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I get where you're going with this, and I am not saying you're wrong, but some of what you've written is, at face value, misleading.

Let's address the one issue you're discussing here, relative humidity. As the term indicates, this is a subjective measure because it is RELATIVE, beings that it is a ratio of the current absolute humidity to the maximum capable, which is relative to the temperature, while also being further relative to the barometric pressure. So contrary to your statement "at exactly the same value", 75% RH at 90F is NOT the exact same value as 75% at 60F (although perhaps I'm arguing semantics over the meaning of "value"), only the relative measure is the same. Now, unless you have some wildly huge (or physics defying) enclosure, we can assume barometric pressure to be pretty much uniform throughout the enclosure (let's assume standard sea level), so at 90F you have an absolute humidity of 0.026 kg/m^3 (from a possible max of 0.034 kg/m^3), and at 60F you have an absolute humidity of 0.01 kg/m^3 (from a possible max of 0.013 kg/m^3). If you truly understand RH, then the VPD should be intuitively apparent - for the same RH, higher temperatures have greater absolute humidity but also much greater ability to absorb even more moisture than a lower temperature.

What you're pointing out about VPD is indeed accurate, and I can see how it is of greater value to people growing plants because 1) plants are stationary, and 2) evapotranspiration/transpiration is likely of greater concern with plants than is evaporation with reptiles.

However, this is not to dismiss your discussion, as I have to admit that in a tegu enclosure, I would be merely speculating that as one moves through the enclosure, I suspect absolute humidity likely doesn't waver that much except at the extremes, and that focal hotspots represent a "sink" for humidity. In relation to a tegu's needs....compared with what I measured in their natural habitat, every day of the year (except during some periods of the winter), relative humidity hit 100%, and did so for a significant portion of the day (quite often the majority of the day) - is this necessary for their health? I doubt it. Should you try to have elevated humidity? Yes. The argument is in what is actually optimal, and I don't think we can accurately assess that with what we have.

<blockquote data-quote="Roadkill" data-source="post: 160112" data-attributes="member: 3844">I get where you're going with this, and I am not saying you're wrong, but some of what you've written is, at face value, misleading.Let's address the one issue you're discussing here, relative humidity. As the term indicates, this is a subjective measure because it is RELATIVE, beings that it is a ratio of the current absolute humidity to the maximum capable, which is relative to the temperature, while also being further relative to the barometric pressure. So contrary to your statement &quot;at exactly the same value&quot;, 75% RH at 90F is NOT the exact same value as 75% at 60F (although perhaps I'm arguing semantics over the meaning of &quot;value&quot;), only the relative measure is the same. Now, unless you have some wildly huge (or physics defying) enclosure, we can assume barometric pressure to be pretty much uniform throughout the enclosure (let's assume standard sea level), so at 90F you have an absolute humidity of 0.026 kg/m^3 (from a possible max of 0.034 kg/m^3), and at 60F you have an absolute humidity of 0.01 kg/m^3 (from a possible max of 0.013 kg/m^3). If you truly understand RH, then the VPD should be intuitively apparent - for the same RH, higher temperatures have greater absolute humidity but also much greater ability to absorb even more moisture than a lower temperature.What you're pointing out about VPD is indeed accurate, and I can see how it is of greater value to people growing plants because 1) plants are stationary, and 2) evapotranspiration/transpiration is likely of greater concern with plants than is evaporation with reptiles.However, this is not to dismiss your discussion, as I have to admit that in a tegu enclosure, I would be merely speculating that as one moves through the enclosure, I suspect absolute humidity likely doesn't waver that much except at the extremes, and that focal hotspots represent a &quot;sink&quot; for humidity. In relation to a tegu's needs....compared with what I measured in their natural habitat, every day of the year (except during some periods of the winter), relative humidity hit 100%, and did so for a significant portion of the day (quite often the majority of the day) - is this necessary for their health? I doubt it. Should you try to have elevated humidity? Yes. The argument is in what is actually optimal, and I don't think we can accurately assess that with what we have.</blockquote>

[QUOTE="Roadkill, post: 160112, member: 3844"] I get where you're going with this, and I am not saying you're wrong, but some of what you've written is, at face value, misleading. Let's address the one issue you're discussing here, relative humidity. As the term indicates, this is a subjective measure because it is RELATIVE, beings that it is a ratio of the current absolute humidity to the maximum capable, which is relative to the temperature, while also being further relative to the barometric pressure. So contrary to your statement "at exactly the same value", 75% RH at 90F is NOT the exact same value as 75% at 60F (although perhaps I'm arguing semantics over the meaning of "value"), only the relative measure is the same. Now, unless you have some wildly huge (or physics defying) enclosure, we can assume barometric pressure to be pretty much uniform throughout the enclosure (let's assume standard sea level), so at 90F you have an absolute humidity of 0.026 kg/m^3 (from a possible max of 0.034 kg/m^3), and at 60F you have an absolute humidity of 0.01 kg/m^3 (from a possible max of 0.013 kg/m^3). If you truly understand RH, then the VPD should be intuitively apparent - for the same RH, higher temperatures have greater absolute humidity but also much greater ability to absorb even more moisture than a lower temperature. What you're pointing out about VPD is indeed accurate, and I can see how it is of greater value to people growing plants because 1) plants are stationary, and 2) evapotranspiration/transpiration is likely of greater concern with plants than is evaporation with reptiles. However, this is not to dismiss your discussion, as I have to admit that in a tegu enclosure, I would be merely speculating that as one moves through the enclosure, I suspect absolute humidity likely doesn't waver that much except at the extremes, and that focal hotspots represent a "sink" for humidity. In relation to a tegu's needs....compared with what I measured in their natural habitat, every day of the year (except during some periods of the winter), relative humidity hit 100%, and did so for a significant portion of the day (quite often the majority of the day) - is this necessary for their health? I doubt it. Should you try to have elevated humidity? Yes. The argument is in what is actually optimal, and I don't think we can accurately assess that with what we have. [/QUOTE]

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