Wednesday, December 8, 2010

The Greenhouse: Lessons Learned on How to Heat and Insulate It

From In the Garden

Normally I'd post some blooms on this frigid second Wednesday of December, but my son and husband had to borrow my camera and I just was not able to get some photos prior to today's posting so I thought I'd talk about my greenhouse. I'd been wanting to share some more of what I've learned about the greenhouse anyhow so my excuse is no pictures of blooms:) Honestly, the only color in the garden is frozen pink camellias that are turning to mush, and some ragged at the edges yellow button mums. You all have seen those two flowers in my garden plenty of times so let's talk about the greenhouse and how it has fared with recent temperatures in the teens!


In last month's Bloom Day post I spoke about my apprehension and worry about heating the greenhouse this winter. A greenhouse is a dream I've always had but not one I thought would realistically come true. When it did, I was a bit taken aback in that I never really expected to have to figure out the workings of a dream I did not think would materialize. Does that make sense? I hope so. Nonetheless, the greenhouse is here and it is my responsibility so today I'll share some lessons learned so far this year. 

Like I normally do I researched various methods on heating and insulating greenhouses. I found bubble wrap is an excellent insulator and does not block the sun's warming rays from entering the greenhouse during the day. I only wish I had added the bubble wrap insulation prior to the weather turning cold. The problem with adding the bubble wrap once the weather turns cold is that condensation tends to form on the metal parts of the greenhouse. The tape I used to attach the bubble wrap to the greenhouse walls does not adhere to moist walls. Lesson learned: add bubble wrap while the temperatures are still warm next year.


While the bubble wrap is not the most attractive thing about the greenhouse it has been a lifesaver as far as retaining heat. It is no surprise I'm okay with the bubble wrap because you all remember I am a functional gardener versus an aesthetic gardener. Functionality will win here at Tiger Gardens before good looks any day and in this case insulation must be my uppermost concern when the temperatures hit a low of 18 degrees! Lesson learned: While the bubble wrap is not the most attractive thing in the greenhouse it is an excellent insulator.


As far as heating the greenhouse I had originally intended to use a ceramic heater because all I read on the Internet talked of ceramic heaters as being safe and efficient heaters in a greenhouse. I tried a small ceramic heater I had purchased specifically for the greenhouse but it did not work. The heater has a switch that will turn off the heater if it overheats. Apparently it overheated a lot because the heater never ran. It is a good thing the extra insulation added to the greenhouse kept the greenhouse about 10-15 degrees warmer than outside temperatures or my plants might have frozen. The heater I purchased should have worked for my 48 square foot greenhouse because I used a special formula to figure out the size of the heater required based on surface area of the greenhouse and other information. You can find that formula here and the math is automatically done for you-a good thing after my leaf posting. Once I realized the ceramic heater would not work (it didn't take long) I dug around my garage and found a small electric radiant heater that has worked like a charm. Yesterday morning when I checked the greenhouse (outside temperature was 18 degrees) the inside temperature was a toasty 45 degrees. Forty five degrees is pretty good for my purpose of keeping my tender perennials and houseplants from freezing. Lesson learned: Try what you have on hand first before buying something new to serve a purpose.


Below is the greenhouse from the northern side of the structure. I took this picture so you all could see the two inch coated rigid foam insulation I used to insulate the northern side of the greenhouse. It is kind of weird having this side closed off but sun would never enter the greenhouse from the north side and I wanted to block the chilling northern winds from ripping through the greenhouse. Insulating the northern end of the greenhouse was a tip I received online and a super good tip. This rigid foam insulation with the reflective material on the heated side (inside the greenhouse) has been a much better insulator than the bubble wrap because it is one solid piece and is in place permanently. The plants are nestled right up against the foil lined foam and get reflected sun from the insulation while staying warm because the foam prevents cold wind or air from penetrating the greenhouse. Lesson learned: Insulate the northern end of your greenhouse with a fairly permanent insulator. If you use the reflective insulation be sure to put the reflective material on the inside of the greenhouse.
 


From In the Garden
I will talk more of solar and passive heating at a later date. But a question for you now: knowing I have a ton of deciduous trees on the southern side of my garden, and knowing that even with all these trees the greenhouse receives some winter sun, just how warm do you think it gets in the greenhouse during the day? Hint: It is a very comfortable warm! Take a guess and I'll reveal the answer in a later post....


in the garden....



Words and Photos Property of In the Garden Blog Team, In the Garden

21 comments:

  1. I was wondering if you used the ridgid foam.
    I want one of these, with the big canvas garage out back, it will have to wait, JOATS thinks we can turn that into the greenhouse thou!Oay...

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  2. plants, all will be fine....
    Trial and error by greenhouse, man, there is more to having one than you realize. Your research and experiments will help me 'when' I get a greenhouse.

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  3. Yep I agree with Darla, your experience will be very helpful to all of us if & when we get greenhouses. :)

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  4. Sounds like you're keeping a close eye on everything to adjust as needed. I'd never thought about just covering the north side. That makes sense. Some people have green houses up against another building. I suppose that would serve the same purpose. I hope your plants do well in there for you.

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  5. Sounds good! we're staying about 10-15 degrees warmer in the garden shed right now with passive solar heating. I wish I could get it warmer but I'm trying to avoid running anything that costs money (Too cheap I guess!) You could try insulating the outside northern wall of your greenhouse with a wall of straw bales. They are a very good insulator and since we don't get much light from the north it should reduce your light much.

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  6. I think having a greenhouse is wonderful. This winter (so far) has been especially cold, just keeping your plants alive is a challenge.

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  7. Sounds like you have learned a lot about caring and using a home greenhouse. Hope it all works well for you. Others will benifit from your first winter of having one.

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  8. Dawn, Your huge window in your craft room would be the perfect spot to grow some flowers. I love that window! No insulation needed since you are already set up.

    Darla, I hope my experiences help others-I tell you greenhouses are new to me and I'm learning-it's a steep curve.

    Racquel, New compost bins can the greenhouse be far behind?

    GSS, I never knew about the north side either-thank goodness for bloggers who helped me out. It has really worked well blocking that side.

    Dave, Ah yes, straw bales are excellent insulators indeed. So glad your sunny shed is staying warm. It will help to winter over plants keeping them out of the elements for sure.

    Janet, It has been brrrrr cold for sure. No working in the garden for me and I'm frustrated as my goal is to get my fence up by Christmas. Not looking good.

    Mom, I hope so. Do you know your full name is showing? You must be playing with the new blog? I hope so as it is for you!

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  9. Wow! I've wanted a greenhouse for a long time. After reading your post, I think the time is right.
    Thanks.

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  10. On this sub-freezing day, a greenhouse sounds delightful. Thanks for sharing what you’ve learned. I like your distinction between a functional vs aesthetic gardener.

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  11. Hi Tina, Thanks for sharing your learning curve on the greenhouse - the rigid foam with reflective material sounds perfect for your purpose. I heat my sunroom with a space heater to keep above freezing and frizzled up a couple before finding an oil filled radiator type that works great.

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  12. Very good information! In fact I may see if I can use any of it on the inside of my shed. I was hoping it would stay a bit warmer in there, but the lemon tree isn't looking so good. I wonder if the rigid insulation would work in there? One day I'd love to have electricity in it.
    My guess is 60 degrees.

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  13. I'm going to aim high and guess 70 - 75 degrees during the day. I'm just thinking if it's 45 degrees in the morning, it must go significantly up during the day??

    Your post was awesome as usual. You always seem so thorough on your research and it sounds like it pays off. I'm making mental notes for down the road. The bubble wrap is a great tip in itself and I love that it's cheap! Having a greenhouse has been a dream of mine forever too and I'm determined to make it a realization in the not too distant future.

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  14. I have a small greenhouse and I heat it with an electric heater which is on a thermostat. I keep it just frost free whcih seems to do the job. The greenhouse is backed by a brick wall and I think this helps retain heat.

    I have been told that you have to be careful with bubble wrap as it can cause lots of condensation which can lead to mildew and plants rotting off. it is better to try and keep plants esp foilage dry at this time of year. Someone I know uses those plastic foam trays that you get bedding plants in (well here in the UK you do) and she stackes them up inside the greenhouse wall - she says it works well.

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  15. The best teachers are the one who learn their own lessons:) I'll guess that the temp gets up to 70 degrees Fahrenheit during the day when the sun is shining. I noticed a ladder up against the house. I hope it's for putting up lights and not for shingle repair!

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  16. Good guesses on the temperature inside the greenhouse. A little on the low side but I'll reveal later.

    Helen, The greenhouse gets a lot of condensation with and without the bubblewrap. The cool thing is now that the greenhouse is sealed with bubblewrap the condensation is on it and not the greenhouse itself. I have one plant that has some mold and I think I have worked out the problem by putting a small fan inside to circulate the air. It is pineapple sage and seems prone to mold and mildew even in the garden but I'm keeping an eye on the other plants too because the greenhouse is such a humid place-that's what I like in the winter along with the heat-such a nice place to be if one is ill. The bedding trays sound like they'd be a great insulator too. That's a wonderful way to reuse!

    W2W, That is actually the storage place for the ladder. Not the best place but it is convenient. Funny you mention the roof as we are bidding out with contractors now because the house is due a roof soon. That should be an experience! Not one I'm looking forward to at all.

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  17. I'm glad you found a heater that works, Tina. After all your hard work, it would be such a disappointment to have your plants freeze. I'm curious just what the temperature is inside without the heater--it's so cold here right now that anything above 20 sounds downright tropical!

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  18. I would guess it gets in the 70's during the day?
    I have no idea.

    I got the advent cupboard at Target last year.

    Thanks for commenting on my blog.
    I am glad it is working now. :)

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  19. Okay Tina, I just had to come back here and tell you how incredibly lucky you are to have found Amaryllis bulbs for $1.00!!!!!!! I would buy out the store if I ever came across a deal like that. Even discounted (like they are here after Christmas) they are only 50% off ~ which is still at least 7.00 but usually more.

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  20. Hi Tina, this is my first year with a greenhouse too, and I am using bubblewrap. Helen is right, there is a condensation issue and I have lost some plants, but I reason this is worth it to not have to heat it, which I can't afford, and ventilation on sunny days keeps it down. I don't know if you can hold of something similar, but in the UK we can get nifty little fixers for attaching bubblewrap to greenhouses, it keeps an air gap which helps increase the insulation level and works no matter how damp the frame. You can use them to fix other things to the frame too. Alliplugs

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  21. You are a great teacher to reveal your lessons learned!!! Great info for Greenhouse owners to be....

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