Welcome to Part two in our series focusing on Awaab’s Law. In this article we will be looking at the causes of damp and mould and the three main areas that, when actioned in conjunction with each other, can help to eliminate damp and mould issues all together.

Awaab's Law, part of the Social Housing (Regulation) Act 2023, was introduced in July 2023 to enhance tenant safety following the tragic death of Awaab Ishak in a housing association property in Rochdale. The law requires landlords to address health and safety hazards, including damp, mould, and extreme temperatures, in accordance with the Housing Health and Safety Rating System (HHSRS). Landlords must act promptly to remediate these issues, document their actions, keep tenants informed, and meet stricter timelines, such as completing emergency repairs within 24 hours. Failure to comply can lead to unlimited fines, legal action, reputational damage, and tenant complaints to the Housing Ombudsman, underscoring the critical importance of tenant safety and landlord accountability.

There have already been reports of landlords receiving hefty fines for failing to act swiftly enough in addressing damp and mould issues in their properties, with many citing a lack of awareness about the new laws and the associated timelines. In many cases, these problems arise because the causes of damp and mould, as well as effective solutions, are not fully understood. As a result, landlords often take inefficient or misguided steps to address the issues, sometimes at great expense, only to find that these actions either fail to resolve the problem or create new issues instead.

Unfortunately, there isn't a single, one-size-fits-all solution to domestic damp and mould problems—no single product or action that can solve every case. Each situation is unique, and the causes can vary. However, there is a discernible pattern that helps us identify the right solutions to tackle the issue. It’s a kind of "love triangle" between three key causes and their specific solutions— a trifecta of approaches that can both proactively prevent and reactively resolve damp and mould issues in our homes.

In many reactive cases, one or two of these causes will often already have a suitable solution in place. This means that the solution typically only requires one or two "fixes" to be implemented, effectively raising the shield against damp and stopping it in its tracks. Ideally, these fixes will also reverse any negative effects that had already taken hold.

So, what are these three solutions that form the moisture-less trinity?

They are:

1. Ventilation 

2. Insulation

3. Heating

Together, these three solutions create a comprehensive approach to tackling and preventing damp and mould.

When combined, these three areas create a strategy and level of protection greater than the sum of their individual parts. They work together to neutralize the factors that promote damp and mould, while also addressing the negative impacts that can arise if these solutions are used in isolation. Let’s break down each factor, its solution, and the potential issues that can arise when they aren’t effectively integrated into a comprehensive approach.

Ventilation is crucial as it expels moist air and allows fresh, dry air to circulate throughout the property. However, when used alone, it can lead to increased heat loss, particularly in colder weather, which can worsen condensation problems. Without proper insulation or heating, the cold air introduced can create additional damp spots.

Insulation helps maintain consistent indoor temperatures and prevents cold surfaces where condensation can form. On its own, however, insulation can trap moisture inside the building if there’s no proper ventilation to let the damp air escape. This can lead to poor air quality and increased mould growth.

Heating ensures a stable indoor temperature, preventing cold spots where moisture can condense. But without ventilation, heating can cause the perfect temperature for mould to grow in, and a lack of insulation provides a perfect cold surface for the humidity held in the heated air to condense onto!

By combining all three—ventilation, insulation, and heating—you create a balanced solution that addresses each factor and eliminates the negatives that arise when they are used separately. This integrated strategy not only prevents damp and mould but also fosters a more comfortable and healthy living environment.

Let’s begin by examining the root causes of mould and the variables that create the perfect environment for it to thrive.

Mould is a form of fungus that typically appears as dust-like, colored growths. It consists of spores that help the fungi spread, with many of these spores being airborne. In household settings, the most common types of mould include Alternaria, Ulocladium, Penicillium, and the two well-known moulds, Stachybotrys chartarum and Stachybotrys chlorohalonata, often referred to as toxic black mould. These moulds thrive in environments with high moisture, which is why they are frequently found in wet rooms and other areas prone to damp buildup. All of these moulds are harmful to health—some more so than others—but they can all cause complications, particularly for individuals with pre-existing respiratory conditions.

To create an environment that is hostile to mould, we need to reduce moisture. However, moisture is an unavoidable by-product of everyday life—through activities like bathing, laundry, cooking, and even respiration and perspiration, not to mention potential moisture ingress from leaks, rising damp, and other structural issues. On top of that, we have the laws of science to contend with. Through processes like evaporation, condensation, and capillary action, moisture can be particularly persistent, making it a challenge to manage in our modern homes when trying to combat mould.

It wasn't always like this. While mould and damp issues have always existed, the scale of the problem grew when we tried to address other concerns, which inadvertently created a knock-on effect that worsened the damp issue. Let’s take a brief journey through architectural history to understand how we got here…

In the past, houses were designed with passive airflow built into their structure. Features like air bricks, underfloor airflow channels, cross-ventilation, and stack effect ventilation were all common. The key term here is "passive." These solutions allowed fresh air to enter the building while stale air could escape. However, there was one major drawback—heat loss. While expelling stale and humid air helped improve indoor air quality, it also led to the loss of heat. Fresh air could enter freely, but during winter, it meant that cold air replaced the warm air leaving, causing heating bills to rise.

To make homes more energy-efficient and reduce heating costs, the decision to design new homes and retrofit old ones with improved insulation techniques was a necessary and commendable step in the fight against energy consumption. By sealing homes to almost airtight standards with new double glazing and UPVC doors, and adding effective heat retention materials to the building structure, a well-insulated home became a much more economical investment. This upgrade significantly lowered heating bills almost overnight.

However, one crucial factor was not given enough consideration - ventilation.

By sealing homes to retain heat, nearly all the natural airflow present in older designs was eliminated. The air bricks, cross-ventilation, underfloor air channels, and stack effect ventilation disappeared. In their place, the newly designed and overly insulated houses trapped stale air and moisture inside, with little natural ventilation to help maintain healthy indoor air quality.

But what about extractor fans, you might ask? Well, this introduces a new issue. Extractor fans were used in homes before the shift in building construction, but the new design approach also created challenges for mechanical ventilation. This is where a bit of science comes into play. We’ve all heard the phrase "nature abhors a vacuum," and while it’s not entirely accurate, the principle behind it is essentially how ventilation works. As air moves, it creates a void that must be filled, or else a vacuum forms. When air is drawn out of a space by a fan, fresh air must be able to flow into the newly empty space to replace the air being removed. In simple terms, when a fan is running, an equal volume of air must be able to enter the space to replace what’s being extracted. This means we need to rethink how we view extractor fans in modern homes.

Instead of viewing an extractor fan as a device that simply removes air from a room, like a bathroom, think of it as a fan that moves air in and out of the space. It’s easy to assume the first interpretation because the word "extractor" is in the name, but in reality, the latter view is more accurate. (For clarity, the term "extractor" in the product name simply refers to the direction of airflow.)

When an extractor fan is turned on, its primary function is to draw stale or humid air out of a space. As the fan pulls air through its impeller, it creates negative pressure in the area where the air once was. Nature, disliking this imbalance, attempts to fill the empty space with more air to prevent a vacuum from forming and to rebalance the pressure.

For instance, in a bathroom, as air is extracted, the replacement air tends to come from within the house rather than from outside—especially in colder weather. This means air will be drawn in through gaps like the base of the door or perhaps through a passive internal grille, bringing in warm air from other parts of the home. However, this creates a knock-on effect: the air from the landing now needs to be replaced, which draws air from the downstairs hallway via the stairwell, and the hallway air needs to be replenished from the living room, and so on.

Unless fresh air is entering the home at the same rate from the outside, the fan in the bathroom will lose effectiveness over time. In a well-sealed, insulated house, this return air can be difficult to obtain, causing the extractor fan to slow down and become less efficient.

It is crucial, therefore, to have a supply of fresh air entering a well-insulated building to maintain the proper balance. While passive air grilles can provide this, they somewhat undermine the purpose of insulating the property in the first place. To address this, a mechanical solution is needed—one that can filter and warm the incoming air. This ensures maximum heat retention, minimizes the introduction of pollutants, and maintains the balance between the air being extracted and the fresh air being brought in.

One option is to install a PIV (Positive Input Ventilation) unit in the property. Typically installed in loft spaces with passive ventilation to the outside, this unit pulls air in through filters and forces it into the home. During colder periods, many units come equipped with heating elements to warm the incoming air before it is introduced into the living space. Pairing these units with constantly running dMEV (decentralized Mechanical Extract Ventilation) fans, replacing traditional intermittent fans in areas like bathrooms, utility rooms, and kitchens, helps create continuous circulatory ventilation throughout the home.

Alternatively, you can install single-room or whole-house heat recovery systems. These systems both extract stale and humid air while supplying fresh, filtered air that is warmed through a heat exchanger. The heat exchanger transfers warmth from the outgoing air to the incoming fresh air, helping to retain heat and minimize energy costs. Whole-house systems are ideal when installed during construction or major restoration work, as retrofitting the necessary ducting from the loft to all areas of the home can be quite disruptive. On the other hand, single-room heat recovery systems can be installed directly through external walls, much like standard extractor fans, and are perfect for protecting more vulnerable spaces in your home directly.

We’ve discussed insulation and ventilation, but without maintaining an adequate level of heating, damp and mould can still take hold. This is due to the concept of the dew point. Imagine it’s a lovely summer’s day. You take a cold can of refreshing drink from the fridge and place it on the garden table. Within minutes, the surface of the can becomes covered in water droplets. This happens because the can is cold, and the warm air is full of water molecules that have been evaporated by the heat of the sun. As soon as these water molecules come into contact with the cold surface of the can, they condense back into liquid form. This same principle applies in your home.

For instance, when you take a shower, the hot water produces steam in the air—evaporated water molecules. When this steam comes into contact with cold surfaces such as mirrors, windows, or unheated external walls, it condenses into water droplets on those surfaces. While it's impractical to install heating pads behind mirrors, tiles, or the plaster on your walls and ceilings, maintaining a consistent, reasonable room temperature helps. Keeping the room warm will prevent surfaces from cooling too much, slowing the condensation process. It also encourages the re-evaporation of any condensation that accumulates throughout the day and night. This approach can help reduce damp damage and eliminate the ideal conditions for mould growth.

But energy costs are through the roof, you might say! Yes, they certainly are, but maintaining a well-insulated home at a temperature of around 17-19°C doesn’t have to break the bank. It can actually save you money in the long run by avoiding costly redecoration to fix damp and mould damage, while also ensuring a safer living environment. If you rent out your property, it’s worth taking the time to explain the benefits of this to your tenants. The Housing Ombudsman Service website offers a wealth of supporting information and resources for both landlords and tenants on the damp and mould key topic page, which can help guide you through the process.

Remember, all three of these actions need to be addressed to effectively solve the problem! Ventilating without ensuring a proper return of air will make mechanical ventilation ineffective. Similarly, a lack of insulation combined with passive external airflow will lower the internal temperature during colder months, leading to higher levels of condensation and/or increased heating bills. Heating to 17-19°C will help slow down condensation, but without adequate ventilation to remove the humidity, you’re essentially creating the perfect breeding ground for mould! All three factors—insulation, ventilation, and heating—must work together to tackle damp and mould effectively.