The threshold of 78 in Laval
Section 380 of the Code gives four choices for a flat roof. The first is a green roof. The second is the white roof in the strict sense: a material that is white, painted white, or covered with a reflective coating or white ballast. The third is a material with an SRI of at least 78. The fourth combines the other three.
According to the section, this index must be attested by the manufacturer's specifications or by a professional's specification. The threshold is the same everywhere in Laval. The section covers main and accessory buildings with flat roofs, with three exceptions.
The Code does not say whether the section applies to an existing roof redone identically. For that case, the answer belongs to the City's Service de l'urbanisme (urban planning department).
What Appendix C says about the scale
The official text contains an inconsistency. Appendix C of the Code defines the index on a scale of 0 to 1, while section 380 sets a threshold of 78. The inconsistency is reported as is. If it raises a doubt about a product, it is also up to the Service de l'urbanisme to clear it up.
Two properties in one number
- Solar reflectance is the share of the sun's energy that the surface sends back right away.
- Thermal emittance is how easily the surface gets rid of the heat it has absorbed anyway.
Manufacturers place their products between two reference points. A reference black surface is 0, a reference white surface is 100. A common black covering sits near 0. Smooth white membranes get the highest values, sometimes above 100. Pale granule finishes fall in between, with large gaps from one product to another.
The shade does not tell you the index. Two roofs that look identical can carry different numbers.
Reading the manufacturer's data sheet
The index appears in the product's table of properties, sometimes under its English acronym, SRI.
- Is it really the product that will be installed? The data sheet must describe the planned finish ply, in the planned colour. The same membrane does not have the same index in grey and in white.
- Value when new or after aging? Many data sheets give both. The second is lower. An exposed surface gets dirty.
The passage of section 380 that sets the threshold does not say which of the two values to use. That is one more question to ask the City.
To settle at the quote stage
- Have the full name of the finish product and its colour written in.
- Ask us for the technical data sheet and find the index line on it.
- Put that number next to the threshold of 78. At the slightest doubt about the scale, have the Service de l'urbanisme confirm.
Frequently asked questions
What index should I aim for on a flat roof in Laval?
Section 380 names an index of at least 78, as one of its four choices along with the green roof, the white material and the combination. It does not say what applies to an existing roof redone identically. Check your case with the Service de l'urbanisme before choosing a product.
Are white granules enough to reach 78?
White granules are not necessarily enough to reach 78. Pale granule finishes give very different indexes from one product to another. Only the data sheet of the specific product, in its colour, can tell you.
What happens if the installed product is below the threshold?
It is up to the Service de l'urbanisme to say what it requires when the installed product is below the threshold. The simplest course is to settle the question before installation, manufacturer's data sheet in hand.
Official sources, consulted on October 8, 2026: