Facades? Ventilated?
Like most people, I too thought that façades were made to enhance the aesthetics of a building. Façades indeed render the desired personality and character as per the intended use, however, that’s not all. I was amazed to learn how ventilated façades work.
It was an eye-opener for me. Ventilated façades (also known as rain screen façades in tropical belts) originated from the Scandinavian countries where the winters and summers, both, were equally harsh. The purpose was to maintain the warmth within the building during winters and vice versa during summers. In tropical areas, just like ours, it is used as a screen to protect the building from the direct attack of rain. It is a known fact that direct rain attacks are the worst, causing the worst damage to the façades.
Ventilated façades, essentially, have open grooves along the horizontal. They seem like architectural grooves but are actually acting as air vents. This arrangement is always necessary to provide natural ventilation in the cavity behind the panels. Thus the name.
How do ventilated facades work?
The working principle of ventilated façades comes from our high school physics. Air when heated expands and moves upwards. The accompanying illustration will make it a little easier to understand (Image 1).
The panels get heated due to the sunrays and, in turn, warm up the air in the cavity behind them. The air thus expands and moves upwards in stacks. This phenomenon is called a STACK EFFECT. This warm air moving upwards is then allowed to escape from the vent below the coping. As a result of this, fresh ambient air is sucked in through the vents (the horizontal open grooves) giving rise to a steady and consistent airflow in the cavity behind the panels. This is how a ventilated façade works.
Importance of ventilated cavity
A steady and consistent airflow in the cavity behind the façade panel is necessary to reduce the thermal bridging. In the absence of this ventilation, the exterior heat will transfer to the interiors, making the ambient temperature of the interiors uncomfortable for the users. Having a ventilated façade ensures a drop in thermal bridging to 3-4 degrees. We all are living in a Warm World today and rely mostly on air-conditioners for our comfort. The reduction in thermal bridging helps us reduce the working load on our ACs by 3-4 degrees, causing substantial savings in power consumption. This airflow also carries with it the excess external noise, causing a reduction in Sound Contamination.
The sound contamination can be reduced by 20-30% depending on the width of the cavity behind. The air in the cavity also bears a high-temperature fluctuation from the start of the day to the end of the day. Especially in the early mornings, the air in this cavity condenses. The airflow in this cavity also helps us ensure that evaporation in the cavity happens naturally and fast. Ensuring evaporation also means ensuring that moisture saturation is completely avoided. In a true sense, since the cavity is always ventilated and kept dry, ventilated façades help us to avoid the external plaster as well.
Overall, the advantages/benefits of a ventilated façade can be summarised as:
- A complete protection from direct attack of atmospheric agents
- Retards aging of the building
- Renders smart aesthetics and imparts the desired character to the building.
- Reduces thermal bridging resulting in power savings on Air- conditioners
- Reduces sound contamination
- Helps in avoiding external plaster
- Helps reduce maintenance costs
Materials for ventilated facades
Any material, with the properties listed below, is a suitable material for ventilated façades:
- Material should be able to withstand the harsh action of the atmospheric agents
- Should be light in weight such that the panels can be supported on aluminium frames instead of MS frames which need maintenance
- Should be eco-friendly and recyclable
- Should have excellent resistance to fire
- Should accommodate an easy mechanical fixing detail
- Colour/texture should have a long life and minimum maintenance
- Should have excellent resistance to fungal and algae growth
- Should have a pleasing appearance and sustainability.
- Should have excellent resistance to temperature and humidity fluctuations
Most commonly used materials
The commonly used materials in ventilated façades are:
- Composite Panels in Aluminium / Zinc with an open groove fixing detail (ACP/ZCP)
- High-Density Fibre Cement (HDF Cement)
- Exterior Grade High-Pressure Laminates (HPL)
- Metals (Aluminium / Stainless Steel 202/304/316/ Copper/ Corten Steel)
- Dense and hard Natural Stone slabs
More studies are taking place across the world to produce better materials that can be considered as serious and better alternatives to all the above.
One thing that I can certainly say here is that we are a growing, dusty, warm country with heavy or moderate rainfall in almost all the areas. Weather is kind to us in many ways but is also an important factor in the aging and deterioration of our masterpieces. Protecting our buildings from rain, dust, heat, and wind becomes imperative, and choosing ventilated façades thus becomes advisable. As a civil engineer, having spent more than 30 years out there on the field (as a civil contractor as well as a ventilated façade Pro), I had the opportunity to study the reasons for damages to buildings and the methods available to avoid them. The last 15 years have been very educating and gave me a lot of good insights on to-do and never-ever-to-do things when it comes to façades. Having worked on European, Chinese, and even Eastern systems, helped me overcome a few shortcomings and develop a completely and proudly Made in India ventilated façade system.
The construction industry today is galloping ahead fast. New theories, new concepts and new materials are born every day. Every project is unique and is the architect’s brainchild. Also, every building is made on a concept better than the last. Every design also throws challenges, a different one each time. To me, they always encourage me to keep pace, think differently and be a little better each time.
