 1 or Level 2 air tester. Testers are expected to belong to a recognised scheme such as ATTMA or the Elmhurst Airtightness Scheme, and their certificate is passed to the Domestic Energy Assessor as evidence. If the tester is not registered, the assessor needs the full test report plus proof the equipment was calibrated within the last 12 months (blower door) or 24 months (Pulse). At Thermova, tests are carried out by ATTMA Level 1 accredited operators using our own Pulse equipment.
How an air test can improve your EPC rating
Since RdSAP 10 came into force on 15 June 2025, assessors can include an air pressure test result in a domestic EPC where the right documentation is available (Elmhurst Energy). The measured figure replaces the worst-case default. The logic is simple. Less air leakage means less heat lost through draughts, which lowers the property's modelled heating cost. A lower modelled cost raises the SAP score that sets your band. The updated EPC is lodged on the national register like any other.
Which properties benefit most
An air test to improve your EPC works best where the score is close to the C line and the building is in reasonable condition. Good candidates usually have:
- A current score in the upper half of band D. In our experience, the strongest candidates sit between D63 and D68.
- Several assumed values on the existing EPC
- Modern double glazing and well-fitting external doors
- No open chimneys or unsealed fireplaces An air test is less likely to be enough on its own if the score is in the low 60s or below, or if the home has open fireplaces, gappy suspended timber floors or old single glazing. One point matters above all: an air test cannot make a leaky home look tight. If the measured result is poor, it will not lift the rating. That is why a property should be screened before it is tested.
When an air test is not enough on its own
If a measured result will not reach C by itself, it is still a sensible first step, because it shows how far the property really is from the line. Lower-cost measures can then close the gap: draught-proofing, topping up loft insulation or upgrading heating controls. For homes with a larger gap, a heat pump may be the better route. The Boiler Upgrade Scheme grant (£7,500 for most homes) does not count towards the £10,000 cost cap, so it uses less of your allowance than the headline price suggests. Our landlord services team can help you plan the order of works.
Step by step: from EPC D to C with an air test
- Check your current EPC. Find the score and look for assumed values, as described above. If the EPC has expired or the property has none, it can be assessed from scratch.
- Get the property screened. Before anyone visits, the existing EPC data should be checked to see whether a measured result could realistically reach C. We do this from the register and only take on properties with a genuine route to a C.
- Fix the easy air leaks. Simple sealing before the test can improve the result: draught strips on external doors, a sealed loft hatch, a letterbox brush, and sealant around pipe holes and gaps under skirting boards. Do not block air bricks, trickle vents or extractor fans, as the home needs that ventilation.
- Book the air test. A Pulse test is low pressure and non-invasive. Tenants can stay at home, and nothing is drilled or fixed to the doors.
- Get the new EPC lodged. A Domestic Energy Assessor runs a fresh RdSAP 10 assessment using the measured figure and lodges the new certificate, usually within 5 to 10 working days.
- Keep the evidence. Store the air test certificate and the new EPC with your compliance records in case your council asks for them.
How much does an air test for an EPC cost?
For landlords, our EPC C service costs £500 plus VAT per property. That covers the Pulse air test, the test certificate and the new EPC, and it is only charged once a C is lodged on the national register. If we do not reach a C, there is no fee. Set against a cost cap of up to £10,000, measuring first is a low-risk way to find out whether a property needs building work at all. For new builds, air tightness testing cost depends on the site. Testing several plots in one visit shares travel and set-up costs, which lowers the price per plot.
What to expect on the day
- Allow two to three hours on site for a rental. The air test itself takes minutes; most of the visit is spent measuring and preparing the property.
- The tester needs access to every room.
- Windows and external doors stay closed during the test.
- You may be asked to switch off extractor fans and any open-flued heating appliances while the test runs.
- Tenants do not need to leave, and nothing needs making good afterwards.
Air testing and EPCs on new builds
Air testing is not only for existing rentals. Under Part L of the Building Regulations, in force in England since June 2022, every new dwelling needs its own air test. Sample testing across a site no longer applies.
What air test result do I need for Part L?
The limit is 8.0 m³/(h·m²) at 50 Pa, or 1.57 m³/(h·m²) at 4 Pa for a Pulse test (LABC). Most homes need to do better than that. The SAP 10 notional dwelling assumes 5.0, so your real target is set by the dwelling's SAP calculation and is often well below the limit. The as-built result feeds into the final SAP calculation and the new home's EPC. A tighter result gives more headroom on energy targets and a stronger EPC. Book the test early enough to find and seal any leaks before completion. Our air tightness testing page covers new-build testing in more detail.
Frequently asked questions
Can an air test guarantee an EPC C?
Is using an air test on an EPC allowed?
Will my tenant need to move out?
Does an air test work for flats?
How long does an EPC last?
Should I wait for the new EPC system?
What if my property cannot reach C within the £10,000 cap?
Do new builds need an air test?
Measure before you spend
The 2030 EPC C deadline is fixed, but the cost of meeting it is not. Many D-rated rentals are marked down by assumed values, and air tightness is one of the easiest to correct. A measured air test is quick, causes no disruption and, on the right property, can move an EPC from D to C without any building work. The best time to check is now. An accurate C lodged before 1 October 2029 can keep a rental compliant for up to 10 years. Measuring first also shows you which properties genuinely need investment, so your budget goes where it is needed. Thermova helps landlords in Blackpool, the Fylde Coast, Lancashire and the wider North West reach EPC C on a no C, no fee basis. Send us an address and we will check the register and give you an honest view of whether an air test could get your property to a C. Check if your property qualifies.
Sources
- GOV.UK: Improving the energy performance of privately rented homes, government response (21 January 2026)
- Elmhurst Energy: Domestic private rented properties required to meet EPC band C by October 2030 (22 January 2026)
- Elmhurst Energy: Optional but impactful: air pressure testing in RdSAP 10 (17 December 2024)
- Elmhurst Energy: Top 10 questions assessors ask about RdSAP 10 (3 June 2025)
- GOV.UK: Reforms to the Energy Performance of Buildings regime (update of 9 March 2026)
- LABC: Don't feel pressurised by air permeability testing