What You Can’t See Can Hurt You: How the Sun is Ruining Your Building Materials

Running behind schedule has an impact on more than your bottom line: it exposes building materials to harsh environmental conditions for longer than they are engineered to withstand. UV damage is a real issue with real consequences – yet it’s an issue that often gets overlooked because the damage can’t be detected through a visual check.

In addition to understanding specific project challenges such as scheduling and installation demands, building professionals need to understand UV exposure conditions of their job sites to ensure they are making the best product decisions.

When it comes to selecting a water-resistive barrier (WRB), it is expected that a product would be durable enough to withstand the day-to-day environment of a building site. However, exposure to UV light begins to have an impact on the long-term performance of the product from the minute it is installed until the moment it is covered with the exterior cladding – and this impact can be quite severe.

Naturally, building professionals turn to their manufacturer datasheets for the information they need to select products. In the case of long-term UV exposure, there is no ASTM standard on which a manufacturer may base its claim of acceptable jobsite exposure time. That means the allowable exposure ranges outlined in product information sheets tend to be merely marketing claims based on the short-term performance of the product and user convenience rather than real-world testing results or research. Therefore, in order to completely understand if your perfect wall will live up to its lifecycle, it’s not enough to simply familiarize yourself with these WRB datasheets.


Effects of UV exposure

Recent research has shown that when WRBs are left exposed for as long as considered allowable by many manufacturers, they can lose as much as 90% of their original water penetration resistance. This is a significant loss that has an impact not only on the effectiveness of the WRB, but on the performance of the entire wall system as well.

Unlike holes, cracks, or tears in a WRB, damage from UV light happens at the molecular level, so it may not appear until well after the exposure has happened and often when the wall is completely enclosed. As a result, a building can be performing poorly without any immediate visual evidence of the cause, leaving building professionals unaware and unprepared to deal with the problem.

Many builders expect their products to perform for the life of building, assuming they will get the performance qualities from the datasheet for the building’s operable life.  But, if the aging process of a WRB is accelerated due to excessive UV exposure, the product may only perform as hoped for a few years, eventually leaving a building completely unprotected.

Understanding the UV radiation expectations at your site can help you plan appropriately for exterior cladding installation and optimal product performance. For instance, Figure 1 illustrates the UV index for North America in July. Manufacturer time exposure ranges don’t include considerations for seasonal changes or geographical differences – something builders will need to determine independently. For example, we know that winters in Ontario would expect to see significantly less exposure than summers in Florida, so six months in both locations should never be considered equal.


(Figure 1) North American UV index in July.

Real-world testing for real-world results

Basic UV tests expose WRB samples to light from UV sun lamps for 10 hours per day for a total of 21 days. The test is designed to mimic the conditions that naturally occur in a typical construction site, but fails to represent some of the extensive exposure times that some manufacturers allow in their product literature – as high as 180 days.

Some builders and architects are taking competitors’ claims as fact and trusting the length of time they believe they have for UV exposure, unknowingly increasing their risk and liability. At Dörken, we believe the building industry deserves better, a solution that will actually stand up to the exposure it promises and deliver the high-quality protection and performance for which it is designed. Taking on this challenge, our product engineers have gone further than any other manufacturer out there by commissioning real-world research to uncover the unseen damage of UV. Complete research details and results of these accelerated aging tests on vapor permeable, self-adhered WRBs using extensive UV light are available here.

Based on this research, we’ve launched a product like no one ever has. Being a true manufacturer means we have the advanced engineering to create firsthand real-word products our users need and deserve, and in the process, advance the profession for smarter, better building.


Unique fourth layer of UV protection

Standing up to prolonged UV exposure on the jobsite, Dörken’s new DELTA®-STRATUS SA is the only WRB with a fourth layer of UV protection.

DELTA®-STRATUS SA is engineered with two outer layers, made up of high-strength, spun-bonded polypropylene fabric, which are thermally bonded to a highly vapor permeable, watertight polymeric middle layer. On top of all of this, the new product features an innovative acrylic UV-resistant coating that is proven to provide true UV protection currently unheard of in the building industry. This level of extreme protection means that DELTA®-STRATUS SA will be able to provide the high-performance weather protection builders need to ensure the long-term integrity of their buildings.


Build smarter, build better

It’s clear that product selection is crucial. Once a WRB is enclosed behind the wall, it’s difficult and expensive to assess its condition and performance. Whether you’re the architect, owner, or a contractor, you need to know the facts when choosing a WRB for a project. From there, using best practices for scheduling, planning, and covering your WRB as soon as possible is always highly recommended. By minimizing exposure, no matter the product, you will help to limit the impact UV will have on the long-term performance of your WRBs, and ultimately your build.