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Green House Install Info

Josh_10Josh_10 Posts: 787Member
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  • Josh_10Josh_10 Posts: 787Member


    Does anyone know about any info on Green House Hydronics? I have been getting alot of work in green houses and it is really touch and go. Typically I get a lot of service calls but since going into business for myself I have gotten alot of installs. I would like to figure out what makes plants grow..
  • David Sutton_6David Sutton_6 Posts: 1,072Member
    All the green houses ...

    That i have done were either steam or warm air, the steam were all modines ,...David

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Ron SchroederRon Schroeder Posts: 998Member
    I would like to figure out what makes plants grow..

    Warm Feet, actually it depends on what the custmer is looking for, some are happy with a gas fired Modine or oil fired furnae to keep heat in the building, some want warm tables for the roots running Pex on the bottom of the bed tables with a ModCon would be ideal.
  • HaroldHarold Posts: 183Member
    My approach

    I have put tubing in the floor of a future greenhouse. I am, however, not sure it was the right approach in my climate (north of Seattle). Watching wheather behavior here, it seems like the thermal mass delay may not be appropriate. I suspect I will have problems with getting night temperatures up in time and not venting a lot of BTUs that I have pumped into the floor during the next day.

    I am thinking of adding a gas line to the greenhouse to be able to use a air heater and possibly something that works without electricity. The site has lost power 6 times in the last 3 months. Longest outage was about 2 days. One outqage was visually impressive. 3 hours of continuous arcing into the road about 100 yards from my driveway.

    I would be interested in thoughts from anyone that has done a radiant greenhouse in this sort of climate.
  • Tom R.Tom R. Posts: 139Member
    Greenhouses

    I have taken care of were mostly on roofs- baseboard H/W (constant pumping, variable temperature) with unit heaters for the coldest days. The source is your choice. You have to add humidity for most plants - steam injected into the air or misting humidifiers. In summer, roof venting, shading and swamp coolers to keep temperatures down. Sometimes if it's sunny, all of these in the same day, so they have to be staged carefully. You can adjust shades and vents manually for cooling, but for heat, if the electric utility is unreliable, a standby generator is the only alternative.
  • Josh_10Josh_10 Posts: 787Member


    Harold... I must be your direct competition because I am also north of Seattle. I do like your aproach though. I am doing an install right now with an Ultra and star fin heat pipe. Seems to be a good heating system in my opinion. I was just wondering if there were some guidlines for the Greenhouse industry..
  • john_27john_27 Posts: 195Member


    It's all in the insulation you use on your glazing material...in my case, I restored a large 1100 sq ft lutton house (circa 1920) which sat unused for fifty years....I do not like the star fin tubing....i prefer the old under bench
    piping because i want more mass in the greenhouse....i used foamboard on the inside knee walls, and a clear insulated pool cover(80 per cent light filter)....because it is well insulated...heat costs are very low....maybe 150 a month...cooling a greenhouse is tougher than heating it...john
  • Eric JohnsonEric Johnson Posts: 174Member
    Greenhouse heat

    I've got a 21x24' Lord & Burnham single-pane greenhouse installed circa 1979 that needs a heating system. Originally it had 4 cast iron radiators connected to a gas-fired boiler zone, but they were hooked up wrong. I bought some fin and tube baseboard to replace the rads (which I had other uses for), but I think a couple of big cast iron radiators would actually work better. Without glycol in the system, it would probably be a good idea to have a way to drain that zone in a hurry, just in case.

    It may be harder to cool a greenhouse north of Seattle than it is to heat it, but that's definitely not the case in northern New York State. Way below zero again this morning.
  • Josh_10Josh_10 Posts: 787Member


    John, that is interesting.. I am not really familliar with glazing or the building methods. Is this something you came up with on your own or can I find a book on it?

    So you don't like star fin? Do you not like it as a product or do you just prefer more mass?

    One of my questions is if you have a large mass right under the roots of the plants you need to heat the roots upwards of 85 degrees to get the greenhouse temp to the setpoint. For all I know 85 degrees is good for the roots which is why I am looking for more info.

    There has been alot of buzz about radiant floor heat but most of the greenhouses that I have been working on require an upward heat flux of about 100btu/sq. ft. Way to much for slab heat. What do you guys think about a combination?
  • Eric Johnson_3Eric Johnson_3 Posts: 38Member
    root heat tolerance

    Depends on the plant, but 85 degrees at the roots is a little warm. Borderline fatal, I would say.
  • HaroldHarold Posts: 183Member


    Greenhouse insulation is indeed a significant design issue. If you are reglazing or starting from scratch you should evaluate multilayer polycarbonate glazing. There is a trade-off of light transmission vs insulation but use your heat loss calculator to see what the cost/benefit is.

    Here is a source of some info and materials http://www.sundancesupply.com/index2.html

    If anyone knows of some software that can model the day/night behaviour of a greenhouse, that would be useful.
  • Josh_10Josh_10 Posts: 787Member


    Harold, you might look into a control that will account for solar gain. The new Tekmar TN4 system does just that. It accounts for both outdoor and indoor temps. It will anticipate those temperature swings pretty well. I also know of a few more controls that may work for you. If you have some time you can stop by my office in Stanwood and see the TN4 system in action..
  • john_62john_62 Posts: 5Member
    Eric and Josh

    Eric...we get zero as well here in pa....if your greenhouse is well insulated....your boiler won't run anywhere near all night....and Eric is abosolutely correct about 85 being too hot....roots like a constant 70-75 tops...maybe seedlings go hotter but i don't think so
    I came up with the idea after reading about a guy in Indiana who wrote an article for sherrysgreenhouse, and a thread on a gardensite that I am trying to find. Get Shane Smith's Greenhouse Companion on Ebay(1-2 bucks)....this is a great read. To Harold, the people I know who use polycarb got rid of it and went plastic....the greenhouse sash bars weren't protected and put too much cold into the greenhouse....also,
    it yellows with age, of course. I don't fear the cold anymore....I do fear heat buildup in the summer...it can kill your plants in an hour. One more thing, greenhouse heat
    builds as a function of hours of exposed sun....regardless of outside heat...last week, on a 25 degree day, without heat, but clear sun, I registered 90 degrees in the greenhouse. Imagine having to vent on a cold day(roof vents)....crazy, isn't it!...John
  • john_62john_62 Posts: 5Member
    Answers I missed in the previous post...Steamhead

    I don't hate starfin...just prefered the extra mass....however, and this is extremely important.....I used Steamhead's article in the Library to size the circulator for a gravity system....I use two taco 7's instead of one
    I looked into radiant...you need this only at the root level....best to use wirsbo tubing or a capillary mat and run a zone off of the boiler....I haven't done this because I grow rooted cuttings, but you should look into this if you are growing from seed.
  • Al Hanson_2Al Hanson_2 Posts: 4Member
    Plant Hydronics


    The old systems in rapid seeding greenhouses were black iron pipe under the beds. The key to consistant growth in the plants is even temperature across the width of the bed (even spacing on the rows of tubing) and keeping the temperature drop in the tubing to a mimumum - 10 deg temp diff. Wide spacing or high Delta T will cause irratic plant growth across the bed.
    Spacing tubing close together say 6" and mounted down 1" from the beds will promote even convection. Then build 6" side boards below the beds to enclose the sides of the beds keeping the heat up under the beds. Some farms use Fin Radiation. Even heat is critical to get even growth on the bed.
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