4 Considerations When Installing Solar PV Panels On Your Commercial Flat Roof

Posted on: 25 March 2015

With a major theme in modern business being a focus on eco-friendly structures, it's no surprise that many companies are installing solar PV panels on their commercial roofs. If you're considering installing these energy-generating structures on your office or warehouse, you're probably already aware of the benefits on offer. However, there are a few considerations you may not have accounted for: 

Getting The Design Right

Flat roofs continue to be extremely attractive structures for solar PV panels as they provide easy installation, easy maintenance and low visibility. This means that you can install PV panels on your commercial roof quickly, whilst keeping them out of sight from passers-by.

With that said, flat roofs can also affect your panels' ability to generate electricity as all solar panels require a slight angle in order to catch the sun's rays. If you choose to install your solar panels parallel to the roof structure, you will be missing out on massive potential for energy generation which might render your PV setup inefficient. Additionally, wind uplift on the edges of the panel can be a problem on flat roofs as they aren't offered natural protection from the underlying structure. As such, you have to account for this when designing your PV setup in order to obtain maximum yield.

Making The Best Use Of Space

In some cases, flat roof systems can cause problems when laying out solar panel modules. The reason for this is that laying solar panels in parallel lines on a flat roof can cause some panels to be kept in the shadow of the row in front. Evidently, this will reduce the amount of sunlight hitting your solar roof which has an effect on the structure's efficiency.

Many roof contractors will suggest leaving a space between rows in order to allow maximum sunlight to strike reach each individual panel. Whilst this will improve the panels' efficiency, it will reduce your overall energy yield as the space required impacts the number of panels you can install.

A great way to achieve high yield and high panel efficiency is to make good use of mounting structures to install the panels. These mounting structures raise the height of the solar panel so that they are clear of the row in front. Clearly, this will have an impact on the aesthetics of the roof; however, it will go a great way towards generating maximum bang for your buck.  

Maintaining The Structure's Integrity

Many flat roofs are supported by an A-frame which sits underneath the roof panels and is held down by a number of fixings. If you plan on installing solar panels on your commercial roof however, you'll have to ensure that any penetration into the roof is properly accounted for. The reason for this is that holes present on a flat roof can exacerbate any problems caused by water pooling, and the additional force present on the roof can cause panels to sag excessively.

Additionally, you have to consider your commercial roof's warranty details when fixing the panels to the structure. Many contractors will explicitly state that penetration of the roof will render your warranty void, so it's important to read the fine print outlined in your contract. In many cases, penetrating the roof is unavoidable, so make sure that the construction work is carried out by a qualified professional to maintain the roof's structural integrity.

Optimizing Your Ballast Layout

With many commercial flat roofs, you'll want to use a ballasted system in order to avoid the need for any holes. Typically, these consist of large dead-weights which are used to anchor the PV modules to the structure. This approach allows fast installation and is extremely effective at holding the panels down when faced with wind loading.

With that said, the major drawback with using heavy ballasting is the amount of ballasting required. Each individual solar panel requires its own ballast which can quickly add to the overall weight of the roof if there are numerous panels.

Tall, slender structures that attract significant wind load will require a heavy amount of ballast in order to keep the panels secure. Depending on the underlying support structure, this can cause excessive force to be experienced in the roof truss. As such, you should hire a fully qualified commercial roofing contractor or structural engineer who will be able to assess the loading present on the structure before you install the ballast. This will give you the best opportunity to optimize your use of ballast, keeping your roof structure from problematic bending.