Allocating the greenhouse’s footprint

Like any structure, there is a cost per square foot to build a greenhouse large enough to enclose a home and it is not inexpensive. Therefore, I put a lot of thought into how every square foot would be allocated to get the highest value for the cost. To put this into a perspective that most people can relate to – have you ever looked at every . single . square foot of your home and asked yourself, “if I had to write a check for $x for that square foot, is that how I’d use that space?” If not, then what would have been a better use? The answer is very personal because each person has different needs for their home.

I’ve been asked various forms of a question that boils down to ‘why did you leave so little space for the food garden?’ The short answer is, food gardening was not the only reason, or even the main reason, for the house inside the greenhouse so my goal was to balance the needs, not to maximize food growing space over everything else. My needs were to have outdoor living space, year-round entertainment and exercise that is out of the rain, to have pleasing views from every window, and to grow food and flowers for cutting.

My greenhouse cost, in 2021 U.S. dollars, about $83,000 including the greenhouse, tax, shipping, and installation. That’s about 10% to 20% the cost of a 2,100 sq ft house in this area.

Living Space

Moving in

Most people who live in a tiny home try to incorporate outside space, such as an attached deck, into the living space. Here in the Pacific Northwest, however, it rains a lot; nearly 9 months of the year. Even a covered deck would not be useful much of the year due to wind and cold. Therefore, my primary reason for living in the greenhouse is not to be able to grow food (that could be done with a fully detached greenhouse), it is to have enclosed ‘outdoor’ living space. It’s like a 3-season porch but at a fraction of the cost. Still, the square footage allocated to living space (i.e., the house and sitting area) is less than the garden space.

I optimized the square footage allocated to the sitting area by:

  • drawing a 2′ planting border around the greenhouse interior,
  • measured the area rug planned for that area plus a 6″ border,
  • added a walkway that is 4′ wide to be comfortable for 2 people to walk side-by-side or for a wheelchair

That set the south and east edge for the house.

Water Features

Why did I give so much space to the water features? My greenhouse is on an almost perfect east-west axis meaning the sun shines on the south, or front, side of the house and casts the space on the north, or back, side of the house in shadow until late in the afternoon. The last hour or so of the summer setting sun shines onto the pool. The back side of the house receives little direct sun so is not useful for growing anything except shade-loving plants. So I considered what else I could use that space for.

Swimming laps is one of my favorite forms of exercise but there isn’t a pool available on this island. The pool has the added benefit of being a temperature buffer; it will be cooler than the ambient air in the summer and warmer than the ambient air in the winter. One of the air-to-ground heat exchange tube systems runs under the pool to cool and dehumidify the air in the summer. Potable fresh water on this island is precious and expensive. As the summers get hotter and drier, the pool water is also a backup source for irrigation or fire suppression if the rainwater tanks go dry.

The purpose of the ponds is for plants in the ponds to filter the water so that I don’t have to use chemicals in the pool. They’ll also provide a nice view from the sitting area, kitchen, bedroom, and shower.

I optimized the square footage allocated to the pool and ponds by:

  • setting the pool width at my outstretched arms plus a couple feet to pour the concrete wall,
  • the east pond fit within the space available after setting the house’s east edge from the sitting area,
  • the west pond dimensions were determined as the least gallons that could filter the volume of pool water.

That set the north edge for the house and west edge of the water features.

Garden Space

The remaining floor space is set aside for gardens and paths between the gardens. My objectives with the garden spaces are:

  • year-round entertainment; I enjoy gardening but not in the cold rain,
  • something nice to look at from the sitting area, livingroom, and kitchen, and
  • to have fresh food most, if not all, of the year.

I do not have an objective to grow enough food to be self-sufficient, or to grow heat-loving plants in the winter.

I live in USDA Zone 8b. Winters are wet, windy, and cold, although there are not too many days below freezing. Deer and chipmunks are the worst garden enemies. Growing food ‘outside’ requires an 8′ fence, not just 6′. My property is ringed with tall evergreen trees so after building the greenhouse there isn’t much land outside that receives enough sun, even in the summer, to grow plants that require full sun.

The garden space will be allocated to ornamentals and herbs on the east (left) end around the sitting area and east pond. The west (right) end will be a food forest with lemon, lime, calamondin, and peach trees in the northwest (lower right) corner.

I’ve only been living here for 2 months and it is working as well as I’d hoped. Although I have to go out in the freezing rain to bring in materials, once inside the greenhouse I can spend hours working comfortably. The fruit trees are in, plus I have kale, dianthus, and some other plants in pots. The plan is to build the raised bed frames, bring in soil, install the irrigation system, and finish the potting bench and seedling racks over the winter.

6 thoughts on “Allocating the greenhouse’s footprint

  1. This is really neat! How did you handle the ventilation that normally is required in a home? Sewer pipe vents, plumbing drain vents, wood burning stove pipe, and so on?

    1. The plumbing stack vents into the greenhouse rather than through the greenhouse root to the outside. This was the only thing that was questioned on inspection. They ultimately decided that the greenhouse is not air-tight even with the ridge vents closed and the ridge vents are open at least 6 months of the year. Also, I think the code is worded that it has to vent outside the home, so it would be difficult for the inspector to say the stack didn’t meet code. I don’t have a wood-burning or gas stove. The electric range hood vents from the house into the greenhouse. That hasn’t been a problem so far since, again, the ridge vents are open most of the year and in the winter when they’re closed I’m spending most of my time inside the house, not the greenhouse’s sitting area.

      1. Thanks for your answer. The inspector then, decided that the internal house was the house and not the internal plus external. Interesting.

        How is it doing for warmth? I would think it would stay fairly warm, but that’s just guesswork.

      2. I’m still setting up the weather station (including temp and humidity probes around the greenhouse) so I only have readings from when I happen to check and yes, the house is staying warmer than if the greenhouse was not here because the greenhouse is warmer than outside. BUT, I do not have any supplemental heat in the greenhouse and this time of the year we don’t get much sunshine so the greenhouse is not warm. Today outside is 20 degrees, inside greenhouse is between 30-36, inside the house thermostat is set to 65 and the minisplit is not running constantly. I turn the house heat off at night and my guess is it is getting down to the lower 60s or upper 50s overnight.

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