Buildings And Climate Change

 

Buildings in the modern world are mainly made of concrete and steel, which are heavy carbon intensive industries. Buildings use 36% of energy and account for 39% percent of greenhouse gas emissions from energy.

There are three major ways that buildings contribute to emissions of carbon. The first is the “initial carbon”. This are the emissions released from disturbing the soil, they are part of soil carbon as well as the carbon from the vegetation cleared. This is done when the site is being prepared and dug up for construction to commence. This carbon is released into the atmosphere.

The second type is embodied carbon, and this is the carbon dioxide produced in the preparation of construction materials. By this, I refer to cement and concrete, steel, aluminum, glass, mortar, and synthetic materials commonly used to erect a building.

All the above, but especially cement, concrete and steel have an extra-large carbon footprint. The chemical processes and energy used to produce them is intensive and release a huge amount of carbon dioxide. The mining and refining of different substances to produce what is known as cement, or steel is a process that produces tons of carbon dioxide in the ration of 1:1.

And all this is released into the air.

Sand used in construction also leads to riverbed erosion.

The third phase of emissions come from what is known as operational carbon. This is the carbon used to run and operationalize a building. This is the heating, ventilation and air conditioning (HVAC). The energy used to power a building: to provide lighting and maintain ambient heat, as well as to cool it and provide air circulation and ventilation is mostly derived from fossil fuels.

Glass skyscrapers also reflect heat and light around the same area, and don’t allow the movement of wind.

All this makes buildings mass consumers of energy and so net-releasers of carbon dioxide.

A picture of Nairobi - Quaint Fotografia

In order to make this sector climate friendly, there are some approaches that are used. One is simply building less. The idea behind this is to ask ourselves whether we really need more buildings especially in cities. One thing that helps here is the work from home concept, which eliminates the need for an excessive number of office buildings.

Another thing is to use a reduced amount of materials. The question here is how can we use less to make more? The point is to eliminate excess production of materials that will end up being wasted. So for example, reduce, reuse and recycle i.e. repurpose as many materials as possible. Use discarded materials to make new products. Try secondhand materials.

The third approach is to use ecologically clean materials. These are substitutes to concrete such as earth and wood.

Energy efficiency in buildings is one of the ways to reduce building emissions. This means utilizing as little energy as possible for maximum output. For example using a reduced number of appliances that are also up to date and so use little energy. Using LED bulbs instead of incandescent ones. Using the stairs instead of escalators and lifts.

Building design is meant to add to this. For example the placement of windows to maximize on sunlight and nature, the use of natural gardens and greenery to cool the building through transpiration and evaporation and provide oxygen.

Additionally, buildings can use insulating materials which prevent the loss of heat in cold weather and release it in summer.

Building design can be augmented by addition of renewable energy such as solar photovoltaic panels, which is renewable energy, on roof tops instead of concrete tops or helipads. Buildings can also be designed to use other renewables such as wind energy and have energy storage batteries.

Buildings that use renewable energy instead of fossil fuels are zero energy buildings, and those that especially put as much energy as they use back into the grid are carbon & climate neutral.

Rooftop gardens absorb carbon dioxide because they are green vegetation. When put on a building, they would ideally absorb some of the carbon generated from the energy used by the building. If they balance the release and absorption of greenhouse gas emissions, this building would be net zero. This is a way of “offsetting” greenhouse gas emissions and a building’s carbon footprint.

The last option to make a building “green” is to buy carbon credits or offsets from elsewhere. This is from carbon trading schemes that allow the sale of carbon credits and so promote climate finance flows.

To come back to building design and materials, there are two very significant outcomes that are going to grow by leaps and bounds in the coming years, as the world seeks to protect and restore the ecological integrity of the planet and act on climate.

The first is the use of natural material earth. Earth buildings are very common and have longer and more enduring history than concrete or cement. They have been used for centuries all over the world and are more known.

Earth buildings are mostly used in hot climates, which augur well with the material. An example is the city of Timbuktu, one of the ancient African kingdoms which was a globally acclaimed center of trade, excellence and learning. Ever heard of the University of Timbuktu? 

Earth as a material has a very small carbon footprint, has low embodied carbon and is widely available. It does not need heavy labour or machinery. It does not require a lot of energy to construct or manufacture. In fact building materials can be made onsite. Earth has very good insulating properties: it is usually warm and comfortable. It repels insects and cannot be harmed by fire. Earth buildings can also be made into storeyed buildings when reinforced with straw or wood. Earth is durable and does not contain toxins. It is also soundproof to a good extent.

Earth buildings can be artistically designed, reinforced and ornamentally decorated. These buildings can be repurposed because the soil used cannot be degraded. It can be brought down and reused to erect another building.

Culturally, these buildings are a way to preserve traditions and culture, because they are a heritage and tradition of communities throughout the world. The construction of such is also a communal event, which is where age-old processes and skills are passed down from one generation to another.

Types of earthen buildings include mud, brick and straw, daub and wattle, rammed earth, cob and many others. These earthen buildings are common in Africa, which is the second biggest continent in the planet and boasts of over 1.2 billion people with diverse cultures. In the future, as focus turns towards sustainability, this is one of the types of construction that will be on the rise.

The second is wood. Yes, wood. This might seem contradictory because forests absorb carbon dioxide and cutting them down will in fact hamper mitigation and contribute to climate change.

But this is how it works. Trees absorb carbon dioxide which they lock in their trunks. When harvested as wood, this can be used to construct buildings without releasing the carbon locked therein. Additionally, wood harvesting and construction emits far less carbon than concrete and steel do. That is, it contains lesser embodied carbon than the other two.

Additionally, wood buildings are sturdy compared to concrete yet are lighter than it. Cross laminated timber (CLT) is whereby two timber blocks are glued together in opposite directions and under pressure. This type of timber has been found to have high structural integrity, and would only need a bit of steel reinforcement. The same is true for nail laminated timber.

Wood performs well in fire because charring of outer layers protects the inside. When treated, it is resistant to insects. It is good for insulation and can be vertically constructed into storeys.

It has aesthetic value and is more eye appealing than concrete buildings. Wooden buildings are more artistic than glass skyscrapers.

Wooden buildings can be repurposed and have a relatively long lifespan.

The catch here is that wood for construction can only be harvested from mature forests. Mature forests are forests that have grown to the maximum. Their trees are roughly over half a century old and have reached maximum growth limit. They don’t grow anymore and so do not absorb a lot of carbon from the air. They instead drop off old branches and leaves, which decompose to release carbon or are locked into soil carbon. When too much debris is on the forest floor, it makes the forest rather susceptible to fire.

These are the forests that are usually harvested for timber, but also to make room for new growth of tree seedlings.

To be very very clear, only mature forests should be harvested, and this should be accompanied by planting of new seedlings. In fact the policy is cut one, plant two. Young forests should be left alone to grow because they actively absorb carbon, while as many areas as possible should be reforested in order to tackle climate change and for their host of ecological functions.

The other source of wood is plantation forests.

However wooden buildings have an end of lifecycle problem. How do you avoid emissions from a building that has reached the end of its lifetime? The question is up to innovation.

To conclude, as more people are born and rural urban migration shoots up, we will need good quality and affordable housing which should also be climate friendly.

This is in order to achieve the aims of the sustainable development goals.