Everyone loves sunshine, yet like fire, it can be either a wonderful warming experience or a hazard to life and property. It all depends on what you do with it. And if what you do is expose your roof to the sunlight all day long every day, your roof can get UV damage, just like your skin can. But how exactly does that affect your roof? Here's how it works and why it can be a problem.
How it works:
When sunlight hits your roof, most of it is absorbed (at least if your roof is the classic black asphalt shingle type). This means that most of it is converted into heat, which is why black roofs get so hot during the day. Heating up a lot every day and cooling down a lot at night isn't good for your roof, as it turns out. Plus, a lot of those sun rays are the UV type, which can actually damage the surface of your roof. This changes its texture and makes it behave differently. It's similar to the effect that sunlight has on asphalt roads (after all, they are both made of asphalt).
Why it can be a problem:
The UV rays change your shingles' texture, making them more brittle and less stretchable. This will mean that they have less flexibility to protect them from temperature-change damage such as thermal shock. When you think about it, that makes your roof a lot more vulnerable to a lot of the situations it gets placed in throughout its life. Plus, the same sun that made the shingles less flexible is still heating them up to boiling (well, not quite that hot, but still pretty hot) on a daily basis. This heating process means the shingles have to expand (because like so many other things, they expand slightly when heated and contract slightly when chilled). The more flexible they are, the better they handle this; and the less flexible they are, the more likely they are to succumb by cracking or tearing or warping.
As you can see, the sun isn't really your roof's friend. If you want to diminish the damage it inflicts on your roof, you have a couple of options. You can either shade the roof (using strategically placed trees, shade sails, or something similar) or make the roof less likely to absorb sun. Doing that will require either replacing your roof with a more reflective, less absorbent roofing material or coating it with a "cool roof" coating. It's possible to find these coatings formulated for asphalt shingles these days, but do be careful; using them might void your roof's warranty, as manufacturers tend to not want you to mess with the roof's surface (it can make the protective granules stop functioning as they were intended, and the manufacturer doesn't want to be responsible for that).
For more information, you will want to check out a website such as http://www.affordableroofingfl.net.