Five Strategies to Decarbonize Existing Buildings

The energy and carbon emissions of existing buildings have been a major concern for a long time. Although building equipment, appliances, and other technologies have greatly improved energy efficiency, the buildings in which they are installed have been remarkably resistant to major change.

This is a major concern, as most countries around the world now mandate more aggressive carbon targets that push new and existing buildings to minimize their carbon footprint.

Today, not many buildings are able to make the transition, and the pace of change is very slow. Strategies such as switching from fossil fuels to cleaner energy sources, or improving energy consumption to prevent expensive grid peaks cannot be readily applied to most buildings.

There is no surprise that new buildings can achieve low or zero-carbon targets easier than existing buildings. Because project teams can work from the very beginning to develop a building that serves the desired outcome. However, the situation for existing buildings is much more complicated. In this article, we want to lay out the best ways to decarbonize an existing building.

So, how can an existing building become a decarbonized one? To find the most viable answer to this question we need to shift our existing perspective for decarbonized buildings.

Decarbonized buildings are much more feasible when the definition is extended beyond the boundary of individual buildings that allow the use of off-site clean energy to those that can generate clean energy and potentially work with other surrounding buildings in a particular city or district.

Here are the top five strategies that can potentially bring the highest return for the effort invested.

  1. Prioritize Energy Efficiency as The First Step

Energy efficiency comes first, since using no more energy than is required also results in less costly pathways, along with substantial additional benefits, including occupant health and comfort.

photo of worker installing insulationFocus on insulation

The first and number one energy efficiency goal should be having a properly insulated building. The exterior enclosure of our building should be designed to reduce heating and cooling needs. The applied insulation should make the building as airtight as possible.

1.2 Choose the right ventilation system

Since your building is as airtight as it can potentially be, you’ll want to use a ventilation system to establish good air quality and prevent the build-up of moisture.

photo of ventilation systemHeat-recovery ventilators are systems that use outgoing air from your building to heat intake air. In the summer, the air from your building could cool the air coming from the outside.

1.3 Use LED lights

Switching to LED lighting can help you to reduce your energy consumption by 75% compared to incandescent lighting. Sensors can also be used in infrequently used areas such as lecture halls and restrooms to reduce energy use.

The energy consumption of a building can be reduced in many ways. What we call basic energy efficiency entails pursuing the minimum level of energy efficiency required by ensuring that the building aligns with local codes and standards.

In many countries, these codes and standards still have the considerable underutilized potential for higher performance. Achieving advanced energy efficiency requires more ambitious energy performance, which goes beyond the minimum regulatory requirements.

Energy-efficient building design and energy-efficient equipment and appliances should be put in perspective before responding to the remaining energy demand from renewable energy sources.

However, it is preferable to use energy-efficient design measures to achieve energy efficiency that exceeds local codes and standards, which often do not take full advantage of the building’s energy-efficiency potential.

  1. Use RE (Renewable Energy) In Any Form You Can

photo of solar panelsNext in the preference hierarchy is the use of on-site Renewable Energy, which adds clean energy to the city’s total installed capacity. Off-site RE is the next other option and could be preferred for buildings that aim to achieve net-zero carbon emissions through their combined energy use.

Further reductions in building emissions can be accomplished through the use of carbon-free renewable energy sources.

The options projects can follow as listed below:

  • On-site RE generation
  • Off-site RE generation
  • Off-site RE purchase

The cost of renewable energy systems for generation and storage has gone down significantly in recent years. Now renewable energy can better compete economically with regular grid energy, making renewable energy a more appealing option.

  1. Become Carbon Neutral or Significantly Offset the Carbon Use

become carbon neutralFinally, carbon offsets may be preferred to compensate for the remaining carbon emissions that cannot be avoided by means of efficiency strategies and carbon-free renewable energy supply.

Sometimes even a combination of energy efficiency and the generation or purchase of renewable energy does not eliminate 100% of the building’s operational carbon emissions.

Existing buildings using fossil fuels, such as propane gas for cooking or water heating may not always be able to fully eliminate carbon emissions. In such cases, carbon offsets could be used to compensate for the balance of emissions.

Such offsets should ideally be used as complementary, and in a way to invest elsewhere in energy efficiency or carbon-free renewable energy projects, preferably within the boundaries of the city. The emission reduction benefits must be claimed through a credible framework, such as carbon credits or a local carbon credit fund.

Stakeholders may consider expanding their interpretation of decarbonization to include embodied carbon. To the extent that such embedded emissions cannot be mitigated or avoided, credible carbon offsets could be used to compensate for such emissions.

These components can be combined in a variety of ways to achieve a 100% (net) reduction of the building’s operational carbon emissions. All combinations start with basic energy efficiency measures and then different components are introduced in different ratios to achieve a complete carbon emission reduction.

In all cases, credible carbon offsets are used only when all other choices have been fully utilized or are not viable.

  1. Prioritize On-site Energy Generation

Having accomplished energy savings through energy efficiency, the aim is to use carbon-free renewable energy. On-site generation is preferable to off-site generation because on-site generation increases the overall installed capacity of clean renewable energy in a district or a city.

In addition, on-site generations will help improve the energy security and energy resilience of buildings in the event of grid disruption. Where an on-site generation of individual buildings is not a viable alternative due to technical, financial, and/or legislative hurdles, off-site energy options may be explored.

There may already be the possibility of purchasing renewable energy locally. If not, stakeholders may explore the possibility of generating renewable energy at the district level to supply a group of buildings within the area.

Distributed generation models of this kind help to enhance local energy security and resilience in the event of power failures. However, high-density urban areas may not have sufficient space for an on-site or local off-site generation. Therefore, buildings in these areas have to rely on clean energy generated far beyond the district or even city boundaries.

Any decarbonization approach should first take advantage of the on-site and/or off-site renewable energy supply options. This encourages building owners/managers to first tap into potentials where they can achieve a greater degree of direct impact and reduce emissions close to the source.

If none of the on-site or off-site generation or purchase are viable options owing to technical financial and/or legislative obstacles, carbon offset options can be explored as the next option. They should only be used to mitigate the carbon generated by the remaining consumption of non-carbon-free energy.

  1. Reduce Embodied Carbon Prior to Carbon Offsets

The life cycle of a building involves construction, operation, maintenance, renovation, and eventually demolition, and all stages produce carbon emissions from materials, machinery, and fuel. These emissions are named embodied carbon.

Progressively, governments are likely to encourage the integration of embodied carbon in decarbonization approaches to address all carbon emissions throughout the building’s full life cycle. Prior to compensating for the remaining emissions with carbon offset solutions, such as carbon credits, the reduction of embodied carbon should be considered. For example, building managers may choose low-carbon products and cleaner fuels.

Other Technologies That Can Support Decarbonization Pathways

Many of the technologies needed to support decarbonization pathways are already available on the global market and increasingly in most local markets.

These technologies cover different climates, budgets, and existing levels of competence. Energy efficiency options range from the use of passive strategies like the smart use of natural daylight, natural ventilation, insulation, and evaporative cooling to active measures like high-efficiency heating, ventilation, and air-conditioning (HVAC) systems, LED lighting, and efficient appliances.

The most commonly used renewable energy technologies are on-site PV panels, solar water heaters, and off-site renewable energy systems, like solar power plants, hydropower plants, and wind turbines.


Not every combination of decarbonization measures are considered to be equally desirable. Financial costs and holistic, social, and environmental factors dictate the hierarchy of preferences between different components. For example, the mitigation of energy uses in the first place (efficiency) is preferable to the constant use of energy even from clean renewable resources.

Some strategies will be more cost-effective than others for large-scale decarbonization of buildings and/or offer greater carbon reductions and other environmental or social benefits. The choice of specific decarbonization pathways will, however, be based on the assessment of building developers, owners, and managers and will depend mostly on local circumstances.

Despite the priority of embodied carbon, current decarbonization approaches most commonly target operational carbon emissions. Dense urban areas, where most buildings are located, will have to be at the top of the list of the decarbonization. Stakeholders at different levels of governance need to work together to overcome hurdles and make decarbonization a viable goal to achieve.

Sustainable Investment Group (SIG) can help businesses set and achieve their sustainability goals through a variety of services. Whether you are trying to improve air quality, need an ENERGY STAR certification, or need a gap analysis our trained engineers and consultants can help cut costs and improve energy efficiency in your building. Contact us here.

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