System Three offers one epoxy system called SB-112 that is UV-resistant. This epoxy system is formulated to have maximum ultra-violet light resistance. However, epoxies in general do not perform well in exterior environments where UV exposure occurs. Exposure to direct sunlight causes the epoxy to break down, which leads to the possibility of moisture intrusion to the substrate. Epoxies which have UV absorbers added, such as SB-112 gain some UV resistance and are good for projects that will only have short exposure to the sun. Projects that will be in long term direct sunlight will benefit from applying paint or a quality UV protective clear coat. See links below for System Three UV protective coatings.
System Three has a detailed procedure for protecting outdoor wood projects from moisture and damaging UV exposure. See detailed instructions below.