Complex building envelope: the most relevant aspects
The most relevant aspects to take into account when designing the envelope of complex buildings are:
- thermally insulated multilayer systems;
- systems with reduced thickness layers;
- new types of glass and coatings for greater reflection or “permeability” of solar radiation towards the inside;
- formal and geometric complexity of the casing system;
- integration with technological services;
- performance-based fire safety through a new approach to fire prevention (Fire Safety Engineering – FSE);
- control of the durability and maintenance needs of the layers most exposed to degradation;
- accessibility, maintenance and safety of the casing system (permanent maintenance units – BMU, temporary suspended platforms – TSP, etc.).
Not only thermally insulated multilayer solutions but also transparency and permeability
The experimentation of thermally insulated multilayer solutions and of construction systems with reduced thickness layers have found fertile ground in the recent period.
At the same time the search for transparency and permeability has made available new glass matrix materials capable of controlling and modulating the thermal and light flow and modifying their performance depending on the stimuli provided to the system. For example the translucent adaptive casing of the Design Hub of the Royal Melbourne Institute of Technology designed by architect Sean Godsell is made with a double skin system with an internal infill curtain wall (equipped with double glazing with low-emissivity crystals and an argon cavity) and an external structure made with galvanized steel rings and frosted glass discs that can be mechanically adjusted using an electromechanical building management system, in order to optimize heat and light gains.
The casing that follows the technological-system evolution
Furthermore, the external envelope system has been designed not only to adapt to weather conditions, but also to follow technological evolution and plant integration: as an alternative to glass discs, the possibility of installing is envisaged Photovoltaic cells to increase the energy autonomy of the building, or systems backlight to transform the casing into a multimedia surface.
This reference represents one of many examples of the progressive diffusion of the concept of “adaptivity”, that is, a technological system capable of self-adapting to changes in external environmental conditions. An approach capable of triggering changes towards an adaptive architecture, of focusing attention on the link between the shell and renewable energy sources and of carefully evaluating plant integration.
Among the most widespread systems are i “Building Integrated PhotoVoltaics – BIPV” (capable of converting incident solar radiation into electrical energy), i solar thermal collectors (capable of converting incident solar radiation into thermal energy), the “Solar Cooling” systems (equipped with absorption thermodynamic machines) and micro and mini wind systems (microgeneration machines for individual users with network exchange).
The complexity of these casing systems requires a design capable of precisely defining the characteristics of the system, identifying and develop the critical nodesconsider aspects of speed and ease of installation, maintenance and control of casing and system performance. The goal is to achieve a adequate satisfaction of comfort requirements and guarantee the safety and security of users.
Enclosure fire safety
It should be underlined how i recent and dramatic cases of fire (Grenfell Tower in London in 2017, Torre dei Moro in Milan in 2021, Skyscraper in Chicago in 2023) have highlighted how it is essential to improve technical knowledge and practical procedures in the design of envelope systems with regards to their vulnerability to fire .
«Since in recent years the thickness of thermal insulation has more than doubled, in the case of use of combustible materials they are inevitably fire loads also increased. I am you also increase the duration of the potential fireand its shutdown, with a possible consequent increase in the risk of fire spread on the facades of the building and, in addition, also towards its interior and/or towards neighboring buildings. A significant contribution to effective modeling Fire Safety Engineering – FSE of fire scenarios and improving the safety of solutions comes from the growing number of real life tests that are conducted for evaluate the behavior of different facade solutions in the event of fireboth in terms of the use of different materials, both as regards the effects due to different geometries and configurations of the facade openings” (Mazzucchelli ES, The envelope of complex buildings: design and construction aspects) as well as recent regulatory updates.
Maintenance of complex building envelopes
A final consideration relating to the envelopes of complex buildings concerns the methods with which to safely access the envelope for maintenance operationsusing complex technological units and components capable of allowing easy execution of ordinary and/or extraordinary maintenance operations (checks, cleaning, repairs, replacements, etc.).