online from indiana, business lights dot com has the best prices. the same company also runs plant lighting hydroponics
dot com or something like that. they are very nice people to deal with, their shipping is reasonable, and I buy my fluorescent lamps there too - they are quite cheap in case quantities, and they also sell HID lamps and ballasts.

(Lermer) Mylar is OK on the wall, but does tend to make
the room hotter. Because Mylar has a coating of aluminum
(which reflects the infra-red) on the plastic. Also Mylar
is more specular than white paint (white diffuses light
better). So generally I recommend flat white paint on the
wall, unless you need more heat. 76F is generally the best.

I advise using mylar for a reflector. I tried that in
1981; after about 6 months the mylar dries, shrinks, and
tears.

Just a quick note:

I use Velcro to attach and detach Mylar sheets. Very very convenient for tending plants.

Also, Mylar is very thin. After use, you can store it away easily.

Lermer's theory about reflectivity of aluminum and white paint makes no sense, as usual. Just check your high school physics.

Aluminum is used extensively in all optical instruments and mirrors because it is a good reflector of all light wave lengths, not just heat.

dcarch

Generally speaking, diffused light on the leaf surface is
good. "Diffuse" means the light is reflected at many
random angles, resulting in better distribution of light
because of fewer shadows on leaf surface.

Mylar is more specular, which means if it does not lay
flat it can create hot spots, and reflects at fewer angles
(resulting in more shadows on leaf surface).

(DCarch) Some shadows are visible. More shadows could be
seen from different angles. Mylar is not 100% specular and
there is more than one light; diffusion and multiple
points of light improve distribution of light. In order to
detect the weak spots, a light meter would be necessary.

Are you disputing that white is a diffuse reflector, and
mylar more specular? That wasn't even my main point; if
the walls are lined with mylar instead of painted white,
the room will tend to be hotter.

I didn't say that mylar would necessarily "deteriorate"
the growing conditions in the room; compared to what?
Perhaps you have adequate ventilation to take care of the
extra heat.

I've talked with many growers and researched to verify the
claims. You have...?