Launching of the Green Roof at the Central Bank main branch in Hamra

 

Nearly 90% of the Lebanese population resides in cities across the country, with 0.8 square meter per person of green spaces available. The world health organization, however, recommends a minimum of 9 square meter of green space per person, and it is acknowledged that a city at an ideal standard would have between 10 – 15m² of green space per person.   Green spaces have positive effect on people; they provide a great way to escape the stresses of day-to-day life, constitute a buffer to the surrounding noises and pollution, and increase value of real estate in surrounding areas

Since we must strive to increase the areas of green space in Beirut and other cities in Lebanon, green roofs provide a supporting action that can be taken to beautify our city in places where green parks can no longer be constructed.

By definition, a green roof is a roof space covered by vegetation that enhances both aesthetics and energy performance of the building, hence increasing the share of green spaces. In addition, green roofs are considered as insulating components reducing energy consumption by 10% due to their layers (soil, plants and water). They absorb the heat and hence reduce the need for conditioning in the space right beneath it, and to lower floors albeit to a lowered extent. On the environmental aspect, green roofs help reduce CO₂ emissions through the lowering of conditioning demand.

An 834 square meter Green Roof at the Central bank main branch in Hamra was completed as a joint collaboration between the UNDP – CEDRO project and Banque Du Liban (BDL). This project is one of the first of its kind in Lebanon and the region, and serves as a model project that will, hopefully, be adopted by the public and private sectors, and encouraged.

The pilot green roof initiative was funded by both BDL and UNDP.  The UNDP contribution is funded by the Government of Spain through the Lebanon Recovery Fund that supports the CEDRO project. The roof was designed by a local company supported by international experts.  It has a growing media consistent of: peat, sand, gravel, old rubber tires, rockwool, perlite or vermiculite and monitored by sensors connected to a control room, measuring water and nutrients level. While phase 1 features a horizontal cover with native species showcasing patterns in their different colors, heights and blooming season, phase 2 emphasizes on the verticality of the elements with three European olive trees. The plant selection stressed on different blooming seasons, to guarantee a continuous flourished roof.

Raising Gardens to the Roofs of Central Bank with CEDRO

 

Green roofs constitute an old construction technique that has been revived in the 21^st century as a reaction to the infrastructure crisis the world is facing. As the population increases, we are lacking green and public spaces.

In simple terms, green roof is a roof space utilized as greenery growing medium to increase the ratio of “green spaces versus built spaces”.

Two types of green roofs are available:

–          Extensive green roof:

Where the growing medium ranges between 2.5 and 15.2cm thick composed of inorganic material referred to as “substrate”. The use of inorganic material reduces the need for replenishment hence maintenance. 

–          Intensive green roof:

The growing medium, min 15.2cm depth, though composed of lightweight soil (mixtures of organic and inorganic material), requires a stronger infrastructure.

The main difference between extensive and intensive green roofs lies in the type of plantation and the garden use. Intensive roofs can support a varied type of plantation; due to its stronger infrastructure, it holds no restriction on height or root depth.

CEDRO is implementing a hydroponic intensive green roof on one of the Central Bank buildings in Hamra Beirut. The 716m² roof is in the centre of the BDL haven, and is overlooked by all surrounding buildings. The roof will have growing media consistent of: peat, sand, gravel, old rubber tires, rockwool, perlite or vermiculite and monitored by sensors connected to a control room, measuring water and nutrients level.

Green roofs, not only provide an opportunity to increase green spaces and beautify the aerial scenery, but they are considered as excellent thermal performance boosters due to the use of soil, plants and water. They absorb the heat and hence reduce the need for conditioning in the space right beneath it.

On the environmental aspect, green roofs help reduce CO₂ emissions through the lowering of conditioning demand. On the other hand, the available vegetation contributes to lowering the greenhouse gas emissions while improving or preserving biodiversity.