Across the nation, rooftops are bearing solar panels. These expanses have become valuable plots of electricity generating real estate. A solar ready roof is one that will make the installation of a residential or commercial solar power system an easier task.
The purpose of this guide is primarily to assist relevant professionals in the building and construction industry in designing roofs that are solar-ready.
Roof pitch
As it is cheaper and easier to install a solar PV array flush with (or parallel to) the roof than to use a tilt frame. The ideal pitch of a roof is 10° to 30°. In addition to help maximizing panel efficiency, a solar PV array needs to have an inclination at least 10° above horizontal to allow rain to clean the modules and to prevent the accumulation of dirt and other deposits.
Static load
A solar panel array will exert a static load on a roof of an additional 10 – 15 kg/m2. In most scenarios, this extra load will not impact the design of a residential building’s frame as the frame will already have design to withstand a live load of 25 kg/m2.
This may not be the case in some large cost-optimised commercial buildings. These may have limitations by a combination of static load and wind down force. In these situations, you will require larger purlins and rafters.
Wind load
An array of solar panels is subject to uplift or down force wind actions as defined by AS/NZS1170.2. How these forces come into play may vary as different zones of the roof have different exposure to different loads. Tilted PV arrays are subject to more pronounced wind forces than flush mounted arrays. In most installations, uplift forces will dictate the design of solar mounting system and its method of attachment to the frame.
Mounting System Fixing Method
The simplest, fastest and overall cheapest method affixes the solar mounting system to the building frame using standard roofing screws. This assumes the building features standard sheet metal roof cladding. We don’t recommend membrane roofs as they are very difficult to fix through.
Roof Cladding Thickness
Sheet metal roof cladding of 0.48 mm Base Metal Thickness (BMT) will be more durable than 0.42 mm BMT which is more common on residential buildings. As commercial solar installations require more time and traffic on the roof than domestic, the thicker 0.48 mm cladding provides a lower lifetime cost.
Parapets
While parapets can reduce wind load on nearby solar panels arrays, their presence can also increase shading. That may significantly impact the electricity production of a PV array.
Roof access
Solar installation and maintenance personnel need to access the roof, move safely on it and to access the solar array from all sides. In residential scenarios, we recommend that you maintain a 1m gap between the roof edge and the array. On commercial buildings, a 4 metre gap is typical. Commercial roofs should be provided with safe access points and also feature harness attachments points.
Residential Solar Ready Roof Summary
SunLock is a manufacturer of premium quality solar panel mounting systems. They recommend using standard sheet metal roof cladding pitched at 10° to 30° and standard roofing screws. In a situation where a building uses lightweight engineered trusses, the truss supplier should be design and warrant trusses capable of supporting sufficient capacity to permit the entire rooftop to have solar panels.
Commercial Solar Ready Roof Summary
SunLock recommends using 0.48 BMT sheet metal roof cladding pitched at 10° and fixed using standard roofing screws on commercial buildings. Spacing between purlins should be a maximum of 1800 mm.
Where a lightweight cost-optimial frame is going onto a building, the structural engineer should design and warrant the building frame to allow the entire roof to have solar panels. This will most likely require some minor changes to the frame, including sturdier purlins and some rafters.
This solar ready roof guide sources material from a document written by SunLock, manufacturers of SunLock mounting systems. SunLock’s design is by installers, for installers and is proudly Australian made. SunLock is wholly owned by Energy Matters’ sister company: Apollo Energy.
SunLock mounting systems are in all Energy Matters residential and commercial solar installations. They provide installation manuals and certificates of structural suitability for download at www.sunlock.com.au.
