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GrowFAQ : Growroom efficiency :
How can I improve my
light efficiency

What reflective materials can I use for my grow
room?

Added by:
snoofer  Last edited by:
snoofer  Viewed: 878 times

Rated by 10 users:
8.40/10

Contributed by: DaChronicKing

Submitted: 05-07-2003

Choosing the right
surface for the walls of your grow room is very
important, as up to 40% of your total yield comes from
the edge, and the right wall surface can increase the
amount of light those plants receive by up to 30%!
Artificial lighting diminishes exponentially with
distance, so it is important to ‘contain’ as much of
this light as possible, and direct it accordingly.
Reflective surfaces also help illuminate the lower
portions of the garden, providing lower buds with light
and heat energy.

To get the best results with
your light and walls, it is important to get the walls
as close as possible to your garden to ensure the least
amount of light is wasted. As a caveat, the percentages
provided are only useful as a general guideline, as they
present the range of reflectivity of the particular
surfaces. The high percentage presents the best possible
circumstances for that material (for example a 99%
reflectivity rating for mylar sheeting would be under
ideal conditions - no creases, completely flat, no
discoloration, etc).

The best way to determine
how well your grow room walls reflect light would be to
purchase a light meter and measure your light directly;
then take an opaque board and hold it a few inches off
one of your walls with the light meter below the board
in such a fashion that the light reflects off the wall
and onto the light meter. You can then compare the
difference between the two and determine a percentage
from those numbers, the closer the two numbers are, the
better your wall reflects light. It is important that in
both measurements, your light meter is the same distance
from the light, otherwise your results will be skewed.

Also important to note is that radiant light
energy refers to electromagnetic (EM) radiation with a
wavelength between 400-700 nanometers (nm) and radiant
heat energy correlates to EM radiation with a wavelength
between 800-2000nm.

Listed below are some of the
most commonly used materials used for grow room walls:

Foylon:

A more
durable version of mylar, made of spun polyester fabric
and reinforced with foil laminate. Foylon is resistant
to most solutions, won't tear or fade, and can be wiped
or washed clean.

A great solution for growers
who are interested in long term use, and though it may
be slightly more expensive than mylar, its durability
will more than make up for its cost. It has the ability
to reflect about 95% of the light and approximately 85%
of the heat energy, so a good ventilation system should
be used in conjunction with folyon.

A
recommended method to attach Foylon to the walls would
be using Velcro, as it makes taking it down for cleaning
much easier nd reduces the risk of tearing, creasing or
bending it. If this is used for your walls, making sure
you get it flush with the wall with no pockets of air
between it and the wall to prevent hotspots.

Mylar:

A highly reflective
polyester film that comes in varying thickness, the most
common being 1 and 2 mm thick. The 2mm thick mylar while
not quite as durable as the foylon, is fairly rugged.
The 1mm thick mylar tears fairly easily, so taking it
down for cleaning is quite difficult without damaging it
in the process. Both types of mylar are able to reflect
approximately 92-97% reflective, giving it the potential
to be more reflective than foylon, but because foylon is
more easily cleaned without damaging it as well as it
being harder to crease, foylon usually ends up being
slightly more reflective. Important to note is that
mylar reflects radiant heat energy just as well as
foylon (around 85%), so proper ventilation is necessary
if mylar is used in your grow room. Attaching this to
walls can be done in a similar fashion as foylon, and
the same caution should be used to avoid creating
hotspots in your room. The 1mm thick mylar stands a fair
chance of being creased or ripped in the process
unfortunately, even if Velcro is used to attach to the
walls.

C3 anti-detection film:

A
specialized type of mylar that exhibits the same
properties as the 2mm thick mylar, but in addition to
reflecting approximately 92-97% of the light, it also is
90% infrared proof, making your grow room all but
invisible to IR scanning. This can also be attached in
the same manner as foylon or mylar, and the same caution
should be used to avoid creating hotspots in your room.

Flat white paint:

Self
explanatory; a great option for large grow rooms or for
people who are interested in a low maintenance wall.
Flat white paint has the ability to reflect between
75-85% of the light, and does not create hotspots.
Adding a fungicide is recommended when painting.

Glossy and eggshell whites not reflect light as
efficiently as flat white. Semi-gloss paint for example,
only has the ability to reflect between 55-60% of the
light. Also important to remember when using paint is
that any smears or blemishes on the surface take away
from how reflective the wall is so care should be taken
to avoid marking or staining the walls. Titanium white
paint is very reflective; however it is usually only
used on reflectors due to its high cost.

Elastomere paint (info by furun)

A rubberized roofing paint with 90% reflection.
Good for growboxes. Mildew resistant. Highly reflective.

Kool Seal White Elastomeric Roof Coating ~
$15.00 (1 Gallon)

Ultra high reflectivity

Forms a rubber-like blanket that expands and
contracts
Adheres to almost any surface (very good
on wood and metal)
Available @ www.lowes.com

White/Black plastic (also known as panda
plastic or "poly"):

"Poly" is useful if you are
setting up a temporary grow room or don’t want to damage
the walls. Poly is easily cleaned.

The purpose
of the black side is to not allow any light to pass
through the plastic, which ensures your dark cycle
remains dark. The white side is 75-90% reflective.
Choose a 6 "mill" thickness of poly for maximum light
blockage and duribility.

If this plastic is put
too close to the light, you will obviously melt it so be
careful!. Panda plastic does not create hotspots. Poly
can be attached to the walls by using carpenter’s nails
or using tape glue or similar means. This can be used as
a cheap alternative to mylar if painting your grow room
is out of the question.

Polystyrene Foam
Sheeting (more commonly known as Styrofoam):

This is excellent for harsh environment
growrooms (your attic for example), provided you have a
good ventilation system and a way to keep the
temperatures from rising too high (an a/c unit or
similar) as it is an excellent insulator.

It is
also a great material for use in a temporary setup or
for use as a "travelling reflector" on a light mover,
where weight is a concern. It is approximately 75-85%
light reflective so it is comparable to using a flat
white paint. Foam will not create hot spots. Rigid foam
can be purchased in sheets, and can be used as a free
standing wall or can be taped, glued or nailed to the
wall, the last generally being the most successful
method.

Emergency Blankets:

These are ultra thin polyester blankets that are
sold in most camping stores and are constructed of a
single layer of polyester film that is covered with a
layer of vapor deposited aluminum.

It is not
very effective at reflecting light because it is so
thin. Holding it between you and a light source, many
small holes are noticed at the intersections of creases
and the entire blanket is translucent to begin with,
this coupled with the many creases that are in it when
you purchase it takes away a significant amount of it
reflectivity. It is very easily creased as well which
also detracts from its ability to reflect light. And
while it is reflects nearly 90% of radiant heat energy,
it is only able to reflect around 70% of the light.

The largest advantage of using this type of
material is that it is very cheap and therefore easily
replaced. Emergency blankets can create hotspots if not
attached flush to the wall so it is important that no
air gaps exist between it and your supporting wall. The
easiest way to attach this is to use tape (Aluminum or
metal tape is recommended), as it tears very easily once
it is cut or punctured.

Aluminum Foil:

Aluminum foil is no more than 55% reflective - if
used, make sure that the dull side is the one that is
used to reflect the light. When it becomes creased its
reflectivity is even lower (around 35%.) It is also very
dangerous to use because it creates hotspots easily, is
electrically conductive, and is a fire hazard when it is
in close contact with HID lighting. Attaching this to
walls is a pain and usually using aluminum tape or glue
is the best way. This should only be used as a last
resort, and even then its usefulness is
questionable.

Last modified: 20:12 - May 10,
2003

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