If you have never considered using a straw bale greenhouse, the first question is: why do you need one? Depending on where you live or what you want to grow, there are several compelling reasons. A greenhouse, while a necessity in some regions, can be cost-prohibitive. Hay bales are strong, economical, insulating, sustainable and even fire-resistant, making them an excellent choice for use in a greenhouse.
For anyone exploring affordable and energy-efficient greenhouse gardening options, a hay bale greenhouse ticks a lot of boxes. Straw bale greenhouse plans may be rudimentary or complex, and can vary according to your budget.
Getting Started with a Straw Bale Greenhouse
The practice of straw bale gardening is nothing new. Indeed, the technique of building with straw bales has been around since the early 1900s, when the use of compressed hay bale technology emerged in the Great Plains.
The first thing to consider is how you will use your greenhouse. Is it meant to be a permanent structure or temporary? What is your budget? You will have to have some type of see-through material, whether it’s glass or plastic. Glass is expensive and quite heavy, so any hay bale greenhouse plan must account for the support of such a weighty object.
Low-cost greenhouses, made complete with plastic sheeting, are vulnerable to the weather. They often end up shredded at the first wind storm. If you choose to use plastic over glass, make sure you purchase thick, resilient plastic sheeting.
Types of Straw Bale Greenhouse
There are two basic types of straw bale greenhouse construction – load bearing, and post and beam infill. Load bearing means the roof and windows are supported by straw bale walls, which need to be protected with plaster. This type of construction will also have to be okayed according to zoning and commercial codes.
By comparison post and beam infill construction is when the bales are placed between supporting studs and roof framing.
Straw Bale Greenhouse Ideas
Wood may also be used in the construction of a straw bale greenhouse. This would likely be the load-bearing portion of the structure, often used to support the weight of the glass. Another option is to use PVC piping, which is lightweight yet sturdy.
One of the least expensive hay bale greenhouse ideas is to make a covered trellis using conditioned hay bales, and two curved cattle panels (fencing) inside a wood frame consisting of four 2x4s. The entirety is covered in four-mil plastic and secured with zip ties, staples and a zipper.
The conditioned bales heat the space for starting seeds and provide an area for seed trays. Once the weather warms, remove the plastic and allow climbers such as cucumbers or squashes to cover the structure.
How to Build a Straw Bale Greenhouse
Once you have given some thought to the materials, budget, location and gardening requirements, follow these basic steps to straw bale greenhouse construction:
- First considerations are the foundation, framing and roof. Load-bearing structures only need the foundation done at this point. Think about the inclusion of a roof overhang to protect the plastered bales.
- Stacking the bales comes next. Depending on how large your structure is, you may want to enlist the help of friends. Bales may be sandwiched between wood framing and may require metal pins to stabilize the bales. Also, a layer of rigid foam or tar might be needed to seal areas where moisture may enter the wall.
- Add lath, like chicken wire netting, to the exterior and interior walls. This layer allows the plaster to adhere better.
- Stitch the walls together using poly twine to secure the straw bales and connect the lath.
- Plastering is a messy job, but can be fun. Plaster is usually applied in three layers of different thicknesses to cover the bales. There may be different recipes for each layer, which may be earth-based (lime, mud, sand) or Portland cement base, which is both sand and lime.
- Finish the carpentry work. This means adding doors, greenhouse ventilation in the form of vents, and windows, as well as a roof if this is a load-bearing construct.
Gardening in a Straw Bale Greenhouse
Straw bale greenhouses are quite environmentally friendly, low cost, fairly simple to construct, pest resistant, and excellent insulators. Hay bales won’t last forever, though, especially if you don’t protect them. Use roof overhangs, plaster coating, high stem walls and drainage channels. You will also need to be able to open the windows of the dwelling to monitor heat and moisture.
If you are building a hay bale greenhouse more for subsistence or commercial use, be aware that you may need supplemental greenhouse heating and blowers. This is an additional cost, even if they’re solar powered. Finally, you need to contact your local government. This type of construction, while age-old, isn’t always certified. You need to find out about local codes and ordinances, and apply for the proper permits.
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Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.
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