Ventilate the area naturally, not the flow

Natural ventilation can be achieved by a regular window; you can design your windows, or PPO that is purposely provided openings.

You need good ventilation. So, you can increase the outdoor air quality supported by passive or active filtration, you need periodic cleaning and maintenance and at the same time, you also need a good air distribution system. Hence, add movement to achieving all these five components are very, very important to achieve comfortable and healthy buildings.

Now, what I’m going to talk about is a combined use of natural ventilation and mechanical cooling in buildings. So, we can have different ways of increasing output quantity an exchange rate. I will focus on one of that technique which is called natural ventilation. Now, there are different ways of achieving natural ventilation. Natural ventilation can be achieved by a regular window, you can design your windows, or a purposely provided openings, we call it PPO.

You might have remembered some historical building visits you know; temples in some of the forts, that there would be some openings on the top end of the buildings, which are naturally ventilated. So, that design was the bit created to allow natural ventilation. Now in the modern context, what we need to look at is some more sophisticated approach of mixed modulating design. Because as the climate gets more and more extreme, we may not be able to provide comfortable environment, just with the natural ventilation. At the same time, if we use air conditioning system 24*7, then we will be spending tremendous amount of energy and increasing the burden on our grid and an hour convention. So that’s a good combinational use of natural ventilation and outside is comfortable, and you have a good quality air.

Strategies for ventilation:

While we talk about indoor air quality, there are times in the year when the outdoor air qualities are extremely bad. But there are times of the year and times of the day, where the indoor-outdoor air quality is something that you can work. So, you need to utilise and find out what is the period of the year where you can use natural ventilation, and then use different strategies.

So, you can use a strategy. On a cool day where you use only natural ventilation and zone, you’re building a certain part of your building operate in a natural ventilation, while the other part operates in air conditioning one that’s called zone x one buildings, or you can do a temporal mix mode.

So, when outside is comfortable, you use the air to provide the ventilation or outside air, if you use a mechanical system to utilise that outside air comfortable air. And it’s called free cooling. So, you can utilise that either through the fan, which becomes a mechanical ventilation or free cooling. Or you can use a window or purposely provided opening on that side to provide to get the outside air in the building. And when it gets extreme, which often does in many cities of India can turn out those openings and you rely on the air conditioning systems to provide comfortable air.

How one goes about designing the natural ventilation?

To explain a little bit more about how one goes about designing the natural ventilation, we did a part of the research, we analysed as many cities in India and analysed the Climatic Data, and from that data you can see, we came up with an image for eight cities, and what operation mode the building has to operate to provide comfortable environment. And, think of many cities, even extreme cities. You know very humid cities like Chennai, Mumbai and Kolkata, you can operate your building 10 percent to 15 percent a year first, while in cities like Hyderabad, where you have a more variation, you can operate 25 percent to 30 percent of your year in natural ventilation. So, this is essentially a source if there is a good potential to use natural ventilation in different buildings in India. Now, how do we go about designing these openings? It’s very important to design and what should be an area because we naturally ventilate the area, not the flow; besides how much area and of course, it depends on many factors.

But, if you have a good opening design, good orientation, good and well-planned opening location, you would actually be able to utilise the air much better. So, there is a design chart that we prepared as part of our research, wherein our x axis defines the air flow rate that we need for different cities, and what’s the opening area you need to achieve that. And then is derived an opening area that we take we typically see in residences in India. So, in Mumbai, Ahmedabad and Delhi, a typical two-bedroom hall kitchen apartment would have an open area; but to achieve effectively utilise native natural ventilation.

So, you actually need to start increasing the opening area. Also, there is a design chart that has been developed to help people design the opening. Once you know the opening areas, you need to select the type of windows or doors or the PPO, like I said, and it’s also important to remember what kind of window is really used. If you use a window, you can only use half of your window. But if you are using a basement window, you will be able to utilise whole opening area for Windows. So that design strategy can be easily incorporated by selecting the right kind of window and right kind of opening it. But you can go and we have a design guide that’s available on our website. And you can register yourself it’s free of course to download and know more about how natural ventilation can be used in buildings, what can be done to do it better.