Tuesday, 5 April 2016

A few tips on making a winter greenhouse

Well it snowed today.  It is mostly melted now, but it did get me thinking about how sadly short our growing season is here in Saskatchewan.  I have all ready planned to use my indoor grow light year round to grow a small herb garden indoors, but being outside is what really makes me giddy.  I've tried to get into more winter sports, such as skiing, but it's difficult to get started with two little girls under age three.  So...I'm currently working on my plan for a small backyard hobby greenhouse and the project has grown to make my summer greenhouse winterizable (not a word, I know). (I'm also making a few cold frames, which I'll discuss soon!)

I really want to do this without a huge hike in my electrical bill.  I don't want to have to pick up an extra shift at work just to heat a small greenhouse in the winter.  Thankfully, it will be a rather small greenhouse.  But I live in Saskatchewan - temperatures easily hover around the minus 30 degrees (that's celsius!  almost the same fahrenheit, that's how cold it is!) for long periods of time.  I will likely have to rely on some kind of heat source if only for those especially cold days throughout the year.  I imagine that until I fine tune the system, I will only succeed in extending my growing season.  But the long term goal is to grow vegetables all year round without a heater (or at least to as great an extent as can be managed!)

Here are a few ideas for my greenhouse design that I'm considering in my preliminary research:

1. Geo-dome shape (such as this one)

The major draw back to this is that I don't have a large yard, and every bit of space is very valuable to me.  (I have a lot of plans for every square foot!).  But I do want to at least take some of the principles behind this design, such as a roof that is angled for maximum sun absorption (take your latitude and add 15 degrees to find the best angle for your roof).

2.  Compost Heat Source

The idea is to dig a trench, or a small hole in the center of a small greenhouse, cover it with a wood or other material so you can walk over it, and let the decomposition of the pile heat the greenhouse (if only by a degree or two).
I still have more research to do for this one, but I am liking this idea.  Even if it doesn't work well as an actual heat source, it would still allow me to continue composting in the winter months.  Plus, easy access plant food!

3. Insulate with Bubble Wrap

In the summer, I will only have an inside layer of greenhouse plastic.  In the winter, I'll lay bubble wrap on the poly from the outside, and seal it with another layer of plastic wrap around the outside frame.  Apparently, larger bubbles let in more light.  But may also cause faster heat loss than smaller bubbles.  Hmm, I see some trial and error experimentation will likely be needed.  You can buy greenhouse grade bubble wrap, which will be more resistant to UV light.

A few things to keep in mind:
You will still need to ventilate your greenhouse, even in the winter, to prevent diseases.  Have vents you can open during the sunny mornings, and close before temperatures plummet again in the evenings.

Here are my sources, and more great information to read:




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