{"id":1773,"date":"2026-11-04T10:53:40","date_gmt":"2026-11-04T15:53:40","guid":{"rendered":"https:\/\/imperguard.com\/?page_id=1773"},"modified":"2026-11-04T10:53:40","modified_gmt":"2026-11-04T15:53:40","slug":"article-reflective-roof-compliance","status":"publish","type":"page","link":"https:\/\/imperguard.com\/en\/article-reflective-roof-compliance\/","title":{"rendered":"Article: reflective-roof-compliance"},"content":{"rendered":"
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Technical insights<\/div>\n

Reflective roofs: why replacement isn’t the only path to compliance<\/h1>\n

Several Montreal boroughs require a reflective covering on low-slope roofs. The default response is often a new white sheet membrane, either heat-welded or fastened after a full tear-off, or installed as a recover over the existing roof. A silicone restoration reaches the same target with a cold-applied liquid membrane, seamless and flame-free, that integrates with the existing roof to renew its watertightness, backed by a 10- to 20-year warranty, at a lower cost.<\/p>\n<\/p><\/div>\n<\/div>\n

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\n Imper Guard Technical Insights<\/span>
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\n October 12, 2025<\/span>\n <\/div>\n<\/div>\n

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A property manager applies for a permit to redo a low-slope roof, and the borough points out the reflectance requirement. The quotes that follow often offer a single solution: a new white sheet membrane, with or without a tear-off.<\/p>\n

That’s an incomplete reading of the bylaw. It doesn’t mandate a white membrane: it accepts several solutions, including any material that meets a minimum solar reflectance index. And a reflective liquid-applied membrane, integrated with the existing roof, can meet that index without sending anything to the dumpster.<\/p>\n

What the bylaws actually require<\/h2>\n

In Montreal, for flat and low-slope roofs, the accepted materials are a white material, a material painted white or covered with a reflective coating, white gravel ballast, or a material whose solar reflectance index (SRI) meets the threshold set by the borough, as certified by the manufacturer’s specifications. Depending on the borough, that threshold is 78, 66 or 56. A green (vegetated) roof is a separate option.<\/p>\n

Two points are worth highlighting, because they often go unnoticed.<\/p>\n

Reflective coatings are named explicitly.<\/strong> This isn’t a loose interpretation: the bylaws list them alongside white sheet membranes, and a cold-applied liquid membrane falls squarely in that category. Rosemont\u2013La Petite-Patrie, the first borough to require white roofs, has recognized green roofs, white roofs, roofs covered with a reflective coating, or any combination of the three since 2011.<\/p>\n

The requirement also applies to reroofing.<\/strong> It isn’t limited to new construction. Replacing the roof covering on an existing building triggers the same obligation. That’s exactly when the question of restoring rather than replacing comes up.<\/p>\n

Each borough has its own wording and its own threshold. It’s still essential to check with the borough concerned before specifying anything.<\/p>\n

What SRI measures<\/h2>\n

The solar reflectance index combines two distinct properties, each measured separately.<\/p>\n

Solar reflectance<\/strong> (ASTM C1549) measures the share of solar radiation reflected rather than absorbed. It’s expressed on a scale of 0 to 1.<\/p>\n

Thermal emittance<\/strong> (ASTM C1371) measures the material’s ability to release the heat it does absorb. It’s also expressed on a scale of 0 to 1.<\/p>\n

SRI (ASTM E1980) combines both on a scale where standard black equals 0 and standard white equals 100. A material more reflective than the reference white scores above 100.<\/p>\n

The distinction matters more than it might seem. Two materials can show similar reflectance and very different SRIs, because one releases the heat it absorbs while the other holds on to it. That’s why the bylaws refer to SRI rather than reflectance alone.<\/p>\n

Where a white silicone coating stands<\/h2>\n

IG8000 coating in white shows the following values:<\/p>\n\n\n\n\n\n\n\n\n
Property<\/th>\nTest method<\/th>\nValue<\/th>\n<\/tr>\n<\/thead>\n
Solar reflectance (initial)<\/td>\nASTM C1549<\/td>\n0.84<\/td>\n<\/tr>\n
Solar reflectance (aged)<\/td>\nASTM C1549<\/td>\n0.71<\/td>\n<\/tr>\n
Thermal emittance<\/td>\nASTM C1371<\/td>\n0.91<\/td>\n<\/tr>\n
Solar reflectance index<\/td>\nASTM E1980<\/td>\n106<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Against a regulatory threshold of 78, that’s a comfortable margin.<\/p>\n

Two clarifications are in order:<\/p>\n

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These values apply to the white finish only<\/strong>, with a tolerance of \u00b15%. They do not apply to the grey finish.<\/p>\n

The SRI of 106 is calculated from initial reflectance<\/strong>, in line with industry convention. Aged reflectance, measured at 0.71, appears on the same technical data sheet, so specifiers have both values in hand.<\/p>\n<\/p><\/div>\n

The real benefit for the building<\/h2>\n

Beyond compliance, reflectance works on two levels.<\/p>\n

At the city scale, a roof that reflects solar radiation instead of absorbing it stops feeding the urban heat island. That’s the whole purpose of the bylaw.<\/p>\n

At the building scale, a roof that stays cooler transfers less heat to the top floor, which reduces the cooling load during summer peaks. The size of the gain depends on the existing insulation, the ratio of roof area to conditioned volume, and occupancy patterns. On a single-storey warehouse with a large footprint, the effect is more pronounced than on a six-storey building.<\/p>\n

Under the summer sun, a dark roof can reach 50 \u00b0C above ambient air temperature, compared<\/p>\n","protected":false},"excerpt":{"rendered":"

Technical insights Reflective roofs: why replacement isn’t the only path to compliance Several Montreal boroughs require a reflective covering on low-slope roofs. The default response is often a new white sheet membrane, either heat-welded or fastened after a full tear-off, or installed as a recover over the existing roof. A silicone restoration reaches the same […]<\/p>\n

Read More… from Article: reflective-roof-compliance<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"class_list":["post-1773","page","type-page","status-publish","hentry"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t