How does the stack effect mechanism work?

The sun heats the external panels. Air in the gap warms up, rises and creates a current that expels heat before it reaches the rock wool insulation.

How much are cooling loads reduced?

In the 10x10 Model, cooling loads are reduced by 20-30% compared to conventional ETICS of the same insulation thickness.

Why is conventional ETICS not enough in summer?

In conventional ETICS, the external render surface reaches 65-70°C and this heat gradually pressures the insulation. The air conditioner runs for many hours.

How the Air Gap in a Ventilated Façade Reduces Cooling Loads in Summer

When we think of thermal insulation, our mind automatically goes to keeping the cold out in winter. Yet, in Greece's Mediterranean climate, protection from the scorching summer sun (also known as summer thermal protection) is equally, if not more, important.

In a typical building, the sun "roasts" the walls all day long. Even if you have conventional ETICS, the exterior render surface absorbs this enormous solar radiation and its temperature skyrockets. This is exactly where the Ventilated Façade changes the rules of the game, thanks to an air gap just 3 to 5 centimetres thick.

Let us look step by step at how this simple gap "deceives" the sun and slashes your electricity bill.

1. The Problem: The "Oven" Phenomenon

Imagine a south- or west-facing external wall at noon in August. The air temperature may be 38°C, but the wall surface (especially if it is painted in a dark colour) absorbs the solar radiation and can exceed 65°C to 70°C.

This enormous heat accumulates in the material (render or brick) and gradually begins to push through the insulation into the room. Your air conditioner (the cooling load of the building) must run constantly to counteract this invisible "attack" of heat coming from the walls.

South-facing wall in August - surface temperature reaching 65-70°C

2. The Solution: The Stack Effect Mechanism

The ventilated façade works like a shield. The external cladding (e.g. aluminium panels or ceramic tiles) takes all the battering from the sun. The secret, however, lies right behind it, in the air gap between the hot panel and the rock wool protecting the wall. Physics takes action through the "Stack Effect":

Stack Effect mechanism - hot air rising through the ventilation gap

1️⃣ Panel Overheating

The external panel becomes extremely hot from the sun.

2️⃣ Air Heating

The heat from the panel warms the air trapped in the gap behind it.

3️⃣ Upward Flow

The hot air expands, becomes lighter and starts rising rapidly upwards.

4️⃣ Suction & Replenishment

As the hot air exits through the ventilation openings at the top, it creates negative pressure (suction) at the bottom. Fresh, cooler ambient air enters from below.

💡 Note: This cycle continues non-stop as long as the sun is shining!

3. Why Your Air Conditioner "Takes a Break"

This continuous, powerful air current acts like an invisible conveyor belt. It carries away (removes) the accumulated heat from the external panel and throws it back into the environment, before it reaches the building's insulation.

Instead of your insulation fighting a panel burning at 70°C, it only has to face the air in the gap, which, due to constant flow, never exceeds the ambient temperature (e.g. 38°C). This enormous temperature difference is what practically eliminates heat transfer to the interior.

Comparison of thermal load on ETICS vs ventilated façade

4. The 10x10 Model Experiment

Mid-July in our digital laboratory. Outdoor temperature 38°C.

10x10 Model - scenario A (ETICS) vs scenario B (ventilated façade)

❌ Scenario A: Conventional ETICS 10cm

The wall surface "roasts" at 65°C. The insulation material faces enormous thermal pressure. The heat eventually penetrates the wall. The air conditioner burns several kilowatt-hours to keep the living room at 26°C.

✅ Scenario B: Ventilated Façade with 10cm Rock Wool

The external panel hits 70°C. However, the air current in the gap expels the heat instantly. The outer surface of the rock wool never exceeds 38°C (air temperature). The thermal stress on the insulation is reduced by 50%!

📊 Result

The interior wall surface feels cool to the touch. The cooling loads of the space decrease by 20% to 30% compared to conventional insulation. The air conditioner barely runs.

💡 Conclusion: The air gap is not just an empty space. It is a powerful, free natural cooling mechanism. This is the main reason ventilated façades dominate in modern, glazed office buildings that suffer from summer overheating.

Ventilated Façade: What It Is & Why It Is the Top Solution for Commercial Buildings Ventilated Façade Support Systems: Aluminium vs Wood What Is the ETICS System (External Insulation) & What Are Its Advantages Insulating Paints & Reflective Coatings: Myths & Truths

Insulation Systems: Complete Solutions for Every Building

Return to category.

Go to category

Central Guide

Return to the central guide.

Go to guide