A common question customers ask is “How will my skylight fair in a hail storm?” While many manufacturers claim hail resistance on their products, there are a number of critical factors that will influence a product’s resistance to hail damage.
While there is a simulated hail resistance test available, it’s very difficult to truly simulate a real and severe hail storm, such as the recent storm in Canberra on January 20th 2020, where hail is coupled with strong gale winds and heavy rain. The best and truest test of hail resistance, is from products that consistently outlast such events.
When selecting products for maximum hail resistance, there are a number of characteristics that will quickly indicate how well the skylight is likely to withstand hail.
- Type of material
- Size of the product
- Shape of the product
- And thickness of the material
Type of material
The most common materials used to manufacture skylight domes are acrylic, glass and polycarbonate.
Acrylic comes with many different qualities, and it is the most common material used due to its resistance to UV damage, discolouring and long term retention of clarity. Skylight manufacturers should always choose the best quality high-impact acrylic, but often cheaper products are vulnerable during severe weather events due to poor standards in manufacturing processes and in the low quality of raw materials used.
Glass also comes in many levels of strength and impact resistance. Price is often a good indicator of quality, and due to the large size of the glass market, many of these products offer quality impact testing.
Polycarbonate is one of the strongest plastics available, and products using this material are often used to demonstrate the sledge hammer test. However, this product is quickly affected by exposure to UV, which brakes-down the material turning it yellow. This quickly deteriorates the product’s ability to provide good quality natural light. These products are commonly used in warehouses with large, long, yellowed sheets that no longer provide good natural light.
Size of the product
The larger the size or surface area of the skylight, the more likely that hail stones are going to hit the weakest part of the surface.
Shape of the skylight
When it comes to hail stones, a skylight’s weakest point is where the hail stones strike the product at right angles to the surface. This makes the shape important, as domed shapes are more likely to allow hail stones to skim and ricochet off the surface, flatter shapes are more prone to take the impact at damaging perpendicular striking angles. The shape can also influence the ability of the skylight to absorb the strike and disperse the impact.
Thickness of the product
Whilst providing a consistent thickness of material is relatively simple on a flat product like glass, many dome shaped skylight products are manufactured using a process called vacuum forming. This process involves “stretching” the material into the desired shape. When stretching a sheet of 3mm material, you often end up with wall sections as thin as 1.5mm which are then very vulnerable to a hail strike. This is also why vacuum formed domes often have flatter shapes, which in turn limits how well they deflect hail stones. The other, superior acrylic manufacturing process is injection moulding. This involves injecting molten plastic into a precise mould, which results in a uniform spread of material and a consistent thickness throughout the entire component. This also allows the dome to have the optimum shape for strength, impact resistance and light capture.
In the end, all skylights are vulnerable to hail, but quality products are engineered and tested not to break until hail stones are large enough to break roof tiles, solar panels, dent roof sheets and damage cars. In these severe circumstances, damages are covered by insurance. In areas that experience regular severe weather events, such as parts of Australia prone to cyclones, reputable manufacturers will offer accessories designed to minimise damage from severe impact or strike on the skylight. This will often be by means of a secondary barrier that will prevent water damage when the main outer dome is impaired in a storm.
During the recent hail storm in Canberra on January 20th 2020, the local Solatube dealership received over 500 calls for skylights with hail damage. As seen by above, the majority of these product where not Solatube Daylighting Systems. In fact, less than 1% of Solatube skylights were damaged in the storm that saw hail stones often larger than a golf ball.
Often after these types of storms, homeowners anxiously search to find replacement parts for the often unique products that they have on the roof. It’s relatively simple to make a cheap skylight, and many manufacturers come and go, so when choosing your skylight – look for reputable brands such as Solatube Australia, leaders in Tubular Daylighting Systems for over 30 years.