Thinking about building your own greenhouse? It can be overwhelming to think about where to start. But luscious greenery and a safe place to enjoy the fruits of your labor isn’t so far out of reach. More than anything, plants need a safe, warm place to grow. Greenhouses provide this by harnessing solar radiation as the sun shines through transparent windows. Heat is trapped inside, where it then rises, pushing cooler air down. There, cooler air warms until it’s hotter than the air above, and the cycle continues. This process isn’t that complicated and can be easy enough to replicate in your own backyard. There are many options when it comes to greenhouse function, design, and style:
What Degree Will Your Greenhouse Be?
Cold Greenhouses: These are heated solely by the sun and are therefore are fairly easy and simple to build. Also known as ‘cold frames,’ these greenhouses have no way to keep warm during the winter, and temperatures can still dip below freezing during the coldest months. Despite this, cold frames can still help start spring crops a few weeks early and extend the growing season at the end of fall. Cold frames can be as simple as a few glass panels placed over the plants in order to shelter them from cold weather, while still allowing sunlight to penetrate.
Cool Greenhouses: Typically, a cool greenhouse maintains a nighttime temperature range between 45 and 50 degrees. This protects plants that are sensitive to frost by preventing temperatures from dipping below freezing. Cool greenhouses typically don't need heating systems. These temperature ranges are maintained through well-constructed, well insulated, passive solar greenhouses. Thermal batteries, or geothermal energy, is often also utilized in order to insulate and protect the plants within.
Warm Greenhouses: Except in very moderate zones, tropical plants generally require supplemental heat of some sort. These are typically heated through thermal batteries or an electric heater. While not warm enough to sustain tropical plants, a warm greenhouse can support most plants throughout a cold winter and can extend the growing season year round. Electric heat is usually very expensive to install and maintain. Kerosene, oil or wood stove heaters present some risk of fire or dangerous fumes, as well as producing pollution. For those wanting to maintain a warm greenhouse, a heat pump connected to a geothermal air system supports even high temperatures at a much lower cost.
Greenhouse Structures
The kind of greenhouse that’ll work best for your dream garden is categorized and determined by a few factors. How you intend to place and build your greenhouse may mean some styles of greenhouse are better fitting for your intentions than others. Firstly, let’s look at foundations and placement of the greenhouse:
Lean-to/Attached: These are considered some of the easiest greenhouses to construct, as most of the supporting structure has already been built. An attached greenhouse naturally abuts an existing wall, that of a garage or house, for example. Alternatively, it may be nestled against an earthen wall or ‘berm.’ These walls provide insulation, wind protection, and thermal mass. This placement and design also usually guarantees that there are electric and water hookups nearby, making the daily functions of your greenhouse simpler.
Free-Standing/Detached: A detached greenhouse is a freestanding building that provides all its own support. This adds some initial cost for construction and installation but allows for more customization. Additionally, free-standing greenhouses allow for more light penetration, although wider space for more air means there’s more space that needs to be warmed.
Sunken: Oftentimes, you’ll find greenhouses with one or more of their sides covered by an earthen wall. Since their conception, it's been advantageous to help insulate and construct a greenhouse by exposing some or all of the structure to open soil. This can be done through carving out a section of mountain or hillside, or by sinking your greenhouse’s foundation a few feet underground.
Once this is determined, the actual design of the greenhouse comes into question. While these can vary and be tweaked for any range of personal specifications, the general designs come in a few main forms:
- Quonset Greenhouses: This is the most commonly found free-standing greenhouse, primarily due to their affordability and ease of construction. These are your standard storybook greenhouses, with a round roof, creating a semi-circle that disappears into the foundation. These can range vastly in materials and scope. Even a small cold frame made out of PVC piping and some polyethylene sheeting can be considered a Quonset greenhouse. Since these are so simple to build, they’re a popular choice among DIY’ers across the board.
- Gothic Arch Greenhouses: These greenhouses share the rounded roof of their Quonset cousins but add a small peak to the top of the roof. This angled roof discourages buildup of snow, rainwater, or debris. More head room means there’s more space for plants to grow. However, this also means there’s more space that air has to travel during periods of heating or cooling.
- Gable Roofs/A-frame Greenhouses: Gable roofs are the classic triangle roofs that many of us turn to when drawing our homes in kindergarten. A-frames expand on this concept, with both sides of the triangle reaching all the way to the foundation. This style of building is more stable than Quonset or gothic arch greenhouses and has the capability to support more hanging or attached equipment. These are sometimes more expensive to build but come with the promise of maximum light during winter months, as well as increased internal strength.
- Gutter Connected/Ridge and Furrow Greenhouses: These styles of greenhouses can combine one or more of the above designs but are all connected via a gutter system. You’ll almost always see these types of greenhouses when there is a large, multi-cell greenhouse operating. Multiple ‘greenhouses’ are connected without interior walls, allowing air and heat to pass freely between the sections.
Questions to ask:
- What do you want to grow? Will your intended harvest need extra heat, headroom, or a specific temperature range?
- How much sunlight does your chosen location have access to each day? How does this change during different times of year?
- What sort of shade is nearby? Would there be coverage from trees during any season?
- Where are the electrical and water connections for your home? Can you use them for my greenhouse? If not, additional sources of power and water will need to be identified.
- Is the surrounding soil suitable for drainage? If I’d require a water recycling system, what would that look like?
- What material will be the best for my foundation?
- What’s the climate in my area? Will I need to make considerations for extreme heat or cold?