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Lighting considerations when building your greenhouse

Wouldn’t it be great to use as much free sunlight as possible?  In this recent post from LumiGrow, the smart horticultural lighting company, we’ll look at the top 4 lighting considerations that can have a huge effect when building or retrofitting your greenhouse:

  • Site Selection
  • Glazing
  • Form Function
  • Supplemental Lighting

Let’s get started.

Select a site for the highest year-round light levels
Choosing the wrong site for your greenhouse can drop your available sunlight significantly. The ideal site for your greenhouse will ensure consistent exposure to light year-round, most critically in winter when the angle of the sun is lower.

That means orienting your greenhouse appropriately for your latitude while minimizing shading from surrounding features.

Quick Guide to Selecting Your Greenhouse Build Site

  1. Gutter-connected greenhouses should always be oriented north/south, regardless of latitude, to minimize shading from the multitude of these structures’ trusses.
  2. Free-standing greenhouses (structures with a single bay) located above latitude 40°N should be oriented east/west to allow the maximum light available to enter from the sides. This keeps the low-angled winter light from being blocked by the greenhouse structure.
  3. If your free-standing greenhouse will be located below latitude 40°N, a north/south orientation will let the sun travel over the greenhouse and provide more light throughout the year while minimizing shading from trusses.
  4. If possible, orient your greenhouse on a slight southerly slope (1-2%) to further increase light exposure while also providing helpful drainage.

Quick Guide to Minimize Your Shading
Surrounding features can block light to the greenhouse differently throughout the year depending on the angle of the sun.

  1. To avoid shading from trees and topographical features like hillsides, position your greenhouse at a distance 2.5 times the height of any trees or features. Any closer and these features will shade your greenhouse to some degree during in the year.
  2. If you have tall hedges or trees around an existing greenhouse that can’t be removed, keeping them pruned to allow light to enter between and above them into the greenhouse will add to your overall light transmission rates.
  3. Remember that any structure will shade its surroundings, including storage areas, delivery and parking areas that will have a lot of large truck traffic, office buildings and other growing structures like shade and hoop houses, so it’s important to consider how that shade will fall on your greenhouse.


Fig. 1 - Ratio of shadow length and obstruction height for selected solar altitudes. (Walker, J. N., & Duncan, G. A.)

Choose a greenhouse glazing that transmits the best light for your crops
Greenhouse glazings have different light transmission rates, from 91% down to 75%, which determine the amount of light that will enter the greenhouse.

Your greenhouse glazing should allow the appropriate light transmission rate and type for your crop throughout the lifespan of the glazing. These light transmission rates should be readily available for all glazings from the manufacturer.

The type of glazing, whether diffuse or direct, and partial or full spectrum, will determine the type of light that enters the greenhouse. As with site selection and other design elements, there is often a compromise when choosing glazing, since cost, insulating ability, maintenance and lifespan vary among the different types.  There are some general aspects of glazings that will maximize light and minimize shading.

Use infrastructure that’s functional and streamlined
Greenhouse managers should assess how greenhouse infrastructure, the greenhouse frame and equipment, affect light quality and intensity while providing the right growing environment for the crop.

Building a greenhouse to maximize light
The less infrastructure you have, the more light you’ll get to your crops because you won’t have as many obstacles blocking light to your plants.

One way to maximize light is by choosing a simple structure like a freestanding greenhouse with lightweight glazing like poly film that doesn’t require heavy framing to support.

But what if you need more substantial infrastructure for a commercial production environment?

When designing a gutter-connected greenhouse, you can streamline its substantial framing by choosing a lightweight glazing like polycarbonate that won’t require as much structural support as would heavy glass glazing.

Greenhouses with more substantial framing also allow for the installation of supplemental lighting, which make up for shading resulting from the additional infrastructure.

Building a greenhouse to minimize shading
This is where you limit the amount of overhead infrastructure and surrounding equipment inside your greenhouse to that which is essential to produce your crop efficiently.

Blackout and thermal curtains will shade segments of your crop even when they’re retracted due to the cabling, motors and retracted fabric overhead. Of course, these are valuable systems that perform necessary tasks like cooling, photoperiod control and heat retention, so evaluate the tradeoff and impact of the light loss when choosing curtain systems and focus on streamlined systems that tuck away when not in use.

Irrigation booms and sprinkler systems will also block light to your crop below, so it’s important that they’re regularly maintained and able to be retracted to positions that don’t block light to the crop when not in use. Overhead electrical and irrigation lines can also run above walkways to minimize shading over growing areas.

Add supplemental light to your greenhouse
Greenhouse production has advantages over field production, including the ability to grow year-round regardless of weather, control ambient light conditions, and stabilize plant growth cycles when you effectively manage your lighting strategy.

Adding supplemental light is often the only way to reach consistent light levels year-round.  Still, there are considerations to make when choosing a light fixture to maximize the power of the sun for your greenhouse.

Maximize sunlight with smart lighting
Not all light fixtures will maximize your use of free natural sunlight for your crops. The benefits of the right smart lighting solution can ensure that you’re using as much sunlight as possible and not spending more than you need to on supplemental.

In the case of the LumiGrow Light Sensor, your LED fixtures are triggered to dim or turn on or off so that your solar and supplemental light combine to hit your crop’s target.

When using the LumiGrow Light Sensor for your LumiGrow fixtures, the daily light integral (DLI) program allows you to add only the amount of light necessary to reach your crop’s DLI needs that ambient light doesn’t supply. This means you save on energy costs as the lights automatically adjust when the sun is supplying adequate DLI to your crop.

This article has been abbreviated for this post. To read the full article, please visit: https://go.lumigrow.com/e/514251/enter-blogs-greenhouse-design-/97j87d/1515618319?h=2zS4y_TAoHWDmQXc366YBA-_f9zeOQbUwsDSQpaN-p0


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