The outer shell of a building is more effective in terms of thermal efficiency compared to any heating or cooling appliances that are used inside. If incorrect materials are selected during the design, then the building will consume more energy, and no heating, ventilation, and air conditioning system will be able to compensate for the loss.
Fabric First, Systems Second
The most impactful large-scale building projects are all based on the same deceptively simple idea: let the physical form of the building do the lion’s share of the work in managing the local climate, well before any kit is specified. Hence “fabric first” in theory and practice. Get orientation, shading geometry, and envelope material right and the kit carries the load that remains, not the primary load in the first place.
The nuance is that the kit to which they refer can get replaced a few times over a building’s lifetime. The envelope can’t, at least not without vast material and energy inputs, and possibly building it all over again. Do the calculations on a cladding or roof membrane decision that gets made one week during the issue for construction drawings, and the envelope will determine your building’s energy demand for the next 40 years.
The performance metrics around this are unequivocal, but high-performance facades in modern aluminium building cladding systems are removing the dichotomy from design decisions by eliminating the traditional compromise. A fabricated aluminium system will provide the peace of mind that non-combustibility brings, the additional design benefits of a façade system that can be tailored to any geometry and that is the material of choice for those building at the cutting edge of architecture.
Space heating and cooling are the largest end-use categories of energy consumption for buildings. The IEA estimates that building operations are responsible for one-third of final energy consumption globally and nearly half of that in the industrialized world. Heating and cooling are the largest components of that, and one-third of the heating and cooling problem comes from dwellings. Most of it is a design problem, not an operations problem.
Where Energy Actually Escapes
Often, the thermal performance of high-rises is not compromised along the full surface of a wall, but at junctions. For instance, where a concrete floor slab intersects the external façade, where window frames meet structural elements, or wherever one material shifts into another, e.g. where they’re brick flats interrupting a continuous layer of insulation, heat ‘bridges’ directly through the materials. These are the junctions where the most heat escapes from the building.
Indeed, this is how a wall system with a great R-value on paper can actually perform poorly in reality. If the detailing at every level junction of the building provides an unbroken conductive path to the outside (around the box) then all that advertised insulating power goes for nought. Fixing this means either using ‘thermally broken’ connections that transmit hardly any heat through materials, or in exactly the case of brick, rethinking the materials themselves to decrease conductivity at the point of contact.
The Glass Façade Problem
Architects constantly want to push the performance and aesthetic boundaries (and why shouldn’t they?) The point is that these concerns shouldn’t be solely on the shoulders of an architect who has little financial incentive to maximize them if they’re at odds with the client’s priorities. The role of the cost consultant is to arm the client with reality so they can make informed decisions about where to sit on that sliding scale.
Safety, Performance, and the Case For Modern Cladding Systems
The requirements for non-combustibility on high-rise buildings should be non-negotiable, and the reality is that they will only continue to increase. It would be unfortunate for owners and developers to see the evolution of modern high-performance facades as an either-or between fire safety and thermal performance, with the latter an increasing priority given the focus on climate change and meeting stringent criteria around energy consumption in buildings.
Lifecycle Thinking Changes the Material Decision
Choosing a material that seems low cost when procured but costs more over the life cycle because it needs frequent replacement or expensive maintenance, or its thermal properties decrease over time, becomes a false economy. Conversely, some materials and systems cost more in construction or installation but make savings in ongoing maintenance, repair, or replacement, serving the building better for longer.
This is not only the case when it comes to carbon, but also for the Total Resource Use, considering the impact over the life of the building rather than just at time of construction. Durable materials and components not only use fewer precious resources over time, but they also score well in whole of life analysis where the cost or benefit of a specific material or design decision is considered in its entirety, including longer term costs such as replacement and maintenance.
The Envelope Earns its Keep
The building envelope should be considered a performance system. For example, if it is designed with the same level of precision that is applied to the structure or services, the peak loads can be reduced, the equipment’s life can be extended, the operating costs can be lower, and the fire safety requirements are also met. There are no compromises. If it is viewed merely as a finish, all those costs will be transferred somewhere else throughout the building’s life, and they will accumulate.
Choosing the materials is not a judgment based on aesthetics that has technical consequences. It is a decision with technical consequences that has an aesthetic output.
