Standards for green roofs widely recognized

Friday, January 30, 2015

The Régie du Bâtiment du Québec (RBQ) is developing guidelines for the design, construction and maintenance of green roofs in that province — a process that many sustainable building advocates maintain is unnecessarily duplicating existing standards. Kees Govers, technical sales manager with the green roof manufacturer, LiveRoof Ontario Inc, responds to Daniel Viola’s recent report on the complicated approval process for green roofs in Quebec, and addresses the issues of structural integrity, wind and fire resistance.

Does the National Building Code’s silence on green roofs mean that there is no recognized guidance for design and construction?

It is a little disingenuous for the RBQ to say that no building standards exist just because they do not exist within the National Building Code (NBC) of Canada as of yet. The issues dealing with structural engineering have already been addressed in a number of ASTM (American Society for Testing and Materials) Standards that have been approved a number of years ago.

These standards deal with testing requirements to measure dead and live-load requirements important to the structural requirements of the building, as well as care and maintenance and plant and materials selection processes. These standards are ASTM E2400-06, ASTM E-2396-11, ASTM E-2397-11, ASTM E2398-11, ASTM E2399-11, ASTM E2777-14 and ASTM E2788-11. These are consensus standards agreed upon by North American building specialists for North American conditions.

What guidance has the City of Toronto used in developing its green construction standard and green roof policy?

I have been involved with the Expert Committee on Green Roofs for the City of Toronto as one of the representatives for the green roof industry for the past few years. The process in Toronto is in its second go-around and the expert committee is expecting to recommend a number of refinements to the requirements so that the standard is more performance-based than when it was first implemented.

The two thorny questions that were the main sticking points were wind uplift resistance and fire resistance of green roofs. For vegetated roofs to be addressed in the building code, reliable test standards need to be in place from the outset. The green roof industry has been helping in the development of independent third-party standards for objectively evaluating code compliance. At least one of these standards will be in place shortly. As soon as they are, the two main concerns that code officials have in regards to green roofs — wind and fire — can be pretty confidently addressed.

How does that apply to wind uplift?

A consortium of interested parties named SIGDERS has been developing CSA Standard A123.21-10, along with test method and test apparatus since the mid 1990s in conjunction with the Building Envelope Research Facility at the National Research Council of Canada (NRCC). This test standard is now a solid wind uplift test standard for fully adhered and mechanically fastened roofing membranes and is widely expected to become part of the 2015 edition of the National Building Code.

When we at LiveRoof found out that Armtec, a paver company, had asked NRCC to evaluate a new type of roof top paver for wind uplift resistance utilizing the equipment and protocols for this wind uplift test standard, we requested the same testing for our green roof assemblies.

As a result of this testing by Armtec and ourselves, a number of green roof manufacturers banded together — at the time an exceptionally rare feat — under the leadership of the Canadian Roofing Contractors Association and encouraged by the federal government and the cities of Toronto and Ottawa to form a consortium aimed at developing a new wind uplift  test standard for vegetated roofing assemblies (the new name for green roofs).

That standard — CSA A123.24-15 — is now almost a reality. It has been approved by CSA and should be published in the spring of 2015. As a result, CSA A123.24-15-tested green roof assemblies should be available Canada-wide from at least five manufacturers in the summer of 2015.

Alternatively, since the NBC already prescribes the methods to calculate wind uplift forces exerted on the building, any system that can be tested by a third party to meet the counterforce required to mitigate the calculated wind uplift forces should be allowed to be installed.

How is fire resistance addressed?

On the fire testing front, the test standard already exists and has been used in the roofing industry for many years. It is CAN/ULC S-107. However it requires some changes or an addendum to the wording to make vegetated roofing assemblies or systems eligible to be tested according to the standard. Once that is done, we have a code-ready test standard that is already part of the building code.

A number of green roof manufacturers have already had their assemblies tested and rated under the insurance giant’s FM Global Approvals Standard 4477 for fire resistance, as well as the US Standard ASTM E-108, and they have been issued certificates of approval under ASTM E-108. The test procedures for both of these standards are identical to ULC S-107. It should be only a matter of time before this standard will be adapted and approved for evaluation of vegetated roof assemblies.

Kees Govers can be reached at

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