In the UK, solar power is becoming more popular than ever before as it makes the transition from an investment leaning on government subsidies to a mainstream choice for cheaper and renewable energy. According to figures from the Department of Energy and Climate Change, the last 12 months have seen a significant growth in installed solar photovoltaic capacity, with well over 8 gigawatts being produced nationwide in December 2015, compared to the 5 gigawatts produced during the same month in 2014.
On-roof systems are the first generation of residential solar panels; whereas roof-integrated systems are a relatively new phenomenon. On-roof solar systems consist of a set of solar panels attached to your roof by a mount, which is bolted onto your tiles. Roof-integrated panels are designed to be incorporated into your roof surface, dual purposing as a MCS 012 approved building material, and when installed will replace a section of your tiles.
While both types of system will perform an efficient job at harnessing the sun’s energy, more people are opting for roof-integrated as opposed to on-roof systems. Read on to find out why this is the case.
One of the biggest risks of installing solar panels is voiding the warranty of your roof. With on roof solar installations the mounting system installation instructions recommend notching the roof tile around the roof hook to ensure it doesn’t disturb the roof plane, modifying this crucial penetration point means susceptibility for water ingress will invalidate any of the major roof tile manufacturer’s warranty.
Avoiding notching out the roof tile means the system will not sit properly on the tile below which will also invalidate the roof tile manufacturers guarantee as it will not be installed as per manufacturer’s instructions as a consequence it will be extremely susceptible to wind driven rain.
Roof integrated PV systems, are installed as an integral part of the roofscape. Certified to MCS 012, they perform as a building product, protecting against wind lift, weather and other elements and are usually installed at the time of installing or replacing a roof, this makes them ideal for house builders, landlords and self-build projects. As both tiles and PV are installed together with PV parallel to the tiling, it means there is no modification to the roof tiles, securing the validity of the warranty.
Installing on-roof solar adds additional weight to the roof structure which puts unnecessary strain on the roof structure. At 20kg per solar module plus the weight of the mounting structure it subjects the timber frame to additional strain under the weight of the system.
Roof integrated systems are installed as part of the roof, as the system weighs approximately 15kg/m2 opposed to a large format concrete roof covering such as a Russell Grampian weighing 56KG/m2. Meaning no additional weight loading or the problems that could occur as a result of additional weight on the roof.
At one point, a major selling point for on-roof PV systems was the fact they were a lot cheaper to purchase and install than roof-integrated systems. This has become less prevalent, however, as the price of roof-integrated tiles has been greatly reduced as they have grown in popularity with homeowners and construction companies. The overheads for each system are marginal, and when considering the additional labour cost for on roof systems; to install the roof covering prior to the PV installation and additional programme cost to install the roof covering prior to the PV, many people are now opting for the solar solution that offers the most advantages rather than the cheapest price.
The installation of on roof standard module systems occurs on a completed roof. As roof tiles are not designed to be walked on, there is an increased likelihood of roof tile replacements due to hairline cracks as a consequence of foot traffic which only become evident 9-12 months following capillary action and weathering.
Although roof integrated tiles can easily be retrofitted, they are usually installed on new-builds or for re-roofing contracts which means the PV tiles are fitted at the same time as the roof tiles, meaning foot traffic and replacements are much less likely to occur.
There is no discrepancy that even though on-roof systems are sleeker than ever before, they hold no comparison to the aesthetic of roof-integrated PV.
The simple fact that the tiles are concealed within the body of the roof, often in the same or a similar shade as the roof surface, makes them a lot more visually pleasing than the bulky look of on-roof mounted tiles. Roof integrated systems make it easier to pass difficult planning conditions and can even be used in heritage sites
Discreet roof-integrated PV systems can add more value to a house, as they do not detract from the aesthetic appeal of the building’s façade. This is often an important factor for owners looking to re-sell properties and house builders.
After taking stock of the numerous advantages that roof-integrated PV systems hold over on-roof systems, it is easy to see why they have had such an increase in popularity. As solar technology is developed, these advantages may grow to be so numerous that consumers have little reason to consider a residential on-roof PV system at all.