Greenhouse Structures, Covering Materials, and Climate Controls By: Heather Dixon

Bell Work What is media?

Today’s Objectives: Identify types of greenhouse structures Define greenhouse covering (glazing) materials. Explain environmental controls. Describe methods of heating and cooling greenhouses.

Types of Greenhouse Structures There are four basic styles of greenhouse structures: Lean-To Even Span Uneven Span Ridge-and-Furrow

Lean-To Greenhouses Lean-To Greenhouse: Attached to building Roof support from attached building Growing Crops South Side

Even Span Greenhouses Roof has even pitch and even width Single Houses Hoop Houses

Uneven Span Greenhouses Roofs have unequal pitch and width Limited to hillsides Disadvantages Few Built Today

Ridge-and-Furrow Greenhouses Number of greenhouses connected along the length of the houses No side walls Lower heating costs Snow is a concern

Headhouses Structure attached to the greenhouse Work area Storage Area Office Space

Covering (Glazing) Materials Glazing is the covering of a greenhouse Considerations: Durability Light Transmission Cost of materials Heat Loss

Polyethylene (poly) Film Most widely used 6-milin thickness Flexible Sheets Double Layered Heating cost 1/3 less than glass covered greenhouse Inexpensive

Structured Sheets Very Popular Constructed of three materials: Polycarbonates Acrylic Fiberglass

Polycarbonate Structured Sheets Most widely used structured sheets Manufactured with a “Twin Wall” held together by ribs Insulating Reduces heat costs Guaranteed for 10 years Good light transmission 80%

Acrylic Structured Sheets Twin Walls much like Polycarbonate Sheets Good insulation High light transmission – 86% Last 8 to 10 years Less flexible

Fiberglass Widely used in 1960’s and 1970’s Light transmission good in the beginning but discolors after 7-10 years. Susceptible to hail damage Flammable

Glass Best material for plant production High light transmission-90-92% Air exchange Initial cost = expensive Long lasting if it doesn’t break Breakable Insurance Heat loss with larger panes

Environmental Controls Devices used to automatically turn greenhouse systems on or off Four types: Thermostats Analog Controls Computer Controls Computerized Environmental Management

Thermostats Low Cost Easy to install 2 types: On-off Proportioning

Analog Controls Use proportioning thermostats or electronic sensors Integrate the operations of heating and cooling equipment Better performance than just thermostats

Computer Controls Utilize microprocessors Gathers information with sensors such as: Temperature Relative humidity sunlight

Computerized Environmental Management Expensive Accurate Greatest range of uses All automated equipment can be controlled together Programmable

Heating Systems Hot Water Systems: Small and efficient Water heated in boilers and pumped through pipes in greenhouse Low maintenance Heat delivered evenly Infrared Heat: produce heat that is absorbed by plants, media, and benches Heat transfers to air space surrounding them

Steam and Unit Heaters Steam Heat: standard heat for cut flower operations Larger boilers produce steam Steam distributed trough pipes Can sterilize medium Unit Heat: hot air heaters Heated within unit and blown by fans throughout greenhouse

Cooling and Ventilation System Fan and pad cooling systems: Based on evaporation of water Fog systems: An atomizer produces water vapor “Mist” system

Today we learned: What types of greenhouse structures? What four types of environmental controls? What is the most widely used covering material? What is a headhouse used for? What system uses an atomizer that produces water vapor?