Why the future of construction is sustainable

Construction has always been a massive industry, providing millions of jobs, enabling crucial infrastructure, and sustaining countless industries worldwide - and it’s only getting bigger. Construction is now set to outpace the manufacturing industry within the next decade, reaching a worth of $15.2 T and accounting for 13.5% of our global GDP.

Given the sheer size of the industry, it’s not surprising that its impact on our environment would be considerable:

  • About 50% of the raw materials we harvest from the earth go into building
  • Construction is responsible for ⅓ of the world’s waste
  • Roughly 40% of the world’s CO2 emissions come from construction
  • Construction accounts for a whopping 36% of the world’s energy usage

However, the tide is rapidly turning. With the global climate crisis increasingly on everyone's mind, governments and companies all around the world are making meaningful commitments to reduce their emissions and operate more sustainably. That includes the construction industry, which has made great strides to build a greener future in recent years. 

Let's take a look at some of the innovations and practices that are making the construction industry more sustainable than ever.

From concrete and steel to mass timber

Concrete, steel, and timber are some of the most commonly used building materials today, each with its own pros and cons. Wood is usually thought of as a supporting or secondary material compared to concrete and steel. This is because traditionally:

  • Concrete and steel were thought to be stronger
  • Its usage was believed to be taxing on forests
  • It was considered to be a fire hazard

While these fears may have had some merit in the past, today’s mass timber products are just as strong as steel and concrete, making it possible to build entire structures made from wood. Mass timber products start out like regular boards of wood, which are then engineered to become stronger and more resilient. Glulam and CLT are the most commonly used forms of mass timber, so let’s take a deeper look at how they work.

Cross-laminated timber (CLT)

CLT glues wood boards together in alternating layers, each set at ninety degrees from the one below it. This creates large slabs with structural rigidity in every direction, giving it a compressive strength comparable to that of concrete.

Glue-laminated timber (Glulam)

Glulam essentially “glues” boards of wood together in the same direction to form massive beams. Each board is selected and positioned according to defects and grain structure to maximize its structural integrity. 

The possibilities with mass timber products like CLT and glulam extend far past small homes to include skyscrapers over 80 meters high (but more on that later). Now that you know a bit more about how mass timber works let’s take a look at how it compares to steel and concrete.

Differences between CLT and Glulam

The advantages and disadvantages of steel

The advantages of steel as a construction material:

  • Durability - Steel structures can last years with little maintenance. 
  • Strength - Steel is a strong material that can be made even stronger with alloys.
  • Reusable and recyclable - You can use it over and over without losing quality.
  • Space efficient - You can use slender supporting columns without losing strength.
  • Prefabricated - Making it easier to work with and control.
  • Predictable - The material is highly regulated, making it consistent and predictable.

The disadvantages of steel as a construction material:

  • Susceptible to rust and corrosion.
  • It conducts heat, so you have to fireproof it to prevent fires. This adds to the cost.
  • It’s made offsite, so there is little room for onsite modifications.
  • It can be costly when compared to wood or concrete. Maintenance costs also apply.
  • It’s susceptible to buckling over time without the proper support.
  • Must be transported onsite, sometimes from far distances causing extra emissions.

The advantages and disadvantages of concrete

The advantages of concrete as a construction material:

  • It’s relatively inexpensive and widely available.
  • Its production is energy-efficient compared to steel (mixing it onsite)
  • It's not impervious to water but does better when compared to wood and steel.
  • It can take higher temperatures than wood or steel.
  • Maintenance costs are low compared to wood or steel (less coating is required).
  • It can be molded onsite into any shape (easy to fill into cracks or add layers).
  • Low risk of biotic deterioration (e.g., insects, fungi), compared to wood. 

The disadvantages of concrete as a construction material:

  • It needs to be reinforced due to its low tensile strength.
  • It can shrink due to dryness or expand due to moisture, causing cracks. 
  • Relies on high-energy processes like mining, blast furnace heating, and calcination.
  • It’s less ductile than steel. 
  • Its weight is high compared to its strength.
  • Formwork for casting can be costly and time-consuming.
  • The mixing of concrete is not as controlled as the production of steel or laminated wood.

The advantages and disadvantages of mass timber

The advantages of mass timber as a construction material:

  • It’s produced naturally, sequestering CO2 from the atmosphere as it grows. This is an improvement over steel and concrete, which create CO2 during production. If we globally replaced steel with mass timber, we could reduce CO2 by 15% to 20%.
  • Less energy consumption compared to concrete and steel production.
  • Good thermal insulation compared to concrete and steel. Wood has low thermal conductivity, so it retains heat and making it more energy-efficient.
  • Wood buildings are about 20% lighter than concrete buildings, which means they require smaller foundations, making them more resistant to seismic forces.
  • It’s produced in a factory, computer-assisted setting, decreasing errors and enabling more efficient use of materials (less waste). 
  • The multi-layered nature of mass timber products makes them more resistant to fires because only the outer, exposed layers get burned or “charred”. 
  • It can reduce onsite labor by up to 50% (offsite production). 
  • It has the time and cost savings associated with offsite production. It can speed up the project schedule by 25% or more.
  • Its structural performance is increasingly predictable.
  • It has excellent long-term performance, with less likelihood of damage or collapse.
  • The use of mass timber products leads to higher investment in keeping our forests safe, healthy, and plentiful.

The disadvantages of mass timber as a construction material:

  • It can be more expensive than steel or concrete.
  • Due to its limited track record, it can be difficult for many designers to use, leading to higher architectural/design costs.
  • It’s more susceptible to mold or insect infestation than concrete or steel. 
  • It may not be available in all areas outside Europe and North America. 
  • There might be higher material transportation costs because there are still relatively few manufacturing plants.
  • Strength properties may vary, particularly tensile and bending
  • Stiff fixings and connections might make it harder to work with
  • It has a relatively low modulus of elasticity 

Which material is the most sustainable?

Although each of the materials we’ve examined so far has its own advantages and disadvantages, there is one clear winner when it comes to sustainability and decreased carbon emissions. According to Architect Magazine:

  • Steel production is responsible for over 10% of the world’s CO2 emissions.
  • Concrete contributes anywhere from 6% to 11% of our global CO2 emissions.

On the other hand, mass timber products like CLT and glulam make it possible for the construction industry to decrease its carbon footprint significantly. That’s because wood sequesters CO2, removing it from our environment and storing it. As the wood industry continues to replace the trees they use by growing new ones, even more CO2 will be removed from our atmosphere. This can potentially cover the emissions produced during the manufacturing, transportation, and construction process with mass timber products. 

Timber elements, picture by Holzbau Vorholz Hawran

Let’s take a closer look at how this could work in practice. 

Sustainable forests: How do they work?

Forests are crucial to the health of our planet, absorbing harmful CO2 and producing life-giving oxygen in return. They’re also a safe haven for endless plant and animal species that depend on them to exist. So how can harvesting trees for construction be anything but harmful?

Enter sustainable forestry.

While traditional practices harvest trees with no prior renewal or replacement strategy, sustainable forestry takes a gentler, more sustainable approach. The main premise is that any tree harvested for building gets replaced, mimicking a forest's natural renewal cycle. Here’s how it works:

Assess the needs of the forest

Different forests will have different needs depending on their specific environment and biodiversity, so the first step to keeping them healthy will be to understand the environment. To that end, sustainable foresters start by creating an inventory of the tree species, the wildlife, and any endangered species in the area. They also take note of the forest's watersheds, their proximity to urban areas, and how often it's used recreationally by humans. 

Determine the harvesting potential and encourage renewal 

The next step is to determine exactly what can be safely harvested from the forest and in what amounts. The goal is to harvest timber efficiently without hurting the overall health of the forest. This can be done in several ways:

  • Pruning, instead of cutting down entire trees
  • Harvesting older trees to make room for new growth (more on that below)
  • Thinning out the tree population in some areas to promote healthier growth
  • In some cases, controlled burning is used to encourage regeneration

Most importantly, new trees are planted in the place of harvested ones, ensuring the continued growth and health of the forest. New trees will remain protected for years until they’re mature enough to harvest.
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Harvesting older trees

As trees age, their capacity to absorb CO2 begins to diminish. The same goes for their oxygen production. Harvesting and using them for building purposes ensures that the oxygen remains sequestered and stored within the wood. On the other hand, allowing them to fall and decay on their own would release the CO2 back into the environment.

Replacing these trees with new ones not only helps restore the forest but ensures further absorption of CO2 from the atmosphere.  

Management and monitoring

The health of the forest is continually monitored to ensure its continued growth and renewal. After all, it’s in the interest of the companies that sell the timber to have a renewable source of business. 

Designing a sustainable future: Hybrid-timber construction and DfMA

Here are just a few ways the design phase in construction is becoming more sustainable:

Hybrid-timber construction

We’ve already established the advantages of mass timber construction, and the benefits of wood as a durable, renewable, and sustainable building material. However, due to issues like cost, limited supply, and physical properties, it’s not always feasible to design structures without adding materials like concrete and steel. This approach is known as hybrid-timber construction. 

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Hybrid-timber construction combines mass-timber with materials like glass, steel, and concrete - bringing out the best in each and integrating them to optimize structural and building performance. It also gives designers the freedom and flexibility to exploit the benefits of each material, resulting in structures that are strong, safe, sustainable, and visually stunning.    

Design for Manufacture and Assembly (DfMA)

While traditional construction practices are characterized by low productivity, high costs, unnecessary waste, and excess energy use, aims to improve on these issues through efficiency. During the design phase, it takes into consideration each part of the final structure and finds the most efficient and cost-effective way to manufacture it. When combined with Building Information Modelling (BIM) it can significantly maximize the benefits of offsite construction (OSC), resulting in:  

  • Reduced building time 
  • Decreased costs
  • Higher quality and productivity
  • Increased overall efficiency 
  • Reduced waste and lower energy consumption

Here are just a few of the other ways DfMA can contribute to sustainable building:

  • Having detailed BIM data for your structure’s DfMA produced parts, makes it easier to track and manage your assets throughout their lifecycle. This results in less waste and improved resource and energy efficiency. 
  • Throughout the DfMA process, BIM can be used to design less material-intensive components, resulting in a reduced carbon footprint.

Applying a DfMA approach starting at the design stage reduces the margin of error in projects, avoiding wasteful and costly rework and using only the resources that are needed. All benefits make the process more sustainable. 

Sustainable Manufacturing

While sustainability in the construction industry starts at the design phase (with careful planning), the biggest results can arguably be achieved during the manufacturing phase. For example, manufacturing DfMA components within a controlled factory setting (e.g., offsite construction) is far more efficient and less wasteful than bringing the raw materials to the site.  

During this stage, digital modeling (BIM) makes it easier to visualize the design, its connections, and how the parts fit together, resulting in a more efficient fabrication process. 

This, in turn, leads to benefits like:

  • Decreased waste
  • Energy and resource efficiency
  • Reduced margin of error leading to less rework

The key to all these benefits? Offsite manufacturing in a controlled factory setting.

Sustainable Timber Buildings

When we think of sustainably built wood structures, a towering skyscraper isn’t the first picture that comes to mind - but thanks to mass timber products like CLT and glulam, it's possible. Case in point: The Holz High-rise, aka “HoHo Vienna”, which boasts 24 floors and is home to a hotel, a wellness center, and numerous offices and apartments.

HoHo Wien by Hasslacher Norica Timber

What makes this building sustainable? Well, for starters, 75% of its outer structure is made of wood, with most of the internal beams and walls made from glulam and CLT. According to the designers, the wood used in this structure will help curb around 2.800 metric tons of CO2 emissions from the atmosphere.

This project was partially realized using hsbcad’s hsbStickFrame and hsbCLT technology for AutoCAD. Click here for more inspiring examples of sustainable wooden structures.

A more sustainable end-of-life for buildings 

In the construction industry, the transition from a linear to a circular model is still in its early stages. This means that globally every year, countless aging or outdated buildings are demolished with:

  • 37% of the waste going into landfills 
  • 33% getting openly dumped 
  • 11% getting treated through modern incineration

Only about 19% gets salvaged through recycling or composting. In fact, estimates show that global construction waste might reach 2.2 billion tons by 2025. According to Construction Dive, more “reduce, reuse and recycle" policies are needed to keep the waste under control, but efforts have been hindered due to insufficient resources, lack of standardization, slim profit margins, policy apathy, and lack of awareness of the severity of the situation. 

However, in recent years, we’ve seen a change in this trend driven by several factors:

  • Dumping has become more expensive, encouraging contractors to opt for waste management companies that can recycle and re-use materials like concrete, wood, and steel. 
  • Heightened awareness of the importance of sustainability has led designers and architects to work with recycled and repurposed materials.
  • New advances are enabling recycling plants to process more materials faster and at less cost.
  • Demolition practices are changing, opting for careful sorting over pulverizing building materials as they did in the past. 

Although much work still needs to be done, the wheels of change are already in motion, with new studies like this one examining new ways to reuse construction materials.

A fully sustainable construction cycle

Although it’s been a slow process, the construction industry has made great strides in recent years, building with sustainable materials, becoming more energy-efficient, and adopting less wasteful building practices. Perhaps most importantly, the industry as a whole is committed to a more sustainable vision. In a recent poll by Mckinsey:

  • 85% of participants reported their organizations were committed to anchoring the company culture and business model in sustainability principles.
  • Over 75% reported being motivated by value-creation opportunities, increased demand, and general stakeholder awareness.

The trend toward sustainability will continue to be driven by favorable regulations, increased customer demand, and access to subsidies and capital to boost technological innovations. These factors, coupled with higher efficiency, cost savings, and reduced margins for errors, will all contribute to a greener future in construction. 

Although there is still a long way to go, these efforts are already making a difference and setting the stage for a carbon-neutral construction industry in the years to come.

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Autor:
Renè Strack
Business Development Manager
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