Posted by Tom Raftery PV Product Manager on 16 Sep 2016 at 2:55pm - tagged with 2016, biosolar

Improving the energy efficiency of existing buildings is an ever-increasingly important challenge. By retrofitting photovoltaic (PV) panels onto a roof it can not only produce electricity for the building’s use, but it also brings all the benefits of low maintenance renewable energy generation to your project that can assist with meeting crucial sustainability targets. However, retrofitting a roof with renewables brings with it many additional considerations that are not necessarily relevant in new build applications...

Arguably the most fundamental considerations when contemplating a PV roof retrofit are weight loadings and design calculations; however another significant factor is ensuring that the life expectancy of the waterproofing system matches that of the new technology. Discounting this consideration could potentially result in the array needing to be removed early in order to reinstate the integrity of the roof. Thus, the ideal time to add photovoltaics is to do it simultaneously when refurbishing the waterproofing system. Shading on the roof area can also have a detrimental impact on PV efficiency, as shading on one module can reduce the output of the entire string. This means that the power output for the series is reduced to the level of current passing through the weakest cell, which is especially important if the building’s roof space is overlooked by buildings or trees. One way to reduce the negative effect of shading on your PV output is to incorporate a performance monitoring system that identifies any irregualities and stops individual modules from impacting the performance of the other modules in the string. Optimising systems like this also typically allow for remote web based monitoring that helps with future maintenance.  

When deciding what PV system to choose for your retrofit project, both weight and profile of the module must be considered. A low-profile module can not only optimise energy generation but also ensures the modules are unobtrusive making it easier to overcome planning issues, especially on protected buildings. Bauder's PV system is the most lightweight module in the market at 9-12.5Kg/m2 (depending on module selected) and is set at a 12° angle making it a natural choice for retrofit applications. The integrity of the roof covering is also completely upheld during the installation, as the Bauder system is installed using a unique penetration-free fixing method. This installation method means that the roof is not compromised by penetrations for fixings nor is it ballasted, which would add additional weight loading to the roof. 

Another common question faced by industry professionals when retrofitting a flat roof is whether they should incorporate PV or a green roof; however these two technologies are no longer mutually exclusive options with the introduction of biosolar roofs. A biosolar roof is the successful combination of biodiverse and extensive green roofs with photovoltaic systems, delivering a duality of technologies for environmental advantage and increased profitability for the building owner. Although designed primarily for new build applications, the biosolar system can also be retrofitted on many existing roofs without the need for any structural modification to the building. However, designs that do not perform optimally for both technologies are often as a result of people assuming that the solar panels require more technical input than the green roof. Getting the green roof element wrong can mean the vegetation is forced to grow around the panels, which results in shading and understandbly reduced energy generation. Therefore, it is crucial that a green roof specialist is involved in the project from the start in order to ensure the most suitable vegetation is selected.

Ultimately, a collaborative approach is needed throughout the survey, design and installation process from all project stakeholders to ensure the maximum benefit for the client and building owner. With Bauder able to supply all of the waterproofing, green roof and PV elements, it gives you total confidence that it can successfully deliver all elements for your retrofit project. 

Tom Raftery
PV Product Manager