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Question: Sub Zero Greenhouse in Montana

My wife and I are considering a green house, but heating them in the Montana winters is giving us pause.....Is there any way to avoid the sky rocketing prices, and still enjoy this treat? We have considered wood stoves, and radiant water through the flooring, and even a wind turbine on the roof, but these all seem a little radical......or expensive, or both - any idea what would actually keep us warm in the sub-zero up here? Is there a removable insulation system that's fairly easy to install? Thanks for your help.

John & Brenda


    Hi John and Brenda -

    Sorry I'm a little slow getting back to you (I've been working too much overtime). There are some great techniques to reduce heat loss and increase solar gain. Here's my top 10 recommendations:

    1) Attach the greenhouse to an existing house facing direct south (Saves 30%) -

    2) Triple pane polycarbonate for windows and skylights (Double saves 30% over single and Triple adds about 15% more)

    3) Solar heat sinks - Lots of options (See Greenhouses book by Ortho and The Passive Solar House for types and effectiveness (h2o (water) is the best)).

    4) Insulated shutters -- close in evening (See passive solar book for designs).  If this is too much work, you can take R-board (thicker the better) and screw it to the frame with decking screws and plastic washers. It's paintable!

    5) Halogen lights -- help with growth, heat and light.

    6) Wood stove - inexpensive and effective. Load up in the evenings.

    7) Back-up gas heat - Automatic start just in case (can use a propane tank and temp control).

    8) Solid roof with a few skylights -- most of the heat loss is through the roof.

    9) "Pit greenhouse" -- a technique commonly used in Canada. Use the Natural heat of the earth and it makes a great solar heat sink (see plans on my plan page).

    10) Solid roof and walls with lots of insulation (only use windows were you need them most (South walls and don't overdue it.)) Use conventional construction on roof and wall with lots of insulation. Lack of natural light can be supplemented with fluorescents and incandescent which don't use much electricity and add a little heat.

    Here's some books articles and sites to help you with your quest:

  • The Passive Solar House (solar shutters and passive solar heating)
  • http://www.h2othouse.com/html/GreenhouseHeating.html
  • http://www.h2othouse.com/html/GreenhouseTemp.html
  • Greenhouses by Ortho
  • http://www.h2othouse.com/html/plans.html (see pit greenhouse and Sundance Supply)
  • http://www.h2ouse.com/plans.html -- a few links on solar / energy efficiency
  • http://www.h2othouse.com/html/greenhouse_glazing.html - glazing is where you lose heat the fastest.
  • Please keep me posted and we'll share the information with others!



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