A living cycle
NASA describes the continuous movement of water between soils, vegetation and the atmosphere. WaterRoofs aims to reintroduce part of this circulation on built surfaces, complementing nature.
Patented concept · Extruded recycled PET compositeWhat if every roof
What if every roof
returned water
to the sky?
A patented roofing platform made by extruding recycled PET composite: retaining rainwater, replenishing channels, supporting evaporation and accommodating additional functions.
A PATENTED MULTIFUNCTIONAL PLATFORMDESIGNED IN SWITZERLAND · VISION 2026
01 Evaporation with water replenishment
02 Independent fire protection circuit
03 Clip-on photovoltaics
04 Reversible micro wind turbine
01 / Our visionReconnecting buildings
Reconnecting buildings
with the living world.
A roof can do more than shelter us. It can reclaim a place in the natural water cycle.
Built surfaces drain rainfall rapidly and limit the evaporation that previously occurred from soil and vegetation. WaterRoofs proposes temporarily retaining some of this water and gradually returning it to the atmosphere.
Our mission: connect architecture and ecology, reduce roof heating and develop more resilient buildings. The system complements vegetation and permeable soils while making use of surfaces already built.
THE SCALE OF THE OPPORTUNITYA roof can reconnect
A roof can reconnect
the city with water.
In nature, rain is retained by soils and vegetation before some of it returns to the atmosphere. On conventional roofs it is generally drained away quickly. WaterRoofs aims to retain some of this water and return it gradually through evaporation.
286,393 km²Estimated global rooftop area
A 2025 scientific study estimated the total area of rooftops worldwide. This is an estimate of all rooftops, not a measurement of dry roofs or of the area suitable for WaterRoofs.
Read the study in Nature Climate Change ↗
Nature, a conventional roof, WaterRoofs
Three paths for rainwater: retention and evapotranspiration in nature, rapid drainage from a conventional roof, and temporary retention followed by evaporation on a WaterRoofs roof. The illustration summarises this idea.
Our V8 presentation also uses a working estimate of 360,000 to 380,000 km² of existing rooftops to explore scenarios towards 2050–2060. This estimate still needs precise documentation; the study above uses a different method. Doubling and adoption on 100% of new roofs are WaterRoofs scenario assumptions.
This illustration presents the WaterRoofs vision: giving roofs an active role in the water cycle.
WATERROOFS · SCIENCE & WATERThe ground beneath the house.
The ground beneath the house.
A function recovered on the roof.
Before construction, soil and vegetation retained some rainfall and returned water to the atmosphere. WaterRoofs brings part of that function onto the roof: collect water, retain it temporarily and let it evaporate progressively.
Globally, each roof can become part of the response. Actual effects depend on the area equipped, climate, available water and measured performance.
An urban challenge
A study of 25 major urban agglomerations links changes in evapotranspiration with drier or more humid urban air. Effects vary by climate and location.
Water carries heat
Evaporation requires energy: it can limit immediate heating of the roof and contribute to local cooling. The design target is 1.6 to 2 litres per m² per day under favourable conditions.
Explore the scientific sources : The water cycle — NASA ↗ · Urbanisation and evapotranspiration — Hao et al., 2023 ↗
Evaporation is part
of the cycle of life.
Natural purification
As water evaporates, it separates from salts and many non-volatile substances. This stage contributes to natural purification within the water cycle; it does not make the water remaining on the roof drinkable.
USGS source ↗The role of plants
Plants absorb water through their roots and return some through transpiration. This movement supports essential physiological functions and connects soil, vegetation and the atmosphere.
USGS source ↗Animals and people
By helping renew freshwater, the water cycle supports habitats, food supplies and the lives of animals and people.
NOAA source ↗WaterRoofs aims to restore a water-retention and evaporation function to built surfaces, complementing soils and vegetation. This ambition belongs within the living water cycle; its local effects on water, climate and ecosystems remain to be measured.
A built desert to reconnect to the water cycle
Our WaterRoofs board uses 3 million km² as a reference to illustrate the global built footprint: roads, buildings, quays, factories and other infrastructure. This scale, comparable to the area of India, concerns infrastructure as a whole, not rooftops alone.
The image of a “built desert” describes surfaces designed to drain rainfall rapidly, where water retention and its return through evaporation and transpiration are greatly reduced. WaterRoofs aims to restore part of this function on rooftops, complementing soils and vegetation.
The 3 million km² figure is the presentation reference adopted in our board, distinct from the scientific estimates of rooftop area cited above.
Dry air, stomata and CO₂ uptake
Very dry air increases atmospheric demand for water. To limit water loss, plants may close their stomata: CO₂ entry and photosynthesis decline, even when water is still available in the soil.
Respiration continues to release CO₂. If these emissions exceed photosynthetic uptake, the plant can become a net emitter over the period considered. Stomatal closure therefore does not automatically cause net CO₂ release.
This connection between water and carbon strengthens the case for studying moisture exchanges on built surfaces. WaterRoofs’ effects on humidity around leaves and on their CO₂ uptake will need to be measured.
Dry air and photosynthesis ↗ · Photosynthesis and respiration ↗
A protected idea.
A transformed material.
WaterRoofs is a patented multifunctional roofing concept. Its tile is manufactured by extruding a recycled PET composite.
The process uses the same industrial principle as the construction system UHCS ↗ : shaping the recycled composite through a die to obtain a continuous profile. The profile geometry combines water-retention grooves and the passages required for the roof’s functions.
A smooth surface, protected by a gel coat
The tiles will be covered with a protective gel coat whose colour can be chosen to suit the project’s architecture.
The smooth PET surface and its finish offer fewer footholds for mosses and small organisms than porous or rough surfaces. Regular maintenance helps preserve the roof’s cleanliness and operation.
The freedom to choose a colour
White, light shades or colours suited to the building: the gel coat allows the roof’s appearance to be customised. Final shades and finishes will be defined with production.
Illustrative palette — not a commercial colour chart.
Favouring white and light colours
With comparable finishes, white or light colours generally reflect more solar radiation and limit roof heating. They can therefore reduce heat transferred into the home in summer and help limit urban heating, alongside evaporation.
The effect depends on the coating’s reflectance and emissivity, soiling, insulation and climate. The annual balance must be assessed for the building.
Understanding reflective roofs — Berkeley Lab ↗ARCHITECTURE & THE ROOFA different line.
A different line.
The same harmony.
WaterRoofs fits naturally into the architecture of a home. The difference is in the direction of the roof lines: a discreet change that complements the building’s design.
Left · Traditional roofLines follow the slope of the roof.
Right · WaterRoofs roofHorizontal lines run perpendicular to the slope.
WaterRoofs Overview / The complete systemA complete system.
A complete system.
On a single roof.
From recycled material to climate-responsive roofing: an overview of evaporation, solar power, the fire protection circuit and the reversible wind turbine.
02 / One roof. Multiple functions.One platform,
One platform,
four possibilities.
Explore the WaterRoofs architecture and its modules. Select a function to understand its role.
The grooves follow the roof’s horizontal lines, perpendicular to the slope.
Retain. Evaporate.
Replenish.
The channels do not depend solely on the latest rainfall. Replenishment from the tank allows their function to continue during hot periods, subject to water availability.
Collect rainfall
The WaterGrooves, transverse grooves in the profile, retain a shallow layer of water. The profile’s relief also contributes to self-shading of the dry surface.
Store the surplus
Above the working level, overflows and bypasses direct water to a storage tank. This reserve supplies replenishment and, depending on the project, irrigation.
Evaporate gradually
Evaporation absorbs heat and returns moisture to the air. Its rate depends on temperature, wind, humidity and sunlight.
Replace evaporated water
A low-power pump and ridge distributor replenish the channels. Controls adapt the supply to water levels and weather conditions.
6–8 L/m²Target temporary retention capacity
1.6–2.0 L/m²/dayTarget evaporation in favourable conditions
27 m/m²Total groove length
The values represent design targets; operation varies with climate and water availability.
Water-conscious management: priority for harvested rainwater, replenishment adjusted to demand and the option to stop when water is scarce. A level threshold protects the fire reserve, which is not used for climate-system replenishment.
From the profile
to the ridge.
Two complementary design illustrations show how water could be retained across the roof and how independent water and fire circuits could be supplied from the ridge.
These illustrations present the profile and ridge designed to integrate the two circuits into the roof. Sizing and connections are adapted to each project.
Retain, distribute, protect
An extruded profile brings together water-retention grooves and a separate pressurised fire circuit. Overflow and bypass features are intended to regulate water between the transverse grooves; the reference fire projection concept uses a longitudinal slit.
A ridge that connects both slopes
A modular ridge distributor is intended to feed the climate circuit at low pressure or by gravity and separately supply the pressurised fire circuit across both slopes. Its geometry, connections and seals are design proposals.
02
Fire protectionTwo circuits.
Two purposes.
The blue circuit supports evaporation. The red circuit is designed for active protection against an external fire, with an independent supply and pump.
A protected reserve, targeted application
The fire network has a reserved volume of water. The concept provides for water and a fire protection product, including a powdered polymer mixed with water on activation to form a hydrogel.
- Circuit routed through the hollow profile, separate from the climate network.
- Updated concept: projection through a continuous longitudinal slit, with a preferred prototype variant of 3.5 mm.
- Reference 6 m profiles supplied from both ends.
- Distribution to be studied for roofs, ridges, gutters and eaves; extension to façades depending on the project.
The fire protection circuit is sized and its performance established with specialists in accordance with each project’s applicable requirements.
03
Solar energyThe sun generates power.
Water cools.
Photovoltaic panels clip onto an interface adapted to the WaterRoofs profile. The roof becomes a mounting platform, with a ventilated space beneath the modules.
Layering functions, keeping air moving
Panel shade limits direct radiation on dry areas. On wet areas, ventilation and evaporation interact with the microclimate beneath the panels.
- Recommended design clearance of at least 6 cm beneath the modules.
- Clip-on fixings, maintaining access for maintenance and drainage.
- Natural ventilation retained, with optional assistance from the reversible wind module.
- Integration to be sized for the site’s wind and snow loads.
Shade and airflow around the panels contribute to the system’s thermal management.
04
Clip-on micro wind turbineWith the wind.
Or to move the air.
An optional reversible module combines electricity generation and on-demand ventilation. One or two units may be considered depending on the roof and its exposure.
One rotor, two modes
Generator mode. Wind drives the rotor to generate local electricity, complementing photovoltaics. Potential depends on actual wind conditions, turbulence and equipment characteristics.
Ventilation mode. Powered by electricity, the rotor creates airflow directed over the wet channels and beneath the panels. It aims to replace humid air, accelerate evaporation when useful and enable drying.
The proposed controls take account of temperature, humidity, water level, rain and wind. Ventilation activates when the expected benefit justifies its energy consumption.
The reversible system combines electricity generation and ventilation, with integration adapted to the building.
04 / Impact & commitmentRestoring a climate role
Restoring a climate role
to the roof.
Evaporative cooling can reduce surface heating when air conditions and available water allow. At neighbourhood scale, the contribution to humidity and the thermal balance must be assessed locally.
WaterRoofs connects rainfall, storage, use and evaporation, helping return water to atmospheric circulation.
Transparency
Share our methods, data and development results with our partners.
Circularity
Extrude recycled PET composite profiles using the same industrial principle as UHCS, with a colourable protective gel coat finish. Durability, reuse and material regeneration are part of the validation programme.
Responsibility
Design for ecosystems and future generations. Assess water requirements, materials, energy and maintenance conditions together.
Consider the cost
of the whole system.
WaterRoofs’ economic value is best understood by assessing the roof and solar fixings together.
The extruded profile is designed to accommodate several functions on one platform. Clip-on panel fixings aim to reduce additional mounting structures and roof penetrations, while modularity can simplify installation.
Assess your project’s cost ↗Cost items to compare
- Roofing composite, extrusion and finish.
- Labour, fixings and roof-edge details.
- Water circuit, storage, pump and accessories.
- Additional equipment: photovoltaics, fire protection and wind turbine.
Cost depends on area, country, production volumes and selected functions. Estimates must compare systems of equivalent scope, including accessories, installation and maintenance.
What does the estimated 31% saving mean?
The working presentation includes an indicative saving of 31% for the combined roof and photovoltaic system. This is a working assumption to be updated with supplier quotations and local installation costs. It is neither a price nor a guaranteed saving for any project.
Measure to deploy.
The platform is designed to be studied on conventional structures as well as with the construction system UHCS ↗. An instrumented demonstrator should allow water, climate, energy and protection to be validated together.
Testing covers retention, watertightness, flow rates and overflows; evaporation and temperatures; fixings and loads; fire; UV and freeze-thaw; water quality and maintenance.
How can prolonged stagnant water be avoided?
Sizing must allow channel water to be renewed, drained and cleaned. Filtration, biofilm control, mosquito prevention and maintenance access are part of the design. Storage must be enclosed and maintained.
What happens during drought or freezing weather?
During drought, controls must reduce or stop replenishment according to available resources while protecting the fire reserve. In freezing weather, a drainage and network protection strategy must be validated for the local climate.
What are the reference geometry parameters?
Nominal profile width: 33 cm, or approximately three profiles per metre. Reference module: 6 m, with 8 or 12 m variants. Transverse grooves approximately 1.5 cm wide and at least 4.5 cm deep. The working water level is around 1 to 2 cm, with overflow and bypass. These parameters remain design targets.
Are all four functions required?
The water cycle is the core function. Photovoltaic panels, the reversible wind module and the fire protection circuit are complementary functions to be configured and validated according to the building, its exposure and local requirements.
Understand the challenges.
Share ideas.
Journal & insights
Explore the WaterRoofs journal
75 articles on water, climate, architecture and circular materials.
Read the journal ↗Explore articles from the original website on the water cycle, architecture and climate adaptation.
INSIGHT · ARTICLE IN ENGLISH
Designing for 2050 – What Rooftops Must Do in a +2°C World
Read the article ↗INSIGHT · ARTICLE IN ENGLISHCities as Climate Systems – Why Rooftops Are Infrastructure, Not Architecture
Read the article ↗INSIGHT · ARTICLE IN ENGLISHWorld Water Cycle Awareness – The Missing Link Between Rain, Cities, and the Sky
Read the article ↗Browse all 75 articles
- Designing for 2050 – What Rooftops Must Do in a +2°C World
- Cities as Climate Systems – Why Rooftops Are Infrastructure, Not Architecture
- World Water Cycle Awareness – The Missing Link Between Rain, Cities, and the Sky
- From Heatwaves to Cold Spells – Why Climate Extremes Require Adaptive Roofs
- Plastic, Water, Climate – How Circular Materials Can Repair the Atmosphere
- Water Scarcity & Urban Design – Why Evaporation Is Part of Water Security
- Architecture After 2025 – What Climate Science Now Demands from Buildings
- Dry Air Season – Why Winter Humidity Loss Is a Climate Problem (Not Just a Comfort Issue)
- New Year, New Water Cycle – Why Cities Must Start 2026 by Rethinking Rooftops
- 📆 Year in Review – Rooftop Innovation & Momentum
- 🎁 Holiday Reflection – Climate Gifts from Rooftops
- 🌓 Solstice Relief – Rooftops & the Year’s Shortest Day
- 🧐 Humidity Collapse – When the Air Dries, Climate Breaks
- 🌞 Solar Impulse Foundation Endorses WaterRoofs – A Recognized Efficient Solution
- 🌍 COP30 – WaterRoofs in the Global Climate Conversation
- 🌪️ Typhoon Lessons – Climate Extremes From the Philippines to Our Rooftops
- 💧 Water Evaporation 101 — The Invisible Climate Engine Cities Forgot
- ❄️ Antarctica Day – Roofs at the Edge of Climate
- 📚 Architecture & Nature – A Philosophical Reflection
- ❄️ Winter Dryness & Humidity Balance – Rooftops that Care Indoors
- 👧🌍 Children & Climate – Designing Cities for the Next Generation
- 🌧️ Rain Returns – How WaterRoofs Performs in Autumn Storms
- 👨 Movember & Men’s Health – Climate, Heat, and Wellbeing
- ♻️ Plastic Policy & Construction – How WaterRoofs Meets Circular Goals
- 🏙️ Rooftops for the Next Urban Era: Rethinking Infrastructure on World Urbanism Day
- 🍂 Seasonal Transition: From Evaporation to Insulation
- 🌊 Tsunami-Safe Coasts & Rooftops – Rooftops in Extreme Environments
- ⚡ Energy Savings Season – Evaporation vs. Heating Costs
- 🌆 World Cities Day: Cool, Resilient, Sustainable
- ♻️ Plastic Waste in Construction – From Problem to Solution
- 🍂 Autumn Rains, Urban Gains – Capturing Seasonal Water with WaterRoofs
- 🏠 World Habitat Day: Rooftops for Resilient Habitats
- 🌍 A Roof for the Future – How WaterRoofs Aligns with the UN SDGs
- 👩⚕️ The Human Side of Cooling – Evaporation and Public Health
- 🏛️ Architecture as Climate Action – Why Every Building Must Give Back
- ☁️ From Rooftop to Rainfall – How WaterRoofs Supports Local Climate Stability
- 🔥 The Urban Heat Island Effect – and Why Rooftops Are the Frontline Solution
- Turning Plastic Waste into Climate Infrastructure
- 💧 Rooftops and the Water Cycle – Restoring What Cities Have Lost
- 🌡️ Cooling Cities Naturally – How Evaporation Outperforms Air Conditioning
- ♻️ Behind the Material: How PET Tiles Are Engineered for Climate Impact
- 💧 Designing with Water: Reintroducing Evaporation in Urban Planning
- 💡 The Missing Link: How Evaporation Reduces Urban Energy Demand
- 🏗️ WaterRoofs in Modular Construction: Climate-Tech Meets Modular Revolution
- 🎙️ Q&A with Igor Ustinov: Designing a Rooftop That Breathe
- 💨 Evaporation’s Hidden Benefits: Health, Air Quality & Urban Wellbeing
- 🌳 Blue–Green Infrastructure Pairings: Supercharging Urban Resilience with WaterRoofs
- 📅 July 2025 Climate Round‑Up: Heat, Water Stress & Why WaterRoofs Matters
- 🔥 Heatwave Response Tech: How WaterRoofs Helps Cities Cool as Europe Sizzles
- 🔏 Patent & Scale: Why Intellectual Property Matters in Climate Tech
- 🛠️ From Prototype to Pilot: WaterRoofs Takes the Next Step
- ♻️ From Plastic Waste to Climate Innovation: How WaterRoofs Turns Trash into a Rooftop Revolution
- ☀️ Evaporative vs Reflective Roofing: Which Cooling Strategy Delivers on Climate?
- 🏙️ Rethinking Rooftops: The Future of Urban Planning
- 💧 Cities Are Built to Drain – But They Should Be Built to Evaporate
- ☀️ 2025 to 2029: As the World Heats Up, the Coolest Solution May Be Right Over Our Heads
- 🏛️ Why Rooftop Design Belongs in Climate Policy
- 🌿 Designing for Rain: Biomimicry Lessons from Forest Canopies
- Rain Isn’t the Problem – It’s What Cities Do With It
- ❄️ Cool Roofs Are Not Enough: Why We Need Evaporative Roofs
- 🏛️ What the EU’s New Water Directive Means for the Built Environment
- 🌧️ Urban Flooding vs. Urban Drought: The Twin Crises Shaping Europe’s Cities
- 🌍 World Environment Day 2025: Ending Plastic Pollution and Rethinking Urban Design
- 🌧️ Comparative Analysis of Sustainable Roofing Systems: Water Capture and Evaporation Performance
- 🧩 Modular by Design: The Technical Architecture of WaterRoofs
- 🔏 Patenting Sustainability: How Igor Ustinov’s WaterRoofs System Redefines Climate Innovation
- 🌫️ The Invisible Impact: Why Restoring Evaporation Matters for the Climate
- 🔄 From Waste to Weather: The Climate Impact of Recycled PET in Construction
- 🌆 Why Rooftops Matter: The Untapped Potential of Urban Surfaces
- Europe’s Climate Crisis: How WaterRoofs Can Help Cities Adapt to Record Heat and Rainfall
- Honoring Innovation: Igor Ustinov, Inventor of WaterRoofs and UHCS, Joins Jury at Geneva Inventions Expo
- Innovative Materials in Sustainable Roofing: The WaterRoofs and UHCS Collaboration
- Harnessing Evaporation to Regulate Climate
- Transforming Urban Rooftops into Forest-Mimicking Systems
- Predictive Analytics for a Sustainable Future
Historical articles remain available in their original versions. The technical description here reflects design developments in 2026.
Building this transition
together.
Igor UstinovFounder and inventor · CEO & President
Jean-Luc MossierBoard member & CFO
Hans-Ulrich SiegenthalerPlastics industry expert
Alain BrogliLegal & licensing
Ali TasbasiCorporate finance
Brahim TasliIntellectual property
Team as presented on the existing WaterRoofs website.
Partners & pilot projects
Architects, local authorities, industry partners and researchers: let’s contribute to practical testing, demonstrators and solutions adapted to each region.
Join the initiative
Environmental engineering, materials, installation, climate or research: specialists, students and collaborators are invited to get in touch to explore a contribution.
Propose a collaboration ↗Your next roof could
take on a new role.
A project, a demonstrator or an industrial partnership? Let’s discuss the possibilities of WaterRoofs.
info@waterroofs.com ↗