If you raise humidity to 70-80% without sealing the room tight as a drum, you will mold everything and rot wood structure.

Take some time and study how to isolate your house from high humidity. You'll have to read, there's no quick answer to your question.

You will need to cover the walls with a moisture-resistant covering, starting with "green board" sheetrock. Think of this room as you would a bathroom. Either use tile or fiberglass panels. Air exchange is critcial to control moisture, otherwise you will develop all kinds of fungal problems in thep lants and in your walls. Some mold spores can be very damaging to your health and most homeowners insurance policies are now refusing claims for mold related losses.

flip69side, if you ever get a mold problem, the repercussions may be so severe you may have to move. A friend of mine had a problem so severe his allergist wrote him a prescription to leave his house. It gets in anything not plastic; wood, clothing, sofas, curtains; etc. Changing the carpet, HEPA & UV filters helps, but will not get rid of it. When the ambient humidity is high, the mold comes back. He is going to have to get rid of all his books, clothing; house; everything & move because of his problem. Furthermore, in the event of a move, he has to worry about the next person buying the place coming back against him for the mold problem. And then there are the issues regarding house insurance & medical coverage for his allergens.
You might consider an outdoor structure that could be easily dismantled in the event of a problem.

Hi Lil Orchid Nut,

If you want to have a grow room, you will have to isolate it from the rest of your house. The mold problems, and windows running with water in the winter, rotting the window sills etc.

When I lived in Toronto, me and my friends who had many aquariums had the same sort of problems.

My one friend had a concrete bunker for his hundred aquariums with a sealed door from the basement built at the back of his house. From the top, outside, it was his patio deck.

One thing you could do is to put up a wire mesh or plaster lath on the non-concrete walls and entire ceiling and plaster it with one part Type S Lime (plaster building supply) and three parts sand. The lime based wall is a bit crumbly at first but densifies into marble over time by taking carbon dioxide from the air. Small cracks will heal themselves.

Look on the net at how they construct ferro-cement boat hulls. On the bright side, you don't need that amount of strength, just to isolate the humidity, so you would need far less steel mesh. If your house has forced-air heating, you must cover up any ducts leading to or from it and provide exhaust to outside. Use an exterior door to seal off the room from the house.

Additionally, you will need an exhaust fan on a humdidstat (not expensive or hard to hook up), and an air inlet either a flap coming IN from the house (opens only when the fan runs) or from outside. Be aware your fan will be sucking cold air either into your house, or your grow room, and in either case it will be expensive to heat. For this reason, as well of resons of plant disease you will find eighty percent humidity way too high. 50%-60% should be ample. 35% would even be okay. Orchids like to dry between waterings and if you use organic medium it will rot in too high humidity, killing the roots.

Also have fans running constantly to circulate air within the room for reasons of plant disease.

As for lighting, you may find you can pick up a few old parking lot light fixtures, or adapt them, or I might suggest Princess Auto, that sells a lot of surplus stuff, and I bought some Mercury Vapor Lamps There for cheap. Most of these fixtures will take varoius kinds of luminares (bulbs). Compare the electrical information on the metal plate or sticker that is on all fixtures to find out if it will suit your luminare. Have more than one, and have a couple of different types as they will make up for each other's deficiencies in the light spectrums. Sodium lamps are cheaper but give give a very ugly pink/orange light and the spectrum emitted is fairly inferior for the plants. I would recommend maybe a mercury vapour (cheaper, Yellowish green spectrum) and Metal Halide (more $, more blue and red in the spectrum; better for plants).

Be aware that these lamps must be sheilded with quartz glass to cut down on the UV light emitted (Mostly for you, but also the plants). One storekeeper I met in your fair city who was proud of having the brightest store windows on Yonge street, had a 5000 watt metal halide lamp in his shop, and also de3adly melanoma tumors on top of his (bald) head.

Those lights can cause tumors, but not, as far as I know baldness. Hair doesn't protect you, but may hide the tumors, if you have them.

If it were my basement, I would dump a bucket of water on the floor, see where it collects, and put a floor drain there that joins to the main basement floor drain. If the water goes toward an interior house wall, I would recess a concrete spillway along that wall leading to a drain. That way I would not have to worry ever about water on the floor, or be careful watering.

I renovated my mother's basement in Mississauga last year and was surprised to find that basement floors don't have steel in them, they break easily with a five pound sledge hammer, and only where you hit them. ABS drain pipe is cheap and you simply fill in over the pipe with rubble that you broke out, and a bit of ready-mix concrete. The whole affair scared the hell out of my Mom and contractors that we asked to quote on it (They refused), and I did it myself with no special skill in about half a day in total.

I wish you all success.

Best regards,

Science Moose