What is a “Cool Roof”?
Literally, a cool roof.
We call a Cool Roof a roof whose white colour reflects the heat into space, thus reducing air-conditioning needs.
A white roof accumulates 10 times less heat than a dark roof.
This principle has been well-known in hot countries for years, like in Greece or Morocco for instance.
In the USA, the principle has also developed largely, after the governmental impulsion in the 2000s that estimated that painting roofs white would save up to 750 million dollars/year (Heat Island Group, US government).
Understanding Cool Roof in 2 minutes
How does Cool Roof France go further than a simple Cool Roof?
The Cool Roof France coating is more than just white paint.
It’s reflective AND thermal.
In other words, it contains components that reflect the sun’s radiation more than normal paint.
And components that considerably slow down the transmission of heat (4x more than traditional paint).
In the summer, the sun’s heat penetrates the building less, so there’s less need for air-conditioning.
Why focus on the roof?
30% des fuites énergétiques d’un bâtiment passent par le toit.
30% of a building’s energy leaks go through the roof.
Installation on a roof is easy and quick.
In France alone, there are 50 million m² of commercial roofs that are over 10 years old.
Most of these have huge energy leakages and are thus expensive to heat and air-condition.
If Cool Roof France managed to cover 1/10th, it would be a huge ecological and economical success!
What are your main creations?
The first full creation occurred on the roof of the E.Leclerc in Quimper (7,000 m²) before the summer 2015.
This was the first Cool Roof in France and it was fully equipped.
Cool Roof France also painted a container that was already white, to compare white vs CoolRoof white.
Several worksites were carried out in 2017 such as those with the group Crédit Mutuel Arkea, the Boulanger store, the city council of Quimper and Paris city council and other operators of large retail notably.
What are the main advantages of Cool Roof France coating?
– It lowers energy bills: for example the property manager of E.Leclerc noticed that his bill was reduced by over 15 %, meaning he saved 20,000 euros in one year.
– It increases the roof’s lifespan while protecting the membrane from solar damage.
– You can continue to use the building while we apply our Cool Roof France solution.
– It’s self-cleaning: dirt doesn’t get incrusted, brushing it every 2-3 years is sufficient to get rid of it.
– It improves your carbon footprint.
– It is far less expensive than other insulation: since it is light, it does not affect the structure of your building.
Quels sont les principaux avantages du revêtement Cool Roof France ?
– Il diminue la facture d’énergie : par exemple le gestionnaire du bâtiment du E.Leclerc a vu sa facture diminuer de plus de 15%, soit 20,000€ en 1 an.
– Il augmente la durée de vie du toit en protégeant la membrane des agressions solaires.
– Vous continuez à utiliser votre bâtiment pendant que nous appliquons notre solution Cool Roof France .
– Il est autonettoyant : les salissures ne s’incrustent pas, un simple coup de brosse tous les 2-3 ans suffit à les faire partir.
– Il améliore votre bilan carbone
– Il coûte bien moins cher qu’une autre isolation : comme il est léger, il n’oblige pas à réviser votre charpente.
How does a Cool Roof work in the winter?
Solar radiation is not the same in winter and summer. In the winter, radiation is lower than in the summer: so on a flat roof, solar thermal INPUT does not pass mainly through the roof, but through windows and walls. What’s more, sunrays are less “strong” and frequent (clouds) in the winter.
The roof however (if it isn’t well-insulated) will be the main cause of heat LOSS (because heat goes up).
Our coating will partially stop the heat transfer.
In short, the Cool Roof France coating is an efficient complement to reinforce insulation.
What IRR – Internal Rate of Return – can I expect if I carry out a Cool Roof?
Example of the E.Leclerc in Quimper: “service pack” = application at 18€/m2 plus annual maintenance 2€/m2 during 10 years
– Initial roof: 7000m2, 1988 sandwich corrugated steel bitumen two layers
– Date the Cool Roof France elastomer coating was applied = June 2015
– Initial Investment = 18€/m2 = 126k€ for 7,000m2. This represents 13k€/year amortisation for the product’s lifespan (10 years)
– Annual consumption savings observed of 20k€/an.
– Savings linked to cost of kWh (which increases by 3% every year)
– Savings linked to cost of roof maintenance (1k€/m2/year = 7k€)
– Creation of a maintenance cost (approx. 1,5€/m2/year for a classical contract, 2€/m2 for a “Service pack” contract indicated here by Cool Roof France that guarantees 100% of the efficiency of the package)
On what surface materials can the Cool Roof France coating be applied?
The Cool Roof France solution can be applied on most common materials: bitumen two layers, corrugated steel, but also asbestos.
However it cannot be applied on: EPDM, PVC, TPO.
What is the guarantee of efficiency and durability?
The product has been tested in an ageing room without any degradation over 3,600 hours of exposure.
There is a completion bond after application and Cool Roof France commits to a goal of 10 years of general stability.
For maximum efficiency, it is recommended to clean the roof regularly (see following point).
Any maintenance tips?
Mushrooms and moss will not develop on the coating.
However, this does not stop dust from settling on the roof.
To optimise the performance and stability over time, simply brushing it every two years suffices to go back to the initial colour and extend the resin’s lifespan. According to the location of the roof, notably if it’s close to a motorway, an annual visit can ensure the roof remains perfectly white.
What is the ecosystem of Cool Roof France?
Cool Roof France is a member of technopole Brest-Quimper, Greentech verte du MTES (French Ministry for the Ecological Transition Greentech), RespectOcean, CoolCoalition, Global Alliance for Buildings and Construction and is supported by the Région Bretagne.
Our technical and scientific partners: Arkema, A-Therm, Incub, CSTB, ATEE, Essor and Elementerre
Our scientific work for the conception of the coating is followed by a European laboratory; by the engineering school, école des Mines de Nancy, and by a biotechnology laboratory (CBB Capbiotek).
Several companies are technical partners of Cool Roof France (Corre peinture, A-Therm, Madec Electricité, BOPS, etc).
After applying this product, does the roof lose its initial fire safety certificate?
With our Broof T3 certification, Cool Roof France neither improves, nor degrades the existing fire safety certificate.
How waterproof are we? Can we intervene if there has been a rip or hole in the coating with a blowtorch?
Cool Roof France neither improves, nor degrades the existing waterproofing. In the event of damage after the application of Cool Roof, you can easily intervene on the roof to repair such damage and if needs be apply Cool Roof solution on the repaired area.
The roof DTU (French building code) specifies that waterproofing products or various products used must be recognised, is this the case?
Our Cool Roof is not a waterproofing solution so the DTU does not apply. Neither do CSTB (French Scientific and Technical Centre for Building) technical instructions, ten-year guarantees, and so on. Cool Roof France is viewed as a substantial and economical improvement solution of your energy footprint.
The ten-year guarantee applies to construction or real-estate works. Our offer is a resin, equipment that has a heat vocation, not structural, so it is not concerned by the ten-year guarantee.
EHowever, Cool Roof France offers a biennial guarantee that imposes us to repair or replace any element of equipment that does not function correctly, during a minimal duration of 2 years after installation.
Cool Roof France supplies a completion bond guarantee that imposes to repair any damage (hidden defects and conformity faults) signalled during the year following the end of works whatever their importance and nature.
Cool Roof France guarantees its CRF BC TC product and the application of the complex over a duration of 24 complete months starting from the date of work acceptance inspection.
The guarantee covers:
– The correct adhesion of the coating on the initial roof surface material.
– 25% maximum loss of reflectance in relation to an average of reflectivity measured at the work acceptance inspection in x random points of roofs via a reflectometer such as Réflectomètre 410-Solar Visible / NIR from Surface Optics
The guarantee can be effective as soon as Cool Roof France is aware of a defect, whether one of adhesion to the surface or loss of reflectivity.
Lastly, for example, after those 2 years, Cool Roof France can offer an annual maintenance contract.
What is the position of your product on the market compared to waterproofing products that are arriving?
– Our offer is not a waterproofing solution. We have noticed that our coating can fill in micro cracks up to 1.2 mm and thus contribute to better waterproofing but this is not one of our commitments. Our commitment regards the non-thermal transmission of your roof, in summer especially.
– Our offer is mainly designed for roofs of over 10 years of age, to give them several more years of life.
– Our product offers better reflectivity, emissivity (more than 90%) and durability on the market. Reflectivity tests of our product are certified by the European Cool Roof Council.
– Our offer is more cost-effective than most other solutions currently on offer (20€ ex. tax/m2 delivered and installed)
– The approach is simple and does not require to review the entire building‘s structure.
– Your clients can continue to shop in the store during works.
How does Cool Roof France meet regulatory requirements?
Whether you come within the framework of a new construction or an important renovation in France, two particular regulations apply:
– RT2012 for new buildings
– Rtex for existing buildings
In both cases, there are thermal performance objectives to reach (which are expressed in kWhEP/m2.year).
The legislator translates this thermal performance into calculation rules (ThBCE 2012 regulations of the RT2012 and Th-CE-ex of the existing RT) which do not “classify processes” but suggest various calculation factors including:
Heat flows* due to absorbed solar radiation
In the RT2012 (ThBCE 2012 regulations), calculations take into consideration heat flows due to solar radiation absorbed by opaque walls via a “solar factor” translating the reflectivity of the wall (see from page 331 onwards, specifically formula (452) on page 334).
The same applies for Th-CE-ex regulations of the RTExistant (refer to page 67 onwards).
In both cases, calculations take into account a solar factor of 0.8 for opaque horizontal partitions (meaning calculations consider by default that 80% of the solar radiation is absorbed by the partition and 20 % reflected). This parameter is accessible and thus adjustable in both modelling tools, if correctly configured. Applying a reflective coating on a partition will impact its solar factor: for example, in the case of Cool Roof France reflective coating, the partition will go from 80% absorption (given by default by the calculator) to 2.5% absorption, meaning a discrepancy of more than 65% (!). It is important that design offices in charge of calculations integrate the “coolroof” process to improve the calculated performance.
RT also mention criteria of “summer comfort” on which Cool Roof has a considerable influence. Excerpt:
“In order to limit the discomfort of occupiers and the use of air-conditioning, the renovated building must ensure acceptable summer comfort, in so far as what is possible according to existing building. Conventional inside temperature reached in summer must be lower than a reference temperature.”
What is the impact on CDAC (French departmental commission for commercial projects) and institutional relations?
The Cool Roof process is an additional argument for sustainable development to add to shop extension or construction applications (CDAC)
Multiple institutional engagements (Paris Agreements; PCET) hold Cool Roofing as a solution not only to limit urban greenhouse gas emissions, but also to limit effects of urban heat islands. We will soon undertake a Cool Roof for a very large French city within this mind-set. For example the city of Paris has summer comfort goals, and also holds the presidency of C40 that recommends the duplication of the New York Cool Roof initiative (see here).
But beyond regulatory aspects, it is in your interest to equip stores, like E.Leclerc in Quimper did, that are not being renovated for reasons of pure profitability (energy savings, extension of roof lifespan, and so on).
How does a Cool Roof increase my chances of certifications (LEED for example)?
In the framework of the LEED accreditation programme, of durability of construction, 7.2 2009 version, heat islands of a roof surface must include at least 75% of a material with solar reflectance index SRI of at least 78. Considering our SRI=112, Cool Roof France coating by far exceeds the LEED requirement.
Green roof or Cool Roof?
There are several scientific publications comparing Cool Roof / Green Roof.
Concerning heat protection, Cool Roofs are at least as efficient, if not more, than Green Roofs. Please refer to the summary of the study: http://www.sciencedirect.com/science/article/pii/S0378778815003527
What’s more, these studies rely on Cool Roof technologies that are less efficient than our coating.
Then comes the question of return on investment, because a green roof will cost more to install, may require structural revision (because it is heavier) and involves more maintenance.
What is the thermal flow difference between our coating, a standard paint and a coloured paint for example?
The difference between a Cool Roof coating and traditional paint (white or blue for instance) resides in the absorption and emissivity coefficient. Hereunder an idea of values for the three types. Absorption impacts the flow absorbed by the surface. Emissivity impacts the radiated flow (that also depends on the surface temperature and absorbed flows, convection and inner load) so it is a little more difficult to quantify simply.
Considering a solar flow of 1000W/m², the difference in absorbed flow between a cool roof surface and a dark blue surface = 790W/m².
To further the brain’s reflection, compared to a classic white paint, one must consider the durability of the coating (UVB and dirt resistance) allowing guaranteed reflective and emissive properties over time.
Will Cool Roofs increase global warming?
When solar radiation (made up of UV/visible/IR rays) has gone through the atmosphere:
– one part is absorbed by the ground and reemitted in infra-red form => if we increase the albedo, this part lowers
– one part is sent towards the atmosphere => if we increase the albedo, this part increases
In the radiation that is sent towards the atmosphere only the IR will contribute to global warming because they will be absorbed by greenhouse gases (and thus reemitted…).
With a cool roof, we increase the albedo, so reduce the part of radiation that is absorbed by the ground and reemitted in IR and thus global warming.