Foil Question??

Pretty new at this and I was wondering what advantage putting foil over the windows in the room im growing in has? I was thinking maybe it has to do with keepn the tempature right in the room??? Thanks in advance!!! Also I have heard about blowing Co2 on the plants, anybody heard about this?

Start at this thread here
101 already asked questions.

You should get alot of answers for alot of questions there..
Foil/Mylar/White paint is used to reflect lights so you use the most amount of lights you can inside the grow area.

Plants need co2, there for if you blow release co2 into the grow room it will help them grow.