Key Considerations for Solar PV Roof Installations

AS SOLAR PHOTOVOLTAIC (PV) systems become increasingly popular across the UK, building surveyors, specifiers, and roofing contractors play a crucial role in ensuring these installations are both effective and sustainable.

This quick guide outlines some of the key considerations to help professionals navigate the design and installation process for commercial buildings, ensuring optimal performance and longevity.

Building Feasibility

The first step in any commercial solar PV project is to assess the building’s eligibility for rooftop solar installation. While solar PV installations typically fall under Permitted Development Rights according to Class J of the Town and Country Planning Order 2015, certain conditions must be met to qualify:

• Commercial solar panels must not project more than 200mm from the roof slope or wall surface.
• For pitched and flat roofs, panels must be positioned at least 0.4m from the external edges of the roof or wall joint.
• On flat roofs, panels should not protrude more than 1m from the roof surface and must not be the roof’s highest point (excluding chimneys).

However, these general rules come with exceptions. Planning permission is required if the installation is on a listed building, a site designated as an ancient monument, or in a conservation area with specific local restrictions, such as an Area of Outstanding Natural Beauty (AONB) or Article 2(3) designated land.

Ensuring Safe Installation

Once a building is deemed eligible, the next critical step is to evaluate its structural integrity to support a PV array. Garland UK strongly recommends that roofing professionals collaborate with structural engineers to assess the roof’s load capacity. This is particularly important for flat or low-pitched roofs, where the added weight of the PV system could exceed safe limits.

There are several ways to manage weight concerns:

• Mechanically fixing the mounting structures to the roof deck will help to distribute the load more effectively.
• Retrofitted torch-on systems, which require no ballast and minimal penetrative fixings, can preserve the roof’s waterproofing integrity while providing a secure base for the PV array.

These solutions can be tailored to meet specific project needs, with system weights ranging between 8 and 25 kg/m². Additionally, factors such as building location and height must be considered to ensure the design can withstand wind uplift forces.

Assessing the Existing Roof Condition

Given that modern PV modules can have performance and product guarantees lasting up to 30 years, it’s essential to thoroughly assess the roof before installation. A technical survey should evaluate the roof’s condition to ensure it will last as long as the PV system. Replacing or repairing the roof after PV installation can be costly and disrupt the expected return on investment (ROI) from energy savings.

Opting for a full-envelope solution, where the roof and PV system have matching guarantee lengths, is often the most cost-effective approach. This strategy ensures that both components are protected under the same warranty terms, reducing the risk of future complications.

Design Considerations

The building’s energy requirements should guide the design phase of a solar PV system. A well-designed system is tailored to meet peak energy demands by analysing the site’s historical energy consumption data. The goal is to maximise self-consumption of generated energy and minimise export back to the grid, as financial returns from exporting excess energy are currently limited.

It is also important to consider the regulatory landscape. For example, systems over 11.04 kWp (3-Phase) require submission of a DNO G99 application, also known as “apply to connect.” As the number of solar installations grows, Distribution Network Operators (DNOs) may impose export limitations to manage the increased load on the grid infrastructure.

Solar Yield Analysis

A solar yield analysis is calculated using industry-specialised software, enabling the client to see potential yearly carbon emissions reductions. By assessing feasibility, structural suitability, and roof condition and carefully considering design requirements, you can deliver solar PV solutions that are both efficient and sustainable.

Garland UK can support you through every stage of your solar PV array design and roofing project, providing a clear solar yield analysis and the PV systems needed to achieve long-term energy and cost savings for your clients.

For more information, visit Garland UK online.

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