5 Tools for Planning an Energy Efficient Commercial Greenhouse

By Haley Bridgnell

5 Tools for Planning an Energy Efficient Commercial Greenhouse

5 Tools for Planning an Energy Efficient Commercial Greenhouse

With demand for local food continuing at a strong pace, a year-round greenhouse is often a good business venture. You can greatly improve your chances for a successful greenhouse business with proper planning.

Planning for a greenhouse business requires basic business planning — thorough research and usually spreadsheets. Here are five essential tools to aid that process, based on the purposes they serve. (Note – these tools do not substitute for all the planning necessary to create a successful commercial greenhouse. “Starting a Greenhouse Business” by the University of Alabama Extension is a good overview of the whole process.)

  1. Basic Budgeting and Planning

Tool: Courses & crop budget templates

Understanding the cash flow and upfront expenditures of a commercial greenhouse is a crucial step to planning your venture. This will require several steps of research (soliciting quotes for an energy efficient commercial greenhouse kit, for example). To assist, there are courses designed for small-scale farmers and commercial greenhouse growers.

If you are unable to take a full course, you may benefit from simple online budgeting tools. Crop budget templates, available for free from many university extension services, can help a beginning grower create a cash flow plan. These templates act as a profit and loss sheet for a year-round commercial greenhouse: they detail revenue streams and expenses for a typical commercial greenhouse.

A Google search of “crop budgets greenhouse” will yield many resources for a beginning year-round greenhouse grower. You can find general templates for commercial greenhouse and then customize the model to suit your operation.

  1. Evaluating your Greenhouse Site

Tool: Light Meters & Climate Maps

An energy efficient commercial greenhouse requires sufficient light levels for good production. Low light, particularly in the winter, will severely hinder production and profitability of a year-round commercial greenhouse.

There are several ways to evaluate light conditions of your greenhouse site. To get a general idea, talk other growers or in your area. Secondly, climate data and information light requirements of specific crops can help you predict what will grow well at what times of year. The brief paper from Purdue University — Commercial Greenhouse Production: Measuring Daily Light Integral — is a very valuable document. It gives light requirements for many ornamental plants and some vegetable crops, as well as generalized light levels for different regions of the US. NREL and many other organizations provide similar maps, but generally have different metrics for light quantities. For more on predicting light levels and productivity, see the chapter on siting a greenhouse in The Year-Round Solar Greenhouse.

Once you have a general idea of light levels in your climate, you can get more site-specific. Light meters measure light intensity over a period of time at a specific location. They are useful if there are nearby obstructions, like trees or buildings, that could shade your greenhouse. The LightScout DLI 100 from Spectrum Technologies is a low-cost and very basic meter that sits in the ground. It will give a basic light reading over a 24-hour period. The advantage here is that it gives a single average reading for a whole day. More advanced light meters are much more precise, but give readings only for a single moment in time. You must take many readings, or connect the light meter to a data logger, to get a full picture of light conditions at your greenhouse site.

Spectrum Technologies DLI LightScout 100 Greenhouse light guage

Spectrum Technologies DLI LightScout 100 Greenhouse light gauge

Beyond light levels, there are several other considerations that go into selecting a site for an energy-efficient greenhouse, including building regulations and access to water and electricity. For more, see our blog on siting an energy efficient commercial greenhouse.

  1. Create a Planting Schedule

Tool: Crop Scheduling Software

You’ll need to create an accurate planting schedule, detailing when plants will mature, and how quickly you can generate sales. Seed packets, online research and growers advice are the typical resources to estimate how long a crop will take from seeding to sale. Advanced commercial greenhouse growers can also take advantage of a “decision support tool” called FlowersOnTime™.

This is an Excel-based program that simulates the effect of air temperature on a range of floriculture crops. It allows you to estimate production times based on a variety of conditions, helping you plan your crop schedule and revenue stream. Though it takes some time to learn, it can greatly help you dial in your production schedule, and thus refine your plan for sales.

  1. Forecast Energy Costs

Tool: Online Heat Loss Calculators

Energy costs are the third largest expense for American commercial greenhouse growers (after labor and material costs), according to research by the University of Wisconsin-Madison. How much you need to heat and cool the greenhouse will have a major impact on your bottom line. Online heat loss calculators help estimate energy costs of a commercial greenhouse, and narrow done a major line item of your budget.

Heat loss calculators allow you to estimate the energy costs of a greenhouse and predict the impact of certain changes, such as how much energy will be saved if you upgraded your polycarbonate glazing to a more insulating material. Several online heat loss calculators are available; a thorough one is available from the National Resource Conservation Service (NRCS) here.

Virtual Grower is another free software program created by USDA, intended for very thorough commercial greenhouse growers. It is a very large file and somewhat esoteric, but packed with functionality: you can create a three-dimensional model of your greenhouse, do a basic energy analysis, and estimate a crop schedule.

A greenhouse designer can also do a thorough energy analysis of your structure, to help estimate the most cost-effective design for your climate. An energy-efficient commercial greenhouse can reduce operational energy costs by over 50% compared traditional greenhouse structures, which will majorly impact profits. Using passive solar greenhouse design; higher quality, insulated materials, and renewable energy systems – such as a Ground to Air Heat Transfer system – can lower your operational expenses.

  1. Start Sketching

Tool: 3D Modeling Software

A energy efficient commercial greenhouse should be professionally designed and engineered. Typically, a professional — either a greenhouse consultant, architect, or the greenhouse manufacturer — provides this step, but you can also do a great deal of drafting on your own to start planning, and help communicate your ideas. SketchUp is a free, three-dimensional modeling tool and relatively easy to learn for those without drafting or CAD experience. You can create a 3D rendering of the greenhouse with accurate dimensions, and your particular specifications.

SketchUp Model for an attached solar greenhouse

SketchUp Model for an attached solar greenhouse

A basic rendering of your ideal commercial greenhouse can help facilitate talks with contractors, manufacturers, and/or your local building department. It can also be particularly useful to lay out the interior growing systems and floor plan. You can draw in the growing equipment, walkways, work areas, storage space to get a sense of your interior space. Finally, SketchUp has the ability to ‘geo-locate’ the drawing, inputting climate data for your specific location. A ‘shadow’ function can allow you to see how light interacts with your greenhouse at different times of day, and over the course of the year, helping you predict which areas of the greenhouse will be fully illuminated (i.e. highest productivity) and which will be shaded.

What are your challenges in planning a greenhouse business? Let us know.

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