Can Fans and Filters have quickly become industry standard. The CF group is continually pushing the bar up a notch with their innovative ventilation products. We just got some great new things from them. People have been asking for these changes and now they are available. 1-866-PGS-GROW
Summer is upon us. And most indoor gardeners, unlike their outdoor counterparts, are hoping for a poor one. A hot summer usually means hot growrooms. High temperatures in your growroom can devastate the quality and quantity of your crop. Plants ‘survive’ rather than thrive. Some growers even shut down their operations all together preferring to reserve their energies for later in the year. But there are many ways to counteract rising temperatures, as Everest Fernandez explains:
48 degrees Celsius. It’s roughly the temperature of my oven when I warm some plates. You can also experience this heat by visiting Delhi in May. Unbelievably, it was also the maximum temperature recorded in my friend’s growroom a few years ago. Despite a generous watering the day before, the vast majority of his plants had wilted, most likely cursing him as they shrivelled. Featherlight pots, frazzled, crisp leaves… it was all a very sorry sight. Tragically they were six weeks into flowering and it all ended right there and then. The yield was poor. And the quality was … embarrassing.
What had gone wrong? Well, everything really. It was the first time my friend had ever grown in a loft and he didn’t fully appreciate that un-insulated roof space is particularly susceptible to extremes in temperature. i.e. in the winter it can get very cold, and in the summer it can become like a furnace. Whereas I was smugly enjoying fairly uniform temperatures all year round in my cellar.
My friend’s attic set-up was overly simplistic – mainly due to his resistance against parting with much cash. Fifty or so plants in ten litre pots were relying on on “natural ventilation”, as he put it, from the eaves. Yes, that’s right, just a few oscillating fans were shifting the air around with no artificially created inflowing air and no extraction! Now add 3,200 watts of light to this monstrous equation, a Great British heatwave, mix liberally with inexperience and downright stupidity, and the result? I could actually smell the plants cooking when I opened the loft hatch…
Ok, enough extreme examples! But what does ‘too hot’ actually mean in botanical terms?
Everest’s Hot Grow Room Rule Of Thumb
If it’s uncomfortable for you to be in your growroom, then it’s highly likely that it’s uncomfortable for your plants too. So, if you find yourself ripping off you t-shirt (grrrr!) after a few minutes of plant-tending and drying your sweaty pits infront of a fan then let this be a clear signal to you that you have a heat problem!
When temperatures are high more water (in the medium) is lost to evaporation. If the nutrients are then too concentrated in the drying medium the roots will burn and the leaves droop and may be lost altogether. When temperatures rise above a certain level plants effectively shut down photosynthesis and just concentrate on surviving, rather than focusing on growth or flower development. Damage will not be obvious but the delay to production will be. High temperatures can also cause some plants to ‘stretch’ and become leggy. Deadly root diseases like pythium thrive in high temperatures.
Everest’s Ideal Growroom Temperature
I’m happiest when the maximum temperature in my growroom is around 25 to 27 degrees Celsius. 28-32 degrees celsius is tolerated but is not ideal. I measure this temperature by placing a probe in a shaded spot in amongst the plants. I like my minimum temperature to be around 15-18 degrees Celsius.
Heat Problems And Growroom Solutions.
Ok so we’ve established excess heat as our enemy. If you grow plants for essential oils then you should be particularly vigilant against high temperatures – ideally you should be looking for a 10 degrees Celcius difference between your daytime and nightime temperatures.
Ambient Temperature (i.e. the actual temperature outside)
It may sound a bit obvious, but it’s worth pointing out: If it’s hot outside it’s going to be hot inside. Make sure your lights come on at night when outside temperatures are cooler. Consider a shorter cycle (eg. 10 hours on, 14 hours off) to speed things up a bit. Keep inflow and extractors on 24/7 – plants are still busy developing at night and enjoy fresh air during this time too. Try to take air from a cool room in the house or an outside vent in a shady area. If your house is too hot for plants, try reducing the thermostat temperature of your central heating. You will get used to the lower temperature in your house very quickly and your health may improve. Your wealth certainly will as your electricity or gas bill drops. The ultimate solution? Seal your growroom and invest in an air-conditioning unit and CO2 emitter. We’ll be looking at AC units, evaporative coolers, ultrasonic humidifiers, and reservoir chillers in the next issue.
Heat from bulbs
H.I.D. lights produce a lot of heat. And as bulbs become older they produce less light and more heat! So there we have two very good reasons to change them regularly! Air-cooled lights allow you to isolate the hot air around the bulb and vent it outside of your growroom! Water-cooled lights have been offered in the past, the dangers are so obvious that we don’t need to mention them. Protect your rootzone by covering pots or tanks with white or silver reflective corriboard or plastic sheet to reflect away the direct heat from the lamps. The roots are particularly sensitiveve to heat. Leave some space around the stem to allow it to breathe.
Insufficient air transfer
It’s no good just moving the air in your growroom around with an oscillating fan. In the absence of an A/C unit, you are going to need to provide fresh air for you plants to breathe. This also means you can replace hot air with cool, and so reduce the temperature in your growroom.
In order to create an effective inflow / extraction system you are going to need to know the volume of your growroom, and thus the amount of air you are trying to exchange.
Everest On Air Transfer
Check out our complete guide to growroom ventilation (based on energy rather than room volume.)
A simple rule of thumb is that you need 12 times the volume of your room in air moved every hour. If your actual room is much bigger than the area used for growing then imagine a comfortably-sized room around your plants and use that size in the calculations. For example:
height x length x width 2.3m height x 4m length x 3m width = 27.6m³ For room measurements in feet divide the ft³ by 35.3 to get m³
12 x 27.6m³ = 331.2m³ so the fan you select should have more than 331 m³ per hour of airflow.
If using a carbon filter multiply the number by 1.5 as some of the power of the fan is used in forcing air through the filter. Ducting should be as straight as possible to avoid reducing the airflow.
CO2 reduces the need for air-changes due to the plants being more resistant to heat and not losing so much water. The plants should still not be allowed to get above 30 degrees celsius. If the heat is not too bad 8 changes of air per hour will be enough.
The air you draw out of your growroom should be taken directly from around the H.I.D. bulbs and / or from the top of your growroom (as warm air rises).
In attics, consider investing in some vented roof tiles fitted. You can fit flexible ducting directly on to these and pump hot air directly out of your growroom to the outside world. Also, note that many modern houses are now built with ducting from bathrooms and cookers that leads straight into the loft and out through the roof. It’s possible to double up these precious routes to the outside world by fitting a ‘Y’ shaped adaptor that allows two ducts to share the same exit. But remember, don’t interfere with chimneys or ducting from boilers, gas fires or any other sources of carbon monoxide – mistakes can be fatal!
It’s important to balance the rate of “air in” with “air out”. When choosing your inflow fans and extractors, I think it’s best to ‘over-spec’ slightly and run them through a fan controller unit such as a Klimavator or Prima. Too much air passing through your growroom will have a drying effect on your plants. Whereas an imbalance of inflow and outflow can have strange effects too – I recall a pair of friends who spent most of their money on half a dozen standard 600 watt lights, blazing away in their attic. The high temperatures and swampy feel in the growroom indicated that they should have allocated more of their budget to more suitable inflow and extraction. They tried to fix the situation by pumping air from the downstairs kitchen (the coolest in the house) up into their attic through a huge ‘elephant trunk’ of ducting attached to a monster RVK 350 fan. They fired it up and the cool kitchen air dropped the temperature in their growroom by 10 degrees celsius in as many minutes. But, because of the inadequate extraction, the hot swampy attic air was simply pushed all the way downstairs back into the kitchen! This, of course, quickly rendered their efforts redundant.
If your growroom is well insulated it will be less affected by changes in ambient temperature. This is why cellar growers (insulated and cooled by moist mother earth!) enjoy such uniform temperatures (albeit often with higher humidity thrown in).
Opt for lights with remote ballasts – more or less the norm these days. Ballasts give off a surprising amount of heat. It’s worth packing these boxes of joy away for a number of reasons – not least, safety! You don’t want ballasts anywhere near your nutrient solution reservoir any more than you want water-cooled lights, for example! Invest in ballasts that have longer cables so you can stash them away from all the action.
Thanks to UrbanGarden Magazine for the Article- Original Page Here
PGA Blog Readers Comments