Urban rooftops can provide the per­fect host-space for fos­ter­ing inner-city eco-systems, but how can we retro-fit our cit­ies in a prac­tical way? Shang­hai author­it­ies have inves­ted close to $1 mil­lion on their cam­paign. Are there smaller-scale solu­tions for reclaim­ing roof-space in other cit­ies?

Urban rooftops provide the per­fect host-space for fos­ter­ing inner-city eco­sys­tems | Photo court­sey of ASLA

The Shang­hai Green­ery Admin­is­trat­ive Bur­eau claim to have “greened” over 500 000 rooftops with grass and shrubs since their pro­gram launched in 2003. Green rooftops are not just a cos­metic meas­ure: they can improve energy effi­ciency by act­ing as insu­la­tion and re-use rain and grey water which would oth­er­wise be wasted. Green­ing rooftops can also provide hab­it­ats for the insects and bird life that exist in our urban environments.

Shang­hai dis­trict gov­ern­ments provided mon­et­ary incent­ives to those want­ing to install green roof­ing last year, offer­ing to pay for nearly half the cost of the con­ver­sion.

“At first, we were not very con­fid­ent about set­ting a goal. But after last year’s sur­vey showed that about 20 mil­lion square metres of roofs can be turned green, we star­ted adopt­ing dif­fer­ent ways to pro­mote green roofs,” said Li Li, sec­tion chief of The Sec­ret­ary Office of Shang­hai Land­scap­ing Committee.

The Bac­sac is a cre­at­ive solu­tion to set­ting up a tem­por­ary garden space

UK-based Green roof con­struc­tion spe­cial­ists, Lindum have developed a com­pre­hens­ive green roof­ing sys­tem that allows for the cre­ation of a small-scale bion­et­work. By installing a ‘wild­flower for green roofs’ veget­a­tion layer build­ing res­id­ents can encour­age but­ter­flies, insects and small birds back into the area. One biod­i­verse roof mat can provide the neces­sary start­ing point, encour­aging wild­life back into built-up spaces.

It is also hoped roofs of this kind will help bol­ster the declin­ing UK bee pop­u­la­tion by provid­ing an increas­ing num­ber of hab­itat areas.

Not every­one has access to sub­sidy sys­tems such as the one offered in Shang­hai, and without cash incent­ives green­ing a roof can turn into an expens­ive exercise.

The French design­ers of Bac­sac have come up with a work­able sub­sti­tute to a green roof. These port­able planter sacks of vary­ing sizes and shapes offer an afford­able altern­at­ive to the struc­tural changes often required by green rooftops. Accord­ing to design­boom, the bags are dur­able, con­struc­ted from permeable/porous geo-textiles. They can cover as much or as little space as desired and can also help semi-green roofs that are not struc­tur­ally suited to com­plete transformations.

Seed­ing the City asks: why have just one roof with 1,000 square feet of green, when you can have 1,000 roofs with 1 square foot of green?

The Seed­ing the City pro­ject is encour­aging New York res­id­ents to view green roof­ing from a community-building angle. The pro­ject centres on empower­ing many people to have small gar­dens. Organ­isers believe that 1,000 roofs with 1 — 4 square feet of green is equi­val­ent of one — or more-  large-scale roof. Each on the rooftop gar­dens are marked with a green flag, link­ing them together in a green network.

Last month Toronto intro­duced a new bylaw requir­ing all new large-scale devel­op­ments are to include green roof­ing, with cov­er­age of 20 – 60%, depend­ent on the size of the building.

Is the Toronto bylaw excess­ive, or should more cit­ies be intro­du­cing sim­ilar check­points? Have you dis­covered other short-term or low cost ways to green rooftops? Tell us your thoughts. Lloyd Alter from Tree­hug­ger is scep­tical of green roof­ing for pub­lic per­cep­tions sake, com­par­ing it to the ‘mirrored glass’ of the 21^st cen­tury. Do you agree with his sentiment?