Green Roof Design Considerations Overview
There are fundamental principles that apply to the design of a green roof, regardless of the proposed landscaping, location or climate. The specified solution must replicate nature within the build up and be able to support the vegetation.
The first step - What is the landscaping finish to look like?
The primary decision is the type of landscape required that best suits the rationale behind the development, whether it is an intensive, simple intensive, extensive or biodiversity roof. Whatever the landscape chosen, the plants will have some basic requirements to sustain them; nutrients, a balance between moisture and drainage to suit the vegetation, and aeration to the root systems.
The next step - Planning the green roof to meet the needs of the vegetation
Once the vegetation finish has been determined, the structural and design considerations and green roof components can be proposed.
Energy efficient roofs
Reducing energy usage through effective roof insulation. There are different options depending on whether you are constructing a warm or inverted roof above a heated building, the usage of the building and if it's domestic or commercial, and the specific project requirements and parameters such as if you need to create falls using the insulation or if there are limited installation heights, such as for terraces.
Uplifting U-values on an existing flat roof
Increasing the thermal insulation within a roof makes perfect sense and has many benefits to the building, including its reduction in energy usage for heating or air conditioning as well as supporting the environment.
Creating falls on a roof
It is a requirement of Building Regulation Part H that adequate provision is made for rainwater to be carried from the roof of the building. According to BS 6229 & BS 8217, flat roofs should be designed with minimum falls of 1:40 to ensure a finished fall of 1:80 can be achieved, allowing for any inaccuracies in the construction. This applies to general roof areas along with any internal gutters.
Insulation for acoustic solutions
The use and combination of insulation in a flat roof can reduce sound transmission into and out of a building and reverberation. Rain noise performance is generally the biggest issue faced by building designers as there are targets to be met in schools and hospitals and these targets vary depending on the room type.