The first thing that is noticed in a building, is its façade. The judgment and opinion about it will mainly be on aesthetics. But façades, (being the envelope includes all the exterior of the structures), act as the first line of defense against the effects of the environment, it must provide comfort and safety to the building’s occupants while spending, as far as possible, the least energy resources. Ensuring resilient façades is essential to protect building occupants, reduce energy consumption, and guarantee the longevity of the structure itself.
There are three aspects to consider about the safety of an enclosure:
Safety During Construction
The design of an envelope is important. For example, the unitized system has more factory work and thus most of its construction activities happen in the factory while few on site, compared to the stick system. This potentially makes the unitized system more secure than the stick.
However, workplace accidents occur mainly because all preventive safety measures do not exist or workers directly ignore them.
General security considerations:
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Figure 2: This figure represents a test, which indicates the category of glass to resists impact Safety First: Emphasize that safety is the top priority for everyone on the construction site through awareness.
- Follow-up of Procedures: Remind workers that they must follow all established safety procedures and protocols at all times and that their violation is a serious offense.
- Protective equipment: Ensure all workers wear appropriate personal protective equipment (PPE), such as hard hats, safety glasses, and gloves.
- Hazard Awareness: Encourage workers to be aware of their surroundings and report any potential hazards immediately.
- Fall protection: When working at heights, emphasise the importance of using appropriate fall protection equipment, such as harnesses, lifelines, and scaffolding with guardrails. Never allow workers to work at heights without proper fall protection.
- Working with glass: Emphasize caution when handling glass panels. Workers must receive proper training in safe lifting techniques and use the proper equipment to avoid breakages and injuries. When handling glass, there are often accidents.
- Anchoring Systems: Emphasise the importance of ensuring that all façade components are securely anchored and properly connected in accordance with engineering specifications.
- Weather conditions: Be aware of weather conditions and adjust work procedures as necessary. Avoid working at heights or with large items during high winds or unstable weather.
- Emergency Preparedness: Make sure everyone on site knows emergency procedures and evacuation routes in the event of an accident or unforeseen event.
Safety of Building Occupants
There are two types of security that affects the occupant:
- The possibility of falls or injuries
- The possibility of suffering due external damage (wind, fire, vandalism, cold or heat, etc.)
In this paragraph, we will refer to the first possibility of direct damage to the occupant. In the next paragraph we will refer to the second possibility, but that depends mainly on the design of the façade, safety and integrity measures and concerns.
In this case, the codes regulate the required level of protection and types of glass to be used. For instance, the British Code BS 6206- 4, establishes criteria for safety glazing (against human injury), indicating locations of safety glass (fully tempered or laminated). Any glass in the grey area (see Figure 1), must be safety glass. This standard, like that for the minimum height of a balustrade, guarantees safety to the occupants, the first from injury the second as barrier against falling.
An important point in the design of envelopes is to consider the consequences after glass breakage. For example, in a skylight (or any other glass above the occupants’ heads) the way the glass breaks is extremely important. Therefore, horizontal glass with the aforementioned condition must be at least laminated with proper laminate.
Quality control during construction is important and some tests must be done. An example is the soft body impact test as specified in the code EN 12600. By this, the glass can be classified, approved, or discarded after the test, which simulates, among other things, the impact of a person against the glass under examination. See Figure 2
Safety of the envelope (structural integrity, durability, frequency of damage, etc.)
- Structural Integrity. The envelope must be calculated to resist the action of the wind, depending on building exposure and location following local standards and international codes and standards. With other loads like the live load applied by the occupants, temperature, earthquakes, and vibrations. In some cases, it may be necessary to design the façade to resist vandalism, explosions, or bullets.
- Vandalism and burglary become everyday occurrences in large cities. This point is something that is normally ignored by many designers, but it is also regulated by codes. Therefore, it is advisable to find out what type of burglary classification there is in the area where the building is located, and choose the appropriate windows accordingly.
- Fire Safety: Utilize fire-resistant materials and cladding systems that meet building codes and regulations. Consider compartmentation within the façade to prevent fire spread.
- For fire, two criteria are discussed: The reaction to fire (whether the material is combustible or not) and the resistance to fire (how long it takes for the material to give way to the action of fire).
Compliance with code requirements will reduce the chances of human or material losses. In the most recent fires (some with tragic consequences) in cities such as Dubai, London, or Valencia, they show non-compliance with the codes regarding the material to be used or the distance between openings (not separated by at least one meter of material non-combustible) were of vital importance in the spread of the fire between different levels. An example of how the codes regulate the aforementioned is the British standard
“The Building Regulations 2000” in part B4 “External fire spread” is in the following figure 3. (Diagram 40 Provisions for external surfaces of walls).
This figure presents what type of materials can be used, taking into account the height of the building and the distance to other buildings. It is very common in architectural designs to see that the distance that separates two levels with material with at least one hour of fire resistance is much less than one meter and this could be fatal in cases of fire.
In February of this year, there was a fire in the city of Valencia (Spain) resulting in 10 people dying. Within an hour the fire had already spread to both buildings. When we see figure 4, we realize that the horizontal distances between windows are small and also the façade material was aluminium composite with a polyethylene core, which is extremely flammable and releases smoke and drops in profusion.
- Adaptation to the local environment & Maintenance: Building resilient façades begins with understanding the specific climatic factors of a location. Architects and designers must analyze historical weather data and even consult climate projections to anticipate future trends. This knowledge guides decisions about material selection, structural design, and possible façade adaptations.
An example of the above is considering what type of corrosive environment you have. This is often ignored by some designers. In areas close to the sea and with high environmental corrosivity (e.g. C5 as per ISO 9223) the coatings of the structural parts must be carefully studied.
Regular maintenance is vital to ensure the continued performance and resilience of a façade. This includes cleaning the façade to prevent dirt and debris build-up, inspecting for any signs of damage, and performing any necessary repairs promptly. A proactive and preventive maintenance approach can extend the lifespan of the façade and prevent costly repairs down the line.
Every good envelope project must be complemented with an inspection and maintenance plan. The necessary equipment, the frequency of inspection and/or maintenance and the useful life of the coatings should be mentioned, especially in those places where there is not easy access. For that, there are instruments to survey and more recently the use of drones, to access easily all the places in an envelope. It is vitally important to comply with these points. There have been tragic accidents in engineering due to corrosion or failure of components, supports and anchors.
The case of interstitial condensation (that which occurs inside the façade) is very important to be studied and considered. In addition to the influence on health, it can be a long-term safety issue as well, since interior elements, bolts or anchors can be corroded over time.
In conclusion, ensuring resilient façades is no longer an option but a necessity. By understanding climate challenges, selecting robust materials, employing sound engineering practices, and prioritizing maintenance, we can create buildings that are safe, sustainable, and prepared for the future. There are other aspects that are key in the design and construction of an envelope. For example, the transmission of energy via conduction (U value) or via solar (SHGC or g value). They are essential for comfort but are not mentioned here, because they are not related to safety.
