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Reading a reflectance, emissivity and SRI test report: standards, new and aged values

A credible test report names the laboratory, identifies the sample, cites three standards (ASTM E903 for solar reflectance, ASTM C1371 for emissivity, ASTM E1980 for the SRI calculation), gives an uncertainty and, ideally, a value after ageing. For PrimaTherm®, the Tipee reports establish 95 % reflectance, 0.89 emissivity, an SRI of 120 when new and of 119 after 4,000 h of accelerated ageing; any figure that does not come with these elements is a claim, not a measurement.

Updated on 17 September 2026 · Hélios Solution Cool Roof

Key points

  • Three standardised measurements: solar reflectance (ASTM E903, integrating-sphere spectrophotometer), thermal emissivity (ASTM C1371, portable emissometer) and the SRI (ASTM E1980, calculated from the first two).
  • Each value comes with the laboratory, the number and date of the report, the identification of the specimen, the reference spectrum and an uncertainty; otherwise, it is a commercial claim.
  • The new condition is not enough: rating programmes require values after ageing; the French CEE sheet BAT-EN-112 requires an SRI above 100 when new and above 90 aged.
  • PrimaTherm®: 95 % reflectance, 0.89 emissivity, SRI 120 when new and 119 after 4,000 h of accelerated ageing (ISO 16474-3), backed by the Tipee reports.
  • The report characterises a sample; on your roof, performance depends on the thickness applied and on the protocol, hence the thickness checks and the site monitoring sheet.

Why a test report rather than a sales sheet

The cool roof market was built on percentages announced with neither standard nor laboratory. For a buyer, a site manager or a local authority, the question is not whether a figure is high, but whether it was measured, by whom, on which sample and in what condition. The stakes are real: according to the US Environmental Protection Agency (EPA), a dark roof sends back only 5 to 15 % of solar radiation and black bitumen reaches 74 to 85 °C at the height of summer, where a highly reflective and highly emissive surface peaks at between 43 and 46 °C; the Lawrence Berkeley National Laboratory points out that a clean white roof reflecting 80 % of sunlight stays about 31 °C cooler than a grey roof reflecting only 20 %. The guide to the solar reflectance index (SRI) of a roof explains the physics; this article focuses on the document.

The three standards a report must cite

ASTM E903: solar reflectance

Standard ASTM E903 covers the measurement of the spectral absorptance, reflectance and transmittance of a material with an integrating-sphere spectrophotometer, then the calculation of the solar properties weighted by a reference solar spectrum, from the ultraviolet to the near infrared — which, although invisible, accounts for more than half of solar energy according to the EPA. The standard is limited to smooth materials, calls for precautions on textured or corrugated surfaces, and requires the reference spectrum used to be stated: ASTM E891 in the Tipee reports for PrimaTherm®.

ASTM C1371: thermal emissivity

Standard ASTM C1371 describes the determination of the emissivity of opaque materials with a portable differential thermopile emissometer, at a temperature close to ambient, with a stated precision better than ± 0.02; it excludes materials that are strongly anisotropic or transparent to infrared, and lends itself to periodic comparative measurements on site to monitor ageing. It is the quantity that sales sheets forget: the EPA reports an emissivity of 0.05 to 0.30 for unpainted corrugated steel deck, against 0.80 to 0.90 for a white paint.

ASTM E1980: the SRI calculation

Standard ASTM E1980 measures nothing: it calculates the solar reflectance index of a horizontal or low-slope surface from the measured reflectance and emissivity, under conventional conditions of sunshine, air and sky, for three wind speeds expressed as convection coefficients of 5, 12 and 30 W/(m²·K). The result places the surface between a reference black (SRI 0) and a reference white (SRI 100); the standard applies to surfaces with an emissivity above 0.1. Our article on the SRI solar reflectance index in cool roofing explains why a value above 100 is possible.

Reading a report line by line: the example of the Tipee reports

The PrimaTherm® values come from the Tipee technology platform (Lagord, near La Rochelle), whose laboratory measures the optical properties of materials within a standardised framework. Report ES-PJ000106-015, which establishes the SRI when new, runs to three pages.

Section In the Tipee report Why it matters
Header Laboratory, address, number, date of issue (5 April 2022) A report can be cited and checked; an undated “internal test” cannot
Reference ASTM E1980-11 (2019), standard white at 100, standard black at 0 The standard and its version are named
Product Reference, supplier, description, identifier, date of receipt The exact product is identified: a PH107 base coat, not “the range”
Specimens Roughness, dimensions (150 × 100 mm), measured thickness (691 ± 27 µm and 632 ± 23 µm) The thickness tested can be compared with the one applied on your roof
Methodology E903 with the E891 spectrum, C1371, E1980 calculation, uncertainties according to the GUM The three standards are present and chained together
Results For 5, 12 and 30 W/(m²·K): reflectance 0.948 ± 0.019, emissivity with ± 0.03, SRI 120.1 ± 2.8 then 120.2 ± 2.7 An uncertainty at 2σ and the statement “the results apply only to the items tested”

The uncertainty is written down: 120.1 ± 2.8 is a measurement, “120” with no uncertainty is a slogan. The PrimaTherm® certifications table sets out these values — reflectance 95 % (ASTM E903-12), emissivity 0.89 (ASTM C1371-15), SRI 120 (ASTM E1980) — with the Broof(t3) fire classification of CSTB report RA23-0010.

The aged-condition report

The second report, ES-PJ000911-003, concerns “sample no. 9 of a batch of samples artificially aged for 4,000 h under UV-B according to ISO 16474-3”: reflectance 0.943 ± 0.019 and an SRI of 119.2 to 119.4 depending on convection, against 120 when new. Standard ISO 16474-3 (paints and varnishes, fluorescent UV lamps) alternates cycles of ultraviolet, heat and humidity; “QUV” is the name of the most widely used apparatus. This is the line that distinguishes a durable product from one that shines the first summer, summed up by the wording “SRI maintained after 4,000 h of accelerated QUV ageing — conventional service life of 20 years (French CEE sheet)”. We do not write “certified for twenty years”: what is certified is the retention of the SRI.

New, aged, soiled: what the new figure does not say

All light-coloured surfaces lose reflectance. Standard ASTM D7897, which simulates the soiling and weathering of roofs in the laboratory, says so: the reflectance of a new surface often changes within one to two years, and rating programmes require values measured after three years of natural exposure. The EPA, citing Bretz and Akbari, states that a maintained coating keeps most of its reflectance, with a drop of the order of 20 %, generally in the first year.

Two approaches produce an aged value:

  • natural exposure under the Cool Roof Rating Council: three years on test farms in Arizona (hot and dry), Ohio (cold and temperate) and Florida (hot and humid), then a new measurement by an accredited independent laboratory;
  • accelerated ageing: simulated soiling and weathering (ASTM D7897, used by the CRRC for provisional ratings obtained in less than a week), or exposure to UV and humidity (ISO 16474-3, adopted by the French CEE sheet).

A report that gives only a new value is incomplete; an aged report with neither method nor duration allows no comparison. Cleaning with low-pressure water (see cool roof maintenance, in French) restores the reflectance lost through soiling, not a binder degraded by UV.

What the frameworks require

  • French CEE sheet BAT-EN-112: the product must have “a solar reflectance index (SRI) above 100 when new and above 90 in the aged condition, assessed according to standard ASTM E1980-11”, the aged condition being understood according to ISO 2810 after twenty years of exposure or according to ISO 16474-3 after 4,000 hours of artificial ageing; conventional service life: 20 years. The eligibility of the operation remains conditional (tertiary building for commercial use, volume heated and cooled by heat pump), as the cool roof incentives in France 2026 page explains.
  • LEED (Heat Island Reduction credit, version 5, according to the Cool Roof Rating Council): low-slope roof, initial SRI of at least 82 or aged SRI of at least 64; steep slope, 39 and 32. See cool roofs and HQE, BREEAM and LEED certifications (in French).

The pitfalls of a product sheet

  1. The round percentage with no standard. “Reflectivity 90 per cent” says neither how the value was obtained, nor on which spectrum, nor in what condition.
  2. Reflectance without emissivity. Without ASTM C1371, no SRI can be calculated; a metallised coating can show a respectable reflectance and remain burning hot.
  3. The missing laboratory, the unidentified sample. Name, number, date, signature; exact product, substrate, thickness: without these, you do not know what was measured.
  4. The new value alone: no comparison possible, no CEE eligibility.
  5. The colour. The certified values of PrimaTherm® concern white; a light shade reflects less and must have its own report (see white vs coloured cool roof).
  6. Confusing a field measurement with a test report. A thermal camera gives a temperature, not a reflectance. On the Airbus Marignane project, the infrared measurement of 19 June 2026 (28.6 °C on the treated zone against 57.8 °C on the control zone, i.e. −29 °C) confirms the effect of the coating; it does not replace the Tipee report.

Our checklist for choosing a cool roof contractor (in French) sets out these points as questions.

From the report to the roof: the role of the applicator

A report characterises a sample prepared in the laboratory; on a roof, performance depends on the preparation of the substrate, on compliance with the coverage rates, on the two passes of base coat and on the thickness of the film. Hélios, applicator of the PrimaTherm® system in four layers (PH169 primer, PH107 reflective base coat in two passes, PH107TCL anti-soiling topcoat), attaches the Tipee reports and the CSTB report to every proposal, then, at handover, provides thickness checks, a site monitoring sheet and infrared measurements before and after. The reports are available on request as early as the free roof study.

Sources

Frequently asked questions

What is the difference between solar reflectance, reflectivity and albedo?

Solar reflectance and albedo refer to the same quantity: the share of solar radiation sent back by a surface, measured across the whole spectrum according to ASTM E903 and expressed from 0 to 1 or as a percentage. “Reflectivity” is a commercial term with no normative definition: it may cover a measurement in the visible range only, a pigment value or a rounded figure. Always ask for the standard and the report.

Can an SRI really exceed 100?

Yes. The ASTM E1980 scale is set on a reference black (0) and a reference white (100); a surface that reflects more than this reference white, with a comparable emissivity, stays cooler than it and obtains an index above 100. The Tipee report for PrimaTherm® gives 120.1 ± 2.8 when new.

What does “aged condition” mean in a test report?

A measurement taken after the sample has undergone a defined ageing: three years of natural exposure on test farms for the Cool Roof Rating Council, accelerated laboratory ageing according to ASTM D7897 for provisional ratings, or 4,000 hours under UV lamps according to ISO 16474-3 for the French CEE sheet. The report must name the method and the duration, otherwise the aged values of two products cannot be compared.

Does a report produced on a laboratory sample hold for my roof?

It characterises the product, not your project. The report states the thickness of the specimen tested; on the roof, performance depends on the preparation of the substrate, on compliance with the coverage rates and on the thickness actually applied. That is why a serious applicator hands over thickness checks, a site monitoring sheet and temperature measurements before and after.

What SRI thresholds do the frameworks require?

The French energy-savings certificates (CEE), sheet BAT-EN-112, require an SRI above 100 when new and above 90 in the aged condition according to ASTM E1980. The LEED heat island reduction credit uses, for a low-slope roof, an initial SRI of at least 82 or an aged SRI of at least 64. These thresholds apply to the product; the eligibility of a CEE operation also depends on the building and on its air-conditioning system.

How can I obtain the PrimaTherm® test reports?

The Tipee reports (SRI when new and after ageing) and the CSTB fire classification report are attached to every Hélios proposal and are available on request for a tender or a grant application. The technical data sheets and the safety data sheets are sent after a first contact.

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