Sustainable BuildingsSustainable Buildings Glossary: Key Terms & Technologies

Sustainable Buildings Glossary: Key Terms & Technologies

Karl Dickinson
Karl Dickinson
Change matters. It takes courage. As a writer - and citizen - I am inspired by stories of those who challenge the 'we've always done it this way' attitude. We can do better - it's time to listen to those who go against the grain.

In case the world of sustainable buildings, planning, retrofitting, and construction is new to you, the CityChangers team has put together a quick-reference glossary to help you navigate some of the most common and technical terms used in our articles.



Acoustic Pollution

Excess sound that affects human and natural life negatively. Noise. Examples include the hum of traffic, construction and road works, and loud music. In people, it can lead to dire health concerns such as stress, disturbed sleep, and hearing loss.

Affordable Housing

See Housing Affordability

Allowable Solutions

These are alternative, cost-effective means of hitting reduced CO2 targets, which aren’t necessarily conducted directly on a building site. Instead, the measures are integrated into the property design or fabric elsewhere. It could be, for example, energy-efficient insulated modular units built in a factory before being transported and assembled on-site.

Anaerobic Digestion Plant

A series of processes by which microorganisms break down biodegradable material in the absence of oxygen. Can be used for industrial or domestic purposes to manage waste or produce fuels.



Mixing waste with organisms to create new building material from old.

Plants, fungi, and microbes act as ‘biobinders’ – a type of adhesive from nature – holding together pulped construction debris, like wood. This is done at the site of demolition to minimise embodied carbon emissions (i.e. from extra transportation). The mixture is processed into bricks and insulation at a later date.

Using plant-based materials can even result in a negative carbon footprint, as they can absorb more than they generate.


A sustainable way of addressing challenges sustainably. This is “a practice that learns from and mimics the strategies found in nature to solve human design challenges”, say the Biomimicry Institute.

Check out this fun short video for more details and examples.

Biophilic Design

Although we spend much of our time in the built environment, connections with nature benefit our wellbeing. Biophilic design seeks to incorporate elements of the natural world in our buildings and cities to sate our innate needs. This includes greenery and natural lighting.

Black Roof

A black roof is oftentimes referred to as a ‘warm roof‘. It absorbs more heat into the home but is typically hotter than the air temperature surrounding it.

Building materials consist of metal, asphalt shingles, slate tile shingles, and concrete tile shingles.

Brownfield Land

According to the EPA, brownfield land is a plot formally used for residential or industrial activity, which can be redeveloped and brought back into use. It usually contains pollutants or other contaminants – such as chemicals – that should be cleaned (often at great expense) before the land can be repurposed.

Not to be confused with greyfield land: moribund or underused malls and carparks.

Building Envelope

In simple terms, this comprises the walls, facades, roof, doors, foundations, and any other components of a building that divide the outside with what is inside and provide a fit-for-purpose internal environment.

People, animals, property, equipment, utilities, and furnishings on the interior are protected from external weather systems and climate by the building envelope. It also constitutes the frame for how energy is managed within a build, e.g. heat transfer between rooms. A tight envelope provides more control; a loose envelope allows freer airflow within a building.

Improvements to a building envelope may make an HVAC more efficient and extend its life and should be calibrated for the local climate.

Building Information Modelling (BIM)

We can envisage the entire lifecycle of a building using BIM. Data feeds 3D models so that inefficiencies can be identified and eliminated in advance, saving costs and time. Bringing various stakeholders in the construction process on board with BIM – increasingly possible with cloud-based software and remote meetings – improves collaboration between planners, developers, and construction personnel.

Building Management System (BMS)

According to SearchDataCenter: “A building management system (BMS) is a control system that can be used to monitor and manage the mechanical, electrical and electromechanical services in a facility. Such services can include power, heating, ventilation, air-conditioning, physical access control, pumping stations, elevators and lights.”

Building-Related Illness (BRI)

Often traced back to airborne particles and contaminants, a BRI is a direct correlation between a diagnosable health problem and the condition or materials of a building. This could be anything from mould to asbestos.

See also Sick Building Syndrome.

Built-Up Area

Is an area of the city with a presence of buildings (roofed structures).


Carbon Negative

If a building is so efficient, or has particular measures in place, that it actually reduces the amount of CO2 in the atmosphere, we consider this to be carbon negative.

Carbon Positive

When a building produces more energy than it needs, and has the potential to feed it back to the electricity grid.


A pliable sealant used to fill gaps and cracks in buildings, such as those that form around window and door frames. Caulking prevents heat loss and unwanted cold air from seeping in. It’s one of the easier do-it-yourself retrofit steps.


Carbon capture and storage is a method for collecting and retaining CO2 from burning fossil fuels, producing energy from biomass, or industrial processes – such as producing steel. The carbon emissions are captured and compressing at the point they would typically be emitted and transported deep within the rock layer (or ‘geological reservoirs‘) where it cannot seep into the atmosphere. Thereby, this decreases harmful climate changing carbon quantities.

Captured carbon can alternatively be used in food production or to produce synthetic fuel.

Circular Design (Circular Buildings)

An increasingly common practice for considering the life cycle of a building, including responsible sourcing and processing of materials and how the build, components, and materials can be repurposed or dismantled with limited environmental consequence.  One route may be dismantling the building to reuse the materials in future constructions.

Circular Economy

The Ellen McArthur Foundation describes the circular economy as one that “is restorative and regenerative by design”.

It’s the principle of a shift to economic growth based on reusing and recycling materials already in use, reducing the demand on finite natural resources and related destruction of ecosystems and environments. Waste, pollution, and embodied carbon releases are reduced.

In contrast, we have in the past sustained a linear ‘take-make-waste’ economy of extraction, processing, using, and disposing of materials and goods.

City Planner

These are the people tasked with visualising the future of a city and making that vision happen. They are representatives of the local authority or city administration that advocate for and regulate development.

City planners don’t just think up ways to build more property and implement the various physical elements that make up a city, like parks, schools, municipal buildings, telecommunications, and healthcare facilities. They look at the bigger picture. “For most planners, urban development is about the broad-based goals of equity and inclusion along with concerns like affordability and sustainability”, says Karin Brandt, CEO & Founder of coUrbanize.

Climate Gap

The impacts of climate change do not affect all people and places the same. Low-income households and people of colour are disproportionately disadvantaged, endangering lives and comfort for these groups more than others.

Climate Neutral

For a concise definition of climate neutral, look no further than

“Climate-neutral means a net-zero emission of greenhouse gases into the atmosphere. This also means that the emissions that occur must be able to be absorbed by the ecological cycle, carbon storage in materials or with technical solutions and thus not contribute to the greenhouse effect.”

Climate Shock

United Nations Development Programme defines climate shocks as “realizations of highly unexpected events that cause welfare losses.” Physical contact of climate shock with humans can bring disruption, injury, or even death.

They can be seen in a form of weather shocks, meaning changes in temperature for a specific place as opposed to what they were like before.

CO2 Equivalent

For ease of comparison, greenhouse gases are sometimes expressed in terms of their equivalent global warming potential (or GWP) as if they were carbon dioxide emissions. Sometimes written as CO2-eq or CO2-eqv. For example, every 1 million metric tonnes of methane is comparable to 25 million metric tonnes of CO2.


Is a community-led housing scheme. A group of people comes together intending to design and create a community. Every resident lives in their own (private) unit but shares several amenities with others. There is a particular focus on sustainability, connectivity, and shared decision-making.

Community Energy

Localised, decentralised energy generation. This may be, for example, from solar panels on a public building or wind power from turbines on a housing estate.

It is made possible when a group of people (often called an energy co-op) club together to fund and install renewable energy generators at a specific site. Those providing financial, professional, and technical support may or may not be from the community the project will feed.

The site (e.g. school) uses the power at a discounted rate, which repays investors with a small return. Any further profit funds projects that support the local community, often with social benefits for the most marginalised.

A key player in decarbonising the energy sector. For more, read our Notable Cities article about community energy in London.

Construction Consolidation Centres (CCC)

Also known as an urban logistics hub. A CCC is “a strategically-located storage and distribution facility where materials can be stored as a jumping-off point for just-in-time delivery”. Multiple suppliers feed a warehouse, which feeds local construction sites. Consolidating materials on a minimum number of (low emission) vehicles prevents traffic congestion, transport fumes, and waste. Additionally attractive for sites with limited storage space.

Similar to Urban Distribution Centres, or Urban Consolidation Centres (UCC): stores for goods from multiple Third Party Logistics Providers that can be combined to make a full truckload for a single inner-city destination, delivered in one journey via green transport.


These are individuals, companies, or organisations that oversee the construction of a building on behalf of a client, e.g. homeowner or developer. Can consist of an entire crew of builders, who do the hard physical graft, or sub-contracting people with certain expertise, such as bricklayers, electricians, plumbers, crane drivers, landscape gardeners, etc.

A contractor is often responsible for project and budget management. They ensure materials are ordered, deadlines are met, professionals are booked, permits are secured, building codes are adhered to. They act as the touchpoint between developers and the construction party.

Whereas the developers and investors make money from how they use property, a contractor is paid for their work, charging for their skills and time spent on a project. Builders generate income from constructing a property.



Used in seismic retrofits (and commonplace in high rise builds), dampers counteract the momentum and oscillation that occurs during an earthquake. By softening movement, hitting structural breaking point is avoided.

Low-rise and residential seismic protections are becoming increasingly popular as life- and cost-saving preventions.

Demolition Embodied Energy (DEE)

This refers to the amount of carbon released through dismantling buildings and either reusing or transporting and dumping or burning the waste. Material sent to landfill “can be an environmental burden to the whole eco-system” due to the pollution it causes via releasing gas.

Demand Side Response

Flexible use of electrical power – often generated from renewables – that ensures the grid is supplied at peak times without having to build new power plants. For example, to counteract all the televisions and devices tuning into a national sporting event, factories can defer energy-intensive processes to another time. Phasing out peak times prevents price-hikes.


Take a plot of land and build on it. Or find a building and improve it. These are the two main activities of a developer. They are also responsible for ensuring buildings are linked to wider infrastructure, such as sewers, electricity supply lines, roads, etc.

As an organisation, developers often have a team of construction workers on board, while smaller outfits may rely on a contractor to carry out the construction work.

The name of the game is the return on investment. Trader developers sell their property on, while investor developers rent out their portfolio for profit. The up-front costs that bankroll a development may be self-financed or involve investors.

Digital Twin

A type of simulation used to visualise and evaluate changes made to a building based on constantly updating data.

Whereas a (computer) simulation shows us what can happen with a given set of parameters, a Digital Twin uses input from the Internet of Things (IoT) – smart technology – to provide a real-world picture of what is happening. This data enhances subsequent retrofits.

Direct Rebound Effect

A phenomenon by which complacent human attitude and behaviour undermine the efforts of energy-saving measures via increased demand. This term applies when we use appliances more often and for longer in the knowledge that they are more efficient. For example, leaving a TV on standby instead of turning it off overnight, or leaving multiple lights on in a room because LEDs produce less heat waste.

District Heating

The name given to producing heat in one location and pumping it via insulated pipes to properties elsewhere. It is used for water and space heating. District cooling can be offered in the same way.

Traditionally, the heat was obtained from burning fossil fuels but the practice is changing to include biomass, renewable sources (e.g. thermal and solar energy), industrial byproduct, and ‘waste’ from nuclear plants. As such, it is considered less carbon-intensive than on-site heat generation.


Ecosystem Services

According to The National Wildlife Federation, ecosystem services are the impacts and benefits of human actions regarding ecosystems and human well-being.

There are four types:

  1. Provisioning services: any type of benefit to people extracted from nature (e.g. food, water, timber, natural gas, oils, plants used for clothes and medicinal purposes).
  2. Regulating services: benefit provided by ecosystem processes that moderate natural phenomena (e.g. pollination, decomposition, water purification, climate regulation).
  3. Cultural services: a non-material benefit contributing to the development and cultural enhancement of people (e.g. creativity born from interactions with nature, recreation, acquiring knowledge).
  4. Supporting services: allowing the Earth to sustain basic life (ecosystems couldn’t be sustained without consistency of natural processes, such as water cycle, photosynthesis, creation of soil, etc.).

Embodied Carbon

Differing from emissions, embodied carbon is all the CO2 involved in the entire construction process and materials used. This is calculated by considering transportation, energy use in extracting and processing raw materials, manufacturing, and future decommissioning. It also includes the “fixtures and fittings”.

Not to be confused with ‘grey energy’.

Energy Efficiency

Stabilisation or reduction in energy consumption.

Manifests as either the current level of:

  • functions being sustained by less energy.
  • energy consumption that sustains an increase in services.

Retrofitting is generally concerned with reducing the amount of energy required to keep a building operational to established standards and expectations.

Energy Poverty

Where as fuel poverty refers just to heating, energy poverty relates to the energy required for the lighting, warmth, cooling, and powering devices, appliances, and services, which provide a dignified standard of living.

Causes range from low incomes, high energy costs, and energy inefficiency.

The EU Energy Poverty Observatory estimates “that more than 50 million households in the European Union are experiencing energy poverty”.


Is a combination of plants emitting ground water through leaves and stalk and through the surrounding soil, and their conversion of water from liquid to gas.


Fuel Poverty

A term given where individuals do not have access to the (affordable) energy they need to sustain a comfortable living temperature. For example, low-income households may be forced to choose between eating and paying for heating.

The European Commission deems a family ‘fuel poor’ if more than 10% of household income needs to be sacrificed for an adequate level of warmth.


Renovating a property in preparation for the decades ahead. This includes steps towards: keeping interiors cool in hotter weather, or warmer in more extreme winters; consuming less energy; safeguarding from decay; and being suited to the occupants’ needs.

Fresh Air Handling Units (FAHUs)

Fresh Air Handling Units control the airflow and quality in a building. They are tasked with circulating fresh or treated air: this includes filtering pollutants, dehumidifying, or cooling. A FAHU regulates airflow by maintaining a regular volume and speed.

FAHUs are a central component of an HVAC system.


Green Employment

Green employment refers to green jobs – jobs that are by International Labour Organization‘s (ILO) definition “central to sustainable development and respond to the global challenges of environmental protection, economic development and social inclusion”.

Green Infrastructure

The connected network of green spaces and vegetation. It could be trees lining a street, a grassy playing field or meadow, an area of woodland, a city park, or even living walls and roofs. These elements collectively provide a multifunctional purpose, e.g., access or transport route, respite, rainwater management, or carbon sinks. It may include elements of blue infrastructure too: ponds, rivers, canals, etc.

Green Roofs

Adding trees, shrubs, plants, and bushes to rooftops leads to direct and ambient cooling effects through evapotranspiration. They also shield built material, thereby preventing heating and reducing the urban heat island effect.


A cynical practice by which businesses and organisations claim to be taking steps to reduce their impact on the environment, but in reality aren’t. It is done to generate beneficial PR.

There may be no real efforts to be green at all or claims of voluntarily taking steps that are in fact mandated by official legislation. Biggest offenders not only make unfounded claims but also fail to declare the polluting, destructive forces of their supply chains.

Grey Energy

This refers not to carbon emissions (see Embodied Carbon), but the amount of energy used for extraction, all modes of transport, storage, sale, and disposal. This can apply to a single product. Net zero efforts should consider grey energy in calculations.

Greyfield Land

Taking their name from the colour of abundant concrete and asphalt, greyfield sites are abandoned or underused places – often shopping centres or real estate – that can be redeveloped and revived. MIT notes they are usually “located in inner ring suburban areas” and “can be redeveloped profitably into mixed-use, walkable neighborhoods”. Innercity sites are also used.

Whereas ‘dead’ former industrial brownfield land tends to contain contaminants, greyfield, due to the nature of its former use, is relatively clean. However, this form of rejuvenation is still not as common.

Greywater Recycling

According to the Guardian, “Greywater recycling systems collect the water you’ve used in your sinks, dishwashers, showers and baths, and then clean it up and plumb it straight back into your toilet, washing machine and outside tap”.

These systems are common in buildings such as hotels and are gaining traction in household builds with the potential to cut residential water use (and costs) by half.

Grid Arbitrage

The practice of acquiring networked electricity when it is cheap and storing it for use when prices are higher. Lithium batteries make it possible to purchase and store electricity in this way for household or electric car use.


Heating, Ventilation, and Air Conditioning systems (HVACs)

Heating, Ventilation, and Air Conditioning systems provide an all-in answer to a building’s environmental control. It’s designed to provide consistent internal comfort, regardless of outside conditions. These are usually old systems that are often replaced during a retrofit.

HVACs use FAHUs to pump air as part of their central operation. In addition to heating or cooling, this guarantees breathable air quality and prevents stagnation, which could lead to bad smells and mould. They make up 51% of a building’s total energy use, so should be optimised for efficiency.

Heat Pumps

By extracting heat from the environment, heat pumps negate the need for energy-swallowing boilers. Air, groundwater, and the earth can provide sources to heat water and occupancy spaces.

They are highly efficient because only electricity is used – no additional heat needs to be generated. Heat pumps generally work by collecting heat outside of a building, passing it through coolant to intensify the heat, then deliver it via a unit (much like an air conditioner) in the room. The process can be reversed for cooling.

Also known as reverse cycle air conditioning (RCAC) units.

Rooftop heat pumps
Image credit: Pixabay / triosolution


Is a way of planting, where soil is not needed, but instead the roots of the plant grow directly in nutrient-rich water. Basic elements for successful hydroponics are: fresh water, oxygen, root support (like perlite, or coconut fiber), nutrients (magnesium, phosphorus, calcium, etc.), and light.

Housing Affordability

There is no one definition of “housing affordability”. A common criterion used to determine housing affordability is the housing price-to-income ratio. The government of New South Wales, for instance, consider housing affordable if it “costs less than 30% of gross household income”.

In contrast, UN-Habitat opt for a more general definition. They define affordable housing as housing “which is adequate in quality and location and does not cost so much that it prohibits its occupants meeting other basic living costs or threatens their enjoyment of basic human rights“.

Housing Cost Neutrality

In response to the climate crisis, buildings are renovated to be more sustainable. According to the IUT, tenants could have to pay for such renovations in the form of increased rents. If these increased rents are fully balanced by energy savings, we speak of housing cost neutrality. Housing cost neutrality helps prevent gentrification and displacement of residents.

Housing Cost Overburdened

Used to describe households who spend more than 40% of their total disposable income on total housing costs.


Indoor Air Quality (IAQ)

The quality of air inside a building. Poor ventilation, damp, and mould can be detrimental to the IAQ. This can be rectified with a coordinated (whole house) retrofit.


Profit is the primary goal of investors. This they achieve by renting out or selling off building stock. They either purchase market-ready buildings or those that need upgrading. Some investors will buy a property to improve and sell on in a short turnaround: this is known as flipping. Other investors, such as banks, offer development funding but are not involved in the construction phase.


Land-led Delivery

Housing associations that own land have more control over the development of properties built there. Instead of acquiring homes constructed by private or volume house developers, the HA can decide what will be built, when, and by whom.

Landscape Urbanism

A school of thought that puts ecological awareness and impact at the forefront of urban design. It heralds a shift away from architecture as the lead role in how our cities are planned, and so horizontal rather than vertical spaces are prioritised.

Biodiversity, human activity, and management of water, land, and infrastructure are all considered in this approach to the environment.

Life Cycle Analysis

The evaluation of all social, environmental and economic impacts, both positive and negative. It examines all the steps of a product, from the extraction of raw materials to the process for creating the material, the combining of semi-finished products to make a final product, including distribution, repair, and maintenance, all the way to its final disposal, composting or recycling.

Low Energy House

Similar to a Passivhaus, but with extra combined measures to reduce energy consumption, including a heat pump, solar water heating, and triple glazing that reinforces the insulation of the building envelope.


External window coverings with horizontal slats that block light and rainwater but allow air to flow through. Can be static or adjustable.

Image credit: Unsplash / Paul Carmona


Mechanical Ventilation with Heat Recovery (MHVR)

Also called Heat Recovery Ventilation. A passive measure, which circulates and purifies air with almost zero heat loss. “it has potentially the greatest impact on the primary energy use, CO2 footprint and heating costs.”

Meanwhile Development

Where there’s an empty plot of land, there’s potential for meanwhile development. It’s the act of revitalising an unused area earmarked for future development with temporary housing, businesses, and facilities. Popup homes provide a way to ease the housing crisis (a lack of homes) and create thriving communities and local economies in a relatively short time. They are removed prior to the commencement of the planned permanent development.

MEP System

Combining the installation and operation of mechanical, electrical, and plumbing components in a building.

Rather than planning and constructing all three separately, MEP engineering oversees it as a package to maximise overall efficiency. Simultaneous installation saves time and expense, prevents conflict for space in a property, and avoids unnecessary delays, damage, and repair work.

Modern Methods of Construction (MMC)

A form of prefabricated building, where components (walls, roofs, floors) are manufactured in a single place before being delivered and fixed in place on-site. There are two main forms of MMC:

  • Panelised MMC is when the fully-formed components are driven by lorry to the building site, where they are secured by a team like flat-pack furniture.
  • Volumetric MMC is when the components are bolted together and completed with features – such as bathroom facilities – before these pre-assembled rooms are delivered to the building site.

Other names include building off-site or precision manufacturing.

Modular Vegetation Trays

Are non-built-in pre-planted trays with vegetation and a built-in water-retention system, ready to be set up on the roof.


Nature-Based Solutions

Are actions to protect, manage and restore ecosystems, while addressing societal challenges. They strive to provide benefits for both biodiversity and human well-being, and are designed and implemented through working with local communities and indigenous people.

Near Zero Energy Buildings

A building of exceptional energy efficiency. It does, however, use some power, meaning it cannot be classed as a Passivhaus. The energy it uses may be taken from the grid or produced locally.

In the EU, the Energy Performance of Buildings Directive dictates all new buildings from 2021 must be NZEBs – nearly zero energy compliant.

Net Zero Energy Buildings

Buildings that produce as much energy as they consume for heating, lights, hot water, and appliances, usually from renewable sources, reducing fossil fuel consumption. They may store and use or export the energy they produce.

NIMBY (Not In My Backyard)

NIMBYism refers to the phenomenon that people do not want something perceived as unpleasant to be placed/done/built near their home.

This blog post from Edinburgh University gives the example of someone in favour of renewable energy but opposed to wind turbines changing a landscape they value.



Used to describe a property too small for the needs of the household inhabiting it. A household is considered overcrowded if there is fewer than:

  • one room for the household,
  • one room per couple,
  • one room for every adult single person,
  • one room per pair of children or teenagers (aged 12-17) of the same gender,
  • one room for every child or teenager (aged 12-17) if they are not the same gender,
  • one room per pair of children (aged 0-11).

OPP: under-occupied


Passivhaus (Passive House)

A voluntary but stringent standard that incorporates practical low-energy, high-efficiency design into the architecture process, mostly aimed at cutting CO2 emissions. Methods of insulation are core to the concept, which applies to both new builds and renovations.

The focus is on heating and cooling with minimal energy use, which is maintained almost entirely through ultra-efficient insulation. Near-zero fuel costs combat fuel poverty.

Passivehaus schemes are up to 3% more expensive than construction which complies with other regulations, but these retrofits provide a 75% reduction in the need for space heating compared to new buildings and 90% compared to older constructions.

Phase-Change Materials

Also known as Latent Heat Storage. In retrofitting, this refers to materials intended to trap and release heat, e.g. absorbing energy during the day and expel it at night, maintaining ambient temperature.

In general terms, PCMs release energy at a time the state of material changes from one to another, e.g. from solid to liquid, or liquid to gas. The resilience of materials prior to change is known as Thermal Mass.

Photo-Voltaic (PV) Modules

The technical term for solar panel units. These convert solar rays into electricity.

Photo-voltaic modules
Image credit: Pixabay / singhvp93

Plus Energy House

Similar to a Low Energy House, with the addition of solar panels, which allows the build to generate more electricity than it uses. This can be sold into the national grid.


A high-rise building (i.e. skyscraper) made from wood.

Power Purchase Agreement

In simplest terms, this is the contract between the party who generates energy and whoever purchases it from them.


Producers create a product for a consumer to use. What if we can be both?

That’s the concept behind prosumers – a hybrid of energy consumer and producer. We don’t just take power from the grid, but we also feed it with distributed energy sources such as solar panels and wind turbines installed on our buildings.


Rainwater Harvesting

The collection of rain, usually channelled from the roof via guttering and pipes, for storage and practical use. Popular in the green building movement, and effective in places where water is a scarcer resource, such as Australia. Non-potable water unless specific filters and disinfectants are incorporated into the system.

Rent Control

Government regulation that determines how high rents can be and under what conditions evictions are legitimate.

Rent Freeze

A form of rent control whereby rents are ‘frozen’ and not permitted to be increased. This measure aims to keep housing affordable and was adopted by some countries during the Covid-19 pandemic.


The act of reviewing, installing, improving, or maintaining an integrated internal controls system, such as lighting and temperature control, HVACs, and water systems. This provides optimum energy efficiency.

Issues that this fixes include missing equipment, damaged or uncalibrated sensors, outdated devices, and automated systems heating and cooling at the same time.

Retro-commissioning may be needed because:

  • It was not originally included.
  • An aged system needs replacing.
  • The building function or occupancy has changed.
  • A property has been expanded.
  • Occupants are uncomfortable.

Revenue Decoupling

A financial mechanism in which the income of energy companies is protected from fluctuations in demand. In times of low demand, providers can increase prices to recoup revenue; during high demand, they drop prices and occasionally even credit consumers.

Return on Investment (ROI)

Forbes puts it succinctly: “ROI compares how much you paid for an investment to how much you earned to evaluate its efficiency.”

In other words, it’s the profit you make after meeting initial costs. Payback may occur in the short or long term.

An example is the reduction in energy bills brought about by retrofitting; over time, the amount saved may add up to more than the original price of the home renovation.

Rooftop Villages

Make-shift houses on top of existing buildings with flat roofs. They occur most in dense cities, like Hong Kong.


This is a measure of heat resistance. i.e., how much a material fights to prevent heat from passing through it. It is measured in watts per square metre kelvin (W/m2⋅K)


Sector Coupling

The power grid is already on its way to decarbonisation. Sector coupling represents an answer to the demand from high-level consumers that still require electrification – namely industry, transport, agriculture, housing, heating, and cooling.

It’s a two-fold concept:

  1. The shift away from fossil fuels towards meeting energy demand with renewable sources.
  2. A holistic linking – or coupling – of power generation, storage, and consumption as opposed to the traditional model of separate entities.

Also referred to as Sector Integration.

Shallow & Deep Retrofits

  • ‘Shallow’ retrofits indicate single improvements to a property. Further changes can be added incrementally. The focus is often on renewable energy sourcing. Offers short-term ROI. Suits limited budgets.
  • ‘Deep’ retrofits consider and tailor multiple measures for the full spectrum of needs. Ensures one measure does not counteract the efficacy of another. More expensive upfront, but better for reaching long-term energy goals.

More details can be found in our Shallow and Deep Retrofitting article.

Sick Building Syndrome (SBS)

Mostly felt by office workers, SBS describes the temporary discomfort such as headaches, tiredness, and rashes caused by the state of the indoor environment. For example, flickering lighting, dust, and cramped workspaces. Symptoms dissipate upon leaving. The US Environmental Protection Agency goes further to state that “no specific illness or cause can be identified”.

It may apply to particular locations or rooms within a given building or apply throughout.

See also Building-Related Illness.

Social Housing

This term refers to housing owned by the government or not-for-profit organisations and is available to people with low incomes.

Social Rent

In the UK, local authorities and certain registered private landlords offer housing with rental rates determined by a national or regional guideline. This is often a lower rate than with private rentals.

Solar Shading

Systems that control how much direct solar radiation enters a building. Optimum levels provide comfort, minimising the need for artificial sources of light, heat, and cooling.

Also known as solar control or solar protection.

Space Heating

Warming of air within a room. As opposed to directing heating surfaces, as is the case with Infrared Heaters. One of the most energy-intensive uses: in EU countries, up to 80% of energy in residential builds is exerted on space heating.

Stranded Assets

Investments that are devalued prematurely. This devaluation is encountered primarily by assets reliant on hydrocarbons and is partially caused by the shift (of investment) towards sustainable assets.

Sustainable Architecture

The practice of designing buildings with a focus on:

  • Creating a high-quality indoor environment to positively influence how occupants feel.
  • Minimising the impact of buildings on the natural environment through constructions and operational emissions.

Non-toxic materials, air quality (ventilation), and temperature all feature highly.

Sustainable Drainage Systems (SuDS)

Management for excess rainwater built into buildings, ground, and infrastructure. Reduce flooding.

Increasingly necessary as artificial ground cover – such as concrete – encourages water to ‘pool’, sitting on the surface rather than returning to the water table, being stored in soil deposits, or being removed via waterways through natural drainage.

Examples include swales and rain gardens.

Sustainable Procurement

Purchasing of goods and services is done with the usual consideration of value for money, with the added focus on social and environmental impact. Human rights, equity, and renewables are examples of concerns.

Purchasing with a priority solely on the life cycle of products is also known as “green procurement”.


Thermal Bridging

A term given to heat loss through material more conducive than that around it. An example is through vertical wooden studs that divide insulated wall cavities in American homes – which make up 25% of wall space.

Passivhaus design includes comprehensive insulating that eliminates thermal bridging as well as employing an airtight building envelope to prevent heat loss via airflow.

Thermal Capacity

Thermal capacity refers to the amount of heat needed to produce a unit change of temperature in a unit mass of a material.

Thermal Mass

The resilience of materials prior to changing state through temperature. Concrete has a high thermal mass, as it can store vast amounts of heat before being subject to state change. Paper has a low thermal mass.

Utilising materials that absorb solar energy during the day and releases heat at cooler hours is an effective, relatively cheap, and somewhat green retrofitting option.


Used to describe the transformation of a place due to tourism. The term often appears in negative contexts criticising the impact tourism has on certain areas.



Used to describe a property too big for the needs of the household inhabiting it. A household is considered under-occupied if there is more than:

  • one room for the household,
  • one room per couple,
  • one room for every adult single person,
  • one room per pair of children or teenagers (aged 12-17) of the same gender,
  • one room for every child or teenager (aged 12-17) if they are not the same gender,
  • one room per pair of children (aged 0-11).

OPP: overcrowded

Urban Canyon

Is a street, covered in buildings on both sides, creating a canyon-like shape. Urban canyons with narrow streets and tall buildings are generally hotter than those with wider streets and lower buildings.

Urban Climate

Is climate, significant for large metropolitan areas. It differs from the rural climate in air temperatures, humidity, wind speed, and amount of precipitation, due to tall buildings, paved streets, concrete, etc.

Urban Heat Islands (UHIs)

Microclimates within cities with a concentration of temperatures higher than the rural land that surrounds them.

Materials traditionally used in the built environment absorb and retain heat, causing the ground and air to heat up. Green spaces and green roofs can reduce the effects of UHIs.

Image credit: Unsplash / s o c i a l c u t

Urban Mining

Raw materials are processed for construction and manufacturing. At the end of their life cycle, they are often disposed of, adding to landfill and contamination. If we instead salvage these pre-processed (yet still durable and fit-for-purpose) materials, we are ‘mining’ the human urban landscape.

A form of recycling and reusing of materials, reducing demand on depleted natural resources.

Urban Soil

Activity in our cities affect what’s beneath our feet. Soil in urban spaces is impacted by construction, contaminants, and by “mixing, importing, and exporting material”. Due to being in an altered state from ‘natural’ soils, this can have a knock-on effect for ecology, water infiltration, and our health.

An active carbon bank, all soil plays an important role in mitigating climate change. The extent that modified urban soils can manage CO2 content can reduce its capacity for storage, with implications for a warming climate and cities.

Urban soils are those within the catchment of a city boundary, including parks, riverbanks, gardens, and industrial spaces. Not all is damaged, and much still retains some benefit.


This is a measure of how effective a material is as an insulator. It describes the thermal performance or heat loss. The lower the U-value, the better the material functions as an insulator. It is measured in watts per square metre kelvin (W/m2⋅K).


Variable Refrigerant Flow Systems (VRFs)

Variable Refrigerant Flow Systems control and maintain temperature levels. One system can provide heating and cooling simultaneously in different locations.

An efficient alternative to other temperature control units, VRFs provide an energy saving of up to 34%. A flexible option: heightened levels of control curtails costs.

Vertical Gardens

Integrating greenery on the sides of high-rise buildings provides shade and cooling. Plants and trees, mosses, and clinging ivies put out on balconies, hanging baskets, and built into facades also help trap pollutants to create better air quality for residents.


Waste to Energy – WtE

Any process of treating waste sources in a way that generates energy in the form of electricity, heat, or transport fuels (e.g., diesel).

Water Reclamation

The UN’s Climate Technology Centre & Network defines water reclamation as the biological, chemical or filtering treatment or processing of municipal wastewater ready for reuse. Also known as recycled water, it is of a specific quality following treatment, and can be used for domestic, industrial, and agricultural purposes, e.g. irrigation.

Reduces the demand for potable water. While not as clean as rain or drinking water, it is used for public consumption: in Southern Nevada, the Clark County Water Reclamation District processed wastewater and returns it to Lake Mead for drinking.

Not to be confused with Greywater Recycling.


You Might Also Like