10 design commandments for cutting your building’s embodied carbon

Choosing wood structures, when the requirements allow for it, can reduce embodied impacts substantially in most projects. In our example building, this embodied carbon reduction – when measured over the whole life-cycle – would lead to a reduction of around 30%.

One Click LCA’s Carbon Designer tool allows users to quickly evaluate the impacts of common structural materials using building geometry.

Potential carbon savings* 30%

The share of embodied carbon impacts for structural materials is always substantial, and in our example building, nearly three quarters.

* In the baseline building

Setting environmental performance requirements for materials and products is an effective way of reducing impact while achieving exactly the same design and performance. The requirements could specify minimum carbon performance targets or other measures such as stipulating the use of recycled binders for concrete, for example. This strategy works effectively for all materials where supply is competitive and some suppliers are willing to supply products with improved environmental performance.

 

One Click LCA’s materials database contains over 10,000 different construction materials environmental impact profiles for different products, technologies, suppliers and products. There’s also a module to create your own product mixes e.g. for specific concrete recipes, and you can send us any new EPDs that you plan to use if you do not find them in the database.

Potential carbon savings* 10%

In the example building, when structural concretes and steels were changed to lower impact products, the whole building materials life-cycle impacts were reduced by 10%. Looking carefully at what you source can make substantially greater reductions.

* In the baseline building

Example from One Click LCA database: Embodied carbon impacts of concrete range from below 200 to over 500 kg CO2e / m3

As a general rule, a simple shape is more materials- and energy-efficient. Building in a square shape is not always possible due to daylighting, zoning, functional, or space distribution requirements. A more complex building shape drives external walls demands, and also requires additional access corridors. If the building requires additional staircase and elevator shafts in different locations, this also creates demand without additional corresponding available room area.

One Click LCA’s Carbon Designer allows users to consider the impacts of the number of floors, building shape, floor height and additional parameters for the materials demand as well as resulting embodied carbon impacts.

Potential carbon savings* 10%

If the example building were built as a three-storey elongated building, the embodied carbon impacts would be approximately 10% higher. Also, this increases the envelope area, and, as a result, the energy loss via the building envelope.

* In the baseline building

 

Slabs are a major contributor to the embodied carbon of a building. Unlike the envelope area, the amount of slabs scales linearly with the internal area required. Slabs provide structural, acoustic and fire resistance capabilities for the building, among others, and may embed piping or other installations. Reducing the net thickness of slabs by 10 cm reduces the building envelope height correspondingly, thus saving materials from slabs and walls, and energy via reduced conductive loss. Some good practices include using innovative technologies, including Deltabeam, Bubbledeck, and hollow core slabs in concrete construction. This kind of change can reduce building life-cycle embodied impacts by approximately 6%.

One Click LCA’s database includes 50+ pre-built slabs as well as ready-to-use solutions for most innovative beam and deck technologies. A module for creating and calculating your own constructions is also available.

It is also worth noting that having shorter grid spans for columns makes it possible to use lighter and less steel- and cement-intensive slabs. This will have to be balanced against the impact it has on the materials used in the columns and the potential impact on the future adaptability of the spaces. Some types of slab systems also have higher impacts, and care should be paid to the overall design and choice of the floor slabs used.

 

 

Potential carbon savings* ~6%

In the example building the share of embodied carbon impacts for all slabs is around 45%. Reducing the net thickness of slabs leads to potential carbon savings of around 6%.

* In the baseline building

If your zoning laws allow it, try to reduce the number of parking spots, in particular, underground parking spots and places in parking towers. If you have to have parking spaces below the building, consider raising the building so that the building stands on pillars with an open area for parking below the building. This will save a substantial amount of materials in needless walls around the parking spaces.

One Click LCA’s Carbon Designer module includes an optional calculation for underground parking floors. Further, operational transport carbon impacts can be accounted for using One Click LCA’s Site Designer.

Potential carbon savings* 4.8%

The share of embodied carbon impacts for parking structures is 7% (in the initial case with the parking mix heavily dependent on private cars). If the initial mix of underground and above-ground parking could be shifted to only above-ground parking places, these impacts would be approximately 69% lower, so an overall potential carbon saving of 4.8%.

* In the baseline building

 

As floorplan configurations may often change, it is good practice to use reusable and possibly movable internal walls to the extent that they work for the building function. Similarly, electrification that tracks seating arrangements in office buildings. If this practice is not applicable to your project, consider applying construction methods that make it possible to remove the boards intact.

One Click LCA allows you to set the service life for each material to reflect their actually foreseen replacement frequency as well as eventual reuse.

Potential carbon savings* 4%

We have assumed that half of the internal walls in our example building are load-bearing, but that the rest would require rebuilding every decade to fit changing floorplan demands. In this case, the material life-cycle impacts would be around 4% higher, compared to a scenario where wall configuration could remain in place until the material reaches the end of its service life.

* In the baseline building

Investing in durable materials means fewer replacements over time, which means fewer carbon emissions, less waste generated, lower life-cycle costs and less tenant disruption. What is a durable and suitable material for your market varies depending on the conditions, however, the principle remains the same.

Potential carbon savings* 3%

 Depending on your project conditions, specifying longer-lived systems can save both carbon and money. This will be dependent on conditions but can achieve several percentage points of life-cycle embodied carbon reductions – in our example project between extreme cases the difference would be in the order of 3%.

* In the baseline building

See also: Low Carbon Refurbishment: 10 ways to reduce embodied carbon emissions