Sustainable refurbishment

One of the objectives of the United Nations Framework Convention on Climate Change (UNFCCC) is the mitigation of greenhouse gas emissions that contribute to climate change. More specifically, the UN supports the immediate reduction of building-related greenhouse gas emissions [1]. Building refurbishment plays a key role in the decarbonization of the current building stock [3]. Other than tearing down existing buildings, it is the only way to improve building performance or to develop zero-emission buildings [1]. Energy-efficient refurbishments are a tool to reduce energy consumption in buildings [4], which will result in lower greenhouse gas emissions and resource use [5]. Studies present the significance of the possible impact of widespread refurbishment implementation on individual GHG emissions, but also worldwide emissions and energy consumption [2].

Social sustainability relates to the impacts of a building on the surrounding or occupying society, community, and individuals [5]. This is considered in environmental impact assessment tools, such as life cycle assessment (LCA). Sustainable refurbishment integrates economic, social, and environmental needs to improve upon the existing building conditions [4]. For example, sustainable buildings are socially sustainable because they are healthier for occupants due to the use of materials that do not negatively impact health [5].

The indoor environmental quality of the existing building stock is known to often be more unsatisfactory and unhealthy than the outdoor environment due to the design and materials used. The leading argument for sustainable refurbishment, and sustainable building in general, is the belief that green buildings are healthier and more satisfactory for occupants [5]. The specifications for sustainable refurbishments take measures to ensure that the materials and building framework does not radiate dangerous particulates and gasses, like sulfur dioxide and nitrogen dioxide, into the indoor environment, and further measures are taken to filter indoor air for inhabitants [4,6]. The “Citizen’s Healthcare Principle” states that sustainable refurbishments must ensure that buildings are safe and improve living quality for those inside [4]. The refurbishment design must consider both the indoor microclimate and the external environment around the building when developing the program [4]. The microclimate parameters that should be considered include:

• Air velocity
• Humidity
• Dew point
• Lighting
• Air circulation velocity
• Acoustics
• Temperature

The preservation of historic buildings is inherently sustainable since it maximizes the lifespan of existing materials and infrastructure [1]. Conserving the materials and existing structures reduces waste and preserves the character of small historic communities. Many argue that the epitome of sustainability is to not build at all, which equites to preservation and refurbishment.

As a society, we have a finite amount of many resources, nonrenewable energy sources for example. Non-sustainable buildings, in terms of their operation, also consume a significant amount of non-renewable energy resources, relative to other industries. Again, it is necessary to increase the energy efficiency of the existing building stick to reduce non-renewable energy resource consumption, or even replace that with renewable sources entirely [1]. Efficiency can be improved through sustainable building refurbishments that modify the building systems and building operations. With buildings becoming more energy efficient it is increasingly important to look at the life cycle impact of the materials that make up the building [3]. Designing and constructing buildings that are not sustainable for long lifetimes allows for the construction and demolition of buildings with short lifetimes, which wastes construction materials that are not used for their entire lifetime capacity. Reusing existing buildings enables building owners to use the embodied energy that is already invested in the building composition, rather than wasting that embodied carbon and consuming more with a new building construction [5].

Sustainable refurbishments aim to reach “total building performance optimization” with the integrates of multiple systems throughout the building and the community [1]. The refurbishment not only decreases energy consumption but also improves occupant comfort in terms of noise, temperature, lighting, etc. It extends the life cycle of the building, reduces environmental impact, and creates healthy occupant conditions [4].

Sustainable refurbishments aim to minimize the negative environmental impacts of the renovation by reducing quantities of harmful materials, utilizing energy-saving technology, and retrofitting the building for renewable energy use, as opposed to non-renewable energy sources [4]. Some responsible environmental measures that can be incorporated in a building retrofit include energy and water efficiency, waste reduction and recycling, use of low environmental impact materials, and effective building operation [5]. An example of energy-efficient designs could include high-efficiency lighting and smart controls. Similarly, an example of water-efficient design could include dual-flushing toilets, greywater recycling, or aerating water fixtures.

A sustainable retrofit ensures that the energy performance of the building after renovation is significantly better than it was before the work. The increase in energy performance must meet the current building regulations for new buildings [2]. The sustainable approach would be to even design beyond the code minimum and plan for future requirements. A deep energy refurbishment should include the integration of energy generation on-site from renewable energy sources, with the goal of developing a nearly zero-energy building. The energy efficiency gained through the architectural retrofit makes the integration of renewable energy sources cost-effective [2]. A study in the United Kingdom showed that, after a refurbishment, buildings had lower operating costs even if sustainability was not a priority of the retrofit [5].

A study of energy refurbishments of residential buildings showed that the refurbishment led to an average thermal energy savings of 59% during the heating season [2]. The savings consisted of 25% from thermal insulation addition in exterior walls and floor, 10% from window insulation improvements, 6% from a reduction in air exchange, and 18% from the installation of heating controls [2]. The retrofit of the building envelope and operation reduced the energy consumption of the building, the associated greenhouse gas emissions during the operation phase, and the overall environmental impact [3,5].

Sustainable refurbishment ensures energy efficiency by improving the following systems [4]:

• Insulation
• Building Envelope Tightness
• Heating
• Cooling
• Conditioning
• Lighting

There are typical strategies to improve upon each of the above systems. Innovative insulation materials can be utilized that have a lower environmental impact, but even non-sustainable insulation additions can improve the energy performance of the building [4]. The building envelope can be improved by replacing the existing windows with efficient windows in terms of thermal bridging and optimizing solar gain [4]. The use of passive ventilation strategies or hybrid systems that use both passive and active strategies reduces the energy required for conditioning [4]. Buildings’ heating and cooling systems can be powered with solar energy, or even use solar-heated water, which both reduce non-renewable energy consumption through heating and cooling [4]. Finally, the electricity used for lighting can be reduced by optimizing daylighting in occupiable spaces [4].

The overall environmental impact of a sustainable refurbishment is highly dependent on the material choices for the refurbishment [3]. The Rational Resources Principle for refurbishment encourages the efficient use of construction materials and natural resources [4]. This is quantified through life cycle analysis that measures the impact of a material over its lifetime, which stretches into the “D phase” that includes end-of-life waste after the building is demolished [3,4]. Waste transportation adds costs to both construction and building maintenance. Designing refurbishments that reduce waste, and maximize reuse, minimize waste hauling costs in the short-term and long-term by using materials for their entire intended life [4].

When materials can be compared on the basis of a common bottom line, through life cycle analysis, an optimum path for the design appears [3]. Ultimately, since the refurbishment will require additional construction materials, there will be a negative environmental impact, but the aim of sustainable refurbishment is to minimize these impacts [3]. For example, reusing on-site timber, using reclaimed timber, and using timber from renewable certified sources are sustainable material choices based on taking advantage of the embodied carbon that has already been invested in those materials [5]. As was mentioned prior, the analysis of the life cycle of building materials’ primary energy demand and global warming potential is becoming more important as buildings are consuming less energy during their operation [3]. The human health impact of materials is also included in their life cycle assessment, meaning that a construction material cannot be sustainable if it harms its occupants. Therefore, sustainable refurbishments should not include adhesives, paints, or glues that expel low-volatile organic compounds into the indoor air of the building [5]. Materials that harm indoor occupants or the exterior ecology are considered lethal and are therefore not utilized in sustainable refurbishments [6].

The image shown is a conceptual model of sustainable refurbishment [4]. The dimensions of the model include technical, economic, architectural, social, ecological, and cultural. The dimensions are all related and influence each other and the refurbishment design itself [4]. The model depicts how stakeholders expect the refurbishment design to yield energy savings, increased occupant comfort and health, extension of the building's lifetime, environmental protection, and, of course, an economic outcome. These expectation align with the goals for sustainable refurbishment that were developed in the previous section. The concept model also introduces the steps of the refurbishment process that will be discussed next in this article.

There is criticism of the efficacy of sustainable refurbishment in terms of decarbonizing the current building stock. This criticism is directed specifically toward large-scale energy refurbishments of industrial structures. One could argue that the embodied and operational carbon of those types of buildings are significantly larger than that of smaller residential or office buildings which are discussed in this article. However, the technology to efficiently heat, cool, and power these structures do not yet exist, and they cannot completely rely on passive strategies due to more stringent code restrictions [2]. It cannot be expected that these large-impact buildings be refurbished if it cannot be done economically. This argument impacts the hopeful global energy consumption decrease that researchers propose for sustainable refurbishments.

Another criticism of sustainable refurbishments is that not all existing buildings are good candidates for refurbishment. Put plainly, it is challenging to improve on buildings that were poorly designed from the start. It was proven that floor plans that are typical, with deep shapes, were more adaptable than irregular designs [5]. Similarly, floor-to-floor heights impact the designer and contractor’s ability to modify utility ducts, meaning that taller buildings are easier to refurbish [2]. Research also shows that structures that qualify as “higher grade” building stock experience greater levels and frequency of sustainable refurbishment [5]. There seem to be a number of reasons for this, one being that premium buildings undergo retrofit earlier in their lifecycle in order to compete with newer sustainable buildings [5]. It can be argued that it is not sustainable to replace building systems early in their lifecycle, just to invest in additional embodied carbon and discard the old equipment into a landfill. However, there is an opportunity for “young” removed materials to be utilized in lower-quality refurbishments in low-income communities [5]. In an Australian study using data from 2007, it was found that about 89% of all premium retrofits were to buildings that were less than 25 years old, with the remaining 11% aged between 26 and 50 years old [5]. The same study showed that no refurbishments occurred in the “least desirable” stock locations [5].

This gap in building improvement should be addressed by policymakers to avoid an environmental justice issue with a “two-tiered” market [5]. Of course, the premium stock has high rental prices which incentivize owners to invest in them further, which is not the case for the lower quality stock. It is not fair or just that only occupants that can afford premium housing get to live in the ensured healthy and comfortable environment of a sustainable refurbishment. The Affordability Principle states that sustainable refurbishments should be affordable for the general population [4]. In addition, information about sustainable refurbishment should be shared and freely available to people of all income levels, ages, races, etc. because everyone deserves an equal opportunity to live better.