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Can my replacement windows block dangerous ultraviolet light in my West Seattle house?

Can my replacement windows block dangerous ultraviolet light in my West Seattle house?
Can my replacement windows block dangerous ultraviolet light in my West Seattle house?
By BettyLoucal Jun 04, 2017


Today, there are thousands of variations of window and glass pane types on the market, so it’s impossible to say for sure that your current windows – or rather, the glass panes within them – block ultraviolet light or not. But, there are definitely ways of finding out if they do. There are simple and cost-effective UV light meters you can use on a sunny day. They’re used for people with kids who want to check the level of UV their kids are likely to be exposed to. Since you can get sunburned under cloud cover, you might never know what level of UV light you are exposed to on any give day, such a device can be very helpful indeed. They can be purchased online easily enough, and you can probably find one in the average department store. On a day – near the middle of the day – when the sun is shining directly onto, for example, your carpet, and through your window, place the meter right where the sun is shining. Then open that same window and let the sun shine directly onto the meter again. Note the reading for both with and without the sunlight going through the glass. That will give you a pretty accurate reading for how much of the UV light is blocked by the glass. Remember, though, that at an angle, the glass might block significantly more of the UV light than if it were to penetrate the glass at a perpendicular angle. Still, it should give you a good idea.

Modern glass can block up to 97% of ultraviolet light

There is type of glass called Energy 3 or something similar. It blocks 97% of all ultraviolet light that shines directly through the glass at a perpendicular angle. More often than not, though, light enters a house through a window at a significant angle, so the UV light must go through a “lot more glass”, because the glass becomes effectively thicker, the steeper the angle. Well, 97% is pretty good protection, and your carpets, furniture, children and pets are going to be safer with that higher level of protection. Still, you probably don’t need that here in the Pacific Northwest. Here, you’d have to stand by the window for a very long time to get sunburned, so it’s probably a bit of overkill. If, however, you live in southern California, it might be a good idea indeed.

The higher the percentage of UV block your window has, the darker the tint. You’ve probably noticed in hot regions of the country – or certainly, if you Google office blocks in warms regions of Asia and elsewhere – whole builds of glass appear to have a significant shade of green. That’s the UV block tint in the glass. It’s hard to produce glass that is perfectly clear and yet blocks most of the UV light.

Double glazing panes are usually a single unit

Double and triple glazed window panes depend on having a perfect seal to stop moisture, materials and even insects from finding their way inside your windows. With older multi-glazed windows, it often happens that moisture finds its way in between the panes. What happens is, essentially the seal breaks (or the glass cracks) and then it’s just a matter of the next rainstorm, or condensation near the seal failure. In the factory, it’s not just a question of sealing the new double or triple glazed window properly, but sometimes a supportive gas is also added. This gas can work as a light filter, as well as an agent to keep the glass protected.

Multi-glazed windows are manufactured that way, and when one pane of a two-pane window cracks, it’s normal to have to replace the whole unit of glass within the frame.

Good protection is not just about blocking ultraviolet light

It’s great to block unwanted UV light, and good windows should also be good at keeping the cold out in winter as well as the cool air inside during the warmer months of the year. But there is another function of windows I consider important, especially in this region as more and more people move into it, and street noise increases by the year. That function is soundproofing. If you’ve ever come home to an urban house that just got all its windows replaced, try closing all the new windows at once. It’s very likely you’ll notice the great quiet that new windows provide.

When windows age, they warp and leak. Even a seemingly small gap between the window frame and the house can let in a lot of sound. Over time, you forget just how much a window has to do for a home. Water, heat, UV light, security and sound insulation are all the jobs of the moder window, which makes them perhaps the single most effective way you can improve the quality of life in your home.

What side of the house are the windows on?

In the first house I owned, the back deck of the house had a great, unobstructed view. The problem was, however, it face south-southwest. This meant that for most of the warm months, when the sun shone, it baked the carpets, floors and curtains on that side of the house. The windows were old, and we also had a seal leak problem in most of them which made them look terrible when the sun shone. Well, I moved out of that house before I got round to replacing the windows, but this is a classic place where high filter window panes would be ideal. It would protect everything in those south-facing rooms, look more aesthetically pleasing, and offer heating, cooling and sound insulation, each at different times of the year.

The solution to your windows issue might be a mixed one. Perhaps on one side of the house, you have triple-glazing, while on the other side, double-glazing is quite enough. In addition, the windows on the front of your home could have a wood exterior, and a vinyl interior frame. That way, you get the beauty of wood with the strength and flexibility of vinyl.

More next week!

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