Deciding on the greenhouse

I was hooked from the very first time I saw a video about a greenhouse-enclosed home! That day I scoured the Internet looking for every one of these kinds of homes I could find. This search produced some in Holland, Norway, Sweden, Belgium, Germany, France, and Poland. Each approached the greenhouse structure in a different manner and these differences gave hints toward design, construction, and cost considerations of the various alternatives. I gleaned as much information about each project as was available from internet blogs, videos, images, and newspaper archives; I did not contact the owners, builders, or architects directly. My goal was to de-construct each of those projects to derive a set of factors to apply to the greenhouse on my project1, such as:

  • Were the greenhouse and house designed as a single and integrated project, or was the greenhouse retrofit after the house was complete,
  • Since the house is sheltered by the greenhouse, how is the home’s roof handled
  • Was the greenhouse fully-custom or a customized commercial-agricultural greenhouse
  • What material was used for the greenhouse glazing
  • Do the greenhouse trusses allow a home taller than 1 story
  • How did they handle the greenhouse heating and cooling
  • How did they address ‘entry’ or signaling how and where guests should enter

For various reasons I excluded from my analysis the structures in Holland, Norway, Poland, France, and 1 in Sweden, but this left 1 in Belgium, 3 in Germany, and 2 in Sweden2.

Integrated or Separate Projects

All projects, except 1 in Sweden, were designed and built as an integrated plan. A benefit of the integrated plan is these homes didn’t incur the expense of insulating and covering a roof against the elements. Another benefit is that a few of these projects included living space on the home’s roof from the beginning. Conversely, the project in Sweden that built the greenhouse over a pre-existing house, removed the home’s roof and the home’s former top floor became a ‘roof top’ deck.

For my project I’ve decided to include a conventional roof for several reasons: first, and by far the most important, it was easier to get past the planning department. Permit review and approval in this County is exceptionally long (see Permit Approved) so I didn’t want to incur further delay (and probably additional cost for lawyers) to convince them that some building codes (like rain gutters) should not be applicable due to cover from the greenhouse.

Another reason to include the roof is for design aesthetics; I like the look of the roof giving context to the different sections of the house. Next, to have a flat roof for a ‘roof top’ deck would have meant a standard 8’ flat ceiling in the livingroom. In a tiny home, the added volume from high ceilings contributes to a room feeling larger than the actual square footage. The angled roof allows for a higher ceiling and a greater sense of space.

I plan to live in this home as long as I’m able but ‘life’ happens so I still considered resale speed and value. The thought was that the house can stand alone if the greenhouse is removed. It’s debatable, however, whether my home would sell faster with or without the greenhouse. It may be many years before the real estate market rises to where an asking-price for the tiny house, without the greenhouse, would cover the cost to build this project that includes the greenhouse (even if there is some resale value for the used greenhouse). My guess is there will be buyers for the greenhouse-enclosed home without too much delay due to the project’s uniqueness even though it’s on a tiny island.

Fully Custom or Customized Package

As I got serious about building a greenhouse-enclosed home I wanted to get at least a ballpark cost for the greenhouse; a 5-digit cost would be doable, a 6-digit cost would not. Due to several states passing legalized marijuana laws, the United States is in a commercial-agricultural greenhouse building boom. The good news is that meant I was able to find the cost for commercial agriculture greenhouse packages of various lengths, widths, and heights on the Internet without having to inquire for a bespoke design and the cost was in a range I could afford.

First hurdle crossed meant it was worth spending time to look carefully at the other projects around the world for clues regarding what customization may be needed and how that may effect the package cost. While it’s possible one of the projects in Germany is a customized agricultural greenhouse, it appears that each of the other project’s greenhouse is fully custom designed for that project. None of the sources I found confirmed this or discussed the rationale for a bespoke greenhouse. Other key considerations are:

  • All of the other projects use glass as the glazing material. Some sources noted this was not likely to break because it is similar in strength and composition to automobile windshield glass, but none discussed why glass was selected instead of alternatives such as double or triple walled polycarbonate.
  • None of the other projects have a truss member running horizontal at gutter height so the house height, or head-room of a roof-top deck is not limited to the sidewall height and most included living space on the house’s roof.
  • The entry door size and placement was different for each project and a couple with the door on the side even included a roof over the door for protection from rain or snow shedding off the roof.
  • None of the sources I found mentioned auxiliary greenhouse heating but several mentioned the need for cooling. All projects included venting windows along the roof ridge, most included shade cloth, at least 1 home in Sweden includes evaporative cooling panels, and 1 specifically mentioned tubes used for ground-to-air heat exchange.

Cost information was hard to find but what I did find, adjusted to 2021 U.S. Dollars, put the greenhouse structure in the 6-digit range. Although that is out of my price range, it provided a sense of the cost implications if I strayed too far from the commercial-agricultural greenhouse package I’d used for a ballpark cost at the start of my research.

Glazing Material

My greenhouse will have 8mm twin-walled polycarbonate glazing panels. These are less expensive, lighter weight, and much faster and easier to install or replace than glass. They are not as translucent as glass and there is greater possibility they will yellow or become cloudy over time. However, the panels have a 10-year warranty and, living in an agricultural area, I am able to visit many long-standing greenhouses that use these materials to verify for myself whether this wear is acceptable.

The polycarbonate panels also come in different finishes so I have selected opaque white for the north sidewall for privacy from the neighbor; especially when I go for a swim. I think the white will also provide a nice backdrop for the plants that will grow along that side. My greenhouse will run along an almost perfect east/west axis so there will be direct sun only on the south-facing roof and no direct sun on the north-facing roof. Therefore, I selected “solar soft” polycarbonate panels on the south-facing roof section to reduce UV exposure and heat gain and clear panels on the north-facing roof. It may not be as aesthetically pleasing to have different materials on the roof but the expectation is this will balance the desire to be able to see the sky with comfort in the greenhouse seating and gardening areas.

Trusses and the House’s Roof

My greenhouse will be from Conley’s Manufacturing, the Gable 7500 series, 35’6” wide by 60’ long with 12’ sidewalls. The only downside to this model is the roof truss has a horizontal member at the top of the sidewall. I had originally planned for 10’ sidewalls but needed to increase to 12’ to fit the house’s angled roof under the horizontal truss. Even if I had decided to have a flat roof for use as roof-top living space, these horizontal members would interfere with that use so I decided to keep the angled roof. Increasing to the 12’ sidewall, however, further limited where the greenhouse could fit on my property as it raises the peak of the roof to the local code restrictions on residential building height.

Greenhouse Heating and Cooling

Unlike all of the other projects, I did not order retractable shade-cloth with my greenhouse package. My thought behind this gamble is that the solar soft roof panels will reduce the radiant effect similar to what the shade-cloth does for glass but without blocking the light like shade-cloth. Like all the other projects, I will have operable windows, controlled by a thermostat, along both sides of the roof ridge. While none of the other project have, nor will I have, a large sidewall or endwall fan due to their noise, I will have 4 independent ground-to-air heat exchange tubing systems that provide positive air pressure to move air out the roof vents. I did not purchase the evaporative cooling option with the greenhouse structure order but I’m still evaluating that as a future add-on.

Finally, the owner of the project in Belgium reminded viewers that just like living in a house that is not in a greenhouse, they don’t live in the greenhouse, they live inside a house. When it gets too hot outside they just close the home’s doors and windows and the temperature is quite pleasant with air conditioning. Ultimately, if I’m totally wrong in the greenhouse cooling systems, my tiny home’s mini-split should provide adequate cooling inside the house.

Finding the Front Door

It may seem like a small thing but I think about whether guests will know where and how to enter my home. Too many times I’ve approached a stand-alone house and not been sure where the guest entry was, or when approaching a home-based business not knowing whether I was supposed to ring and wait at the door or enter to a reception area. If I were a guest approaching a greenhouse-enclosed home, would I be able to find the door into the greenhouse? Would I know whether to ring at the greenhouse or enter and ring at the door to the house? If waiting at the greenhouse entrance, is the door on the sidewall or endwall with cover from rain or snow from the roof?

There are a number of ways to signal the guest entry – a door color that stands out from the walls, a roof over a door, or a pathway between the public right-of-way and a door. This was actually one of the most difficult features to verify from the other projects because not a single interview discussed ‘entry’ so I was at the mercy of what the photographer or videographer captured. It was often difficult to see any door because the glass door was a continuation of the glass walls. One home had car parking on both long sides of the greenhouse making it even more difficult to determine which was the correct side to enter. A couple of the other projects include a commercial business inside the house but did not show whether they differentiate commercial-customer entry from personal-guest entry in any way.

For my home, guests will approach from a public road on the east end where a paved path will run from the edge of the driveway, down stairs (and an alternate wheelchair ramp) to a courtyard between the garage and greenhouse endwall. There will be a standard hinged door on the greenhouse end wall so it is both human-scale and not under runoff from the roof. I have the option of replacing the clear door panels with colored panels to make the door stand out even more. In our rainy climate it’s best to get under cover as fast as possible so I’ll probably have a sign at the door indicating that guests should enter and ring at the house’s door which will be about 15’ straight in.

There will be double-wide sliding doors on the west endwall that should not create confusion because it won’t be visible from the public/east side nor will there be a path outside around either side of the greenhouse. The large door on the west end will be accessible from a private road and from the auxiliary buildings on the property. This door will be large enough to pass with a wheelbarrow or even a truck for soil, mulch, or large plant deliveries.

Some Miscellaneous Thoughts

Given the business my greenhouse manufacturer is doing with marijuana-growers, my “small order” didn’t get the kind of timely responses from the sales person that I would have liked. I suspect I would have received better service from a fully custom greenhouse supplier. Before submitting my order, they estimated shipping in 12-14 weeks which put shipping in early February 2022. After my order was officially in the manufacturing pipeline, however, I received email that my package should ship January 3, 2022! It is manufactured in the U.S. and shipping from California by truck so I’m estimating arrival January 10, 2022.

This is getting real!


1 To the extent the sources are incomplete, my analysis is incomplete and some findings may be incorrect.

2 NORWAY: This house is in the arctic circle so their greenhouse is a geodesic dome to withstand snow loads and wind sheer. It is a custom steel and glass greenhouse that was planned and built as a single project with the house. The house is 3 stories, made of cob and other natural materials. The greenhouse significantly extends the growing season such that the owners are able to grow food they would not be able to otherwise. This project includes solar power, plus grey and black water treatment and recycling. While beautiful, this project’s brief is so different from mine that I can appreciate the owner’s dedication to sustainability but not take away lessons for my design.
POLAND: This home was designed as the result of a contest among architects and includes space for livestock and fodder within the same structure as the human shelter so its requirements are too dissimilar to mine and is not included in my analysis.
FRANCE: This project is not a home enclosed by the greenhouse. It is arranged as a greenhouse attached to opposites of a separate home/living-structure.
HOLLAND: The home in Holland was designed and constructed as a temporary experiment by a University. It was constructed of experimental materials and not intended to endure so is also excluded from this analysis.
SWEDEN: One of the greenhouse enclosed homes in Sweden is excluded because it isn’t an independent home inside the greenhouse; the greenhouse is connected to an older home with only some of the home’s rooms and functions moved to inside the greenhouse.

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