Beginner question - sun light via window glass vs uvb light

[Rayc]

I don't have own backyard, i bring my tortoises to the garden downstairs every weekend if it is sunny. During weekday, should I place them beside the window which they can enjoy 2-3 hr sun light or keep them in the enclosure with the UVB light on? Which one should be benefit better in terms of absorbing UV?
If I want a general idea of how much of UV light % lost after window glass, will it be 50%? 30% or even lower?

 

[dmmj]

Modern Glass Blocks most of the UV light do to imperfections in the glass itself as high as 95% from what I can gather put them next to a window if you want but it's next to useless a UVB light would be much much better

 

[JoesMum]

Modern Glass Blocks most of the UV light do to imperfections in the glass itself as high as 95% from what I can gather put them next to a window if you want but it's next to useless a UVB light would be much much better

Agreed. There's no benefit from sunlight through window glass.

If your tortoise is only going outside on sunny weekend days then it must have a UVB lamp indoors as well as a basking lamp.

 

[Rayc]

Thanks a lot for your advice, it save me a lot of effort and risk putting them next to window.
I should have proper lightings in the enclosure.

 

[Gillian M]

Hi @Rayc and welcome to the forum!

Any pics of your tort?

I also take Oli (my beloved Greek tort out for a so-called "walk" when the sun is striking here in Jordan. He loves it.

Where do you live?

 

[Rayc]

Hong Kong, I do not take many photos, here is one by the CCTV in the enclosure

 

[Kapidolo Farms]

I wouldn't say there is NO benefit, but glass has iron in it and that is what blocks the UV. However much light that is otherwise 'natural' and warmth can come through glass. But the UV does not.

A part of the enclosure that does not get window sun might be an important feature so the tortoise does not get overheated, glass can have a magnifying effect as well.

You can use a UV tube in a way that compliments your tortoise for when it does sit in the 'sun' for just a few hours a day (on a timer) extending the UV life of the tube.

 

[Markw84]

Agreed. There's no benefit from sunlight through window glass.

If your tortoise is only going outside on sunny weekend days then it must have a UVB lamp indoors as well as a basking lamp.

Actually, @Will it is because of the actual makeup of glass - Silicone Dioxide and Sodium dioxide. These combined components have a bandgap of 4 eV which means that it will absorb any wavelength shorter than 310 nm. Its really the molecular makeup of glass, and the way light passes through... Sorry to bore so many!