02. Facade embodied carbon studies

According to LETI guidance, the façade constitutes 13% of a building’s total embodied carbon. Although this figure is subject to debate (an issue we’ll delve into soon), architects bear direct responsibility for designing the façade and its environmental impact.

A common inquiry we face is the carbon footprint of our façades. While existing research attempts to address this, it often oversimplifies and primarily pertains to low-rise brick facades. Therefore, we initiated a study to unveil the embodied carbon of our façade design.

The study aimed to:

1. Enhance our understanding of embodied carbon.

2. Identify the key contributors to the embodied carbon of a masonry brick façade.

Beyond merely assessing the embodied carbon of a brick façade, we sought to explore the influence of design complexity. The study focused on four bay configurations, each featuring the same wall structure with an external brick layer and SFS infill. Structural frames were not considered.

1. Wall only

2. Vertical window

3. Horizontal window

4. Horizontal window with piers

The study is not intended to be exhaustive. Rather, it is intended to understand the relative differences that result from adding simple brick articulation to the facade – in the form of piers, horizontal bands, or creating brick recesses.

What’s in a brick?

Undoubtedly, brickwork is a significant contributor – up to 30% in a typical wall. However, presently in the UK, all brickwork falls under a single Environmental Product Declaration. Consequently, it’s challenging to discern how various types of bricks impact embodied carbon, particularly considering the diverse methods used in brick production that influence their environmental footprint.

It’s all about the support!

The findings from the wall-only construction buildup revealed that the brickwork represented just one aspect of the embodied carbon. The substantial amount of steelwork needed to support and secure the brickwork emerged as the primary source of embodied carbon, underscoring the importance of understanding how a particular façade material needs to be installed.

Load Bearing Masonry

The results show the importance of understanding how the brickwork will be supported. With the changes in the fire safety likely to produce more buildings under 18m to avoid two staircases there arises an opportunity for the resurgence of load-bearing masonry—a traditional design approach that has been employed for many years. This approach could help significantly reduce the embodied carbon of a brickwork façade. This is something we successfully implemented at our scheme in North West Cambridge.

Glazing

The inclusion of glazing represents another notable contributor to the embodied carbon of the façade. Our study integrated a conservative amount of glazing, yet even this led to a roughly 22% increase in the embodied carbon quantity. This once more underscores the critical role of glazing design in the sustainability of a building. Not only does the proportion of glazing impact daylighting and the risk of overheating, but it can also markedly influence the overall embodied carbon footprint.

Articulation

Currently, we’ve made initial assumptions regarding the necessary steelwork to support different bay types and are collaborating with support manufacturers to obtain more precise data. The findings indicate that while there is a carbon cost associated with detailing the façade, as long as it remains within reasonable bounds, the limit of embodied carbon is not the primary concern.