How to improve internal ventilation in buildings with airtight facades
We’ve come a long way in designing and building homes and spaces for people.
In older buildings, the nighttime chorus was full of creaks and moans, as air snuck in around the weatherboards and whistled through the cracks in the mortar that had developed with age. During the day, the indoor air was kept fresh by these same little gaps, helped exponentially by his grandmother’s habit of throwing open all the windows, no matter the weather. Sometimes it was cold enough to leave the milk out day and it would stay fresh.
We’ve come a long way in designing and building homes and spaces since then, and todays residents benefit greatly from modern building design and modern materials.. Importantly, we now know how to build so the completed space, be it a single level domestic home, an apartment block or any building that humans will use, is both airtight and watertight. This results in homes that are warmer, more energy efficient and less susceptible to outdoor temperature changes than older buildings.
In principle, this is a very positive result. However increased airtightness carries with it its own slew of issues that also reduce the liveability of a space. An airtight building, by its very nature, doesn’t allow air in or out. Without human occupancy this isn’t a problem, however as soon as we begin living, working or playing inside the air quality begins to suffer. Temperature can begin to rise, humidity increases, pollutants start to accumulate, and oxygen levels can plummet.
Of all of these negative by-products from an airtight façade, by far the most insidious is increased humidity and moisture build-up. Beyond the obvious signs such as crying windows and condensation in utility areas, mould and rot can begin. The spores from mould growing in walls, on curtains, within ducts or on ceilings can be hugely damaging to occupant’s health.
What’s the secret sauce to successfully constructing an airtight yet healthy building? It’s very simple yet often not adequately thought out – the incorporation of a suitable ventilation strategy into your building design. This strategy could be passive (relying solely on natural air currents), mechanical (using fans to create the airflow), or our favourite – mixed mode ventilation, where natural (and free) air movements are utilised to their maximum and mechanical fans are included to pick up the slack and provide additional airflow where necessary.
A ventilation strategy can be as simple or as complex as your building design requires it to be. For example, a typical three-bedroom, standalone house usually be adequately ventilated with a low-cost, balanced ventilation system (ideally with heat recovery – which is another topic!) that runs continuously ensuring a suitable level of air changes per hour (ACH) are maintained. Larger buildings such as shopping centres or hospitals will usually require the heating and cooling systems to be integrated with the ventilation, and industrial buildings such as warehouses and factories may incorporate elements such as fume or dust extraction.
There is a danger to relying solely on traditional ventilation devices such as windows or external doors. While these are an obvious choice for passive ventilation, given their dual purpose of providing light, view and access, the operation of them tends to rely on the occupants thinking to open them. It is by no means uncommon for an unwitting building occupant to leave all of their windows tightly shut during cold weather (we want to keep the place warm, right?) and be unaware of the dangerous build-up of humidity and moisture inside that occurs as a result.
Luckily, there is a wide range of both passive and mechanical ventilation products available to the modern building designer. Products such as ventilation louvres, trickle vents, silent fans, heat recovery units, louvre windows, roof turbines, duct systems, air filtration and smart IoT control systems can all be used in the construction of a successful ventilation solution.
Bringing all of this together and designing a solution that specifically meets your building's needs is key. A poorly designed ventilation system may not only include unnecessary upfront costs, on-going inefficiencies and wasted energy, but could ultimately be contributing to an unhealthy indoor environment. Relying just on passive ventilation and occupant control may not be the best solution, however, neither may a fully automated mechanical system be required. Traditional air conditioning systems, either centrally ducted or high-wall units, can offer great benefits around temperature control however they certainly aren’t a complete solution in themselves. In other words, it’s complicated. So what do you do?
A project-specific design is a good starting place. It looks at all of the criteria for your building including items such as location, occupant type, building usage, construction methodology and targeted energy efficiency levels will result in the best solution and give the occupants of your building the fresh clean air indoors that they deserve.
And guess what? We provide product-specific design services, allowing you to ensure your ventilation and airflow solutions are exactly what your building needs. We also provide a range of standard solutions that can be quickly and easily included in simple building designs. Get in contact to find out how we can help you.