Solar Panels On Flat Roofs

Installing solar panels on flat roofs for your home or business allows you to use the wide, Installing solar panels on flat roofs for your home or business will enable you to use the wide, unobstructed surface area to harness solar energy and generate free, sustainable electricity.

Changes to permitted development rights for solar panels in December 2023 have made installing solar panels on flat roofs easier by eliminating time-consuming red tape and bureaucratic hurdles.

However, there are various considerations unique to flat roof solar panels. Exploring solar panel installation on flat roofs and the benefits and challenges to expect can ensure you make an informed decision.

Quick Takeaways:

Installing solar panels on flat roofs is possible and beneficial
You no longer need planning permission for the installation
A survey is necessary to ensure the roof can support the added weight

Can Solar Panels Work on Flat Roofs?

Yes. You can install solar panels on flat or nearly flat roof structures. You can find solar panels on the flat roofs of many commercial buildings like warehouses and manufacturing facilities. However, you can also fit them on domestic properties with flat roofs.

Flat roofs usually have ample space, making them ideal for installing a solar panel system that can help reduce your electricity bills and household emissions. Panels on flat roofs can work as efficiently as those on sloped or pitched roofs, provided you mount them at the optimal angle for capturing sunlight.

How Are Solar Panels Installed on Flat Roofs?

Solar panel installation on flat roofs requires specialised mounting systems for panel positioning:

Ballast Mounted Systems — Ballast mounts help hold the system in place and are usually tray-like containers or tubs with a titled design. They sit on your roof and hold heavy concrete blocks, sandbags, or weights in the bottom, with panels secured along the edges. The weight prevents the panels from shifting and provides stability against high winds.

Adjustable or Fixed Tilt Frames — Some mounting systems use stainless steel or aluminium tilt frames. The frames attach to the roof using anchors, screws, or ballast for stability in high winds. Adjustable frames allow optimal panel angles to maximise sunlight exposure and energy generation.

Installation involves a few crucial steps:

1. Roof and Energy Needs Survey

An installer or engineer must survey your roof and determine the size, orientation, and structural integrity. They’ll also look for shading issues and calculate your energy needs to design the best setup for your needs.

2. Design and Planning

This involves creating a layout, choosing equipment, and ensuring compliance with building regulations.

3. Installation

The actual installation usually takes a couple of days for a residential system. The installer sets up the mounting system, secures the panels, and connects them to an inverter, which converts solar energy into usable electricity.

4. Testing and Commissioning

Once everything’s in place, the installer tests the system to ensure it’s working as expected.

What Should You Consider When Installing Solar Panels on Flat Roofs?

Roof Suitability

Your roof must be structurally sound and capable of bearing the extra weight of the panels and mounting system. Standard solar panels usually weigh between 18 and 20 kg per panel, and you must add the weight of the ballast mounts to determine the total load. Roofs have weight limits, and some may not support the extra weight.

Shadows and Obstructions

Things like chimneys, air-conditioning units, or even nearby trees can cast shadows on your panels, reducing their efficiency. During the planning phase, installers will look for potential shading issues and help you work around them. It’s also essential to check for vents, outdoor units, air conditioning systems, or other structures that can block space.

Orientation

The orientation of your solar panels determines how much sunlight they capture throughout the day. In the UK, solar panels generate the most energy when oriented toward the south, as this direction receives the most consistent sunlight throughout the day.

If south-facing placement isn’t possible (due to shading or roof layout), an east-west orientation can still work. This setup spreads energy generation evenly across the day, capturing morning and afternoon sunlight.

Unlike pitched roofs, where orientation depends on the roof’s natural slope, flat roofs offer the flexibility to position the panels exactly as needed.

Angles and Pitch

The angle at which solar panels are installed, or the tilt, is crucial for optimizing energy production. The ideal tilt angle for solar panels in the UK is generally between 30° and 40°. This range allows the panels to absorb maximum sunlight throughout the year.

However, this is rarely achieved on flat roofs due to high winds, so the most achievable angle is between 10 and 15 degrees.

What are the Challenges of Flat Roof Panel Installations?

Space Issues

Solar panels must be spaced out more on flat roofs to prevent the rows from casting shade on each other. They’re usually further apart than panels on tilted roofs, meaning you’ll need more space for an effective solar system.

Edge protection also restricts the available space by requiring a 0.5-1m border between the panels and the roof’s edge. You may be limited in the size you can install on a flat roof, which may not be enough to meet your household’s needs.

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Reduced Output Due to Improper Positioning

Solar panels in the UK work at their best when positioned in a south-facing direction at an angle of 30 to 40 degrees. Such positioning on a flat roof may be challenging or require heavier mounts that can compromise your roof’s integrity.

Most panels are installed at lower angles on flat roofs, which reduces the system’s overall output.

Leakage Risks

Installing solar panels on flat roofs may require penetration where the roof is drilled to fix the mounting system or solar panels firmly. If improperly sealed, this can cause leaks, so you must prioritize waterproofing to prevent water infiltration.

Frequent Cleaning

Environmental contaminants like leaves, dirt, or debris accumulate more easily on flat surfaces, potentially affecting your panel’s performance and output. To ensure optimal energy generation, you must frequently clean the panels and the surrounding area.

Pooling Risks

Unlike sloped roofs that direct water to gutters and eaves, flat roofs tend to collect water in certain areas. Water can quickly accumulate on a flat roof, increasing the risk of leakage and solar system damage.

Proper drainage is necessary to prevent water from pooling around the solar panels. A tilted mounting system allows rain to run off the panel surface, preventing water from collecting on the surface.

Added Costs

The installation can be costlier due to the additional requirements. Surveys, extra mounting equipment, and ballast can increase the expenses. The process can also take longer and be more complex than a standard installation, translating to higher labour costs.

What Are the Benefits of Flat Roof Panel Installations?

Easy Installation and Maintenance

Flat roofs are more accessible than sloping roofs, so installation and maintenance are smooth and straightforward.

Installers don’t have to worry about angled surfaces, making placing and maintaining panel systems more effortless and cheaper. Fewer adjustments translate to less time and effort, which can help you save on costs.

Better Aesthetics

Flat roofs allow solar panels to be less visible from the street. Passersby won’t be able to notice them, and they won’t alter the visible impression of the property or building where they’re mounted.

Improved Safety

With flat roofs, you don’t have to worry about solar panels being positioned at steep angles or slopes that can make them susceptible to damage from heavy rain, strong winds, and snow.

There’s less risk from extreme weather events, keeping your investments safe and potentially extending their lifespan.

Design Versatility

Flat roofs give you a versatile canvas to design your solar panel arrangement. They offer flexibility in panel arrangements and placements, allowing creative layouts that can optimize sunlight exposure.

Cheap and Easy Removals

Thanks to easier access and a hassle-free path to the solar panels, installers can easily remove and swap out failed panels or replace the entire system on a flat roof. They can move freely on flat surfaces without worrying about navigating steep angles, allowing for a stress-free, less costly experience.

Do You Need Planning Permission for Flat Roofs?

Solar panel installation on flat roofs in the UK currently falls within permitted development rights. The government amended permitted development rights for solar equipment in December 2023 to allow installation on the flat roofs of domestic premises.

Generally, you’ll not need to obtain planning permission unless your property is listed or located in a conservation area. However, there are some specific conditions your installation must comply with:

The solar equipment must not exceed 0.6 metres above the highest part of the roof, excluding the chimney. You may need permission if the installation exceeds this limit.
The system must be installed with the least visual impact on the building and nearby amenities.

Ensure you contact your Local Planning Authority before starting any work to ensure your project complies with planning permission rules. Most councils offer pre-application consultations.

Are There Building Regulations to Consider?

Building regulations focus on the safety and structural aspects of the installation. You must follow them strictly regardless of whether you need planning permission. Key compliance areas include confirming the roof’s structural integrity, waterproofing, and ensuring electrical and fire safety.

All electrical work must comply with Part P of the Building Regulations, which governs the safety of domestic electrical installations. Panels must be installed with appropriate clearances to reduce fire risks. This is particularly important for commercial installations and buildings with shared roof spaces.

To ensure compliance with all regulations, only work with a certified electrician or installer accredited by the Microgeneration Certification Scheme (MCS) and keep thorough documentation. MCS certification ensures your system meets industry standards and qualifies you for incentives like the Smart Export Guarantee (SEG).

Keep records of structural surveys, planning permissions if applicable, and certificates of compliance with building regulations. You’ll need these documents if you sell your property or if council inspectors request proof of compliance.

Are There Solar Panel Alternatives for Flat Roofs?

You consider various solar panel alternatives for your flat roof.

Solar Roof Tiles or Solar Shingles

Solar roof tiles are photovoltaic cells integrated into roofing materials, offering a seamless design for generating energy while serving as a roof covering.

They offer excellent aesthetic integration and are virtually invisible from the ground, making them ideal for listed buildings or properties in conservation areas.

Roof tiles or shingles can be a suitable choice if your roof cannot support the weight of traditional panels and a mounting system. They act as both a roof and an energy source, eliminating the need for mounting systems.

Portable or Modular Solar Systems

Portable or modular solar systems can be a great choice if you’re looking for flexibility. You can quickly move or expand them to meet your growing needs. They’re ideal for rented properties or temporary installations since they’re not permanently fixed on the roof and can be easily relocated.

The best solution for your flat roof will depend on your budget, structural limitations, energy needs, and preferences.

Can You Hide Solar Panels on Flat Roofs?

You can discreetly conceal solar panels on flat roofs using practical methods like:

Low-profile Mounting – It can keep panels closer to the roof surface with a slight tilt of 5 to 10 degrees, making them less visible from the ground or surrounding areas.

Parapet Walls— You can position the panels within the boundary of the parapet wall, concealing them from view without additional structures.

Green Roofs – Integrating solar panels into a green roof design can help blend the system into the natural aesthetic of your property. It usually involves incorporating greenery to hide the panels or support structures.

Final Thoughts

Flat roof solar panel installations can help generate free, renewable electricity. Flat roofs allow easy installation and maintenance, but you must account for challenges like space issues, added costs, leakage risks, frequent cleaning, and lower output.

A qualified MCS-certified installer can help you determine your roof’s suitability and guide you through the process.

Sources and References

https://www.legislation.gov.uk/uksi/2023/1279/pdfs/uksiem_20231279_en_001.pdf