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