Everything you need to know about building a grow box

Growing tomatoes or other plants at home in a controlled environment is entirely achievable with the help of a well-equipped grow box. In this guide, we take a step-by-step look at how to build your own grow box, presenting two options – a compact one for 4 plants , and a larger one for 12 plants . We will discuss tent selection, lighting, ventilation, irrigation, optimal growing conditions, and specific example configurations. The information is structured in clear sections with practical advice, suitable for both novice and more advanced gardeners.

In this blog post we will take tomato growing as an example, but the principles are valid for many crops.

1. Choosing a tent (Growbox)

A grow tent is the foundation of your home garden – it provides an enclosed space with reflective walls where you can control the climate. The size you choose depends on the number of plants you will be growing and the space available at home.

• For 4 plants, a compact tent with dimensions of approximately 80×80×160 cm or 100×100×180 cm is suitable. These dimensions accommodate 4 medium-sized plants and allow enough height for lighting and growth.
• For 12 plants, you will need a significantly larger grow box – for example, a 240×120×200 cm tent (or two 120×120 cm tents). Such an area accommodates 12 plants, providing space between them for air circulation and access for maintenance.

In this table you can find out which tent will work best for you. All are available with us.

Tent	Size (cm)	Number of plants
HOMEbox Classic White S	80x80x160	3-6
HOMEbox Classic White 1.8	100 x 100 x 180	4-9
HOMEbox GrowLab 100	100 x 100 x 200	4-9
HOMEbox Light L100	100x100x200	4-9
HOMEbox GrowLab 145	145 x 145 x 200	9-14
HOMEbox Ambient Q150+	150 x 150 x 220	9-16
HOMEbox GrowLab 120	120x120x200	6-12
HOMEbox Light L120	120x120x200	6-12
HOMEbox GrowLab 120L	120x240x200	12-20
HOMEbox Homelab 120L	120x240x200	12-20
HOMEbox Ambient Q240+	240x240x200	16-25
HOMEbox Ambient Q300+	300x300x200	25+
HOMEbox Ambient R300	300x300x200	25+

⛺︎ To all home greenhouses ->

Advantages of different sizes: A smaller tent is easier to control and requires less lighting and heating energy. A 4-plant grow box can fit in a garage or even a larger room. A large 12-plant grow box provides a higher yield, but requires more equipment and space. It is important to consider the balance - a tent that is too big can remain half empty and inefficient, and a tent that is too small will not accommodate the desired plants.

Materials and quality: Most tents are made of durable fabric (e.g., canvas with an internal reflective coating (mylar). The thickness and quality of the fabric determine durability and light insulation - thicker material minimizes light leakage and maintains a stable temperature. Interior walls with highly reflective foil increase the efficiency of the lamps, distributing light evenly to the plants. The frame is usually made of metal pipes that can withstand the weight of the lighting, fans and filters. Make sure the tent has enough ventilation holes (inlet and outlet), observation windows and a strong zipper for tight closure.

👉 Tip: Always check the frame's load capacity (how many kilograms of equipment it can hold), especially for larger tents where you will be hanging heavy LED panels and fans.

Basic assembly steps:

1. Assemble the frame – start with the top and bottom square pieces, then attach the vertical supports. Make sure all the tubes are fully secured – they should click into place (or apply firm pressure if they are plastic corners).
2. Spread the cover out – place it on the floor with the reflective side up. Then carefully place the frame inside. The easiest way is to place the frame on the long side of the tent and wrap it around.
3. Stand the tent up and put down the groundsheet – this groundsheet is usually attached with Velcro or ties to the vertical supports.
4. Install the hanging rods – these are metal tubes that will support your lighting and ventilation system.

👉 Important: Always assemble the tent in the room where you will use it - most models do not fit through standard doors once fully assembled.

2. Lighting (LED lamps)

Lighting is one of the most important elements for successful indoor growing. In another blog post we will discuss their selection in detail and compare them to other technologies such as MH / HPS. Regarding your new grow box, the important thing is to choose the right lamps to evenly and sufficiently illuminate your plants.

In the description of most of our grow boxes you will find a recommendation for the lamps to use. If you have any questions, please contact us.

How to install lighting correctly:

1. Choose the position of the lighting – place it on the floor to orient yourself in relation to the electrical cable.
2. Use rope hangers – these mechanisms allow for easy adjustment of lighting height , which is important for optimal growth.
3. Securely attach – if the lamp is over 200W , it is recommended to use four hangers for stability.
4. Adjust the height – after hanging the lamp, adjust the height by gently pulling on the ropes.
5. Test the temperature – run the lamp for 1 hour and measure the internal temperature with a thermometer.

👉 The optimal temperature for most plants is between 22-28°C . If it is above 28°C, you will need more effective ventilation.

👉 Tip: When starting tomato seedlings or cuttings, you can use weaker lights for the first 1–2 weeks. Then move the young plants under the powerful lights for vegetative growth and fruiting.

3. Ventilation and environmental control

Climate control in your grow box is critical to success. Even if you have the perfect lighting and nutrition, your plants won't thrive if the temperature, humidity, and air exchange aren't optimal.

Elements of good ventilation:

• Exhaust fan: This is the suction fan that pulls warm and humid air out of the tent. It is usually installed at the top (warm air rises). For a small grow box (up to 1 m³ volume) a Ø125 mm fan with ~200–400 m³/h flow rate is sufficient. For a large one (4–5 m³ volume, e.g. 240x120x200 cm tent) you will need a more powerful Ø150 or 200 mm fan, with a flow rate of 600–1000+ m³/h. Connect the fan to a flexible air duct that takes the air outside the room (or to a window). It is recommended that the capacity of the exhaust fan be slightly larger than that of the inlet fan to create a slight vacuum in the tent - this way odors and spores do not escape uncontrolled outside, but pass through the filter.
• Carbon filter: Although tomatoes do not have as strong an odor as some other plants, a filter is useful for purifying the air from moisture, dust and volatile organic compounds. Prima Klima offers activated carbon filters with different capacities – choose a model that matches the flow rate of the fan (e.g. 300 m³/h filter for a 280 m³/h fan). The filter is installed inside the tent, at the top, connected to the fan via an air duct. When used correctly, the filter eliminates odors and prevents mold spores from spreading. Change or refill the filter cartridge every 12–18 months for optimal effect.
• Air Inlet: Can be passive (fresh air is drawn in through the tent openings by negative pressure) or active – a separate fan that draws fresh air in. In most cases, passive inflow is sufficient, as long as the openings are wide enough. For larger, heat-intensive boxes, an active inlet fan (with ~20% less flow than the exhaust fan) provides better cooling and CO₂ supply.
• Internal circulation: In addition to air exchange with the environment, it is also important to move the air inside the plants. Place 1–2 small oscillating fans (20–30 cm diameter) inside the grow box to gently blow air through the plants. This prevents the formation of “pockets” of stagnant, humid air, strengthens the stems (mimics natural wind) and helps distribute heat and CO₂ evenly. Aim them so that they do not blow constantly and strongly in one place (which can damage the leaves), but create a gentle breeze around the entire plant.

Temperature and humidity control: Tomatoes grow best at temperatures around 18–27°C during the day and slightly cooler, 15–20°C at night.

To maintain these conditions, fans play a key role – in summer, rapid air exchange removes excess heat, and in winter, reducing the flow helps retain heat. Install a thermostat-controller or thermo-hygrometer with automatic control: such devices can increase or decrease the fan speed based on the measured temperature and humidity. For example, above 28°C, they can speed up the fan to maximum, and when it drops below 18°C, they can temporarily turn it off or turn on a heater. The humidity in the grow box should be around 65–80% during the growing season , dropping to 60–70% during flowering and fruiting to avoid fungal diseases. It may be necessary to use a humidifier (if the air is too dry) or a dehumidifier (if it is too humid) – both devices can be connected to a climate controller.

Three ways to adjust ventilation:

1. If the temperature in the tent is above 25-28°C:
   • Hang the filter and fan at the top of the tent.
   • Connect the fan to an external air duct to exhaust the warm air.
   • Leave the bottom vent open to allow fresh air in.
2. If the temperature is below 25°C and you have space inside:
   • Place the filter and fan on the floor inside the tent.
   • The air will circulate internally without going outside.

3. If you have limited space in your tent:

• • Take the fan outside the tent by connecting it to an air duct.
  • The air will be sucked into the tent and filtered outside.

How to install the filter and fan correctly:

1. Mount the carbon filter – if hanging it, use adjustable straps .
2. Hang the fan – it should be at the same level or slightly higher than the filter .
3. Connect the air duct – direct it to the top outlet of the tent.
4. Organize cables – use Velcro straps to prevent tangling.
5. Set up an internal circulation fan – it will move the air inside to prevent hot spots.

👉 Tip: If you have an outdoor thermometer , place it at plant level to monitor conditions.

Why air control is critical: Proper climate control provides plants with comfortable conditions that are close to ideal. This means that tomatoes will not experience stress from overheating, cooling, or suffocation. Constant fresh air provides enough CO₂ for photosynthesis, and the removal of excess moisture prevents mold and disease . As experts note, disease prevention includes environmental control and good sanitation - these measures significantly reduce the risk of plant epidemics. In other words, a well-ventilated and air-conditioned tent creates conditions in which tomatoes can realize their full potential.

👉 Tip: At first, you can adjust the fans with a simple manual speed controller (rheostat) until you find the ideal mode. Monitor the thermometer and hygrometer - a temperature of about 24°C and humidity of ~70% during the day is a good goal. If the parameters are out of range, adjust the fan speed or the time it runs. With a properly set system, the tomato leaves will sway slightly, and the inner walls of the tent will not condense. This means that the air is fresh and its movement is sufficient.

After this process, you will have a ready space to grow a top-quality crop!