Preparing your roof for a new photovoltaic installation
Going green and installing a new photovoltaic system on your roof ? Like any other endeavor, proper planning is essential, and this applies both to new roofs as well as existing ones. Water tanks, satellite dishes, aircon units and water pumps are all competing for space on our roofs, so it can be quite challenging to organize all this clutter when you want to maximize the generation of clean energy. On top of this, we want to be able to have safe access to maintain all this equipment on our roof.
Planning is everything
Propper planning starts by taking stock of all the equipment that must be located on the roof. On existing roofs, we sometimes find old unused equipment that can be disposed off or moved in order to free up space. Next, we need to take dimensions of the roof, the parapet walls and the equipment and draw up a sketch. A PV system should ideally be facing south and the buildings orientation can be found with the use of a compass, googlemaps or the direction that satellite dishes in the vicinity are usually facing. If the roof if off south by up to 30 degrees, no significant degradation in performance will occur and it might be more practical at times to keep the PV system aligned with the roof in order to allow for better access and to be able to fit in more PV panels. We must also bear in mind that the planning authority’s maximum height restriction for PV panels is that of 1 meter from the roof’s base.
Since PV panels should be kept clear from any shading caused by obstacles in order to minimize losses, they should be the first items to be placed facing south and all other equipment on the roof should be placed behind them. The panels should also be kept around 2 meters away from south facing parapet walls which are 1 meter high. If this means that the PV system must be pushed further back, you could also consider using specially sloped water tanks that can be placed under the panels to save space. These also have the added advantage of keeping the water cool in summer and acting as a barrier to wind blowing against the PV panels. Aircon units can optionally be placed next to the southern facing wall if this is around 1 m high. If the roof has many obstacles which might pose shading on the PV panels, a professional PV company should be contacted so that they can perform a proper shading analysis using computer aided design tools in order to assess the level of shading and propose alternative design layout configurations to maximize the yield form the system.
Waterproofing comes first
Water proofing measures for the roof such as liquid membranes or bitumen membranes must be installed prior to a PV installation. It is never a good idea to have the roof penetrated by the PV installer as this can result in water ingress and possibly void the membranes effectiveness and warranty. Another point worth mentioning is that the strong windloads imposed on PV systems can eventually damage the roof screed when a PV system is anchored directly to the roof. Ideally, the PV system should be anchored onto concrete ballast blocks which are placed on a protective membrane sheet so that they do not damage the waterproofing material. A PV system which has windbreakers installed on its structure also reduces the amount of ballast required on the roof and guarantees that the system is safe for wind loads up to force 12.
Old roofs ?
Old townhouses or houses of character which have roofs made from stone slabs must be given special consideration. These stone slabs were not designed to withstand both the vibrations caused by windloading as well as the weight of a PV system. The same applies to roofs where the concrete is not strong enough for the added weight and windloading of a Pv system. In most cases, a separate sub structure made from galvanized steel needs to be installed to support the PV systems aluminium A-frames.
Other system components
Another important component in a PV system is the Solar inverter. Ideally this should be located outside, on a north facing wall and close to the exit from the roof so that it can be switched off safely and conveniently when lighting storms are about to take place. This protects the system from unnecessary voltage surges and ultimately damage to the PV system. It is also worth considering which path the cable from the inverter must pass through to reach the exiting households consumption meter where the new PV meter will be located. Sometimes this can be passed through shafts or conduits specially prepared for the PV installation at the building stage. Otherwise, this cable must be passed along the building’s façade.
In some modern villa developments, tenants are contractually obliged to have their PV systems installed at extremely low angles in order to avoid any visibility from neighbouring properties for aesthetic reasons. In this case, special mounting structures should be employed to ensure compliance.
Need more help ?
For more information on planning you roof for a new photovoltaic installation feel free to contact one of our representatives today for a free onsite visit on firstname.lastname@example.org.