How can I increase heat in Grow room?

Cold temperature kills plants. Specially indoor grow plants where ‘Mother Nature’ isn’t there to take care of them. And you as a smart grower must be acknowledged of it.

So, what are the threats when your grow room is too cold? To be precise, such critical fall in temperature may cause damage to leaves and roots that leads to less germination and eventually less yield.

None of us growers want that, right?

To deal with the problem, you might have already bought heaters or made a few changes to the growing system. But still, it’s too cold while the lights are off. Specially if your tent is located in a poorly isolated room.

However, we’ve been concerned about this very problem for quite a long and written a guide that’s going to bring the smile back for every grower. Take a moment and pat your back, as this article has got your attention. Get yourself a cup of coffee, take a breath and let’s start gliding through the whole post-

Why are you need increase heat in Grow room?

Plants and air temperature

Plants like their air to be kept reasonably temperate. As the colder weather begins to draw in, it can be difficult to keep the air around your plants in the sweet-spot of 23C – 28C (28C being the absolute maximum temp you ever want at the tips of the plant without CO2 supplementation).

23C-28C is the ideal temperature only during the lights-on period. During the dark-period a few degrees of temperature drop is a desirable thing (see below), although the temperature should ideally not go below 18C, and should never go below 15C (see below).

Obviously, a grow lamp creates quite a bit of heat. While this can cause problems of high temperature during the summer months, it is actually a very useful side-effect during the winter.

For most growers, the simple addition of a fan speed controller to reduce the amount of hot air being exchanged for cold air within the grow environment, is enough to keep the air within the right limits. As long as enough air is being exchanged to refresh CO2 levels and to keep humidity moderate then this approach can be a great solution to keeping temp in the 23C-28C range during the lights-on period.

When the lights go out

Temperature during the dark-period is something that many growers do not consider. Maintaining the right temperature during the lights-off period is just as important as getting the temps right when the lights are on. As stated before, while it is a good idea to have a temperature drop of a few degrees during the lights-off period, it is important to not let the temperature go below 18C and it is absolutely vital the temps NEVER go below 15C.

Plants sense the temperature even during the dark-period. A temperature drop during the lights-off period actually helps plants to respond better to the photoperiod. A drop of a few degrees when the lights go out will help kick plants into flowering/fruiting more quickly when they are switched to 12/12, and promotes stronger flowering/fruiting thereafter.

Brrrr It’s cold, winter must be coming, I think I’ll stop growing now…

Plants use temperature to sense when winter is coming. Plants also need certain temperatures for the biological act of living and growing. Plant growth goes down markedly below 18C and plants can “stall” (stop growing completely) below 15C. It may only take one or two cold (sub 15C) lights-off periods for the plant to decide that winter is coming. This sets off a process whereby the plant ends flower/fruit bud production, finishes-up the flowering/fruiting maturation process in a hurry, and then gets ready to die or recede until the springtime.

If plants “stall” in this way, it can take up to 2-3 weeks for them to get back to normal flower/fruit production. Usually, they will never recover what has been lost during the “stall” period. As I’m sure you can imagine, 2 wasted weeks out of an 8 week flowering or fruiting period will have a huge detrimental effect on the size of the final crop.

Grow Room Too Cold Symptoms

Placing a thermometer and acknowledging the best comfortable temperature range is the best way to identify a ‘too cold’ grow space. Apart from that, check for these following symptoms as well-

Small and Weak Growth.

Damp areas and unwanted mould.

Chilled out root systems(Hydroponics).

Bad taste, smell, color or density of grow plants.

Problems that A Cold Grow Room Suffers From

Among the plethora of issues that a ‘too cold’ grow room can suffer from, here are three of the most critical ones-

Low Germination

Most grow plants germinates well in between a temperature of 65-75 degrees Fahrenheit. Some warm-season flowers and vegetables like this range to be 80+ degrees. But with a grow tent cooler than 60 degrees, you can’t expect the plants to even start the process of germination. Eventually, leading to low and poor yield.

Higher Oxygen Concentration

Below-temperature of your grow space will chill the water, leading to a higher concentration of oxygen dissolved in it. While plants intake that through roots, it hinders the metabolism and enzymic processes of plants.

A Damp And Unhealthy Grow System

Low temperature may cause a few cold or hot spots popping up in some places of the entire space. That eventually creates a damp environment and unwanted mould. Both of the issues may leave your plants with severe damage and over-purpling leaves.

How to increase heat in Grow room?

Soil Mats

One of the first options available for heating your growroom is focusing on heating the soil rather than the air. Soil or seedling mats sit underneath your trays and pots to provide the warmth that growing plants need. These soil mats are a great option when you want that ideal soil temperature between 75-85°F but can’t imagine trying to keep the heat in your home or greenhouse at that temperature. Some people only think of this as a germination mat, but it’s valuable for heating plants that have already germinated.

Heat Lamps

Another option is heat lamps, but depending on your set-up, this may not be an ideal solution. Some people may opt for heat lamps rather than heated soil mats, but this can sometimes backfire. Depending on where you have it located in your set-up and how long it’s left on, the heat lamp can dry out your plants and result in burns to your foliage. When using a heat lamp, you’ll want to keep it on just for a short period of time and ensure that you’re checking the moisture levels of your soil. There’s a good chance that you’ll need to water regularly to keep the dirt moist.

Compost Generated Heat

It may sound crazy, but you can use compost to warm your plants. This option is one way to create a heat sink and is excellent for greenhouses and hoop houses. You can dig a trench inside of your greenhouse, and cover it with a type of removable walkway so it’s not a problem.

This compost will heat up thanks to your daytime temperatures and will release this heat later in the day. Plus, you’ll get the bonus of having all that black gold ready to add to your garden. Just keep in mind you’ll have to carefully consider where you’re going to put that mainly open compost pile.

Water Storage

Another heat sink idea is to store water around your greenhouse or hoop house. You want the water storage to be placed in an area where it can be heated by the sunlight during the day. Then, during the night, the heat energy will be released into the surrounding area as the water cools off.

This option offers the benefit of having water on hand for your garden, but you have to make sure that you add the water back in as you siphon it off. Removing the water means that you’re eliminating heat storage space.

A good starting place for this method is a 55-gallon barrel, but you can use whatever water storage containers you have handy. To help get the most heat absorption, use dark materials for your tanks.

Electric Room Heaters

A popular option is an electrical room heater. There are some horticultural options that are made explicitly for greenhouse heating, but others do use regular room heaters. This type of heater means that you’ll need either an extension cord or outlets in the area where you plan on using the heater. Keep in mind that you have to use these types of heaters appropriately; you don’t want to create a fire hazard because your heater was too close to flammable materials.

Circulation

One thing that you need to keep in mind when using any of these heat sources is to circulate the heated air throughout your space. You don’t want hot and cold spots popping up in your greenhouse. Plus, this helps with the condensation that can happen when heating an area in which you’re watering or growing plants hydroponically. Some heaters will have a circulation method, such as a fan, built in, but you’ll have to determine if you need additional circulation for your set-up.

Insulation

While insulation is a passive heater, it can make your efforts more worthwhile. Insulation may not be appropriate in every situation—like covering up greenhouse windows for insulation, as you’ll then be blocking the sunlight from coming in—but there are other areas where adding some insulation can come in handy. Gardeners that grow in basement areas or different rooms inside of their homes may find that merely adding insulation goes a long way towards keeping the chill out of the room and the heat inside.

The temperature that you need in your growroom is going to depend on what you’re growing and your current set-up. Once you determine what temperature you need to try to reach, you’ll be able to personalize your heating plan based on your needs. You may find that you need to mix and match some of these options to get the right level of heat in your growroom.

Frequently Asked Questions(FAQ)

Question: What’s the best time for heating?

Answer: It depends on the temperature outside of the growing tent, and how much heat is demanded plants. Usually, it should be after evening, when it’s starting to cool down. However, in winter, heating quite often is an evil necessity.

Question: How to keep grow room warm when lights are off?

Answer: Use something like an automatic fan speed controller that works on whether the light of your grow room is on or off. While it’s night, it will automatically deduce the fan speeds, resulting in a gradual increment in temperature.

Question: What is the cheapest way to heat a grow room?

Answer: If you’re not interested to buy a whole unit of an electric heater, some cheaper options to get a water storage, soil mat or aquarium heater. Providing intake air from a warmer space is maybe the most cost-effective idea.