PV Flat Roof Design Considerations​

In the UK, solar photovoltaic (PV) is the most popular renewable energy and its deployment is rising rapidly across the globe, particularly because climate change and resource scarcity are on the agenda of every government and major corporation in the world. With recent fluctuations in energy markets and carbon reductions initiatives coming to the fore,  the number of large, flat roof installations will continue to rise as local authorities and businesses look to reduce their carbon footprint and gain energy security for the future.

All too often within the construction industry, photovoltaic specifications focus on energy generation and outputs of the solar system. Any solar designer or specifier should give the same focus to ensuring the rooftop array is installed with methods that have as little impact on the building and its waterproofing as possible and that the array works to its maximum potential for its entire lifespan, rather than just becoming a ‘tick box’ exercise to achieve sustainability credits.

Tonyrefail, Porth
UEZ Bristol University
Sybil Andrews Academy, Bury St Edmunds
This information is aimed at designers considering the inclusion of a PV array on flat roof construction projects and outlines the key elements to be mindful of to ensure the design is sustainable, protects the building and meets lifespan expectations.

You will learn about:
  • The drivers and solutions - Flat roofs provide the ideal location to site a PV array as they are unlikely to suffer from shading and provide easy access for installation and maitenance. The drivers differ for new build and retrofit applications.
  • The sizing of PV systems - The sizing of a PV array can be determined by the overall aim of the scheme. In all instances the system size will be determined by the buildings energy consumption, non-shaded roof space and the clients budget. 
  • Roof design considerations and conditions - Durability of the waterproofing system is key and its life span should match that of the PV scheme, as well as be able to withstand any additional access requirements for maintenance. 
  • Fixing and installation methods - There are two options available when fixing a PV system to a flat roof, ballasted or mechanical. A ballasted system adds additional weight to anchor the array to the roof whereas mechanical installations are fixed to the deck penetrating the roof covering.
  • Six steps to delivering a PV system - Delivering a PV can be a complicated process, we have identified the key design considerations that must be acknowledged at each stage. Starting from delivering the brief, through to monitoring and maitenance.