How to Keep Grow Tent Warm in Winter (9 Best Methods)

The chill of winter comes with unwanted trouble for indoor plant growers. Keeping your grow tent warm becomes difficult as temperatures drop.

If it gets too cold inside the tent, your plants will become stressed. On the other hand, if the tent gets too hot, plant growth may slow, resulting in lower yields.

Fortunately, there are proven ways to keep your grow tent warm even when it’s freezing outside.

This blog post uncovers all of them for you.

Things to know

Ideal Temperature
Seedling stage: 75°F to 85°F (24°C to 30°C).
Vegetative stage: 70°F to 85°F (21°C to 30°C).
Flowering stage: 65°F to 80°F (18°C to 26°C).
Ideal Humidity
Seedling stage: about 70%.
Vegetative stage: about 40% (no more that 55%).
Flowering stage: about 40% (no more than 50%).
Lighting
Use lights that provide radiant heat, like HPS or CMH. 18 hours of light per day for vegetative growth.
Insulation
Insulate tent walls, floor and ceilings to retain heat.
Heating
Using small supplemental heaters or heating mats. Avoid direct hot air blowing on plants.
Automation
Use a thermostat controller to regulate temperature. Can automate lighting schedules as well.

Why You Can Trust Farmingram

Our advice comes from real science and intense research—not sponsored posts. Our goal is simply to translate unbiased info into practical guidance that boosts your tent or farm. When it comes to dialing in ideal conditions like temperature, you can trust we’ve done the homework. These winter grow tent tips will help maximize your space and get your plants thriving!

Quick Key Takeaways

1. Insulate the Tent: Insulate the tent walls, floor, and ceiling with reflective insulation, rigid foam boards, or bubble wrap to retain heat.

2. Seal Air Leaks: Seal any air leaks around zippers, ducting ports, floor seams, and frame joints with tape, caulk, or insulation panels.

3. Choose the Right Size Tent: Aim for the smallest size that can comfortably fit your intended number of plants.

4. Place in a Warm Spot: Position the tent in the warmest area of your home, away from exterior walls, windows, vents, and drafty spots.

5. Use the Right Growing Lights: Use grow lights that emit radiant heat, like HPS, CMH, or incandescent bulbs. Balance with LEDs for full spectrum light.

6. Use a Thermostat: Install a thermostat to precisely control temperature and prevent overheating.

7. Consider a Space Heater: Consider a space heater on a timer to provide supplemental heat matched to the lights-on period. Opt for ceramic or oil-filled heaters.

8. Consider Heat Mats: Use heat mats under pots to gently warm plant root zones. Choose mats with built-in thermostats.

9. Choose Cold-Hardy Varieties: Select naturally cold-tolerant plant varieties like kale, lettuce, spinach, radishes, cabbage, and peas.

1. Insulate the Tent

Adding insulation to your grow tent is one of the most effective things you can do to retain heat in winter.

There are several economical insulation materials commonly used by indoor gardeners:

Reflective insulation: Reflective Mylar or foil insulation panels are very effective at blocking radiant heat transfer (source). For maximum benefit, install these panels with the reflective side facing toward the tent interior.
Foam boards: Rigid foam insulation panels have an R-value of around R-5 per inch of thickness (source). They resist heat flow while also providing good structural rigidity. Use high-density foam for maximum insulation factor.
Bubble wrap: A budget-friendly option, bubble wrap has an R-value of about R-1.25 per layer. While less effective than rigid foams, it’s readily available.

Learn more about R-value here.

FYI: While Fiberglass batts are also a popular insulation option, I didn’t recommend using them mainly because they can be itchy and irritating to the skin, eyes, and lungs (source).

To keep grow tent temperatures ideal during winter, use these materials to slow heat transfer.

2. Seal Air Leaks

While tent walls may be insulated, small gaps and leaks can still allow warm air to escape and let cold drafts in.

Sealing these potential air leaks is crucial for keeping your tent warm.

Here are some trouble spots to look for:

Zippers: Use strips of insulation, foam, or Velcro to seal gaps along tent zippers. Also, check that zip flaps are lying flat without gaps.
Intake/exhaust ports: Seal around ducting with duct tape, caulk, or rigid insulation panels cut to fit. Gaps here can release a lot of warmth.
Floor seams: Tape over or caulk along seams where the floor meets tent walls. Weight down loose floor corners. Reflective insulation underneath helps too.
Frame joints: Look for gaps where tent poles meet hub connectors. Cover with tape or use insulating foam strips to close gaps.

Take time to seal any crack or crevice where air could sneak in or out.

Worth Trying: Monitor your tent interior with an incense stick to help spot problem areas.

3. Choose the Right Size Tent

When trying to keep your grow tent warm, bigger is not always better.

The more interior space that needs to be heated, the more challenging it will be to maintain ideal temperatures.

Aim to purchase the smallest tent that can comfortably accommodate your intended number of plants.

As a general guideline:

Tent Size	Ideal Plants
2′ x 2′ tent	Great for mother plants (1-2 plants)
3′ x 3′ tent	Ideal for 3–9 plants
4′ x 4′ tent	Spacious for 9–16 plants
5′ x 5′ tent	Can hold 16–25 plants

Remember that plants need some room between them as they grow larger in the bloom phase.

So don’t just default to the largest tent you can buy.

Carefully consider your plant count and choose a tent size to closely match that number for easier winter heating.

4. Place in a Warm Spot

Where you locate your grow tent within your home can make a big difference in how easy it is to keep warm.

Some tips on finding a warm tent spot:

Avoid exterior walls and windows where more cold seepage occurs.
Locate away from vents, returns, and drafty areas. Cold air sinks and settles in basements or crawlspaces, so avoid those areas.
Central areas and interior rooms tend to be the warmest zones of the home.
South-facing rooms get more passive solar warmth on sunny winter days. North-facing rooms can be significantly cooler (source).
Upper floors are warmer than ground floors as heat rises. A second-story spare room is ideal if possible (source).

By planning ahead, you can position your grow tent to benefit from the natural warmth around it.

This gives you a head start on keeping the perfect conditions inside.

5. Use the Right Growing Lights

When it comes to growing plants in a tent during winter, the type of grow lights you choose is important.

Here are some of the best types of grow lights for a grow tent during winter:

Big bulb lights: These HID lights, especially HPS and CMH, give off plenty of heat, which helps keep the room warm. If you get any big bulb to grow light, it is recommended you get a “dimmable” model, which means you can adjust the brightness levels as needed (source).
LED grow lights: LEDs are a good choice for indoor gardening in general, as they are energy-efficient and produce less heat than other types of grow lights (source).
Incandescent lighting: Plain incandescent light bulbs radiate plenty of infrared heat along with light. Great for a quick heating boost (source).

I always recommend pairing these heating lights with LEDs to balance heat and complete spectrums.

The right lighting is definitely key.

FURTHER READING: How to Use a Grow Light for Indoor Plants: No-Nonsense Guide

6. Use a Thermostat

Monitoring and controlling temperature is critical for success. This allows you to precisely regulate the environment.

A thermostat serves two important functions:

It can turn supplemental heating on and off as needed to maintain your desired temperature range.
It prevents overheating, which can happen quickly in a small insulated tent. Once you achieve the target temperature, the thermostat automatically shuts the heater off.

I recommend choosing a digital thermostat with a built-in humidistat as well. Keeping humidity in check is also crucial during the winter months.

A good location for a thermostat is at plant height near the center of the growing area (source).

SIDENOTE: Thermostats and sensors should be shielded from direct sunlight, as this can give false readings (source).

7. Consider a Space Heater

During the winter, it’s a good idea to keep a space heater in your tent for extra warmth. Based on extensive research and participating in forum discussions, I have some advice:

Go for a ceramic or oil-filled radiator heater. These provide steady, even heat distribution without getting dangerously hot themselves.
Look for safety features like automatic shut-off if tipped and overheat protection. Check that any electrical parts are UL certified (source).
Oscillating models can help distribute heat more evenly in a space. For example, a ceramic heater with an oscillating fan can cut propane use in half in cooler weather.
Use a heavy-duty timer outlet to control when the heater runs. Match the schedule to your lights-on period for efficiency.
For larger tents, use two smaller heaters on opposite sides rather than one huge model. This evens out the heating (source).

While space heaters require caution, a good quality model paired with a thermostat and a timer provides reliable hands-off heating.

8. Consider Heat Mats

Heat mats are an excellent supplemental heating source for your winter grow tent.

They provide gentle warmth directly to your plants’ root zones and the surrounding tent floor area. This helps maintain optimal root temperatures for better nutrient uptake and growth (source).

Here are some best practices I’ve learned:

Place the mats underneath propagation trays or pots to warm the roots. Don’t let plants sit directly on the mat (source).
Use a rubber mat or wood slats as a buffer between the heating mat and the tent floor. This allows air circulation (source).
Look for mats with a built-in thermostat, so they don’t risk overheating. Models with adjustable temperature settings are ideal.

In my experience, heat mats are very useful for warming plants that are sensitive to cold, like basil or pepper.

Pairing mats with an interior tent heater provides well-rounded heating.

9. Choose Cold-Hardy Varieties

I’ve learned that plant variety selection plays a big role in the ease of winter growing. Some of them naturally tolerate colder temperatures better than others.

Here are some cold-tolerant options worth considering:

Kale: Extremely hardy down to 10°F. Dwarf Siberian and Winterbor varieties excel in winter (source).
Lettuce: Many lettuces can tolerate cold temperatures as low as 20°F, especially oakleaf and romaine types (source).
Spinach: Very frost-tolerant. Bloomsdale Long Standing and Winter Bloomsdale handle winter well (source).
Radishes: Quick-growing and can withstand freezing temps with protection. Champion, Daikon, and China Rose work great (source).
Cabbage: Withstands frost well. Favorite cold-hardy varieties include Early Jersey Wakefield and Copenhagen Market (source).
Peas: Many pea cultivars are cold-loving and can even sprout under snow cover outdoors. Little Marvel and Lincoln peas are produced indoors.

To state the obvious, choosing naturally resilient varieties allows you to rely less on supplemental heating.

Conclusion

As this post has shown, there are many effective methods to maintain ideal temperatures even when it’s freaking frigid outside.

With the right strategies, winter doesn’t have to limit your indoor farming ambitions.

In fact, it can be the perfect time to experiment and expand your skills.

Imagine all the things you could grow this winter in a cozy indoor environment!

FURTHER READING: 3 Best Air Conditioners for Grow Tent and Grow Room (2024)

FAQs

This is a very personally subjective question and there is no one right answer.

The amount that a grow tent heater will increase your electricity bill depends on several factors, including the size of the heater, how often it is used, and the cost of electricity in your area.

One Reddit user estimated that running a 4×4 tent with a 400w AC Infinity light would add $35 to their electric bill (source).

It is generally safe to use a space heater in a grow tent, but it is important to follow safety precautions and choose a heater that is appropriate for the size of your tent.

Make sure the heater is placed in a safe location where it won’t come into contact with any flammable materials or plants.

Insulating your grow tent is one of the most effective ways to reduce energy bills and maintain a stable climate inside the tent.

While LED grow lights do not provide enough heat to heat up a grow tent, they are efficient in turning electric energy into light, which is beneficial for plant growth.

Therefore, LED grow lights can be helpful for growing plants indoors, and they do not produce enough heat to harm the plants in the grow tent.

Meet your guide
Dhruvir Zala

I’m the guy behind Farmingram, where I nerd out on all things indoor agriculture. Through rigorous research, my goal is to get more people excited about where agriculture is headed.