I have seen several good ideas on this forum over the last couple weeks and would like some more targeted thoughts.

The set up is a garden center in central Texas highs 100F+ lows 20's -. Oriented North-South. Is 24X30 feet. It has single white poly that blocks 55% of sunlight. This set-up was obtained by Polytex.com as a seasonal GH but I have plans as Garden Manager to protect and grow plants and start veggie and herb from seed throughout the November.-March time frame to be ready for extra spring sales beyond what I can buy in from local growers. I have been in the nursery biz for almost 20 years now but this is the first time that I have managed a garden center by myself. The GH has single clear 6ml poly end walls and has 4mm double wall poly carbonate side wall that slide for ventalation (almost useless IMO). Each endwall has 2 6 foot sliding doors with 4ml poly carbonate on the outside with big gaps at the top and bottom. I am trying to prioritize and winterize in a logical and economical fashion.

1. I have so far sealed the gaps around the base of GH.

2. Sealed the doors the best I could and still have them open and close for access to customers and for venting as needed.

3. Used 4 32 gal black plastic garbage cans along mostly dead space on the south wall for heat sinks.

4. I am still in the process of applying tek-foil (aluminum coated bubble wrap) on all the North wall.(no sunlight).

5. I am evaluating and consider poly coverings. I plan to go to double poly with inflating fan. I am leaning toward Koolite 380 from Klerk's but want to get with rep to get about 70% usable diffused light. The single layer white that is in use blocks too much for winter but worked well for our summers. I am looking at a compromise. Can see this at klerk.com (I have used their koolite in Hawaii and the results were very dramatic but never in a double poly and HOT Texas summer set up!!

6. I am debating how many more tubs (heat sinks) to place along the rest of south and west wall.

7. I am considering using black weedmat to get additional heat gain to the decomposed granite floor.

8. The owner gave me 2 1500W cheap electric heater says that will do it. I told me he'll know in a couple of days with the first freeze. It only held 35F at about 30F outside. (granted I lost a lot of heat through gap area not done yet and the areas along the base and sliding doors allowed more gaps because of the near 60 mph wind that came in with that front.

Another front comes in tomorrow and will get in the mid 20'sF with at least freezing temps at night the following 2 days.

Short term I am going to try and finish sealing north wall and adding more tubs, maybe the black weed mat if the benefit outweighs the cost. I am also looking to deal with the flimsy poly carbonate sliding side walls. I opened them some this last summer so I don't want to do anything to not make them functional.

Mean while I have to water and tend to a couple thousand plants that are winter hardy outside but will need attention as well.

Ideas short term and long term are welcome as well but remember this is a retail setting and I have to work around that and anything I do need to make economic sense for a commercial operation cost verses ROI (return on investment).

P.S. Sorry this is so long but I wanted to lay out the scene a much as possible to allow for the broadest exhange of ideas based on the reality at hand.

Thanks for all the ideas already generated just by reading various posts already. I look forward to sharing my growing experience and exhanging of practical ideas for the Greenhouse environment.

Happy Growing David