🔥 Arinsal fire: reflections from an architectural perspective

The recent fire in Arinsal leaves us with a striking image, but also an opportunity to analyse, from a technical standpoint, how buildings behave in a real fire scenario.

From direct on-site experience, one aspect stands out: the fire did not primarily spread through façades or interiors, but through the roofs of the buildings.

The roof as a path for fire spread

The affected buildings featured a common energy retrofit solution: a new insulation layer installed over an existing wooden roof deck, with a ventilated air cavity between both layers.

This configuration is technically sound. The ventilated cavity helps prevent condensation and extends the lifespan of the timber structure. However, in the event of a fire, this same cavity can become a continuous channel for flames.

Air movement feeds combustion, while the empty space allows rapid and often hidden fire spread beneath the roof finish. Under these conditions, fire can travel uninterrupted from one building to another.

The role of materials

Not all materials behave the same in fire, and this difference is critical.

Common insulation materials show very different performances:

• Materials such as extruded polystyrene (XPS) are combustible and can contribute to fire spread.

• Others like polyisocyanurate (PIR) perform better, but remain organic and combustible.

• In contrast, mineral wool is non-combustible and can act as an effective barrier.

This distinction, often secondary during design stages, becomes crucial in real-life scenarios.

Extreme conditions: the wind factor

An additional key factor was the wind.

Strong winds on that day continuously supplied oxygen to the fire, increased its intensity, and helped spread embers. These conditions made firefighting operations significantly more difficult and accelerated fire transmission between roofs.

The challenge of extinguishing hidden fires

When fire spreads בתוך a ventilated roof cavity, locating and extinguishing it becomes especially challenging.

Emergency teams often have no direct access to the actual fire source, requiring them to open up roof layers and act destructively to control the situation. This highlights the importance of designing buildings that also consider ease of intervention.

Reflections from design

Beyond this specific case, the fire invites reflection on key aspects of contemporary architecture.

1. The importance of materials

Material selection cannot rely solely on cost or energy efficiency. Fire performance is a critical factor.

In roofs and critical areas, the use of non-combustible materials should be a priority.

2. The need for roof compartmentation

In large roofs or continuous building complexes, it is essential to avoid uninterrupted ventilated cavities.

Introducing fire barriers can prevent horizontal fire spread and limit its extent.

3. Evacuation: the fundamental principle

No building is immune to fire. Therefore, the primary design principle must be to ensure that all occupants can evacuate safely within a reasonable time before conditions become critical.

The main objective is to protect human life.

4. Integrating fire safety from the start

Fire safety cannot be treated as an afterthought. It must be integrated from the very beginning of the design process.

This involves combining passive measures —materials, compartmentation, fire resistance— with active systems —detection, alarm, and suppression—.

Final reflection

The Arinsal fire highlights how many current construction solutions, although effective from an energy perspective, may present vulnerabilities under extreme conditions.

As architects, we have the responsibility to strike a balance between efficiency, sustainability, and safety.

Ultimately, buildings must not only be comfortable and efficient, but also resilient in the face of the unexpected.