Sustainable refurbishment means improving existing buildings to make them better for the environment by using eco-friendly methods and materials. Refurbishment or retrofit refers to any work done on a building beyond regular maintenance to change how it works, its purpose, or its performance. This can involve adjusting, reusing, or upgrading parts of a building to meet new needs. Refurbishment can affect a single part of a building, an entire building, or a group of buildings like a school or office complex. Sustainable refurbishment goes further by making the building perform better in terms of reducing its environmental impact and improving the comfort and health of the people inside.

Most sustainable refurbishments are also green retrofits. A green retrofit is any improvement to an existing building aimed at reducing its carbon emissions and harm to the environment. This can include making heating, ventilation, and air conditioning systems more energy efficient, improving insulation in the building’s outer parts (like walls and roofs), adding renewable energy sources, and enhancing the comfort and health of the people who use the building.

Green retrofits have become more common because they are included in many building rating systems, such as the USGBC’s LEED for Existing Buildings: Operations & Maintenance, Passive House EnerPHit, and Green Globes for Existing Buildings. Some governments provide financial support for green retrofits because existing buildings make up most of the buildings currently in use, and they are a key focus in efforts to address climate change.

Overview

Sustainable refurbishment means improving older buildings to use energy more efficiently and protect the environment. This includes adding insulation to reduce heat loss, installing renewable energy sources like solar water heaters and solar panels, reducing water use, and making changes to improve ventilation and comfort. It also involves reusing existing parts of buildings, recycling materials, and using eco-friendly products to cut down on waste, noise, and energy use during repairs.

Many buildings in use today are not new. They were built when energy standards were weak or missing and may not meet modern needs. These buildings are often kept for many years because tearing them down is costly, causes problems for people living nearby, or because they are historically or architecturally important. To solve this, buildings are renovated to meet current energy and comfort standards.

Sustainable refurbishment is not a new idea, but it is becoming more important because of concerns about high energy use, climate change, and the need for healthier living spaces. Governments are now creating guidelines, offering financial help, and supporting efforts to improve older buildings instead of focusing only on new construction. Experts and organizations continue to promote these practices, leading to new projects being tested in many countries.

Techniques for sustainable refurbishment have been developing for years. While the goals are similar to building new structures, older buildings have unique challenges. For example, the way a building is positioned relative to the sun affects its energy use, but this is usually not changed during a retrofit. Budget limits also affect the types of energy-saving improvements that can be made.

In the past, green retrofits were often done as one-time projects for specific buildings. However, because of the need to improve energy efficiency and fight climate change, governments are now looking at these projects more broadly. This is difficult because older buildings vary in use, location, and construction methods.

Recent research has focused on retrofitting older buildings to reduce their environmental impact. About half of all buildings are more than 40 years old. These older buildings use more energy than newer ones because of poor design, aging systems, and leaks in the building structure. In the U.S., energy use in homes decreased by 9% between 1985 and 2004 due to better efficiency and updated building codes. However, the total number of homes has increased, which affects overall energy use.

Reasons

The United Nations Framework Convention on Climate Change (UNFCCC) aims to reduce greenhouse gas emissions that cause climate change. A specific goal is to lower emissions from buildings. Building refurbishment, which involves improving existing buildings, is important for reducing carbon emissions. Instead of tearing down old buildings, refurbishment is the best way to make buildings more energy efficient or create buildings that produce no emissions. Energy-efficient renovations help buildings use less energy, which lowers emissions and resource use. Research shows that widespread use of refurbishment can reduce both individual and global emissions and energy use.

Social sustainability refers to how buildings affect people, communities, and society. This is studied using tools like life cycle assessment (LCA). Sustainable refurbishment combines economic, social, and environmental goals to improve buildings. For example, sustainable buildings are healthier because they use materials that do not harm people’s health.

Organizations like "Her Retrofit Space" in the UK help women in the retrofit industry by offering training, resources, and networking. This supports more women in the field and promotes sustainable building practices. As many countries need more workers, including women in the workforce is important for growth.

The indoor environment in many existing buildings is often less healthy than the outdoor environment because of the way they are designed and the materials used. Sustainable refurbishment and building practices aim to make buildings healthier and more comfortable for people. Sustainable refurbishment includes using materials that do not release harmful gases, like sulfur dioxide and nitrogen dioxide, into the air. It also includes systems to clean indoor air. The "Citizen's Healthcare Principle" states that buildings must be safe and improve living conditions for people inside. Refurbishment plans must consider both the indoor climate and the outdoor environment. Important factors to consider include:

• Air movement
• Humidity
• Dew point
• Lighting
• Air flow speed
• Sound levels
• Temperature

Preserving historic buildings is sustainable because it keeps materials and structures in use for longer. This reduces waste and helps protect the character of small communities. Some people believe that the most sustainable action is to avoid building new structures altogether, which means preserving and refurbishing existing ones.

Society has limited resources, such as nonrenewable energy. Buildings that are not energy efficient use a lot of nonrenewable energy compared to other industries. To reduce this, it is important to make existing buildings more energy efficient or switch to renewable energy. Sustainable refurbishment improves energy efficiency by updating building systems and operations. As buildings become more efficient, it is important to consider the environmental impact of the materials used over their entire lifespan. Building short-lived structures leads to waste because materials are not used for their full potential. Reusing existing buildings allows owners to use the energy already invested in the building, instead of wasting it by building new structures.

Development of the Goals of Sustainable Refurbishment

This section explains the timeline and development of the goals for sustainable refurbishment as described by different authors:

In 1996, Baldwin outlined the main goals of "sustainable development." These goals include reducing harm to human health and the environment, using non-renewable resources efficiently, using renewable resources, and planning for the future. Reducing greenhouse gas emissions helps protect the climate and ecosystems, which also supports the goal of using non-renewable resources wisely. Using less non-renewable energy in building construction and operation lowers emissions from buildings. Refurbishment can also protect local ecosystems through landscape design. Improving indoor air quality by increasing ventilation and using safe materials helps protect human health. Reducing waste can be done by reusing or recycling materials. Using renewable resources in refurbishment can include electrifying heating and cooling systems, installing renewable energy systems, or using materials like wood. Making buildings more durable through refurbishment extends their lifespan.

In 1996, Keeping and Shiers described the goals of "green refurbishments" as having three parts. The first part focuses on reducing energy use through efficient heating, cooling, and passive design systems, which lowers utility costs. The second part involves lower maintenance costs because refurbished systems are simpler and easier to repair. The third part states that green refurbishments improve health and comfort for building occupants.

In 2006, Sitar and others defined the principles of "sustainable refurbishments." Their goals include reducing energy use during building operation, such as for heating, cooling, ventilation, and lighting. Another goal is using renewable energy and low-impact materials for both indoor and outdoor environments. They emphasized improving living conditions through better health, user-friendly controls, and adaptability for future needs. These goals aim to be achieved through innovative planning that creates designs beneficial to the environment, economy, and society.

Characteristics of Sustainable Refurbishment

Sustainable refurbishments aim to improve how buildings and communities function by combining different systems. These improvements help reduce energy use and make buildings more comfortable by controlling noise, temperature, and lighting. They also help buildings last longer, protect the environment, and create healthier spaces for people.

Sustainable refurbishments reduce harm to the environment by using fewer harmful materials, adding energy-saving technology, and changing buildings to use energy from the sun or wind instead of non-renewable sources. Ways to do this include using less energy and water, reducing waste, recycling materials, and using products that are better for the environment. For example, using lights that use less energy and systems that adjust lighting automatically can save energy. Similarly, using toilets that use less water or systems that reuse water from sinks can save water.

After a sustainable retrofit, a building uses much less energy than before. The energy savings must meet the same rules that new buildings must follow. A truly sustainable approach goes even further by planning for future needs. A deep energy retrofit includes adding energy from renewable sources, like solar panels, to create buildings that use almost no energy from non-renewable sources. A study in the United Kingdom found that even if saving the environment was not the main goal, buildings used less energy and had lower costs after a retrofit.

A study of residential buildings showed that after a retrofit, buildings used 59% less energy for heating. This included 25% from adding insulation to walls and floors, 10% from better window insulation, 6% from reducing air leaks, and 18% from using systems that control heating. Improving the building’s structure and how it is operated helped reduce energy use, pollution, and harm to the environment.

Sustainable refurbishments improve energy efficiency by focusing on these systems:
– Insulation
– Keeping the building sealed to prevent heat loss
– Heating
– Cooling
– Air conditioning
– Lighting

Ways to improve these systems include using insulation materials that are better for the environment, replacing windows with ones that reduce heat loss, and using ventilation systems that save energy. Heating and cooling can use energy from the sun or solar-heated water. Lighting can use less energy by letting more natural light into rooms.

The environmental impact of a retrofit depends on the materials used. Using materials wisely helps reduce waste and save costs. Life cycle analysis measures how much a material harms the environment over its lifetime, including what happens to it after the building is torn down. Reducing waste and reusing materials saves money now and in the future.

When comparing materials, life cycle analysis helps choose the best options. Even though using new materials has some environmental cost, sustainable refurbishments aim to reduce these as much as possible. Using wood from existing buildings, reused wood, or wood from certified sources is better because it uses carbon that was already used in making the material. Life cycle analysis also checks if materials harm people or the environment. Materials that release harmful chemicals into the air or damage the environment are not used in sustainable refurbishments.

The image shows a model of sustainable refurbishment. The model includes six areas: technical, economic, architectural, social, ecological, and cultural. These areas are connected and influence each other and the design of the refurbishment.

Steps of Sustainable Refurbishment Process

The principle of sustainable refurbishment should be included in the project from the very beginning, during the first plans, through to when the building is completed and handed over. This section explains the general steps in the design process for a sustainable refurbishment:

• Data Collection: This step involves identifying the problem and setting clear project goals.

• Assessing the Need for Refurbishment: Before creating models, the condition of the building must be studied. This includes checking for physical damage, moisture, thermal bridging, whether the building meets current safety standards, if it uses a lot of energy, the quality of indoor and outdoor air, and if the people living there are not satisfied with their environment.

• Modeling Phase: To create a model, architects must examine the collected data, set standards for comparing different options, and develop design ideas. This process should consider the needs of people involved and follow best practices.

• Selection Phase: Once multiple design options are available, architects must compare them, review their advantages and disadvantages, and then choose the best option to improve the design.

• Implementation Phase: During this phase, the impact of the refurbishment on the surrounding environment is considered. Social and political factors in the community, such as living conditions and standards of the people in the building, are also evaluated. Additionally, natural environment factors like temperature, humidity, soil quality, natural resources, and land features are studied. After considering all these factors, the necessary changes can be carried out.

Components of a green retrofit

Green retrofits use a team-based design method. This is different from the traditional step-by-step method, where architects, engineers, and contractors work separately. In a team-based design method, these groups work together to share their knowledge and solve problems while considering the whole building. This is important for green retrofits because design choices are often limited by the current building. These limits might include the building’s shape, the size of the land, or the needs of the heating and cooling systems. Since these limits affect all parts of the building, the only way to create sustainable, effective, and cost-efficient solutions is by considering all these factors from the start of the project.

Many sustainable building practices are automatic, like insulation or light controls. Others depend on how people use the building to work well. For example, an energy-efficient heating system does not help if windows are left open in cold weather. According to a study by Ascione et al., "the first step to saving energy is teaching users how to use energy wisely." Green retrofits can include training building users about sustainable practices and systems they will use, which helps ensure energy-saving measures work as planned. Training can be provided by system makers or the project team.

Smart energy management can be added to buildings using AI-controlled heating, cooling, lighting, and climate systems. AI can manage these systems based on how people use the building to save energy. Water systems can also be made more efficient by using fixtures that adjust based on how people use water.

One common type of green retrofit is replacing or partially replacing a building’s lighting system. A lighting retrofit usually involves changing lightbulbs to newer, more efficient models. This might also include updating light fixtures, ballasts, and drivers. LED bulbs are often the best choice because they use much less energy than older incandescent bulbs, though other types like compact fluorescent or metal halide bulbs may also be used.

Lighting retrofits are popular because they are easier to plan and carry out than other energy-saving methods, and they often save money quickly. Most modern LED and compact fluorescent bulbs work with existing fixtures and usually only require removing and replacing old bulbs. Installation is also faster than more complex energy-saving projects.

Lighting retrofits can also include adding controls like motion sensors, daylight sensors, and timers. These controls can reduce the need for lighting when it is not needed. However, some people debate whether these controls are effective because predictions about energy savings are sometimes too high, and it is hard to know how people will use them.

Heating, ventilation, and air conditioning (HVAC) systems use about half of a building’s energy. Improving these systems can save 40–70% of energy. This is a major focus of many green retrofits, especially in cold areas where heating uses over 60% of energy. Parts like heating systems, cooling systems, air handlers, humidifiers, and ducts are often considered.

Heat recovery ventilation is recommended for homes that are sealed tightly. It uses heat from warm, moist air leaving the home to warm cool, fresh air entering the home. This reduces heat loss while keeping the home safe from harmful gases.

Other HVAC retrofits may include replacing old systems with newer, more efficient models, such as upgrading a boiler to a more efficient one for a heating system. In some cases, a complete system change may be needed, like replacing an old boiler with a newer heat pump system.

Thermal insulation and the building’s outer layer are important for how well a building uses energy. Many older buildings do not meet modern insulation standards. These buildings often waste energy heating or cooling air that leaks out through cracks or poorly insulated windows.

During green retrofits, the first step is to check the building’s outer layer for problems. Air-sealing is a simple and cost-effective way to improve energy efficiency. Caulking can fill gaps in areas that do not move, like window or door frames. Weather stripping can seal areas where parts move, like between a door and its frame. Drafts can be found by feeling for temperature differences, watching smoke from incense, or using a blower door test. In a blower door test, a fan and gauge are used to measure how much air leaks out of the building.

Windows are the weakest part of a building’s insulation and greatly affect how well the building stays warm. Like lighting retrofits, windows are easy to update and have clear payback periods. Modern windows are usually made to fit existing openings and can be installed with little extra work.

Most green retrofits replace old single-pane windows with more efficient triple-pane windows filled with gases like argon or krypton. These windows have higher R-values, meaning they insulate better than single-pane windows. Some windows also have special coatings to control how much heat enters from sunlight.

Green roofs, also called living roofs, have many benefits. They reduce stormwater runoff, lower urban heat, improve insulation, reduce noise, and support plant life.

When planning a green roof, factors like the type of plants and the strength of the building must be considered. Extensive green roofs use thin soil layers for small plants. Intensive green roofs use thicker soil for larger plants. Semi-intensive green roofs are between the two. The building’s structure must be strong enough to support the weight of the green roof.

Sustainable Refurbishment Case Study

In 2019, a study in Vienna examined how a sustainable renovation using a Multi-Active Façade System affected a building's energy use. The study focused on the building's outer layer, called the façade shell, because improving this part was believed to be most important for saving energy. Insulation was found to be a key factor in reducing energy use during the building's operation. To choose the best insulation material, researchers needed to analyze how the material would perform over its entire lifespan. The façade system used insulation and corrugated board to lower the building's energy needs. These materials helped increase heat from the sun during winter when extra warmth was needed and reduced heat from the sun during summer. This was done by placing the façade at a specific angle so that sunlight could enter only when the sun was lower in the sky during winter. The façade also included renewable energy generation and storage systems to provide power when sunlight was not available. After the renovation, the building's heating needs were predicted to be about 53% lower than before. The building's low energy use was even higher than the 2021 standards for new buildings by about 45%, showing the design was both adaptable and strong for the future.

Costs, barriers, and benefits

Green retrofits can offer several advantages. These include better energy security, less air pollution, improved indoor air quality through systems like mechanical ventilation with heat recovery, lower greenhouse gas emissions and effects on climate change, greater comfort from temperature control, better indoor air quality and health for people living or working in the building, creation of local jobs, and reduced use of electricity during peak times.

Challenges to green retrofits may include the initial cost and finding ways to pay for it, limited knowledge or experience among those involved in the project such as designers, builders, and inspectors, rules set by building codes, and lack of interest from people who might use the building.

The work involved in a green retrofit can vary. It may focus on specific parts of a building, like lighting, or involve updating all non-structural parts. A lighting retrofit is usually easier to do and less disruptive to people in the building, but it generally provides fewer benefits or costs compared to a retrofit focused on insulation. When considering the benefits and costs of a green retrofit, all parts of the project are usually evaluated together.

Although green retrofits require an initial cost, the amount depends on how large the changes are. The type of retrofit chosen also affects how quickly the cost is recovered through savings. Whether a green retrofit is economically practical depends on the condition of the building’s current systems, the proposed design, local energy costs, and the climate of the area. Financial support available for the project may vary by country or region. For example, in Ireland, "shallow" retrofits are often economically practical, but "deep" retrofits usually require government funding to cover the initial expenses.

The European Union has found that green retrofit programs can improve energy security, create jobs, reduce fuel poverty, and improve health and comfort indoors.

Green retrofits can also help reuse existing building materials. Concrete and steel are materials that use a lot of energy to produce and can account for up to 60% of the carbon used in building construction. These materials are typically part of a building’s structure, which is often left unchanged during retrofits.

Most green retrofits involve adding new building materials, which may release harmful indoor air pollutants. The amount and type of these pollutants depend on the materials used, their purpose, and how they are installed. Green retrofits often include sealing leaks in a building to keep conditioned air inside, but if this is not balanced with enough ventilation, it can increase the concentration of indoor air pollutants.

Responses and Criticism

Policymakers are increasingly working to address gaps in building improvements to prevent unfair environmental issues, such as a "two-tiered" market where high-quality buildings have higher rental prices. These prices encourage owners to invest more in premium buildings, while lower-quality buildings receive less attention. The Affordability Principle says sustainable building upgrades should be available to everyone, not just those who can afford expensive housing. Improving building efficiency can help reduce health differences and carbon emissions, creating a fairer future for all. Many also believe information about sustainable building upgrades should be shared freely with people of all income levels, ages, and backgrounds to give everyone equal chances to live in better conditions.

Some people criticize the ability of sustainable building upgrades to reduce carbon emissions from existing buildings, especially large industrial structures. These buildings often have much higher carbon levels from materials and energy use compared to smaller residential or office buildings. However, technology to efficiently heat, cool, and power these large buildings is not yet available, and they cannot rely fully on passive strategies due to strict building codes. It is unlikely that these buildings will be upgraded unless it is done in a cost-effective way, which affects global efforts to lower energy use through sustainable upgrades.

Another criticism is that not all buildings are suitable for upgrades. Buildings that were poorly designed from the start are harder to improve. Studies show that simple floor plans with regular shapes are easier to adapt than irregular designs. The height between floors also affects how easily utility systems can be changed, making taller buildings easier to upgrade. Research also shows that higher-quality buildings are more likely to receive sustainable upgrades. This may be because premium buildings often get upgrades earlier in their lifespan to stay competitive with newer buildings. However, replacing building systems early can lead to more waste and higher carbon emissions. Some materials from older buildings can be reused in lower-quality upgrades in low-income areas. A study from 2007 in Australia found that about 89% of upgrades to premium buildings were done on structures less than 25 years old, while only 11% were on buildings 26 to 50 years old. No upgrades were found in the least desirable building locations.

Case Studies

A study by the Journal of International Affairs found that 41% of people in urban areas, 34% in suburban areas, and 46% in rural areas are very interested in smart street lighting. Smart street lighting uses technology to make street lights more efficient, safer, and easier to manage. These systems use energy-saving LED lights and sensors connected by wireless technology to adjust brightness based on real-time conditions, such as time of day, traffic, and weather. This helps save energy by controlling how much light is used. Additionally, 52% of people in urban and suburban areas and 53% in rural areas want free public Wi-Fi as part of smart city projects. Free Wi-Fi helps smart cities work better by connecting people to the internet, reducing the gap between those who have access and those who do not, and creating more economic chances. Also, 31% of urban residents, 23% of suburban residents, and 31% of rural residents support monitoring critical city systems. Monitoring critical systems means using cameras, sensors, and devices to track city functions in real time, collect data on infrastructure and public safety, and quickly solve problems to improve city operations. Finally, 40% of urban residents, 23% of suburban residents, and 31% of rural residents support public transportation as part of smart cities. Technology helps improve public transportation by providing real-time travel updates, reducing traffic jams, and making it easier for people to move around cities.

A study by the BIO Web of Conferences measured carbon emissions in four cities before and after smart city projects were introduced. All cities saw a big drop in carbon emissions, especially those with high starting emissions. For example, City B had 400,000 tons of carbon emissions yearly before the projects and 320,000 tons after, a 20% decrease. City D had 180,000 tons before and 160,000 tons after, an 11% decrease. The biggest factor was likely that City B had much higher starting emissions than City D.

Another study by the BIO Web of Conferences tested how different smart city projects reduced carbon emissions. Green energy projects cut emissions by 250,000 tons yearly, public transportation upgrades reduced emissions by 320,000 tons, energy-efficient buildings cut emissions by 180,000 tons, and improved waste management reduced emissions by 150,000 tons. All smart city projects helped the environment, with some, like public transportation, having a bigger impact.

Sources of technical guidance

• The website http://www.herretrofitspace.com helps professional women in the retrofit industry in the UK
• http://www.energysavingtrust.org.uk
• http://www.ademe.fr
• nps.gov /think