Just as defining your market and finding your greenhouse location have variables that impact your business success, so too does the greenhouse structure. This does not only matter to new businesses but also for those of you wanting to expand or renovate your existing greenhouses. Up front, I will say what might not be the traditional thought behind buying a greenhouse and that is, each business is different and the greenhouse needs to be tailored to each business for them to be successful. Your greenhouse is the end product of your planning, not the starting point. Often, the greenhouse is thought of before the market you will be selling to, the product you are growing and even the systems that will be growing the products.
We believe and have found that intentional planning leads to a better greenhouse. The opposite of this is giving up control and either buying an industry generic kit greenhouse or letting someone who doesn’t know your specific business design one. By giving up control your input is disregarded. Kit greenhouses are a one size, tries to, fit all, when in reality it’s the details that make or break the outcome and if your input isn’t part of the design it will be based on assumptions. Business is always an uncertainty, but why risk the risk?
Deciding which greenhouse structure you need is accomplished by working through a process. This process, in its simplest form, is answering a list of questions. The real work and success lie in the quality of answers. Quite a bit of research will need to be done but the research isn’t any different from your business planning research. The same information you will be gathering to write your business plan, visualize sales and plan your growing procedures will be used to determine your greenhouse structure.
Let’s jump into an example and through this I hope to show the benefits of this process and what questions will need to be answered. The example will be for structure and covering only. In the future I will get into choosing and sizing equipment for this examples.
Montana entrepreneur starting a leafy greens vegetable greenhouse:
First thought is mountains and snow! The consideration with this location is snowfall totals. What the structure needs to stand up to will be the first frame of reference. Let’s assume the greenhouse will be in the eastern part of the state where snowfall totals are less but still a concern. You want to have the greenhouse hold up to weather regardless of building codes that may or may not be needed. Think about building codes as a formality that is verifying your structure. The structure would need to be designed and built the same either way.
Covering choices for this project are similar and are between double polyethylene and twin wall polycarbonate. Budget is always the bumper lanes when building a greenhouse. For this project the budget allows for double poly and not polycarbonate covering. This grower, although has already pre-sold a crop, doesn’t want to build beyond their planned budget. They have plans to expand but only when they are selling through what can be produced in this first greenhouse. Double poly has a durability time span of 4-5 years before needing to be switched out for new. Polycarbonate lasts 15-20 years but is more expensive upfront.
So far we have snow loads on the radar and double poly as a covering. Next we are going to look at the crop, determined by the market, and get an idea of the needed environment. This grower will be growing leafy greens including several lettuce varieties and some herb varieties. At this point they don’t have plans to grow vining or fruiting crops. Beyond the snow concerns this geographical location has four true seasons with cooler springs and falls and an extended winter. The summer may get hot but cools off in the evening and the heat of the summer doesn’t happen in prolonged blocks of time.
For these plants a tall sidewall isn’t needed for the head room of the crop but air volume will be a factor. Fluctuations in temperature are evened out with larger volumes of air. It will heat up and cool off, as a whole, slower. Energy costs will go up with larger air volumes but not exponentially. The scale for heating 100 cubic feet of air will be the same as heating 1000. With that said, the benefit to having a larger volume is the plants having a more stable environment. The more control you have over the crop environment, the better quality your crop will be. Tall side walls for vining crops start at 12 feet. This again is dependent on the crop and how much labor is allocated to growing the crop, i.e. dropping tomato vines. It can be done with shorter side walls but this should be planned out, not surprised after the build. 8 foot sidewalls will give the lettuce enough air volume but will still help keep the heat above the crop in the summer.
We are now at a point where we can start to narrow down the structure type. “A”-frame structures are generally the strongest due to the triangle roof shape. This roof shape is best for deflecting snow accumulations. Also, generally speaking, they are more expensive. Next is the bowed roof greenhouse. These have a rounded roof or can come in a rounded roof shape with a raised peak for snow deflection. The roof can be ground to ground or have sidewalls.
This grower wants medium height sidewalls, 8 feet, for increased air volume and a rounded roof shape. Column spacing will be determined when the calculations for the snow load is ran but is estimated to be 6-8 feet between columns.
The foot print of the greenhouse is based on the needed growing space. This is determined by the market. How much can they sell and how often. This grower, with their pre-sold product along with market forecasts, is needing 3,600 square feet for the first greenhouse. For easy math, this works out to be 30’ x 120’.
Looking into the future, this grower is wanting to expand. The greenhouse type will need to be cutter connectable, again, for this specific grower.
As mentioned before the budget is key. The budget guides you as you move through this process. When working with a greenhouse company even a frame of reference to the budget will help them and you work through the design together.
In this example, we have come up with a 30’ x 96’ greenhouse based on their sales projections, a rounded roof greenhouse covered in double poly based on budget, with 8’ tall side walls for added air volume along with keeping heat off of the plants in the summer and 6-8’ column spacing based snow expectations.
The greenhouse in the end is not a crazy design or really complicated. It is simply tailored to the business. A lot of factors will go into the structure design and each one will have an impact on the business. Take time to verify your business projections, market, growing plans etc then use this information to design your greenhouse.