The Rooftop Activation Ontology describes how building rooftops can be activated through colour-coded activation types (blue, green, yellow, red, purple, orange and gray) defined by the functions they host, such as water management, vegetation, energy generation, social use or mobility. It links rooftops and buildings to their attributes, owners, urban districts and the urban challenges they address, and classifies the incentives that regions implement to support activation by nature, function, funding source, allocation mechanism, obligation attachment and project stage. Morales Hernandez, A. (2026). Rooftop Activation Ontology (Version 2.1.0) Université libre de Bruxelles. 2026-08-14 The Rooftop Activation Ontology describes how building rooftops can be activated through colour-coded activation types (blue, green, yellow, red, purple, orange and gray) defined by the functions they host, such as water management, vegetation, energy generation, social use or mobility. It links rooftops and buildings to their attributes, owners, urban districts and the urban challenges they address, and classifies the incentives that regions implement to support activation by nature, function, funding source, allocation mechanism, obligation attachment and project stage. Users can register weighted associations between rooftop activation types, urban challenges, owner types and incentive types, optionally per region. 2026-09-30 2026-09-30 Rooftop activation ontology rooftop_activation https://w3id.org/rooftop_activation# 2.1.0 Urban rooftops are increasingly recognised as multifunctional infrastructure that can help address challenges such as urban heat islands, flooding, energy demand and biodiversity loss. However, rooftop interventions, the owners who carry them out and the policy incentives that support them are usually described separately, which makes it difficult to align rooftop activation with urban policy. The Rooftop Activation Ontology provides a shared vocabulary to describe these elements and their relationships. It classifies rooftops into colour-coded activation types (blue, green, yellow, red, purple, orange and gray) according to the functions they host, and links rooftops and buildings to their attributes, owners, districts and regions. It organises urban challenges into thematic groups and classifies incentive instruments by nature, function, funding source, allocation mechanism, obligation attachment and project stage. Beyond this classification, the ontology allows users to register weighted associations: how strongly a rooftop activation type contributes to addressing an urban challenge, how likely an owner type is to activate a rooftop activation type, and how suitable an incentive type is for an owner type. Each association carries a degree between 0 and 1 and can be defined for a specific region, so the same model can hold the assessments of different cities. Using the queries provided in the documentation, users can retrieve, for a given rooftop, the challenges it addresses, the owner types likely to activate it and the incentives available to those owners. Additional resources: the [guide to registering and querying association degrees](https://github.com/alejandro3500/Rooftop_activation_ontology/blob/main/docs/association_degrees_documentation.md), [registering CityJSON buildings in the ontology](https://github.com/alejandro3500/Rooftop_activation_ontology/blob/main/buildings_from_cityjson_documentation.md), and [registering an incentive in the ontology](https://github.com/alejandro3500/Rooftop_activation_ontology/blob/main/incentive_registration_documentation.md). Relates an incentive to the project stage at which it acts: pre-investment, investment or operation. An incentive may apply at more than one stage. applies at stage Relates a rooftop type to the rooftops it classifies. Inverse of has_rooftop_type. classifies rooftop Relates a district to the buildings located in it. Inverse of is_located_in. contains building The region whose authority defined the association. If absent, the association applies to all regions. defined for region Relates an incentive to the mechanism by which it is allocated to recipients: competitive, entitlement, first-come or negotiated. Functional: an incentive has at most one allocation mechanism. has allocation mechanism Relates a building to a characteristic that constrains or enables rooftop activation. Inverse of is_attribute_of. has attribute Relates a district to its built-form intensity. has density Relates a district to the urban challenges most pressing within it. Inverse of has_urban_challenge_district_priority. has district urban challenge priority Relates a rooftop to the activities performed on it. Inverse of is_done_in. has function Relates an incentive to the source of the resources that fund it: community, private or public. An incentive may combine several sources. has funding source Relates an incentive to the effect it has on an owner's decision to activate a rooftop, such as reducing up-front costs, de-risking or raising additional capital. An incentive may have more than one function. has incentive function Relates an incentive to the kind of lever it uses: contractual, financial, informational, organisational or regulatory. An incentive may have more than one nature. has incentive nature Relates a district to its dominant land use. Inverse of is_mainly_used_in. has main function Relates an incentive to what its benefits and obligations are attached to: the person, the project or the property. Functional: an incentive has at most one obligation attachment. has obligation attachment Relates an owner to the urban challenges they prioritise, used to match incentives and activation types to owner motivation. Inverse of has_urban_challenge_owner_priority. has owner urban challenge priority Relates a building to the rooftops it carries. Inverse of is_part_of. has rooftop Relates a rooftop to its geometric classification. Inverse of classifies_rooftop has rooftop type Inverse of has_district_urban_challenge_priority. has urban challenge district priority Inverse of has_owner_urban_challenge_priority. has urban challenge owner priority Relation that states that an incentive is implemented in a region to activate a rooftop. implemented in Relation that states that a region implements an incentive to activate a rooftop. The inverse is implemented_in. implements Relates an incentive to the rooftop types it supports or funds. Inverse of rooftop_associated_to_incentive. incentive associated to rooftop Relates a region to the districts it contains. Inverse of is_part_of_region. includes districts Relates a building attribute to the building it characterises. Inverse of has_attribute. is attribute of Relates a rooftop function to the rooftops where it is performed. Inverse of has_function. is done in Relates a building to the district in which it is located. Inverse of contains_building. is located in Relates a district function to the districts where it dominates. Inverse of has_main_function. is mainly used in Relates a building to the party holding decision rights over it. Inverse of owns. is owned by Relates a rooftop to the building it belongs to. Inverse of has_rooftop. is part of Relates a district to the region it forms part of. Inverse of includes_districts. is part of region Relates an owner to the buildings under their control. Inverse of is_owned_by. owns The urban challenge involved in the association. relates challenge The incentive type (Incentive subclass) involved in the association. The value is the class IRI used as an individual (OWL 2 punning). relates incentive type The owner type (Owner subclass) involved in the association. The value is the class IRI used as an individual (OWL 2 punning). relates owner type The rooftop activation type (colour class) involved in the association. The value is the class IRI used as an individual (OWL 2 punning). relates rooftop type Inverse of incentive_associated_to_rooftop. rooftop associated to incentive The identifier of the building in a CityJSON city model, that is, the key of the Building or BuildingPart in the CityObjects of the file. has city model id The year in which the building was constructed, expressed as an integer. The construction era attribute of the building is derived from it automatically. has construction year 0.0 1.0 Strength of the association, from 0 (none) to 1 (strongest). has degree A free-text description of an incentive, summarising its purpose, eligibility conditions and main features. has incentive description Links a building to the OpenStreetMap way or relation that represents it, as a full openstreetmap.org URL. OSM identifiers may change, so the geometry should also be kept. has OSM element 1 1 A physical structure with one or more rooftops, owned by an Owner and characterised by a set of Building_Attributes. A building is a GeoSPARQL feature. Its geographic position is given by a geometry linked through geo:hasDefaultGeometry, normally its footprint as a WKT polygon, and optionally by a point linked through geo:hasCentroid. A building can be linked to its OpenStreetMap element through has_osm_element and to its city object in a CityJSON model through has_city_model_id. Building The upper covering of a building. Superclass of Rooftop. Roof A legal or social body of people used to represent the affiliation of the people working with this ontology Organization An individual human being used to describe people interacting with this ontology Person Requirements on how a rooftop may be reached and by whom, governing public and semi-public use. Access Regulation Difficulty in providing enough suitable housing at affordable cost, including shortages, mismatches between supply and needs, and heritage restrictions on transformation. Affordable Housing Challenge Water, energy and transport networks that are outdated, lack capacity for new demands such as electric vehicle charging, or are constrained by heritage protection. Aging Unfit or Fragile Infrastructure Challenge Facet capturing how access to an incentive is decided among applicants, which drives the certainty and effort of obtaining it. Functional: an incentive uses at most one mechanism. Used with has_allocation_mechanism. Allocation Mechanism A weighted link between two types of the ontology, expressed as an individual so that it can carry a degree. Association Follows the individual or legal entity. Ends or moves with them if the property changes hands. Attached to Person Tied to a defined intervention and its delivery, ending when the project ends. Attached to Project Follows the building or parcel. Transfers automatically to the next owner or occupant. Attached to Property Buildings whose dominant construction material is the one named. Brick A characteristic of a building that constrains or enables rooftop activation. Attributes are grouped into independent facets: material, era, construction method, height, location, primary use and regulatory constraint. Building Attribute Increases the knowledge, skills or motivation of owners and intermediaries. Building Capacity or Awareness The dominant structural or envelope material of a building, which affects load capacity, thermal behaviour and retrofit options. Building Material The historic and functional core, with the highest density and the strongest heritage constraints. City Center Exposure of the city to climate impacts such as flooding, heat, drought and water scarcity, and the need to improve water management. Climate Adaptation and Resilience Challenge Retail, hospitality and other trading activity. Commercial Use Resources pooled from citizens, cooperatives or civil society organisations. Community Source Applications are ranked or selected against criteria, with no guarantee of award. Competitive Allocation An incentive allocated through a competitive procedure, where applicants are ranked or selected against criteria. Defined class: membership is inferred from has_allocation_mechanism. Competitive Incentive Buildings whose dominant construction material is the one named. Concrete The period in which a building was constructed, used as a proxy for structural standards, insulation levels and heritage status. The era of a building is derived from its construction year through has_construction_year, so it does not need to be asserted. Construction Era and Typology How a building was assembled, which determines the predictability of its structural capacity. Construction Method Operates through an agreement negotiated between parties, with obligations and remedies defined in the contract itself. Contractual Nature An incentive with a contractual or organisational nature, acting through agreements between parties or through structures and governance arrangements. Defined class: membership is inferred from has_incentive_nature. Contractual or Governance Incentive Aligns the decisions of multiple parties, typically through planning, programming or governance arrangements. Coordinating Actors Museums, theatres, sports and recreation facilities. Cultural and Leisure Use Transfers or absorbs part of the project's technical, financial or performance risk. De-risking The need to cut greenhouse gas emissions from energy use by adopting renewable sources, improving building efficiency and adding storage and low-carbon heat. Decarbonizing Energy Systems Challenge A delimited part of a city or its surroundings with a characteristic built form, density and function. Buildings are linked to districts through is_located_in, and districts to regions through is_part_of_region. District The dominant land use of a district, as distinct from the primary use of an individual building. District Function Any applicant meeting the stated conditions receives the incentive automatically. Entitlement Allocation Early industrial-era construction, masonry-dominated, often with heritage constraints (1830-1918). 1830 - 1918 A grant funded, fully or partly, by European Union resources. Defined class: membership is inferred from has_funding_source. European Grant An incentive funded, fully or partly, by European Union resources. Defined class: membership is inferred from has_funding_source. European Incentive Public resources originating in European Union programmes, funds or institutions. European Source An incentive with at least one financial nature, that is, one that operates by moving money or altering the cost of capital. Defined class: membership is inferred from has_incentive_nature. Financial Incentive Operates by moving money or altering the cost of capital. Financial Nature Requirements on escape routes, compartmentation and material behaviour that affect rooftop occupancy. Fire Safety Regulation Applications are granted in order of receipt until a budget or quota is exhausted. First-come Allocation A financial nature exercised through the tax system, including credits, deductions, exemptions and rate reductions. Fiscal Nature Roof with no or minimal pitch. Suitable for the widest range of activation types. Flat Type Roof combining both geometries, allowing different activations on different sections. Flat and Pitched Type Interwar construction, introducing early reinforced concrete and standardised housing types (1919-1945). 1919 - 1945 Facet capturing the origin of the resources behind an incentive. An incentive may draw on several sources, as in blended finance. Used with has_funding_source. Funding Source Buildings whose dominant construction material is the one named. Glass Institutional barriers such as lack of funding, fragmented competences, and missing regulatory or data frameworks for implementing urban strategies. Governance Challenge Residential fabric set within substantial open and planted space. Green residential district Districts dominated by open and planted land. Green Areas The vertical scale of a building, which affects wind exposure, access logistics and visibility of the rooftop. Height Limits on total building height, restricting additions and superstructures. Height Regulation Compact fabric with minimal open space, where rooftops represent the main remaining free surface. High Density Buildings above roughly eight storeys. Significant wind loads and dedicated access requirements. High Rise The protected historic fabric of the core. Historical city center Improves recurring revenue or reduces recurring cost once the rooftop is in operation. Improving Operating Economics Any measure that changes an owner's decision to activate a rooftop. Subclasses of Incentive form a single taxonomy by instrument type. Function, nature, obligation attachment, funding source, allocation mechanism and project stage are represented as separate facets via object properties, not as subclasses, because they vary independently of instrument type. Disjointness is asserted only between siblings within one facet. Incentive Facet capturing what an incentive does for a rooftop activation project, independent of its instrument type. Values are mutually exclusive as a partition, but an incentive may have more than one function. Used with the object property has_incentive_function. Incentive Function Facet capturing the kind of lever an incentive pulls, independent of its instrument type and its function. Values partition the facet, except Fiscal_Nature which is a subclass of Financial_Nature. An incentive may have more than one nature. Incentive Nature Degree to which an incentive type is suitable for, or used by, an owner type. Incentive-Owner Association Production, storage and logistics. Typically large flat roofs with high structural capacity. Industrial Use Areas of production, logistics and services, characterised by large flat roofs. Industrial and Service Districts Districts functioning primarily as places of production and work. Industrial and Services Operates by providing knowledge, advice, visibility or recognition. Informational Nature At the point of construction or installation, when capital expenditure occurs. Investment Stage Construction with modern structural codes and higher live load allowances (1976-2000). 1976 - 2000 The position of a building within the urban-to-rural gradient. The geographic position is given by GeoSPARQL geometry. Urban Location Context Decline of species, habitats and ecological corridors in the city, including competing land demands such as food production. Loss of Nature and Biodiversity Challenge Dispersed built form with high open-space ratios. Low Density Buildings up to roughly three storeys. Easy access, low wind load, high overlooking from neighbours. Low Rise Obliges or forbids an action rather than encouraging it, altering the baseline against which the owner decides. Mandating or Constraining Moderately compact fabric, typical of interwar and postwar extensions. Medium Density Buildings of roughly four to eight storeys. The most common context for collective rooftop projects. Mid Rise Districts with no single dominant function. Mix Use Recently developed or redeveloped parts of the core. Modern city center Public resources originating in city or local authority budgets. Municipal Source Public resources originating in national government budgets or agencies. National Source Terms are agreed bilaterally between the provider and the recipient rather than set in advance. Negotiated Allocation A local hub serving the surrounding residential fabric. Neighborhood Center An incentive that does not operate by moving money or altering the cost of capital, acting instead through contractual, informational, organisational or regulatory levers. Defined class: an incentive that is not a financial incentive. Non-Financial Incentive Facet capturing what the incentive's obligation or benefit is tied to, which determines whether it survives a change of occupant or owner. Functional: an incentive attaches to at most one of these. Used with has_obligation_attachment. Obligation Attachment Workplace buildings, a subtype of commercial use with distinctive daytime occupancy patterns. Office Use After commissioning, covering use, maintenance, revenue and repayment. Operation Stage Operates by creating structures, programmes or governance arrangements through which action becomes possible. Organizational Nature The party holding decision rights over a building and therefore over any rooftop activation. Subclasses distinguish owner types by their motivation, capital access and decision process. Owner Degree to which an owner type is likely to activate a rooftop activation type. Owner-Rooftop Association Designed and managed public open space. Parks Sport Facilities At the urban fringe, where built fabric and open land interleave. Peri-Urban Location An incentive whose benefits and obligations follow the individual or legal entity that receives it, and end or move with them if the property changes hands. Defined class: membership is inferred from has_obligation_attachment. Person-based Incentive Sloped roof. Restricts activation largely to energy generation and lightweight interventions. Pitched Type Reconstruction-era construction, often rapid and lightly built, with limited structural reserve (1946-1975). 1946 - 1975 An incentive that acts before the investment decision, supporting awareness, feasibility, design or preparation of a rooftop project. Defined class: membership is inferred from applies_at_stage. Pre-investment Incentive Before the investment decision, covering awareness, feasibility, design and preparation. Pre-investment Stage Pre-industrial construction, typically load-bearing masonry with timber roof structures and frequent heritage protection (< 1830) Before 1830 Assembled from factory-produced components, with documented and repeatable load characteristics. Prefabricated The dominant function of the building itself, which determines who occupies it and who benefits from a rooftop intervention. Primary Use Resources originating in commercial actors, including banks, investors, developers and utilities. Private Source Facet capturing when in the rooftop activation lifecycle an incentive applies. An incentive may span several stages. Used with applies_at_stage. Project Stage An incentive whose benefits and obligations follow the building or parcel, and transfer to the next owner or occupant. Defined class: membership is inferred from has_obligation_attachment. Property-based Incentive Resources originating in public budgets at any level of government. Public Source Schools, hospitals, administration and other public facilities, where the owner is often the municipality. Public and Institutional Use An incentive funded, fully or partly, by a public authority at European, national, regional or municipal level. Defined class: membership is inferred from has_funding_source. Publicly Funded Incentive Mobilises third-party capital that would otherwise not reach the project, without necessarily lowering its total cost. Raising Additional Capital Districts functioning primarily for leisure and ecological value. Recreational and Nature Lowers the search, negotiation, procurement or administrative effort required to realise the project. Reducing Transaction Costs An incentive whose function is to lower the initial capital an owner must commit to activate a rooftop. Defined class: membership is inferred from has_incentive_function. Reducing Up-Front Cost Incentive Lowers the capital the owner must mobilise at the moment of investment, whether by direct payment, discount or deferral. Reducing Up-Front Costs A geographic area containing multiple districts, used for administrative and policy scoping. Region Public resources originating in regional or provincial authorities. Regional Source A binding rule that limits what may be built or done on a rooftop, independent of structural feasibility. Regulatory Constraint An incentive with a regulatory nature, acting through binding rules, permits or legal obligations. Defined class: membership is inferred from has_incentive_nature. Regulatory Incentive Operates through binding rules, permits, standards or mandatory disclosure. Regulatory Nature Places of worship and associated buildings, frequently heritage-protected. Religious Use Districts dominated by housing. Residential district Districts functioning primarily as places of residence. Residential Housing Buildings used primarily for housing Residential Use The roof of a building considered as a potential site for activation, that is, for being put to a productive, ecological or social use. A rooftop is a GeoSPARQL feature. Its shape and position can be given by a geometry linked through geo:hasDefaultGeometry, normally a 3D polygon or multipolygon in WKT built from the RoofSurface surfaces of the building in a CityJSON model. Roof surfaces have no identifier in CityJSON, so a rooftop is linked to the city model through the building it is part of. Rooftop ex:rooftop_001 a ra:Rooftop ; ra:is_part_of ex:building_001 ; geo:hasDefaultGeometry ex:rooftop_001_geom . ex:rooftop_001_geom a geo:Geometry ; geo:asWKT "<http://www.opengis.net/def/crs/EPSG/0/XXXX> MULTIPOLYGON Z (((x1 y1 z1, x2 y2 z2, x3 y3 z3, x1 y1 z1)))"^^geo:wktLiteral . Degree to which a rooftop activation type contributes to addressing an urban challenge. Rooftop-Challenge Association A specific activity or service performed on a rooftop, such as water retention, food production or energy generation. An activation type is realised through one or more functions. Rooftop Function Classification of a rooftop by its geometry, which determines which activation types are physically feasible. Rooftop Type Agricultural and undeveloped land within the wider urban region. Rural Areas Uneven access to services, facilities and safe shared spaces, and spatial separation of social groups between neighbourhoods. Social Inequality and Segregation Challenge Buildings whose dominant construction material is the one named. Steel Develops supply, demand or technology in the rooftop activation market beyond a single project. Stimulating Market or Innovation Buildings whose dominant construction material is the one named. Stone A secondary concentration of activity within the urban area. Sub-center In the lower-density belt surrounding the urban core. Suburban Location Congestion, pressure on public space from parking, and lack of infrastructure for walking, cycling and shared mobility. Sustainable and Equitable Mobility Challenge Built in place, requiring individual structural assessment before rooftop loads are added. Traditional Low recycling and material reuse, and resource flows such as waste and water that are managed linearly rather than kept in use. Transition to a Circular Economy Challenge Districts with no current active function. Unused Vacant, derelict or awaiting-development land. Unused Areas Compact residential fabric with limited open space. Urban residential district A structural problem faced by a city that rooftop activation can help address. Used to link owner and district priorities to suitable activation types. Urban Challenge The intensity of built form and population in a district. Urban Density Compact residential fabric with significant integrated greenery. Urban Green residential district Environmental and social conditions that harm physical and mental health, such as poor air quality, noise, loneliness and lack of green space and facilities. Urban Health and Well-being Challenge Within the continuous built-up fabric of a city. Urban Location The most compact built fabric, with continuous, tall building blocks and almost no open space at ground level. Very High Density The tallest buildings, where wind, evacuation and structural constraints dominate feasibility. Very High Rise Sparse, scattered built form dominated by open land, typical of peri-urban and rural edges. Very Low Density A formerly independent settlement absorbed into the urban area. Village Center Requirements on the resistance of rooftop elements to wind, scaling with building height and exposure. Wind Load Regulation Buildings whose dominant construction material is the one named. Wood Contemporary construction, typically insulated, code-compliant and most readily adapted for rooftop use (> 2000). After 2000 Alejandro Morales Hernandez mailto:alejandro.morales.hern2014@gmail.com Alejandro Morales Hernandez ULB Universite libre de Bruxelles Declining abundance and diversity of species in the city. Abundance of species Housing costs that rise faster than incomes, placing adequate housing out of reach for a growing share of residents. Affordability crisis The Brussels-Capital Region, Belgium, used as the geographic scope for the incentives it implements. Brussels Loss of the continuous green and blue connections that allow species to move through the city. Decline of ecological corridors Limited capacity of the city and its green infrastructure to withstand prolonged dry periods. Drought resistance The city of Dublin, Ireland, used as the geographic scope for the incentives it implements. Dublin Electricity grids that lack the capacity or coverage to support the charging demand of electric vehicles. Electric grid for charging EV Poor energy performance of the building stock, and the need to reduce its energy demand. Energy-efficient buildings Production of energy on the rooftop, for example with photovoltaic panels, solar thermal collectors or small wind turbines. Realises the yellow activation type. Energy generation function Exposure of the city to flooding from heavy rainfall, rivers or the sea. Flood risk Growing food on the rooftop, for example in open-air gardens, urban farms or greenhouses. Realises the green activation type. Food production function Competition for limited space between food production and habitats for biodiversity. Food security vs biodiversity Division of natural habitats into small, isolated patches that cannot sustain viable populations. Habitat fragmentation Lack of low-carbon heat sources to replace fossil fuel heating. Heat/lack of heat sources A gap between the size, type or location of available dwellings and the needs of households. Housing mismatch An insufficient number of dwellings to meet the demand of the population. Housing shortage Using the rooftop for inhabited built space, such as housing, offices or other extensions. Realises the purple activation type. Human occupation function The Île-de-France region, France, including Paris, used as the geographic scope for the incentives it implements. Ile de France Pollution of rainwater, surface water or groundwater, and the need to improve its quality. Improve water quality Difficulty in introducing shared mobility systems, such as bike, scooter or car sharing. Introducing sharing systems Energy networks that cannot absorb new loads or feed-in from local generation because of capacity limits. Lack of (energy) network capacity Insufficient public or private resources to implement urban strategies and projects. Lack of funding Insufficient green space and sport facilities within reach of residents. Lack of green space, sport facilities Insufficient public facilities, such as community, educational or care services. Lack of (public) facilities Insufficient shared mobility services and the infrastructure, such as hubs and docking stations, needed to support them. Lack of shared mobility services and infrastructure Insufficient capacity to store energy, limiting the integration of intermittent renewable generation. Lack of storage capacity Shortage of safe, accessible shared spaces outside home and work where people can meet. Lack of third spaces, social safety/security Insufficient water availability to meet the needs of residents, activities and green spaces. Lack of water Using the rooftop for the handling, storage or delivery of goods, including delivery hubs and drone landing. Realises the orange activation type. Logistics functions Social isolation and low subjective well-being among residents. Loneliness and happiness Low share of waste that is collected separately and recycled. Low recycling rates The city of Mannheim, Germany, used as the geographic scope for the incentives it implements. Mannheim Limited reuse of building materials and products, which are discarded instead of kept in use. Material reuse gaps The city of Mechelen, Belgium, used as the geographic scope for the incentives it implements. Mechelen Prevalence of mental health problems linked to urban living conditions. Mental health problems Using the rooftop for mobility, such as vehicle or bicycle parking and electric vehicle charging. Realises the orange activation type. Mobility functions Spatial separation of social, economic or ethnic groups between neighbourhoods. Neighbourhood segregation Absence of a common framework to collect, share and monitor data on urban interventions and their effects. No framework for data and monitoring Absence of a regulatory framework that makes it possible to enforce adopted urban strategies. No regulation framework to enforce strategies Exposure of residents to harmful levels of noise from traffic, industry or other sources. Noise pollution Water, energy and transport systems that are obsolete and poorly suited to current and future demands. Outdated water, energy, and transport systems Pressure on public space from demand for vehicle parking. Parking demand in public space Concentrations of air pollutants that harm the health of residents. Poor air quality Inadequate infrastructure for walking and cycling. Poor slow mobility infrastructure Heritage protection rules that prevent or delay retrofits and installations needed for the climate transition. Protection of cultural heritage blocks climate transition Covering the rooftop with vegetation to support biodiversity, reduce heat and provide visual or recreational amenity. Realises the green activation type. Provide vegetation for biodiversity, cooling and amenity Slow uptake of renewable energy production in the city. Renewable energy adoption Low reuse of rainwater, which is drained away instead of being stored and used. Reuse rainwater The city of Rotterdam, the Netherlands, used as the geographic scope for the incentives it implements. Rotterdam Insufficient supply of social or subsidised housing for low-income households. Social housing Using the rooftop as a space for gathering, recreation, sport or cultural activities. Realises the red activation type. Social use function Fragmentation of responsibilities across administrations and levels of government, hindering coordinated action. Split of competences Difficulty in handling stormwater volumes, leading to overloaded drainage systems and runoff. Stormwater management challenge Capturing and slowing down stormwater on the rooftop to reduce peak runoff into the drainage system. Realises the blue activation type. Stormwater management function Road traffic volumes that exceed network capacity, causing delays, emissions and noise. Traffic congestion Heritage protection rules that limit the installation of energy systems, such as solar panels or heat pumps, on protected buildings. Transformation (heritage) restriction for energy systems Heritage protection rules that limit the conversion, extension or densification of buildings for housing. Transformation (heritage) restriction for housing Waste collection systems that are inefficient or poorly suited to separation and recovery of materials. Trash collection systems Uneven distribution of services and facilities, leaving some groups or areas underserved. Unequal access to services/facilities Higher temperatures in dense urban areas than in their surroundings, caused by built surfaces and lack of vegetation. Urban heat islands Using the rooftop for technical installations, such as building services equipment, telecommunications antennas or network infrastructure. Realises the gray activation type. Utilities and infrastructure functions Overflow of sewer and drainage systems during heavy rainfall, discharging untreated water instead of retaining or reusing it. Water overflow Storing rainwater on the rooftop for later use, infiltration or evaporation. Realises the blue activation type. Water retention function Technical, legal or financial advice provided to owners to assess and prepare a rooftop activation project. Advisory Service A programme that combines public grant money with private capital, using the public share to lower risk or cost for private investors. Blended Finance Program A rooftop activated for water management, retaining, storing or delaying stormwater. Defined class: membership is inferred from has_function. Blue Rooftop A debt security issued to investors to raise capital, repaid at maturity with periodic interest. Bond A grant awarded through a call for projects in which applications are ranked and selected against published criteria. Call for Projects or Competitive Grant A tax credit granted to citizens who make small investments in local rooftop or energy projects, for example through a cooperative. Citizen Micro-investment Tax Credit A clause in a lease, sale, concession or permit agreement that requires or rewards rooftop activation as a condition of the contract. Contractual Condition Instrument type grouping incentives set out in negotiated agreements or governance arrangements between public authorities, owners, developers or service providers. Contractual or Governance Instrument Collection of small contributions from many people, usually through an online platform, as donations, loans or equity stakes in a rooftop project. Crowdfunding Crowdlending and Crowd Equity Collection of ideas, rooftop offers, volunteer work or other contributions from the public to develop rooftop projects. Crowdsourcing Instrument type grouping incentives that provide repayable capital, where the recipient returns the principal, usually with interest. Debt Instrument A fee or charge levied on developers or owners, such as a development or impact charge, whose amount is reduced or waived when a rooftop is activated. Developer or Charge Fee An online platform that connects owners, providers, investors or users of rooftops, or manages the related processes. Digital Platform Service Instrument type grouping incentives that transfer non-repayable money or value directly to the recipient. Direct Transfer Instrument An obligation to report or publish information about a building or its rooftop, such as its activation potential or performance. Disclosure An agreement with an energy service company or similar provider that designs, finances and operates a rooftop installation, recovering its investment from the savings or revenues it generates. ESCO or Sustainability Agreement Instrument type grouping incentives that raise capital by pooling contributions from investors or citizens in exchange for ownership, returns or repayment. Equity or Collective Finance Instrument A guaranteed price paid for each unit of renewable energy fed into the grid from a rooftop installation, over a fixed period. Feed-in Tariff Instrument type grouping incentives delivered through the tax system. Fiscal Instrument A tax-based measure, such as a levy, fee or rate adjustment, that makes non-activated rooftops more costly relative to activated ones. Fiscal Measure A pool of capital managed to finance multiple rooftop activation projects. Fund A dedicated legal entity, such as a special purpose vehicle, set up to hold and channel capital into rooftop projects. Funding Vehicle A non-repayable sum awarded to fund a defined rooftop project, subject to conditions on its delivery. Grant A rooftop activated for utilities and technical infrastructure, such as building services, telecommunications equipment or network installations. Defined class: membership is inferred from has_function. Gray Rooftop A bond whose proceeds are earmarked for projects with environmental benefits, such as green, blue or solar rooftops. Green Bond A green bond issued for one or more specific green projects, where investors are exposed directly to the risk of those projects. Green Project Bond A green revenue bond, repaid from the revenues, fees or taxes generated by the financed projects rather than by the issuer's general balance sheet. Green Revenue Bond A rooftop activated with vegetation for biodiversity, cooling and amenity, or for food production. Defined class: membership is inferred from has_function. Green Rooftop Pooling of demand from several owners to buy equipment or services jointly, or to deliver a shared rooftop project, at lower cost. Group Purchases and Collective Project Collective bodies of apartment owners. Decisions require a qualified majority, which lengthens timelines. Home Owner Associations Social housing providers with large portfolios, long horizons and a public-interest mandate. It also includes Social Housing providers. Housing Corporations Owners of production and logistics buildings, typically holding large flat roofs. Industrial owner Campaigns, events or outreach that raise awareness of rooftop activation and engage owners and residents. Information or Engagement Instrument type grouping incentives that act by providing information, advice, recognition or tools to owners and intermediaries. Informational Instrument Pension funds, insurers and similar, seeking stable long-term returns at portfolio scale. Institutional Investors An investment fund that takes equity or quasi-equity positions in rooftop projects in expectation of a financial return. Investment fund A certification, label or award that recognises activated rooftops and can raise their visibility or market value. Label or Recognition Owners renting to occupants, subject to the split-incentive problem where the investor is not the beneficiary. Landlords Capital lent to an owner or project and repaid over time, usually with interest. Loan Maps and cadastres that show the activation potential of rooftops, for example for solar energy, greening or water retention. Mapping Tools A mechanism that allows rooftop activation to offset or be deducted from other obligations, such as required green space, parking provision or stormwater retention on the plot. Offset or Deduction Mechanism A loan for rooftop measures repaid through the owner's utility bill, typically sized so that the savings cover the repayments. On-bill Financing A variant of on-bill financing in which the capital comes from a third-party lender while repayments are collected through the utility bill. On-bill Repayment Financing repaid through a surcharge on the property tax bill, so that the repayment obligation stays with the property when it is sold. On-tax Financing A rooftop activated for mobility or logistics, such as parking, vehicle charging, delivery hubs or drone landing. Defined class: membership is inferred from has_function. Orange Rooftop Instrument type grouping incentives that act through spatial planning, strategies and public programmes. Planning Instrument A plan, strategy or policy document that sets objectives or priorities for rooftop activation in a territory. Planning or Policy A grant paid, fully or partly, before the works are carried out, so that the recipient does not have to advance the costs. Pre-financed Grant A single natural person owning and usually occupying the building. Short horizon, limited capital, simple decision. Private Individual Actors building for sale, deciding at design stage and rarely retaining ownership. Private Project Developers A programme or zoning rule that designates areas, targets or requirements for rooftop activation, such as a green area factor. Program or Zoning Approach A loan secured on and attached to the property rather than the borrower, so that the outstanding balance transfers with ownership. Property-linked Loans A long-term arrangement in which a public authority and private partners share the financing, delivery and risks of rooftop activation projects. Public-Private Partnerships A rooftop activated for human occupation, such as housing or other built extensions added on top of the building. Defined class: membership is inferred from has_function. Purple Rooftop Professional property-owning organisations. Real Estate Real estate held by companies for their own operations or as an asset. Corporate Real Estate Owner Real estate held by a local authority, where public objectives may outweigh financial return. Municipal Real Estate Owner A rooftop activated for social use, such as meeting, recreation, sport or cultural activities open to a community or the public. Defined class: membership is inferred from has_function. Red Rooftop A binding rule that requires, permits or forbids rooftop activation, such as a mandatory green or solar roof for new buildings. Regulation Instrument type grouping incentives that act through binding rules, obligations or prohibitions. Regulatory Instrument Faith organisations, often owning heritage buildings with limited capital and community-oriented objectives. Religious Institution Use of rooftop space or equipment through a rental or lease, for example an owner leasing the roof to a solar operator or leasing an installation instead of buying it. Renting or Leasing A revolving fund in which repayments and returns from earlier projects are reinvested in new ones. Revolving fund A credit line that the borrower can draw, repay and draw again up to an agreed limit. Revolving Credit A secured green bond, backed by collateral from one or more green projects, such as the installations or their cash flows. Secured Green Bond A green bond with recourse to the issuer's full balance sheet, whose proceeds are allocated to eligible green projects. Standard Green Use of Proceeds Bond A fund or company in steward ownership, where control stays with people connected to its mission and profits are bound to that purpose rather than distributed to shareholders. Steward-Owned A recurring payment or price support that reduces the cost of, or raises the return on, an activated rooftop during its operation. Subsidy A reduction or exemption of taxes, or a reduced VAT rate, granted automatically for eligible rooftop works or installations. TAX or VAT Incentive An amount deducted directly from the tax owed by an eligible taxpayer who invests in rooftop activation. Tax Credit Tools that help owners and professionals identify, assess or plan rooftop activation. Tools Instrument type grouping incentives that give access to rooftop space, equipment or services without full ownership or up-front purchase. Use or Access Instrument A voucher of fixed value that an owner can redeem for eligible goods or services, such as a feasibility study or an installation. Voucher A rooftop activated for energy generation, typically with photovoltaic or solar thermal installations. Defined class: membership is inferred from has_function. Yellow Rooftop 1830 1918 1919 1945 1946 1975 1976 2000 2000 1830