Soaring natural gas and propane priceshave made fuel conservation a toppriority for businesses of all types, and

as a greenhouse owner you’re probably feelingthe pinch more than most. You need to maintainplant-friendly temperatures regardless ofoutside conditions, which means that energycosts, especially heating, are one of yourhighest expenses—typically second only tolabor. Here are ten tips to help you create theenvironment you need in the most cost andenergy efficient way possible.

HEAT LOSS 1. Infrared (IR) plus anti-condensation

treated films Many greenhouses use a double-layer ofpolyethylene to reduce heat loss. This solutionhelps to retain heat but it’s far from perfect.Standard polyethylene film allows infrared orlong wave radiation to be transmitted to theoutside, especially on clear nights and cancause condensation to form on the insidesurface. Interestingly enough, condensationactually helps to reduce thermal radiation lossby as much as 50 percent, but also reduceslight and solar radiation levels by 15 percent to25 percent and can compromise plant health.Instead, opt for a combination IR/anti-condensation-treated film. IR film should beinstalled to the inside of the greenhouse with a

standard film on the outside. This duo reducesspace heating energy use by 10 percent to 20percent without condensation problems, andthe costs are quite low—typically as little as anadditional 1.5 cents per square foot or about$60 for a 30 foot by 96 foot greenhouse. Thisputs payback at less than one heating seasonin the Wisconsin climate, even if you only heatyour greenhouse for a few months of the year.

2. Insulated side walls Use a bench system? With a bench system,energy savings can be achieved by insulating sidewalls, end walls and perimeter with one inch ortwo inch foam insulation board. Insulation shouldbe dug in 12 inch to 24 inch deep and can extendup to plant height. The foam should have aprotective cover such as aluminum foil to preventUV deterioration and reduce fire hazards. Spray-on foam on framed walls are another good option,but also need to be protected. If foam is placedon the inside of the greenhouse, make sure it’stopped with a reflective coating aimed toward theinside. This will reflect direct solar radiation backto the crop canopy and aid in plant growth. Energysavings can be substantial: just two inches offoam insulation around the knee wall of a 28 footby 100 foot greenhouse will save about 400gallons of fuel oil, 610 gallons of propane or 558therms of natural gas annually if your greenhouseis heated throughout the year.

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F A C T S H E E T

Ten Easy Ways to Cut Energy Costs in Existing Greenhouse Spaces

B U S I N E S S

PROGRAMS

Energy can easily be one of the most costly expenses for greenhouse operations. Maintenance and proper materials canreduce energy use.

3. Night curtains While many businesses have their highestenergy usage during the day, greenhouses tendto peak during the night: research indicatesthat a greenhouse uses 80 percent or more ofits heating energy after dark. Consequently,greenhouse owners should focus on limitingnighttime heat loss whenever possible, andone excellent way is with a movable insulatedcurtain. There are several types of curtainmaterials: porous curtains cut heat loss byabout 20 percent to 30 percent when closed,can be used for shade in the summer, andallow water to drain through. Non-porousaluminized materials provide shading insummer and heat retention in winter by up to70 percent, but hold water which can cause thecurtain system to fail from the water weight.Semi-porous aluminized materials do the bestjob of cutting heat loss—up to 65 percentwhen closed— provide summer shade anddrainage of condensation.

INFILTRATION LOSSES Infiltration refers to air movement into and outof a greenhouse through small cracks andopenings in the building’s shell. The followingideas can help to limit these types of losses.

4. Close the gaps Any hole or crack—no matter how small—canresult in unwanted air movement. Eliminatethese with weather stripping or caulk andreplace any worn out gaskets. Pay particularattention around doors and windows and anypoint where the greenhouse cover or glazingattaches to the foundation, side walls and endwalls, and seals around vents. A 36 inchentrance door with an 1/8 inch wide crackaround it will allow about 500 cubic feet perminute of infiltration requiring about 25,000 Btuper hour of additional heat. At $1.60 per gallonof propane, the cost is about $0.40 per hour.

5. Poly film coverings on glass houses Glass greenhouses tend to have moreinfiltration because they have a large numberof joints. A single or double layer of poly film—installed permanently or only during the wintermonths—can reduce infiltration and heat loss,but be aware of potential problems. Reducinginfiltration can lead to increased humiditylevels and faster depletion of carbon dioxide.A double poly cover can reduce heat losses byup to 50 percent, but can also reduce lightlevels by as much as 18 percent, and mightrequire mechanical ventilation to controlhumidity and replace carbon dioxide. Weighthe trade-offs and determine which optionsmake the most sense for your greenhouse.

6. Wind breaks Wind velocity has a direct effect on theinfiltration rate. If your greenhouse is locatedin an open, windy area, a wind break in thepath of the prevailing winter wind will help toreduce infiltration losses. A permanent windbreak can be created with four or five rows ofdeciduous and evergreen trees planted four-to-six mature tree heights upwind of thegreenhouse. Plant a mix of tree species toguard against losing the entire windbreak from

Moveable insulated curtains can reduce heat loss from 20 percent to 70 percent depending oncurtain material.

disease or insects. Proper fertilization andirrigation can accelerate tree growth, and withcare and a little luck from Mother Nature, yourwindbreak will provide some protection inabout five years. Need protection now? Makea temporary wind break. You can protect thetypical 11 foot to 14 foot high greenhouse witha 10 foot to 12 foot high snow fence placed40 feet to 60 feet away from the greenhouse.

HEATING SYSTEMS A consistent, thorough maintenance schedulewill help to keep your heating systems inenergy efficient running order.

7. Thermostats Clean thermostats regularly—a dirtythermostat will not read temperaturecorrectly—and calibrate them annually toensure accuracy. If you purchase a newthermostat or controller, use electronic modelswith 1ºF differentials. Consider a low-cost solidstate controller to ensure optimum efficiency;most models offer multiple control options.

8. Furnace checkup Furnaces and unit heaters should be servicedand tested yearly by a professional. This helpsto ensure furnace safety and energy efficiency,and the increased efficiency will easily pay forthe cost of the inspection and tune-up. A twopercent increase in efficiency will save anestimated 179 gallons of fuel oil, 259 gallonsof propane or 250 therms of natural gas peryear for a 30 foot by 96 foot greenhouse thatis used year round. Replace older deterioratingunit heaters or gravity-vented unit heaters withpower-vented unit heaters or with 90 percentefficiency condensing type unit heaters. Thepower-vented unit heater will pay for itself in36 days versus purchasing a gravity-ventedunit heater, while a high efficiency condensingunit heater could provide a simple payback ofapproximately two years.

Gas Burners – The flame should burn as blueas possible; a yellow flame indicatesinsufficient air. Check gas supply linepressures and check all fittings for leaks.

Oil Burners – All parts replacement/maintenanceshould be completed as per the furnacemanufacturer’s specifications, but here aresome general pointers. Replace the nozzleannually and change oil filters twice a year.Check pump output pressure: this will typicallybe between 100 to 120 psi; low pressurecauses incomplete combustion. Check thespark jump between igniter contacts and installnew 14,000 volt electronic igniters; clean ignitercontacts and ignition sensors. At temperaturesbelow 20ºF, oil viscosity increases, waterdroplets freeze and paraffin precipitates out. Toreduce the possibility of these problems, movethe oil storage tank inside, add fuel treatmentsand raise pump pressures.

Chimneys – These should be air-tight, have thesame diameter as the furnace connection, andbe at least eight feet high and at least two feetabove the greenhouse peak. A chimney cap isalso a good idea: it will help to reducebackdrafts and keep rain out.

Control systems can optimize the efficiency of your greenhouse.

© 2007 Wisconsin Focus on Energy BP-2017-0307

Focus on Energy works with eligible Wisconsin residents and businesses to install cost effective energy efficiency and renewableenergy projects. Focus information, resources and financial incentives help to implement projects that otherwise would not getcompleted, or to complete projects sooner than scheduled. Its efforts help Wisconsin residents and businesses manage risingenergy costs, promote in-state economic development, protect our environment and control the state's growing demand for electricity and natural gas. For more information call 800.762.7077 or visit focusonenergy.com.

9. Central heating systems Each uninsulated linear foot of two-inchheating supply pipe will lose an estimated $4worth of heat this winter. Eliminate this wasteand expense by properly insulating the heatingpipes and air ducts in headhouses and boilerrooms. Insulation is simple to install andusually has a payback of less than two years.

It’s also important to have the heating systemserviced regularly. This includes changing fuelfilters, cleaning nozzles, checking valves andcontrols, checking and aligning belts, lubricatingbearings, testing combustion efficiency andremoving soot from inside the firebox. Sootremoval is especially critical. Improper air tofuel ratios or plugged nozzles can cause soot tobuild up in fire tubes and it takes very little sootto compromise fuel efficiency: just an 1/8 inchof soot can increase fuel consumption by 10percent or more.

10. Bottom heating The location of your heating system canimprove your energy efficiency. Move heatingpipes and air distribution systems fromoverhead to either under bench, on floor or in

floor, and you can save 20 percent to 25percent in heating costs and have the addedbonus of faster plant growth. One studyreported a seven percent average yieldincrease from greenhouse tomato production,largely due to a 7ºF higher root mediumtemperature. If you have a gutter-connectedgreenhouse, heating pipe will still be neededunder the gutters to speed up snow melt.

Want to learn more about energy savingsmeasures for greenhouses? Contact Focus onEnergy at 800.762.7077 and ask to speakwith an Energy Advisor from the Agricultureand Rural Business Team. Or visit our Website at focusonenergy.com.

FOR ADDITIONAL INFORMATION SEE THE FOLLOWING: � Energy Conservation for Commercial

Greenhouses, J.W. Bartok Jr, NRAES,Ithaca, NY, 2001.

� Greenhouse Engineering, Aldrich,R.A, J.W. Bartok Jr, NRAES-33, NRAES,Ithaca, NY, 1994.

� "Grower 101: Heating Systems –Maintenance Pays," J.W. Bartok Jr,Greenhouse Product News, September2003, Vol 13, No. 9.

Infloor heat can reduce energy costs, produce faster plantgrowth and eliminate wet floors pictured here.