Are UV bulbs really necessary?

[Merlin M]

They will get very little UV through glass I know window glass does let in a bit of UV (don't know the split between UVA and UVB though) but it drops off rapidly, you will see this with objects in a room those closes to a window fast most, and it is mostly UV to blame, you have lost all UV half way into a room I believe UVB drops off faster than UVB though

[romski]

Use a UV meter and measure yourself, UV does not have range limitations as implied. If UV passes through the glazing medium then it keeps going until blocked or attenuated.
The heat from the sun can also do significant damage.
Rom

[Merlin M]

I work in conservation, I have used UV metres and seen this myself, UV does just drop off, if you think about it we do not live in a vacuum the UV is hitting a "medium" those tiny molecules that make up air...

Heat does do damage, as does visible light, however the main culprit for furniture ect fading is UV, or so the conservation experts tell me... We do take into account the heat from direct sunlight... Ever gone to a historic house and seen blinds partially drawn?

More the point I was trying to make was that UV can get though glass, not huge amounts and it does not penetrate the room much. So in a green house there will be a small amount of UV close to the glass, but most likely not enough UVB...

[Catwoman63]

Xena one of my adults is roaming around my garden today and it is pouring down with rain, she has had a good warm up in the shed for a few hours and decided to go for a long walk in the rain, the younger ones are in the shed basking, not so keen on the rain, so they have heat and uv, so because I have my torts in sheds and no uv can get in to the sheds if is raining all day then the uv is on. I agree with Karen that one of my other adults zelda would bask and stay in the shed all day if I let her, I think she's a couch potatoe definitely, if I didn't have heat and uv light in the shed then it would be extremely dark in there and they wouldn't get going even with the light coming in through the window x

[kazzabb]

Originally Posted by Catwoman63

Xena one of my adults is roaming around my garden today and it is pouring down with rain, she has had a good warm up in the shed for a few hours and decided to go for a long walk in the rain, the younger ones are in the shed basking, not so keen on the rain, so they have heat and uv, so because I have my torts in sheds and no uv can get in to the sheds if is raining all day then the uv is on. I agree with Karen that one of my other adults zelda would bask and stay in the shed all day if I let her, I think she's a couch potatoe definitely, if I didn't have heat and uv light in the shed then it would be extremely dark in there and they wouldn't get going even with the light coming in through the window x

I've just had a thought Bev, do you think I should take the sky tv out of the tort houses? maybe it was the tv that was keeping them in? I wondered why the young males were in one house, and the females in the other - I bet one lot's been watching Discovery Shed and the other Corrie

[Catwoman63]

Ha ha, yeh Karen that would do it, I should mines Xbox out of their sheds then they will be so bored they will have no choice but to come out x

[romski]

I work in conservation, I have used UV metres and seen this myself, UV does just drop off.

The value read by the meter does drop off but its not due to the UV becoming weaker. As you move the UV Meter away from the window the light source effectively becomes smaller and the walls surronding start to have an impact on the reading. You can get the same effect with a camera. Close to the window the light reading will be high but as you move away the light levels decrease. Incidentally the same will be true in a greenhouse.

if you think about it we do not live in a vacuum the UV is hitting a "medium" those tiny molecules that make up air...


The UV light has travelled 93 million miles without attenuation. The 5 miles of dust and atmospheric water molecules will have removed all of the UVc but UVb and UVa remains (remeber the higher you are then the more UV there is). The glass will allow say less than 1% of the uv to be passed, the few water molecules in the room will have no effective attenuation effect compared to the 5 miles just travelled.

Heat does do damage, as does visible light, however the main culprit for furniture ect fading is UV, or so the conservation experts tell me... We do take into account the heat from direct sunlight... Ever gone to a historic house and seen blinds partially drawn?

More the point I was trying to make was that UV can get though glass, not huge amounts and it does not penetrate the room much. So in a green house there will be a small amount of UV close to the glass, but most likely not enough UVB...


Measurements of Uv will depend on the meter that is used, specific measurements of UVb can be made with a Solar meter 6.5 directly as UVI units. The 6.2 will has a different sensor and will measure UVA component also in uw/sqm. Each will give a different reading for the same solar irradiation. Other UV meters easily available may have unspecified spectral performance.

There will be no useable UVb in a greenhouse with conventional glass.


Rom

[Merlin M]

Originally Posted by romski

I work in conservation, I have used UV metres and seen this myself, UV does just drop off.

The value read by the meter does drop off but its not due to the UV becoming weaker. As you move the UV Meter away from the window the light source effectively becomes smaller and the walls surronding start to have an impact on the reading. You can get the same effect with a camera. Close to the window the light reading will be high but as you move away the light levels decrease. Incidentally the same will be true in a greenhouse.

if you think about it we do not live in a vacuum the UV is hitting a "medium" those tiny molecules that make up air...


The UV light has travelled 93 million miles without attenuation. The 5 miles of dust and atmospheric water molecules will have removed all of the UVc but UVb and UVa remains (remeber the higher you are then the more UV there is). The glass will allow say less than 1% of the uv to be passed, the few water molecules in the room will have no effective attenuation effect compared to the 5 miles just travelled.

Heat does do damage, as does visible light, however the main culprit for furniture ect fading is UV, or so the conservation experts tell me... We do take into account the heat from direct sunlight... Ever gone to a historic house and seen blinds partially drawn?

More the point I was trying to make was that UV can get though glass, not huge amounts and it does not penetrate the room much. So in a green house there will be a small amount of UV close to the glass, but most likely not enough UVB...


Measurements of Uv will depend on the meter that is used, specific measurements of UVb can be made with a Solar meter 6.5 directly as UVI units. The 6.2 will has a different sensor and will measure UVA component also in uw/sqm. Each will give a different reading for the same solar irradiation. Other UV meters easily available may have unspecified spectral performance.

There will be no useable UVb in a greenhouse with conventional glass.


Rom

Yes 93 million miles THROUGH A VACUUME! An awful lot of UV is cut out by the atmosphere, also you fall down by pointing out that you get more UV the Higher you are, so something is causing it to decrease... so when you have less than 1% as the glass has cut it out the drop off will be more acute...

I also know that the humidity in a room can easily be well in excess of 50% so there is a fair bit of water in the air in a room.

Remember also that UV is a wave, a form of energy, the more it passes through the more of that energy it loses...

Also as I have said UV causes furniture and fabrics ect to fade, it is PROVEN that the further from the window the less it fades, this I have observed myself.

[romski]

Yes 93 million miles THROUGH A VACUUME! An awful lot of UV is cut out by the atmosphere, also you fall down by pointing out that you get more UV the Higher you are, so something is causing it to decrease... so when you have less than 1% as the glass has cut it out the drop off will be more acute...

Why? For a given wavelength attenuation is linear and is proportional to molecule size and density.


I also know that the humidity in a room can easily be well in excess of 50% so there is a fair bit of water in the air in a room.

The number of water and dust molecules in 2 or 3 metres in a room is infentesimally small compared to it just having traveled through 8000 metres of atmosphere. The attenuation in a room would probably not be experimentally measurable.

Remember also that UV is a wave, a form of energy, the more it passes through the more of that energy it loses...

Attenuation of electromagnetic waves depends on the wavelength and the molecules it meets, doesnt it?

Also as I have said UV causes furniture and fabrics ect to fade, it is PROVEN that the further from the window the less it fades, this I have observed myself.

We have all observed this and if its on the other side of the room it is shaded and gets no decay at all. The further into the room it is , it will get less light as the sun moves across window front. Your conclusion is false.

UV radiation into a room will be in the low teens of microwatts per sq metre. Its so low I cant measure it on my 6.5 meter in my front room. The solar radiation today was about 950watts per square metre, most of it was in the longer wavelength and infra red (heat). The ratio of heat to UV seems to be about 60 million to one.


Anybody out there with a 6.2 that can do a measurement?

Rom

[Ozric Jonathan]

Hi folks

I can confirm that with a 6.2 solarmeter I get basically nill uvb in my living room which has standard looking house glass in the widows of single pane type. Right at the window and pointing the sensor at the the glass I do get a tiny bit but not enough to be of any relevance to a tortoise.

Having said that I got a bit lost a while back!