Reflective materials like aluminum foil are often used in the cannabis grow room to make better use of indoor grow lights by reflecting more light back at your plants – but which reflective option is best? It’s important for any grower who is cultivating cannabis indoors to maximize on the power of their grow lights. Indoor cannabis grow lights have gotten insanely bright over the years and this has enabled growers to provide their plants with an abundance of light. However, you can make your grow lights seem even brighter and more powerful without actually increasing the amount of electricity you use. Proper reflection of the walls near your cannabis plants, and a great hood/reflector will bounce the light from your indoor grow lights back at your plants instead of letting all the light that hits the sides be absorbed.
As you probably know, light is what cannabis (and most plants) use to make energy and light is what powers the growth of your buds. In fact, proper reflection can get up to 30% more light to your cannabis plants! This is all without changing anything else about your setup. No extra electricity, just 30% more light!
It’s important to understand that indoor cannabis grow lights are most effective when you get as much of the light they produce to your plants as possible. The further light has to travel to your cannabis plants, the more light that gets “lost” on the way. By making sure light is reflected back at your plants, your plants get to use even more of the light that gets produced which would normally be “lost”. Reflective walls will also help prevent parts of your plants from sitting in a dark or shadowy spots.
Outdoors, growers get to use the sun! The sun is almost 93 million miles away, but it produces so much light that very little light is lost over small distances. That means reflectivity isn’t important when growing outdoors in direct sunlight; the sun already gives your plants all the light they need!
The walls of your grow area
Your plants will get more light if they are in a contained space with reflective walls compared to plants sitting in the middle of an open room, even if the walls of the room are reflective. This is because the amount of usable light a wall can reflect to a plant diminishes as the wall gets further away.
This is partly why grow tents and grow boxes are so effective – in addition to helping you provide the perfect environment to your plants, they help contain the light so your plants get more of it!
Make sure reflective walls are set up to achieve the greatest reflectivity:
- Avoid creases/wrinkles in materials that should lay flat
- Walls should be flat with as few bends or turns as possible
- Smooth curves are better than 90° bends in the shape of the reflective coating
- Avoid creases or bubbles
When covering the walls with something that comes in a flat roll like mylar or foylon, make sure the material is placed flat against the wall to avoid air bubbles which can create hot spots and reduce reflectivity. Velcro is a great way to place up reflective materials with minimal creasing or tearing.Hammered style texture provides some of the best reflection because of the angles at which it reflects light and it cuts down on hot spots. Most professionally made grow tents have a hammered style reflective material on the wall. This hammered finish is also what you find in high-quality light reflectors.
Reflectivity Options for Your Cannabis Grow Room
Different reflectivity options vary in their efficiency. It’s also important to find a solution that fits your personal setup and budget. I will cover some of the most popular options – along with the pros and cons of each one – to help you pick the right option for your cannabis grow room.
- Grow tent walls (best reflectivity)
Getting a grow tent will give hobbyist cannabis growers probably the best light reflectivity of any option. Grow tent walls are easy to clean, light proof, water resistant, won’t melt (like some plastics) and most grow tents are created with built-in cooling options. When it comes to growing personal amounts of cannabis indoors, grow tents are one of the best options for your grow area “walls” as they have been designed over several decades to create the best indoor grow environment for your plants. Grow tents can be found in many sizes, and generally will give you the best results for your money. After I got my first grow tent, I realized I could never go back to growing in anything else!
- Flat white latex paint (85-95% light reflectivity)
This is a highly recommended option for those who can’t invest in a grow tent or for the crafty DIY grower who opts to build a grow cabinet (or a whole room). Excluding the hammered style texture you see in grow tents, this paint will give you some of the best “bang for your buck” of any reflection option. Flat white paint is inexpensive, effective, and there’s no way to create air pockets or hot spots behind the reflective material. Just paint the walls, let them dry, and you’re done!
- Flat white paint spray – use on your cannabis grow room walls for increased reflectivity
White paint absorbs a lot of heat without reflecting it back into the room (which would require more venting to keep heat down) and painted walls are easy to clean. Do not get glossy paint even though it seems like it would be more reflective – you want flat (called ‘matte’) white paint for the greatest reflectivity. If you have the option, you can paint the ceiling and/or floor for even greater reflectivity. Sometimes paint containers will list the reflectivity, and the more reflectivity, the better.
Flat white paint is an easy and effective reflection option for your cannabis grow room walls
- Panda Plastic (85-95% light reflectivity)
Panda plastic (also known as “Black and White Polymer”) gets its name from being white on one side and black on the other. Although it can be a bit expensive, panda plastic provides great light reflectivity. You point the white side towards the lights, and the black side will help trap light from getting in or out. Panda plastic can be nailed or otherwise attached (velcro works great) to your walls and is easily taken down. The thicker the panda plastic, the more durable it is. Remember, this is made of plastic, so it can melt if it gets too hot – be careful to never let Panda Plastic sit too close to your lights!
- Orca Grow Film – (90-94% light reflectivity)
Orca grow film is made of white plastic microfiber and uses a unique structure that is similar to snowflakes or the skin of orcas (killer whales) to scatter light. Although expensive (even more so than panda film), Orca grow film is mold-resistant, easy to clean and thick – these features make it more durable and less likely to tear compared to some other reflectivity options. Using a highly reflective crystalline structure, Orca grow film evenly distributes reflected light so it doesn’t tend to create hot spots even when it has some creases. Orca film is used like panda film in that you point the white side at your plants with the black side facing outwards. Orca grow film tends to reflect back infrared light as well, which means it will tend to keep heat inside the grow room. Good for areas where the temperature gets low.
Good Reflectivity Options
- Kool Seal White Elastomeric Roof Coating (90% reflectivity)
This is another option than can be quite expensive though it gets the job done. White elastomeric roof coating is a great option for some growers; it’s made of 100% acrylic elastomeric resin and sticks to almost any surface. Once dried, it forms a thick blanket of mold-resistant protection that expands and contracts like rubber and will tend to keep heat inside the grow area (good for cold regions) and it even helps absorb sound. The biggest drawback to this method is the cost. It’s recommended that you use a primer like Kool Seal Kool Lastik Primer in order to make sure the coating sticks properly to your walls, however, this only makes the price that much more unappealing.
- Mylar (90-95% light reflectivity)
Mylar is an inexpensive reflective material that looks shiny and usually comes in sheets or rolls. “Foylon” is a more durable version of mylar and “C3 anti-detection film” is an infrared-proof version of mylar (which means it contains more heat). Mylar generally is offered in 1mm or 2mm thickness – the thicker the mylar, the more durable it tends to be (resistant to tearing or creasing). Mylar can be difficult to clean and may need to be replaced after a few grows. It is not light-proof, but does help contain heat in the grow room, so it’s important you create a good ventilation system to get rid of all the extra heat that’s being contained in the grow area. If there are creases, tears, or the film gets dirty, the light reflectivity is dramatically reduced, so make sure it’s placed flat on the walls and kept clean. Mylar is effective until it gets dirty… unfortunately it is difficult to clean! Dirty walls reduce the reflectivity.
Other Reflectivity Options
- White Poster Board (up to 60% light reflectivity)
White poster board is inexpensive and readily available. Some growers will use it around the edges of the grow room, as well as for the floor and ceiling. While it is reflective when new, white poster board is difficult to clean and gets soft and/or moldy if it gets wet.
- Aluminum foil (55-60% light reflectivity)
Aluminum foil (also known as tin foil) is often used in the kitchen, and many growers will see that it’s shiny and deduce that it may be a good option to reflect light back at your cannabis plants. Despite what seems intuitive, the dull side of aluminum foil actually reflects light better than the shiny side. Unfortunately, one of the problems with aluminum foil is that it’s extremely easy to crease, and any uneven creasing can dramatically reduce the reflectivity. In fact, anyone who has used aluminum foil knows that it’s a challenge to not crease it! Some growers will crinkle all the aluminum foil, which can help diffuse the light more evenly. Having everything creased all over actually works better than laying it flat with just a few creases. Aluminum foil will not burn your plants like some growers claim, but there are much better reflective options out there and foil should only be used as a last resort before replacing it with something else.
- Emergency blankets (70% light reflectivity)
Emergency blankets are usually made of mylar, but they tend to come folded up instead of in a roll (making them easy to crease). These blankets tend to be very thin and easy to tear by accident. One of the advantages is these blankets are cheap so can be replaced often, but it is difficult to get them to lay flat against your walls.
“Do Not Use”
- Mirrors (good reflectivity for images but not for light…)
Mirrors seem intuitively like a great choice, but in reality they are “just okay” (at best) for reflecting the light of indoor grow lights back at your plants. While mirrors are great at clearly reflecting your image back at you, they’re not meant for reflecting light; especially light that is actually usable to your cannabis plants. Mirrors don’t reflect light from the grow lights in optimal patterns and tend to create light/heat spots. While better than a black wall, I strongly recommend not using mirrors for reflection in the cannabis grow area.
- Styrofoam (60-70% reflectivity)
Styrofoam (Expanded Polystyrene Foam) is cheap, can be purchased in sheets, is durable and doesn’t weigh much at all. You can hang them on the walls, or styrofoam sheets can even be used as a “wall” all by itself. The uneven surface of styrofoam helps diffuse light without creating hot spots. However, the pros of styrofoam are outweighed by the fact that it’s super flammable! For that reason alone, I strongly recommend not using styrofoam for reflection in the cannabis grow area.