Maximum Yield Australia/New Zealand March/April 2018 | Page 12

i
ask the experts
Q
Hello,
I have a sealed growroom with CO 2 in my fruit cellar
in my basement. I find the lights can get the room up
to 31°C and wanted to know if I was to hook up a fan
and draw the 4°C outside air in, would I be passively
pushing the CO 2 out through small cracks? Your
insight would be greatly appreciated. 
Thanks!
David
A
Hello David,
Thank you for your question. Enriching a grow environment with CO 2 is
a great way to boost growth rates and a garden’s overall productivity. To
operate a CO 2 -enriched environment most efficiently, a grower needs to
make some adjustments to the growroom’s atmospheric conditions. As an
example, a typical growroom with an enriched CO 2 level of 1,200 parts
per million (ppm) will have an optimal operating temperature that falls
in the 26-30°C range. This is roughly two to five degrees higher than the
optimal operating temperature of a growroom without CO 2 enrichment.
Assuming you are enriching your environment to around 1,200 ppm,
the 31°C operating temperature isn’t too far off the mark. An intake
fan connected to a thermostat, or even an intermittent timer, would
most likely be all that you need to control the operating temperature.
When using an intake fan without an exhaust fan, the growroom will
experience a positive pressure. When growrooms have a positive
pressure, the air (CO 2 and all) within the growroom is forced out through
cracks and crannies. For some growers, this can become an odour
control issue because the air escaping contains the odours of the garden.
If odour is not an issue for you, I would proceed with the intake fan
installation (ideally teamed with some sort of thermostat or atmospheric
controller). If odour is a concern, you may want to consider a single
exhaust fan combined with a carbon filter, which, when operating, would
create a negative pressure in the room and draw cool, outside air into the
room through the cracks and crannies. I hope this helps.
Keep on Growing,
Eric Hopper
Eric Hopper’s past experience within the indoor gardening industry includes
being a hydroponic retail store manager and owner. Currently, he works
as a writer, consultant, and product tester for various indoor horticulture
companies. His inquisitive nature keeps him busy seeking new technologies
and methods that could help maximise a garden’s performance.
TEMPERATURE & PHOTOSYNTHESIS
Temperature affects a plant’s ability to photosynthesise and plays a key role in fruit and flower development. An increase
in temperature under CO 2 enrichment enables plants to properly process the additional CO 2 in the atmosphere and
increase the rate of photosynthesis, which increases plant growth. Carbon dioxide levels of 1,200-1,500 ppm will equal
an increased temperature range of 26.6-32.2°C
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