Tag Archives: greenhouse season extension

Season Extension: Ventilation & Heating

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To make your greenhouse more of a year round functioning entity, there are two main areas in which you have to make the structure more efficient-Heating and Ventilation.

1. Heating is your biggest expense for the winter so retaining heat is a priority.

The easiest way to retain heat in your greenhouse is to install a double poly cover with air in between. A small squirrel cage blower attached to the inside layer of plastic aids in maintaining air between layers.

The more dead air space between these layers you can create, the closer you will be to achieving a 30% reduction in heat loss. Holes will result in air movement and therefore less efficiency. 3″-5″ consistent space is ideal. It is a given that you would have less than that around the edges and over the ridge.

Double plastic will have a considerably longer life span. It is important to realize that as plastic gets older, the light transmission will be reduced which will reduce production.

Infrared plastic (IR poly) does further reduce heat loss and increase light diffusion so it can also be a consideration when looking for ways to reduce heating costs.

2. Ventilation is also one of your biggest considerations for the warmer times of the year. Ventilation can be done through forced or mechanical methods or passive through vents or roll up sides.

Vents are extremely effective since they can be placed higher up where the heat needs to be expelled. Mechanical ventilation is more costly both up front and to operate but it is easier to control since it is attached to a thermostat. For mechanical ventilation to be effective, it needs to be sized and located properly.

Roll up sides are less costly and simpler to install but are restricted by the fact that you have to be there to open and to close.

Climate control is especially challenging in the spring and the fall since most days you will have the need for both ventilating and heating.

One area that you need to be especially aware of is stagnant air. Without proper air movement, circulation and exchanging, stagnant air can cause many different types of diseases. It is important to understand what your plants require

Season Extension: Moving Your Structure

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A significant part of season extension involves moving an intact structure.

This basically allows you to get two (or possibly three) plots of production from one investment.

The idea is to start a relatively cold tolerant crop very early in the season (the timing will be different in different locations).

  1. Once the crop is firmly established in location A, (and it has warmed up) you will move the structure to location B and start another crop.
  2. You will harvest the crop in location A and then after working the soil, plant another crop in location A which is intended for fall harvesting.
  3. After location B is harvested and before frost you will move the structure back to A.
  4. Instead of doing twice in location A you could also choose location C.

A structure can be equipped with wheels which will run over the soil. There is quite a bit of flexibility where you go and the terrain you navigate.

The structure can be equipped with rollers on a track. This will determine where you go and this is usually intended for moving a bigger structure with fewer people.

The most common method of moving is sliding the structure on the soil. The base rail can be wood or steel.

It is critically import to understand the logistics of moving on a structure before you start. It is not hard to move a structure but it is also not hard to do damage.

Having a plan for proper anchoring is very important for a movable structure. Your structure is at a vulnerable state when you release the anchors. Once you start, the job must be completed quickly. You have to be aware that the anchors may not come out or go back in easily so you may need to give yourself some extra time.

One other area of consideration on a movable structure is the ends. There must be some sort of a flap or vent along the bottom so that when a structure is being moved, the ends will not uproot plant material. Generally speaking to have this ability in the ends takes away from the structural integrity, so some extra anchoring may be required.

You can see more information and photos on our movable information page. Please don’t hesitate to call us with ANY questions you may have. This can be a very useful addition to your structure, but must be understood correctly.

Season Extension: Hanley Caterpillar Tunnels

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The first area to discuss regarding season extension are those structures that are simple enough to disassemble and relocate to another spot-primarily referring to Hanley Caterpillar Tunnels.

The real lure of these buildings is their low cost and simplicity to move. Generally the area is prepared in advance and then the tunnel is moved over the area when the planting is to be done.

Since the original design specified 6′ hoop spacing, the intent was always to remove the cover before risk of heavier snow fall. More often now, growers are going to 5′ spacing (and sometimes 4′) to allow the covers to remain on longer or even permanently.

By having a smaller hoop spacing, it allows the cover to stay on permanently, which allows for a much earlier start in the spring.

The key to the concept of the Hanley working is in the rope.

  • The back and forth pattern of the rope resembles the way a person would lace up a boot.
  • Typically there is a spring loaded clip at the base where the rope passes through.
  • Once the rope is fully installed, it is important to tighten it through three passes from end to end.
  • If the rope is not tight enough, the wind will create wiggle and movement sideways.
  • When the plastic is tight enough, it also allows the grower to slide the plastic up the hoop to allow ventilation.

Generally the plastic is about 25′ longer then the tunnel.
This allows the installer to bunch up (pig tail style) the extra poly at both ends between a pair of posts.
It is important to get the plastic as tight as possible lengthwise first.
There must also be a rope from the top of the last hoop to the tie off post.

There are a couple of challenges to consider with the hanley tunnels.

  1. One of these challenges is to create a proper entrance. Typically entrance is achieved by slightly lifting the plastic and ducking underneath.
  2. The other are of challenge is the low shoulder height of the structure. This restricts the use to a couple rows of taller items in the middle and a couple rows of shorter plants along the side. The width of the tunnel does lend itself to three regular size beds.

Once you have learned about the nuances of the hanley tunnels, and asked any questions that come up, you will be better prepared to have these efficient season extenders work for you and your application.

Feel free to look at our Hanley Application page for more information and photos, and give us a call with anything else you require.

We are pleased to have many happy customers these structures are working for, and look forward to you being next!

Check out our book if you want to know more “So You Want to Buy a Greenhouse…Your Guide to Planning a Greenhouse Purchase”

Large Greenhouses

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We have a variety of widths and lengths of greenhouse structures from which to choose.

If you’re just trying to get a head start on the garden vegetable season (and maybe extending the growing season by a couple of weeks) consider our free-standing structures which use just one layer of poly.

If your intent is to grow all year round and heat the greenhouse then you should be looking at our greenhouse packages that offer a double poly roof, inflator fan kit and roll-up sidewalls for better heat efficiency.

COLDFRAME vs. GREENHOUSE

A COLD FRAME usually has a single plastic covered structure and used as a season extender
A GREENHOUSE usually has a double plastic cover with air in between and sides that roll up for year round use for better heat efficiency.

AVAILABLE OPTIONS

  • Custom widths, heights & hoop spacing
  • Roof vents & forced ventilation packages
  • Various types & sizes of doors with end framing priced separately
  • 8mm polycarbonate sheeting for roof and/or ends
  • Roll up sides for natural ventilation & reduced condensation
  • Cross ties for added rigidity, hanging baskets or crop support