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My House Has plenty of Windows—Why Do I Need a Ventilation System?

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By Ruth MacEachern

Product Manager

Jun 18, 2019

Most British homeowners are aware of at least some of the reasons why proper ventilation is crucial. The British climate is the most obvious: with year-round rain, it’s nearly impossible to prevent the build-up of moisture in buildings without a ventilation system in place. The English Housing Survey recently found that more than a million English homes have a damp problem: millions more regularly experience higher than optimal levels of moisture. 

Despite the problems posed by the British climate, homeowners in this country continue to place their trust in passive ventilation solutions: in other words, opening the windows. However, the increasingly strict requirements of legislation concerning energy efficiency have made this never-very-effective system less effective than ever. Sealed energy-efficient doors and windows provide little or no baseline draught, so that sufficient airflow in sealed houses can’t be achieved unless most or all of the windows are open—and we rarely have the weather for that! Plus, of course, this approach also results in either a very chilly home or very high energy bills.

What’s more, even in houses well set-up and situated for passive ventilation, there are significant downsides to a passive approach, including the health risks of an unstable internal climate or exposure to pollutants from external air, the build-up in your home of allergens, toxins and moisture, and trapped pockets of stale or unclean air. 

Buying a dehumidifier is little better: not only do they come with significant energy costs, but they also take up space and require regular cleaning and servicing.

For all these reasons, more and more homeowners are opting for some form of whole-house ventilation system. The options are many and varied, and most homeowners will be able to find the right system for them.

The dangers of inadequate ventilation

It’s important not to underestimate the dangers posed by inadequate ventilation in a family home. Few aspects of ongoing maintenance are as crucial to ensuring a healthy environment.

Most Britons have some experience of the issues caused by excess moisture. The most common of these is damp. At a minimum, damp is a costly problem. Even when poor ventilation and a build-up of excess moisture is the likely cause, it’s generally necessary for an expert to diagnose the problem. The reason for this is that the various forms of damp—rising, penetrating, interstitial and straightforward condensation damp—are easily confused, especially because several problems can co-exist and compound one another. If a damp problem is misidentified, costs rise as many repair efforts become necessary. Even when a damp problem is tackled effectively and speedily, without improvements in ventilation, damp is all but guaranteed to recur.

When damp problems are allowed to worsen—or where they are misdiagnosed and inadequately addressed—larger costs can start to rack up. Damp can lead to wet rot and ruinous damage in timber structures. In the long term, a recurring damp problem can affect the resale value of a property. Almost half of homebuyers say they wouldn’t consider buying a property with visible damp problems.
Another significant consequence of excess moisture build-up is black mould, which can exist independently of damp or be concurrent with it. Black mould is common in homes without adequate ventilation, and its spores have been found to cause a range of breathing problems, including asthma and allergies, especially in young children.

Damp and mould are just the most common consequences of inadequate ventilation. Poor ventilation can also result in a build-up of stale air in your home. As well as retaining cooking smells and other unpleasant odours, stale air can contain a range of potentially hazardous substances. Dust mites, pet dander and other allergens build up in homes without sufficient airflow, putting occupants—especially children—at risk of developing allergies, or of worsening existing allergic conditions. Pollutants from external air, such as industrial or traffic fumes, are also likely to build up in homes without sufficient airflow.

Insufficient ventilation can be costly, trap homeowners in a cycle of yearly expenditure, cause long-term damage to property and even threaten occupants’ health.

Why can’t my windows provide adequate ventilation?

Many homeowners in the UK tackle ventilation issues by opening windows. It goes without saying that this is a costly solution, both financially and concerning the environment. Even the most efficient central heating system will struggle to cope with the extreme temperature fluctuations that result when you depend on unheated external air for ventilation, and an unstable internal climate may create health risks for occupants. On top of that, it’s simply irritating not to retain full control over the internal temperature of your home.

Beyond temperature-related issues, relying on windows for ventilation exposes you and your family to external pollutants. Few areas in the UK are entirely unaffected by air pollution. Urban areas are blighted by traffic fumes, which can be as dangerous as cigarettes to the health of your lungs (and will visibly soil your carpets and furniture). Rural areas may be less affected by traffic, but in the countryside, you’re potentially vulnerable to whatever local farmers are spraying on their crops, which may include toxic pesticides. Other sources of air pollution include local factories or processing plants and quarries (which can generate large volumes of toxic dust).

Another major disadvantage of using open windows to ventilate your home is a lack of controlled circulation. Although passive draughts will certainly move air around your home, you have no control over how quickly it moves, or where it moves. On a still day, you might find yourself with almost no airflow, while on a windy day you might find doors slamming on you. Inevitably, there will be areas in your house with less airflow, and over time, pollutants will collect in these areas that would be removed by an active mechanical ventilation solution. You may even find that draughts are simply moving stale air from one part of your house to another, rather than removing it. And finally, there’s no guarantee that open windows will shift enough moisture to prevent the build-up of excess, especially in rooms with small or no windows, or on wet days.

The solution: whole house ventilation systems

The only way to guarantee effective ventilation in a family home is to install a whole house mechanical ventilation system. There a range of systems available, and we recommend a product from the Atmos range. It’s best to seek expert advice as early as possible if you’re planning to install one of these systems. With the right expert input, you will be able to find a system that guarantees clean, fresh air for you and your family.

The most sophisticated form of whole house ventilation—and an increasingly popular one—is Mechanical Ventilation with Heat Recovery (MVHR for short). MVHR can’t be implemented in every home, because it is only effective at a relatively high level of airtightness, but it is suitable for almost all new-builds and energy-efficient homes. 

An MVHR system draws air from each room in the house and passes it through a heat exchange, so that no heat is lost as stale air is expelled from the home. At the same time, external air is filtered for freshness and passed through the heat exchange to bring it up to room temperature before it is circulated into each room. The benefits include an optimally stable temperature, clean, dry air, and reduced energy bills.

The installation process is technical, and the cost will vary from home to home. Expert advice is recommended.

An alternative is a PIV, or Positive Input Ventilation, system. PIV works much like MVHR, but without heat recovery. PIV does not offer the energy-efficiency of MVHR, but it provides all of the ventilation benefits, including filtered air and a thorough, universal circulation of air throughout a property. Even without the energy savings of MVHR, PIV can be highly cost-effective. Ultra-efficient motors power EnviroVent's PIV units, and each component can be individually repaired so that the system rarely needs replacement or large-scale servicing.

Some homeowners are reluctant to explore these options because they fear ventilation systems will be noisy. There are horror stories out there, but the truth is that the only noisy ventilation systems are improperly installed ones. Both MVHR and PIV are very quiet if adequately implemented. 

Consult a professional

If you’re relying on open windows to ventilate your home, you may be exposing yourself to unnecessary costs and health risks. Contact EnviroVent to discuss a variety of ventilation products available that will help with implementing a more effective, and permanent solution to your needs.