Why compliant snapshots (internal temperatures of 18–21°C and 40–60% relative humidity) can still conceal an underlying hazard and what that means for diagnosis, liability, and intervention.
As we currently undertake damp and mould surveys at scale for our clients, we are consistently confronted with a technical paradox. Our surveyors enter properties where ambient temperatures are a compliant 18–21°C and relative humidity sits within the 40–60% acceptable range. There are no leaking pipes, no failing roof tiles, and no rising damp. Yet… mould is present.
In these cases, the ‘underlying cause’ is rarely a discrete defect; it is a failure of the thermal cycle.
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The ‘In-Repair’ Paradox
Awaab’s Law, specifically the insertion of Section 10A into the Landlord and Tenant Act 1985, is fundamentally an enhancement of the landlord’s repairing obligations. For the surveyor on the ground, this creates a significant challenge. If the building fabric is sound, the heating is functional, and the ventilation is clear, the ‘lifestyle’ argument, or more accurately, the ‘operational use’ argument, is difficult to ignore.
However, Awaab’s Law, alongside the Homes (Fitness for Human Habitation) Act 2018, has shifted the focus from ‘Is it broken?’ to ‘Is it safe?’. The law now targets hazards, as opposed to disrepair.
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The Affordability Defence: A New Legal Metric
The most significant evolution in case law and the point where the tenant finds their strongest defence is the concept of ‘Affordable Warmth’.
Under Section 9A of the Landlord and Tenant Act 1985, a lessor is not liable if the unfitness is caused by the tenant’s failure to use the home in a ‘tenant-like manner’. Historically, ‘failure to heat’ was the ultimate landlord defence. But modern case law suggests that a tenant’s failure to heat is only a valid defence if hitting that 18–21°C target is financially reasonable.
If a property is uninsulated, it requires constant, high-output heating to keep wall surfaces above the dew point. If the resident cannot afford this, the building fabric undergoes a ‘cold soak’. When the heating is eventually turned on, the air warms quickly, but the walls remain cold, causing immediate condensation. In this scenario, is the building’s thermal inefficiency the ‘underlying cause’ or is it the tenant’s choice not to heat the property sufficiently?
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A Strategic Alternative: The Rent Reduction Model
If the ‘underlying cause’ is a mismatch between the building’s thermal performance and the resident’s income, providers face a difficult choice. Either incur capital expenditure or provide revenue support to residents.
Remediation, such as external wall insulation, is a relatively high-cost, long-term solution. However, if the primary legal risk is the ‘Affordability Defence’, we must consider more agile interventions.
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Removing the Defence via Subsidy
If a landlord provides a targeted rent reduction or a heating subsidy specifically to offset the modelled excess cost of heating an uninsulated property, it could be claimed that they effectively neutralise the affordability argument.
By providing the financial means to heat the property to the 18 / 21°C standard as described in HHSRS, the lessor arguably reinstates the tenant’s duty under Section 9A. I.e. If the resident still chooses not to heat the property despite the subsidy, the landlord’s defence that the resident is not acting in a ‘tenant-like manner’ becomes robust once again.
In many instances, the distance between the cost of providing external wall insulation and the cost of a long-term heating subsidy for a specific tenancy is significant. This approach potentially allows providers to maintain compliance with Awaab’s Law by addressing the economic underlying cause while planning for longer-term fabric upgrades. The landlord of course will still need to take into consideration Minimum Energy Efficiency Standards (MEES) requiring properties to have an EPC rating of C by 2030.
There is a further question that must also be answered as a result of Awaab’s Law and that is has the landlord ensured ‘…so far as is possible, that the hazard in question does not recur…’? Would providing funding for heating meet the threshold of ‘…so far as is possible…’ without the inclusion of external wall insulation? This question remains regardless of the resident’s ability to afford the heating bills.
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The Surveyor’s Struggle and The Impossibility of an Instant Diagnosis
Despite the rigid timeframes imposed by Awaab’s Law, the greatest challenge remains the point-in-time nature of the survey.
When a surveyor stands in a room that is currently 20°C and 50% relative humidity, they are seeing a compliant snapshot that contradicts the physical evidence on the walls. Identifying the underlying cause in that moment can feel like intuition rather than evidence-based diagnosis.
Awaab’s Law demands ‘…so far as is possible, that the hazard in question does not recur…’, yet the physics of properties often defies a simple binary answer. For the surveyor, the difficulty isn’t just seeing the mould; it’s proving whether the home is failing the tenant, or the tenant’s economic reality is failing the home.
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How Potter Raper Can Help
Our Building Surveying team works with housing providers, local authorities, and registered providers across the UK to carry out damp and mould surveys and support Awaab’s Law compliance. We understand that the causes of damp and mould are rarely straightforward, and we bring the technical expertise to identify underlying issues accurately, even when a property appears compliant on paper.
Whether you need surveys carried out at scale, support interpreting your legal obligations, or advice on the most appropriate remediation strategy for your stock, our team can help you respond to Awaab’s Law with confidence.
To find out more about our Building Surveying services, visit our Building Surveying page, or contact us directly at info@potterraper.co.uk.
