Comparing Reflective Materials For Grow Room & Tent: Mylar, Alu Foil, Panda Film, White Walls

We set out to compare common materials used to reflect light in grow rooms, grow tents, and general grow spaces. Our mission was to test how much light, or photons, reflect off of various materials to determine which is best suited as reflective walls for indoor growing, We've seen growers use everything from mirrors to aluminium foil so we decided to test the materials that were most commonly talked about online.

The reflective materials we tested follow:
Open space (no reflective materials)
Panda film
Mylar (diamond shaped)
White painted walls
Emergency blanked (mylar)
Aluminum foil (matte & shiny side)

Inside our grow closet we dressed the walls with all of the materials listed above and then measured the PPFD (PAR or light intensity) results with an Apogee MQ-500 quantum sensor. A LEDTonic Q2 LED grow light was fixed to the top of the closet and the floor has pre-drilled holes where the measurements were taken.
We'll discuss the test and the results in this article, but for those of you who prefer video, here's a Youtube-video of the test.

The idea behind this test was get a definitive answer which material has best reflective properties out of the most commonly used materials for grow rooms. As light (photons) are emitted from a light source, they fall and scatter. As they land on a surface, they are mostly absorbed. The fewer photons that are absorbed, the better for growers as these photons could potentially be reflected back onto the plants under the grow light. The more reflective a material is, the fewer photons it will absorb and more photons bounce off it. Dark colored materials absorb maximum amount of photons and light colored materials absorb the least amount of photons.

Most growers we see DIY-ing their grow space appear to use mylar. This is also the same material used in most grow tents. It's shiny and for the naked eye appears to be reflective and good for the purpose of dressing grow rooms. But is mylar the best material to use as reflective material or even the cheapest? Short answer: no.

Grow closet dressed in mylar.

We dressed the walls of our grow closet as shown above with all the different materials we wanted to test and measured each material individually, removing and installing the films one by one. To keep this article short and and on point, we'll go right to the results. First in text format, then comparing light footprint maps.

Material
Min PPFDAvg PPFDMax PPFD
No walls5787125
Panda film (black)6192128
Panda film (white)152188223
Mylar221242268
White walls (wardrobe)221255287
Alu foil (matte side)276299319
Emergency blanket (mylar)277302325
Alu foil (shiny side)283322346

Here are the measurements of all materials displayed as light footprint maps with PPFD values.

Q2 LED grow light no walls light footprint
Q2 LED grow light black panda film light footprint
Q2 LED grow light white panda film light footprint
Q2 LED grow light mylar light footprint
Q2 LED grow light white walls light footprint
Q2 LED grow light matte aluminum foil light footprint
Q2 LED grow light emergency blanket light footprint
Q2 LED grow light shiny aluminum foil light footprint

In summary, the results clearly show how poor black colored material is at reflecting light -- no surprise. It's barely better than using no walls at all. The next material in line, white panda film, is significantly better than black panda film but still, rather poor results. Mylar is clearly better at reflecting light than white panda film but still worse than white pained walls, which is a bit of a surprise to us. It's worth mentioning that there are various types of mylar and some may reflect better than our mylar with diamond pattern. White painted wardrobe walls (wardrobe) is a pleasant surprise in terms of how much light it reflects. Comparing with no walls, white wardrobe walls increase the light almost threefold within our 2x2' space. The matte side of the aluminum foil reflects light very well, almost identical to an emergency blanket made out of mylar. The shiny side of aluminum foil is the best reflective material in our test and it's also cheap and relatively easy to work with. It tears easily when working with it but once it's in place, it's doing a great job at reflecting light.

Finally, the most common material, mylar, is clearly not as good as we're lead to believe. Sometimes mylar is the only option, e.g. when buying a pre-made grow tent, but if one is to build a grow room and the walls can be customized, there are better options out there.