Quote Originally Posted by silent leprechaun
Hey, first I'd say go LED to keep the heat signature at zero. You can check my grow journal for ideas.
I have to use CFL supplementary lighting just to keep my plants warm.

Secondly, have a nice tent in the attic and place it between 2 rooms below the attic floor. Cut a 4 inch hole in each bedroom ceiling and place a vent cover on them to hide the hole. One 4 inch hole is your warm intake from downstairs bedroom 1. Pipe this into the top of the tent as your fresh air intake.
Then, from the bottom of the tent, pipe from the opposite side of the tent to the second bedroom (exhaust). So you now have fresh air coming from one bedroom and an exhaust into another bedroom. You will need a good extractor and a carbon scrubber. (detailed in my grow journal).

In the winter you will need to insulate the outside of the tent and the in-take/out-take pipes. If you use the 600w HID lighting you will be keeping most of the heat as it will be pumped into the bedroom. But some will be lost to the attic. At night you can leave the extractor on and this might keep the plants warm enough. If they freeze they will die and when cold they will be stunted in their growth.

In the summer you will have to keep the air moving at a high rate and have extra fans up there to keep good air movement and stop mould.This will increase the number of waterings though.

I was thinking of doing an attic grow sometime too. Need to move into a house first. But it is very safe when your gear is in the attic. No clues of what you are doing. Be careful of the heat signature in the winter.

Hope I was some help.

Take care

excellent idea i can borrow heat from the actual house. i can also cool during the summer aswell. i will have a close look at you grow journel silent l thanks for your very interesting reply.