CROSS Safety Report
Solar panels and effect on snow slides from roofs
This report is over 2 years old
Key Learning Outcomes
For PV panel suppliers, installers and homeowners:
All roofs should be appraised for the suitability of accommodating PV panels
Evidence of structural competence should be provided prior to installation
Inspection by a competent person should be carried out to ensure the works are installed in accordance with the design intent
For civil and structural design engineers:
Load effects of snow and wind uplift acting on the roof structure due to PV panels should be carefully considered, particularly for sliding snow
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A reporter writes in connection with report 246, which discussed dangerous snow slides from buildings, and asks if any of the roofs had solar panels? Would this make any difference to the ' the slide off factor ' and would the extra dead load of the panels make any difference in this respect to the failure of the roofs?
Expert Panel Comments
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The installation of solar PV panels is a material alteration under the building regulations and needs assessment. In England this is to be done either under a competent persons scheme (such as the MCS scheme) or the local authority requires notification. Some competent person’s schemes only operate for electrical requirements of the regulations and then need the local authority to check other relevant aspects such as Parts A and C of the building regulations.
Issues of loading on existing roofs whether wind or snow or dead therefore come under control. Clearly there is a need to assess whether an existing roof structure can carry the extra load and that applies globally and locally (at fixing points). But there are additional concerns.
In the past CROSS has reported on many cases of danger following parts becoming detached from roofs. It is essential that panels are properly fixed down against the very high suction loads that might occur. In areas of higher snow load sudden thaws can cause snow slides with significant impact and danger if the slides fall on people or adjacent lower lying roofs.
Are concerns likely to increase?
The potential for large slides might exist given the nature of panel surface material. The concerns are likely to increase as pressure to reduce energy consumption grows. Insufficient attention being paid to structural integrity is not new on small works. The examples quoted above all relate to competence and so far, the solar panel industry is unregulated.
Notwithstanding this the installation of solar panels is covered by the CDM Regulations and hence all those involved have statutory duties to safeguard others. It may be that a code of practice could be a good starting point. The Scottish Government has published a report: Risk assessment of structural impacts on buildings of solar hot water collectors and photovoltaic tiles and panel – final report.
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