Environment is Everything -perfect your grow room environment now!

The Growing Environment

Having worked in the industry for many years and hearing the same questions throughout this time we find ourselves giving the following advice over and over again. It really is the single most important piece of growing advice you will ever hear, get this right and growing is easy…..


“Environment is Everything!........”


If your still buying expensive bottles of the latest super boosting agent to hit the shelves but you don’t know what your humidity is or the night time drop in temperature in your grow is more than 5 degrees then STOP! PUT DOWN THE FANCY NEW SHINY METAL BOTTLE OF WHATEVER!..... And pay some attention to the most important aspect of indoor growing.

Seriously though you get this right and everything is a lot easier, 90% of deficiencies or overfeeding issues are caused by a poor environment. Perfect your environment and you can get some amazing yields and quality without using fancy bottles of anything.

 Don’t get the wrong idea most of these boosters and stimulant products do have a place and do work, some can even make up for a poor environment, but if your environment isn’t right and your plants aren’t working at their best to start with then their effects are limited if even noticeable,  you may as well be pouring that £200 booster down the drain!

Plants grown in the perfect environment can be pushed to their full potential and will feed hard and make the best use of the boosters and extra additives you are giving them.  Do your plants and yourself a favour and take some time to get these things dialled in!



The temperature in your grow room is very important, too hot and your plants will be transpiring hard (losing water through the leaves in simple terms) leading to stressed plants that can’t feed effectively. Too cold and your plants can be very slow to grow and struggle to move nutrients around the plant leading to yielding poorly.

There are things that affect the ideal daytime temperature, such as light sources being used, but generally you want your daytime temperature (lights on) to be around 25-28 degrees Celsius with a night time drop of around 5 degrees so if your 28 degrees lights on you ideally need to be 23 degrees lights off (night time). In fact a drop below 18 degrees can shut down the processes happening within your plants cells for up to 48 hours, so if this is happening every night it’s slowing photosynthesis rates and seriously limiting the potential that your plants can achieve. Achieving this temperature when the lights are off is nearly impossible without some kind of heating even in the summer months; don’t look at a heater as being just a winter necessity.

How do I maintain the perfect grow room temperature?

Firstly let us look at the main cooling method of your grow room, that’s the ventilation system, this needs to incorporate some sort of fan controller that will turn your ventilation down when the temperature drops below a set point otherwise this is pulling out the heat in your grow room during the dark period. For most fans such as the Maxibright Tube Fan you can use a simple resistance based fan controller such as the SMS Twin 4.5A for controlling one or 2 fans or the SMS Smart Single Fan Controller if using just an extractor fan and no intake. For other fans such as the Isomax Acoustic Fans you need a voltage based controller such as the SMS Hybrid Controller or the Control Freak Frequency Controllers. (If you need help with controlling your ventilation come and see us or get in touch and we can talk you through all aspects of ventilation control.)

Using an appropriate controller is a great step and when you add the right heating your ventilation isn’t then removing all the heat you are providing. You could turn off your extractor on a dark period but regular air exchange is necessary for healthy plant growth and removing unwanted odours.

The next step is choosing the appropriate heater for your grow space, this depends on the size of your room and how cold it is getting, lets have a look at a few different heating options.

Oil filled radiators – These low cost heaters are available in a range of sizes to suit most grow spaces and are very efficient at heating and staying warm, they take a while to get up to temperature and a while to cool down too so if running on a timer we recommend having them come on 5 to 15 minutes before the lights turn off and turning off a similar time before they come on. They feature a basic thermostat but  pair with a digital thermostat such as the Lighthouse Wireless Thermostat for more accurate temperature control.  Below is a rough guide to which oil filled heater you need for your grow space:


Oil filled heater wattage

Suitable for


Small grow room up to 1.2m2 or slightly larger if only a small heat increase required

1 KW

Small to medium grow room 1m2 up to 3m2 depending on location and extra heat required

2.5 KW

Medium to large grow room 1.2mx2.4 m tent up to 3m x 3m depending on location and heat required, use multiple for larger rooms.




Oil filled radiators are popular as they are easy to use, readily available from many places and are thought to be cheaper to run than the alternative fan heaters. However when used with a quality external thermostat fan heaters can be just as economical and have some other benefits for many growers.



Fan heaters – these types of heaters use a heating element and a internal fan to push the heat around the area, they heat spaces up quickly and also have the added benefit in the later flowering stages of drying the air and lowering humidity which helps prevent moulds such as botrytis (bud rot) taking hold and ruining your hard work. When paired with a quality digital thermostat such as the Lighthouse Wireless Thermostat they are the most accurate way to control temperature in a grow room and if matched to the right size room you can keep the temperature within a degree or two of the set point. We sell two types of fan heater the Premiair 2kw Fan Heater suitable for rooms from 1.2m2 up to roughly 3m x 3m or the 3kw Lighthouse Greenhouse Heater suitable for rooms from 1.2x2.4m up to 5mx5m again this depends on the location and the amount of heat that needs to be added. Both of these heaters can be used with the Lighthouse Wireless Thermostat or can be used on their own with the basic integral thermostat but don’t expect as much accuracy.


For smaller spaces such as propagation and mother/veg rooms you can get away with the smaller oil filled radiators or the Premiair Tube Heaters available in several sizes.


Note for LED growers – As LED lighting creates a lot less radiated heat than traditional HID lighting, you often have to run your room a bit warmer to achieve the right leaf temperature when growing under LED light. We highly recommend purchasing an infrared thermometer if using LED lighting so you can keep an eye on your leaf temperature, we have found you often need to run your LED grow rooms as warm as 29-30 degrees Celsius to achieve a desirable leaf temperature. Check out or guide to led growing for more info.




As important as temperature but often overlooked by many growers is humidity, this is the amount of moisture in the air and is measured in relative humidity or RH as a %. Maintaining a humidity level of 65-70% throughout the vegetative and early flowering stages means you can feed your plants as much as they need without worry of overfeeding, healthy lush growth will then lead to big yields.

Humidity too low will make your leaves transpire too hard, the dry air surrounding them causes them to ‘suck up’ more water through the roots and stems and out the leaves (high transpiration) this leads to concentrated levels of nutrient and ‘overfeeding’ type symptoms occur. In low humidity environments we have to run a much lower EC value (nutrient strength) to avoid this occurring, in doing so the plants are not getting all the nutrients they require and are not performing at their optimum. To add humidity to a grow room there are various humidifiers available to suit different room sizes and budgets. Check out our range of humidifiers and get your vegetative stage perfected!


RAM Ultrasonic Humidifer – This small humidifier is ideal for a small grow room with one or two lights and features a 4.5l tank and output control. It creates a lovely fine mist that hangs in the air and doesn’t make your room wet.


Ultrasonic Mist Makersavailable in 2 models, 3 disc and 5 disc and are suitable for small to medium/large grow rooms (3 disc 1-3 lights, 5 disc 2 -6 lights). These misters need to be placed in the float (available separately) that keeps them just below surface of the water, and floated in a bucket or tank of clean water. The mist produced will hang on the surface of the water so a fan needs to be placed behind to blow the mist around the room. Ideally install a float valve to the bucket or tank linked to a larger reservoir so that the mister never runs out of water.


Centrifugal HumidifersThese large humidifiers from Faran use centrifugal force to create a heavy mist/fog that is pushed out into your grow space. Suitable for larger spaces they produce a larger droplet size mist than ultrasonic humidifiers that tends to fall out the air easier and can make things a bit wet in smaller spaces. Pair this humidifier with the Faran Digital Humidistat for accurate automatic humidity control.


As plants get bigger and the amount of water being added to the surrounding environment through transpiration means the need for a humidifier usually stops, this can be anytime from late veg to mid flower depending on the time of year and other factors. You then normally experience a period where humidity is just about right for the stage of growth until later in flower when the humidity needs to be lower to stop moulds such as botrytis (bud rot) and powdery mildew taking hold. These moulds and mildews love high humidity, just like your plants, and they also love dense flower buds and fruits, for this reason we lower the humidity in the later stages of flower to 40-50%RH. This lower humidity level is hard to achieve when you have a room full of big plants transpiring hard without the use of a dehumidifier to reduce the moisture in the air. Dehumidifiers remove the moisture in the air and it collects in a tank, some have a constant drain outlet allowing them to be plumbed into a drain or other run off system (such as a run to waste brain if using a drip system). For small to medium sized grow rooms we recommend the Premiair Exsteem dehumidifier and for larger spaces we can supply the Ora 60l/day dehumidifier that’s capable of controlling high moisture in large spaces.


 Air Movement and Exchange

Another important aspect of your environment to consider is air movement. Grow rooms can quickly become crowded when you are growing large plants and inevitably without good air circulation throughout the grow space you will end up with areas or small pockets within the space where air is not moving, these stagnant pockets of air are the perfect breeding ground for moulds and mildew to first take hold and then spread throughout your crop. Using a combination of low level or floor fans under the canopy and fans positioned higher up above the canopy is the easiest way to ensure good airflow, use multiple smaller fans spread around the area rather than using fewer large ones. You don’t want to be blowing your plants about, indeed too much air flow over your leaves especially in hot drier rooms can lead to your plants over-transpiring as the hot air blows over them. You just need gentle airflow all around the grow space often blowing a fan over the canopy between the lights and the plants and a couple of small fans blowing up through the plants is enough to achieve good air circulation.

Air exchange is equally important in general you should be exchanging the air within your grow space every five to ten minutes so matching your extractor fan size to your room size is essential.


Thanks for reading and good luck with achieving the perfect environment for your plants they really will repay you for it. As always if you need any help in choosing the right equipment for your room or just need some general advice we are always more than happy to help just get in touch or come and see us.