Some weeks ago my colleagues (from the University of Applied Sciences in Geneva and the City of Lausanne, Nature and City Department) and I organized a half-day event: an exchange of experiences on the Swiss green roof standards practice with the Swiss Society of Engineers and Architects (SIA) in Lausanne.
“The SIA is Switzerland’s leading professional association for construction, technology and environment specialists. With 16,000 members from the fields of engineering and architecture, the SIA is a professional and interdisciplinary network whose central aim is to promote sustainable and high-quality design of the built environment in Switzerland” (http://www.sia.ch/en/the-sia/).
“The SIA and its members stand for quality and expertise in architecture and construction. The SIA is well known for its important work on standards. It develops, updates and publishes numerous standards, regulations, guidelines, recommendations and documentation, which are of vital importance for the Swiss construction industry. Some 200 committees are responsible for further developing these standards” (http://www.sia.ch/en/the-sia/).
The standards SIA 312 were published and printed in November 2013. The goal of this event in Lausanne was to see, after more than three and a half years, if these “practices“ are used and if they are an instrument to achieve requirements.
Standards in general
In this article, I discuss technical standards within the construction sector. There are various standards, meaning technical requirements that apply to various systems. Although not a legal tool, the standards insure that there are certain tested applications and practices which should guarantee a good quality planning, application and maintenance.
What is special about the standards SIA 312 “green roofs”?
SIA 312 is a highly technical document, which leads with very precise and short sentences, taking the reader from the main chapter of project study, through materials and implementation. I was a commission member when the project started in 2008, and the challenge of creating these standards was to integrate ecological parameters in order to achieve green roof quality as well improve biodiversity. Quality in terms of creating well thought out projects: planned wisely to achieve the desired vegetation, consideration of the life cycle of materials to be used, and the fauna and flora to be established in the long term. For the first time, ecological compensation matters and requirements were integrated in such a document in Switzerland.
The commission members represented all stakeholders involved in the building sector: architects, engineers, green roof companies, waterproofers, substrate producers, seeds and plant nurseries and city authorities. So, the points of reference were appropriately broad.
A brief overview of our federal law.
One key element is that the law incorporates the idea of ecological compensation. Ecological compensation is a collective term for measures that serve to maintain and restore the function of the habitats and their networking, especially in intensively used or densely populated landscapes. The Federal Act on the Protection of Nature and Cultural Heritage (NCHA) requires the cantons (federal states) to provide ecological compensation (Article 18b (2) NHG, Art. 15 NHV). One of the goals of ecological compensation is the promotion of indigenous biodiversity.
The following measures are suitable ecological compensation:
- Strengthening and re-creating natural areas
- Biodiversity support areas (formerly ecological compensation areas)
- Ecological improvement in urban areas (cities etc.)
- Measures in the forest (for example by natural forestry, old woodland, forest reserves)
- Habitat connection and networks
The goals for ecological compensation can be subdivided according to quantitative, qualitative and disposable criteria, which are explained in the Swiss Landscape Concept.
Digging into the law itself can be very helpful, and reveals other requirements for the purpose of protecting the environment. Specifically, with regard to the green roof standards, there are the following:
22.214.171.124 Where ecological compensation measures are required, the following criteria shall be considered:
- thickness of the substrate (variation). This means two things: 1) mix natural or recycled substrates (the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached) like sandy-graveled, excavation soil, gravel, sand, compost, crushed bricks, crushed ceramic etc. and 2) vary them in thickness for the application all over the planned surface (builds more micro habitats)—the minimum is 100mm thickness.
- type of vegetation (plant associations), combination of species, depending on the environment you want to establish. For example, a dry meadow—open spaces with low and scarce vegetation, mixed perennials etc., this has to be considered in the planing process.
- distribution of the substrate (variation): designing various landscapes on the surface.
- storage of meteoric waters: the more variation in substrates thickness the more retention and buffer of meteoric waters / rain waters.
- structures and networks for animal species (fauna), like wood logs, stones, piles of branches
- seeds species and seedlings (local & indigenous species); choose local species and support the local flora and fauna (genetic diversity as well).
126.96.36.199 The following local conditions have an influence on the success of the greening of a roof; They are therefore to be taken into consideration during the study:
- solar radiation (drop shadow, reflection, thermal radiation)
- precipitation (sites that may be sheltered from rain)
- wind regime (exposed roof, protected roof, turbulence, suction effects)
- emissions (exhaust air, dust, gas)
- quality of the surrounding nature.
188.8.131.52 The requirements for ecological compensation shall be classified as follows:
- basic requirements (Table 2),
- high requirements (section 2.7.2),
- special requirements (section 2.7.3).
Within this classification we offer three choices, as well as the option to go directly to the utmost classification (special requirements). In the standards only the high and special requirements are described in detail. The basic requirements are included in the general information found within the standards (like 184.108.40.206. and plant species details).
220.127.116.11 High Requirements:
- basic requirements as a function of climate
- variable distribution of the vegetal layer: shaping of the vegetal layer on surfaces (From a static point of view, e.g. Minimum thickness of the vegetal layer of 80 mm, 120 mm and 150 mm, distributed for each thickness on 1/3 of the total area.)
- plant class 3 (Table 6 within the standards).
18.104.22.168 In addition four other criteria are to be defined according to the following list:
- use of two or more substrate types (mixes)
- use of topsoil or earthy materials of local origin, provided that their quality (permeability, part of clay, etc.) is appropriate, or of mineral substrates produced locally
- Biodiversity-improving structures (facilities): sandy areas
- Biodiversity-improving structures (facilities): gravel areas
- Biodiversity-improving structures (facilities): dead – wood (piles of branches)
- Biodiversity-improving structures (facilities): dead – wood (logs)
- Biodiversity-improving structures (facilities): stone pile / mount
- Biodiversity-improving structures (facilities): for target species, etc.
The list is extensive, providing specifications for plant associations and species. Of course you can also find information on extensive and intensive green roofs, plant species and vegetation methods (seeds, seedlings, plugs and hay mulch/dry meadow cut grass) water retention, grey water usage, biosolar (combination of biodiverse green roofs and solar panels) in this document.
What is the connection between a standard or a norm and nature in the city?
Standards are a tool or instrument, which can be used to require from any stakeholder in the construction environment, “standards” for ecological measures, on how to implement biodiverse nature in the building environment, in order to be sure that nature and biodiversity can be improved. Cities normally add to the base standards, providing additional documentation with graphics and photos in order to provide greater detail about the topic.
Another possible method of communicating standards is a demonstration installed by the city of Lausanne a year ago; a green roof exhibition square. The exhibition features different types of green roofs, including combinations of different natural substrates (mixtures), different vegetation methods (local & indigenous plants) and projects from biosloar roofing to urban farming on roofs.