COVID is an airborne disease. That single fact is set to revolutionise architecture, particular in designing for fresh air in buildings. After 120 years of sealed buildings with HVAC (heating, ventilation and air conditioning) we are set to learn lessons from the nineteenth century and before. Back to the future.

It wasn’t always the case that fresh air was thought to be the key to avoiding COVID. At first the World Health Organisation (WHO) assumed it was about surfaces - remember the ads of people washing their hands and discussions of how long the virus lasted on stainless steel or copper. Now we know that prevention is through masks, social distancing, and more fresh air.

Just as we are improving our understanding of better masks (N95 anyone?), that social distancing is actually spatial distancing, and what makes the ‘freshest air’, so is our understanding of what design improvements in ventilation will be needed in our current and future buildings.

Let’s start with what we mean by ventilation. There are three kinds. Firstly, fresh air ventilation is replenishing oxygen and removing condensation and odours; secondly, cross ventilation is air movement to provide evaporative cooling for occupants; and thirdly, diurnal ventilation is using cooler night air moving through buildings to remove daytime heat and store ‘coolth’. Details on each can be found in ToT #42 here.

Covid raises issues with the first type, and a quick history can illustrate the difficulties with where we are heading. The relationship between human health and poor air quality, in particular deadly odours, was not identified until the mid-19th century. Not long after, the British Building Regulations, upon which ours was based for one hundred years, introduced two types of controls.

The first was to ensure that buildings had adequate window openings to encourage occupants to open the building for fresh air. It introduced the ‘opening of 5% of floor area’ rule that still exists today. The second was to mandate permanent exhaust vents in case occupants didn’t use the windows. We can only imagine the smells in British homes when Queen Victoria said, “I have a bath once a month, whether I need it not”.

One example of permanently open vents are the terracotta grilles inside and out of Federation houses, a hangover from the need to vent the burnt gases from candles and gasoliers before electric light. Incidentally, the burnt carbon-based gases left a sooty build-up during the long dark nights, hence the need to brush it out when days were longer: called spring cleaning. The grilles, like the saying, lasted long after their original need.

In 1902 when Willis Carrier introduced the first AC in a building, everything changed. Thousands of years of architectural design based on local climates, wind patterns and orientation were suddenly junked. Le Corbusier advocates for technologically based designs for buildings, irrespective of their location: the same building on the equator as in the Arctic.

Even before WW2, AC becomes more affordable and more universal. The external envelope is minimised, a cost saving dressed up as being ‘modern’. The HVAC engineer intimidates the architect, and we get one hundred years of buildings increasingly ignoring the local climate, and along with it, the need for fresh air.

Now a reckoning has come, in the demand for fresh air, and every typology must change. And each one is fraught in rediscovering the past.

Our houses have increasingly relied on mechanical ventilation and ducted AC. We now discover that there should be wide openable windows in every room. Except, unlike the widely-spaced, modest bungalows on large blocks of 120 years ago, our houses are twice the size on half the area. Those open windows create problems of acoustic privacy; the home theaters, surround-sound systems and gaming screens create indoor noise levels twice those of a hundred years ago. And the windows stay shut. You can read about inflated suburbia, called 2x2x2x2x2, and its novel issues, in ToT 49 here.

Office buildings, the greatest users of HVAC, are now being rethought. Instead of the recycled V being used to carry the H and the AC, only 100% fresh air ventilation is introduced, and the heating and particularly cooling are handled through radiators and evaporators, often called chilled beams. Given the need to replace AC every 20-25 years will we see the external envelope change at the same time? Forget the corner office, the new prestige could well be an openable window.

Modern hotels, the most spectacular failure in the COVID quarantine debacle, will go the same way as offices: the 5-star traveller will want an openable window, or preferably a balcony door, in their upmarket suite. As remarked previously, the ultimate irony during COVID was that the only hotel designed specifically for quarantine, in pavilions with openable windows, was the one hotel NOT used for quarantine.

But the building type most under fresh air scrutiny right now is schools. With the rise of open plan learning in the 1970s school layouts became increasingly deeper; large areas of flexible space relied on mechanical ventilation mostly, with some roof vents and AC, to provide (often un)reasonable thermal comfort for students and teachers. We are rediscovering the delights of classrooms openable to sheltered corridors that provide air movement through cross ventilation. But what do we do with the hot, stuffy boxes where learning rates decline?

As we go back to the future, rediscovering a forgotten recent past design history, forthcoming ToT columns will examine each of these building types that are threatened with major design disruption through the demand for fresher, and less mechanical, air. With a special edition on the key solution: better windows. Steve King will be riding shotgun the whole way.

Tone Wheeler is principal architect at Environa Studio, Adjunct Professor at UNSW and is President of the Australian Architecture Association. The views expressed here are solely those of the author and are not held or endorsed by A+D, the AAA or UNSW. Tone does not read Instagram, Facebook, Twitter or Linked In. Sanity is preserved by reading and replying only to comments addressed to toneontuesday@gmail.com.

Tone Wheeler

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