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Whether you’re getting started with your first grow room, or you just want a refresher on the best method, keep reading for our step by step guide.

1. Make Space

There are several factors to consider when designing your own indoor grow room. Here are some to think about.

Match Your Growing Goals

Even quite a small space is suitable for a grow room, but it depends on what you want to grow, and how much of it. You can convert a room or closet, or you can use a grow tent.

Power Outlets

A couple or regular light sockets will often suffice for a one or two light grow room setup. If you need more, you could use an extension lead, or consider some custom wiring work.

Water Source

Never use unfiltered rain water, as it may contain toxins and other impurities that are harmful for your plants. Filtered water is best.

Noise Pollution

If you use certain lights, fans or pumps, these can produce noise that may disturb you in other parts of your home, so be sure to place a grow room in a location that is most suitable to the degree of noise it is likely to produce.

Solid Flooring

Carpets hold moisture and insects, and can lead to mould and infestations, so it is best to use a clean, wipeable flooring like linoleum.

2. Light Control

Reflective sheeting is a great way to keep light in your grow room, making the most of your lighting efforts and power. It is important to keep external light out, as well, if you are controlling your light cycle and do not want regular daytime light to interfere with it.

3. Mapping Out Your Grow Room

Whether you are using the whole room, part of a room (as with a grow tent) or a converted cupboard, you will want to plan out where everything will go, ensuring room to move around within it to care for and harvest from your plants. You also want to make sure your grow lights are not too powerful for your plants, but still provide ample light for good growing.

You have a few options of how to setup your grow room:

Use The Whole Room

One grow light is not enough for a large room. Provide a minimum of one light for every 1.2m2. Some people divide a large room into several tents for greater control.

Grow Tent/Room in a Room

Using a grow tent is the cheapest way to set up a grow room. These are designed to prevent infestations and diseases, to keep light in (or out), and are great for consistency of climate within the tent. They can also protect the rest of your house from potential damage from humidity.

Convert Small, Enclosed Room/Space

Small spaces, like closets, may seem easier to set up, but they do have some problems associated with the small space.

For one, they heat up more easily. A higher space, at least 1.4m, is a good way to help control this as it gives the heat somewhere to rise to. Keep your bulbs within the 250-315-watt range. Finally, make sure there is good airflow through the use of an extractor fan and air intake holes (an air input fan, with outflow holes, works even better).

4. Lighting System

Use at least one grow light in your grow room, and add others as size demands. Remember not to over-light you grow room, as this can cause damage and other problems to your plants as well.

What is a Grow Light?

Typical grow light systems are made up of a ballast (which controls the energy supply to the light), the lamp (the light source itself), and the reflector (which aims or intensifies the light).

Main Light – MH, HPS, LED

Metal halide (MH) lamps have been losing popularity in favour of dual spectrum HPS (High Pressure Sodium) lights, which do not require a separate sodium light when it comes time for flowering. Metal halide does produce more blue light, which helps for more vegetative growth, but lacks the sodium component for flowering.

Many people also use LED lights throughout the process, and fluorescent lights from propagation.

Extra Lights – Plasma, CDM

Supplemental grow lights can broaden the spectrum outside of the PAR range, which does not increase growth, but can increase the quality of the yield. Of these, Plasma has more wavelengths outside of the PAR range, whereas CDM have many outside the PAR range, but also more within the PAR range than plasma lights do. A CDM can sometimes be used as a main grow light, if proper reflectors and bulbs are used.

Supplemental bulbs are just what the name implies – supplemental. You will not require one, but the use of one or more of these may increase both plant growth and yield.

Consider the Costs

Choose lights with economy in mind. Some take a lot of power and are not suitable for many home purposes. Compare the input with the output, and then consider the area you are planning to light with it.

Money Saving Tip – Running at Night for Cheaper Power

Remember that you are controlling the ‘daytime’ and ‘night-time’ cycles for your plants, and you can put them whenever you want to. Power is generally cheaper at night, so keeping your grow lights on during the night and off during the day can be a great way to lower costs. The lights also produce some heat, so keeping them on during the cooler parts of the 24-hour cycle can save on heating the grow room and keep a more constant climate within the room or tent.

If you need to go into the grow room during daylight hours, when your plants are in their night cycle, try using a headlamp, so as not to disturb them.

4. Fans, Filters & Air Control

An air exchange system is a great way to control the climate in a grow room, especially for beginners. Plants consume CO2 and give off moisture. Bringing in fresh air will flush out that CO2 and moisture – and can even dissipate some of the heat from your lamps.

The size and power of air exchange system you’ll need will depend on the intensity and number of your lights, the size of the grow space, and the time of year (summer, for example, will require more air flow than winter).

Extractor Fans

To determine how many extractor fans you will need in your setup, find the volume of the grow room by multiplying length times width times height. Multiply the result by 60, and you will have the amount of air you need to extract each hour.

Certain conditions may add a modification to that number, here are some estimates:

  • a warm attic will need 20% more
  • a cool basement needs 15% less
  • south-facing rooms need 20% more
  • a carbon filter adds 20% to your needs
  • long ducting needs 20% more
  • air cooled lighting means 25 – 30% less extraction needed

Fan speed controllers are a good idea too, as they will slow down or speed up your fan according to current conditions.

Intake Fans

For smaller rooms, using vents to bring air in is sufficient. For larger ones, or for rooms with more intense lighting, you will want to use air intake fans. Intake fans should be slightly less powerful than the extractor fans they work with – about 15% to 20% is suitable.

Where possible, placing the extractor fan(s) on the opposite side of the room from the intake fan(s) is ideal. Placing them too close together can result in a strong current of air between the two fans, and a lack of air current throughout the rest of the room, making them far less effective.

Safety Advice

Grow room lighting systems tend to be very safe. They use low wattage and when wired correctly are like any other appliance or light bulbs. Since they are used in a growing situation, however, there are some common-sense measures that should be taken to ensure they don’t become dangerous.

Keep wiring up and out of the way. This prevents damage to connections and keeps the electrical power out of the water if there is a flood or leak in another part of the grow room system.

Ballasts and other components should never come into contact with water, unless specifically designed to do so. Small children and animals can sometimes cause damage to systems, or the placement of systems, and appropriate measures should be taken to keep the grow room off-limits where appropriate. Uncoil extensions and reflector cables to prevent overheating.


Now you’re ready to setup your grow room!

If you need any more products, we have a great range to buy online here at Acorn Horticulture.

We also have discreet click and collect services, with our shop based in Sheffield just off the M1, for easy reach within a lot of the UK. You can get directions on Google maps here.

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