Purpose

The purpose of this guide is to give best practice advice on wind- and weather-resistant installation of PV, solar thermal and microwind turbines on residential buildings. It includes examples of good and bad installation practice and detailed guidance on design for wind loading.

Drivers

There are a number of drivers that are leading to an increasing rate of installation of renewable energy systems in residential buildings; these include increased consumer awareness of the impact of climate change, the increasing costs of generating heat and power by conventional means, the introduction in 2006 of the Code for Sustainable Homes, the Feed-in Tariffs introduced in May 2010 and the Renewable Heat Incentive scheme introduced in 2011 and which will be extended to residential installations in 2012.

This has led to a surge in popularity of microgeneration systems such as photovoltaic (PV), solar thermal, and microwind turbines installed on residential buildings in the UK. In turn this has led to cases of wind-induced failures and rainwater penetration through the roof envelope.  This can be due to a number of reasons including poor design and bad workmanship, but a main contributing factor is that there are no British or European standards for the installation of these products on buildings, although the individual microgeneration systems are themselves well regulated.

Requirements

PV, solar thermal and microwind turbines are installed on or above roofs where they can be exposed to harsh environmental conditions such as strong winds and driving rain.  It is an essential requirement that these systems can both resist the wind forces and safely transmit these forces back to the building structure.

It is also essential that roof-mounted systems are weather-resistant and do not compromise the existing building envelope by allowing rainwater to enter or damage the fabric of the building.

Regulation

PV, solar thermal and microwind turbines are all regulated by a range of British and European standards which ensure that they are ‘fit for purpose’.  In the UK, there is also the Microgeneration Certification Scheme (MCS) which is an initiative to drive the Government’s carbon and energy strategies and to provide consumer confidence that renewable technology products and installers meet, and continue to meet, robust standards.

The MCS covers product and installer certification schemes for a wide range of microgeneration technologies including PV, solar thermal and microwind turbines. However, there are currently no European or British standards that regulate the mechanical installation of PV, solar thermal or microwind turbines on buildings to ensure they are resistant to wind and rain action.

Installation

General requirements for the installation of these technologies are given in the NHBC Standards Chapter 3.1 Low or zero carbon technologies; guidance is also given in the MCS Product Certification Scheme Requirements.  For example, the MCS guidance] states that the installation instructions shall give ‘full instructions of how the module is to be installed to provide a weatherproof installation (ie details of any flashing or sealing kits and how these are fitted to the module and to the adjoining roof covering)’.

However, it is left to the manufacturer or installer to provide this guidance, generally based on ad hoc testing and/or experience.  Because of the lack of authoritative guidance, there are inevitably some failures; either wind induced or from rain penetration through the roof envelope.

NOS

This guide is not intended to replace accredited learning to National Occupational Standards.