The Smart Growth Blog

Lightning type vs VPD - The hidden implication of your lightning choice

Written by Geoff Brown | Dec 8, 2022

In this episode of FAQ with AGIQ, we're going to talk about some of the considerations between lighting type and vapor pressure deficit, or overall, how the temperature of your space versus your lighting choice matters.


Episode Transcription:

In this episode of FAQ with AGIQ, we're going to talk about some of the considerations between lighting type and vapor pressure deficit, or overall, how the temperature of your space versus your lighting choice matters. We talked about how LEDs have the potential to reduce your leaf surface temperature or discharge lights, increase it, requiring different room conditions.

One of the biggest impacts on this for you as a grower, though, is it means a significant change to your space temperature and relative humidity. If you want to be in the same part of the VPD curve and you probably do. A flower room in discharge may have been at 75 degrees and 50% relative humidity and LED lit room to achieve the same leaf temperature might be at 85 or 86 degrees and more like 65% relative humidity again to stay within that same part of the VPD curve.

And that requires a broadly different approach to your HVAC. The dew point coming back to the machine, the total energy in air coming back to that machine is vastly different. Even more than that, though, you probably haven't changed your lights off temperature because for the lights off condition, nothing has changed in that room. Obviously, your lights aren't on, so LED versus discharge no longer matters.

What that means is that you need an equipment, or a piece of equipment, that can accurately control your space at a high temperature, high entropy condition, you know, 85 plus degrees and 60 plus percent relative humidity. But that's also able to accurately control your space during the lights off condition, as low as 65 degrees and 50% in relative humidity, not uncommon.

So, the range in sensible heat ratio in the range and output capacity is much bigger than it's ever been. And when you're selecting your HVAC system and designing your HVAC system and building your ductwork for this facility, you need to ensure that the system you choose can accurately control that very wide range of conditions, much different than you've ever had to before.

If you have any questions about that, please get a hold of qualified mechanical engineer, MEP firm, design build contractor, or we're happy to help out in any way we can as well.

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