Heating a Small Green House in Winter

[Anton]

I have been pondering a cheap and efficient method of heating my new GH.

If possible, I don't want to use electical appliences as our power bill in winter is very large because we have a ducted reverse cycle air con going 24 / 7.

Gas heating I have been told dries the atmosphere, as does reverse cycle aircon. I was wondering whether a small kerosine heater would do the job, or would the vapours be detrimental to the plants ?

There obviously would be venting, but whether it would allow most of the vapours out, I don't know. I have a 12 volt fan going 24/7 for air movement already.

I JUST WANT TO HEAT IT EFFECTIVELY WITHOUT BLOWING THE BUDGET. I have already invested over a Grand in rebuilding the GH so far, NOT to mention plants that I have bought over and above that budget, and "she who must be obeyed " is starting to get twitchy if the "M" word is uttered from my lips.

Ok people I am open for comment, ridicule, scorn, sympathy, whatever.

[kmarch]

The "M" word? What's the "M" word?

[Anton]

(whispered quietly) money. shhhhhhh.

[pikevi]

Yes, gas heaters and humidity are dead enemies!!

I do have a central gas heating( forced air furnace ). Since I bring the plants indoors to tide over winters,though I have a central humidifier built in, I use I use individual humdifiere inthe areas where I have plants and orchids.

I bought two small indoor GHs and the heating and air circulation posed a big problem.

Since they are free standing stuctures ( 4 shelves each) I tried a wide container with water and used an immersible aquarium heater in it.( used a wire mesh to keep the heater from coming into contact with the palstic container). Humidity was OK but heat did not build up.

Tried place it over the central heat-vent it was too much heat and dryness.

Eventually I let the lower part of the GH opening unzipped and let the heater (portable oscillating heater) blow into it along with the mist from humidifier( they are both seen in the foreground and to the right of the photo). Heating was OK but I still needed more humidity so I placed two trays-full of water inderneath the GH( which I have pulled out to show here). It seemed to work Ok since the weak and neglected orchid which I have been buying seem to flourish.

I unzip the front panel and roll it up in the morning and close it at night leaving about a 30cm ( a foot) of space at the bottom.

I hope to come up with a better and less messy system for the next winter. Last 8 months have been overwhelming for me with the unplanned additions of orchids

[Anton]

My "small GH" is 2.5m X 1.5m X 2.5m high.

Tonight I was looking at caravan heaters on the Web. I JUST DON'T KNOW WHICH WAY TO GO.

[pikevi]

That is big, Anton.
Mine are 60"X27"X18" ( 1.45mX0.7mX0.5m approx), each.

[Anton]

That's NOT small, THAT'S TINY.

I was talking about REAL green houses, as in outside, that you can walk into. Mine IS small when you consider the one I actually want is 18 FEET LONG, 8 FEET WIDE AND 9 FEET HIGH!

Compared with THAT, mine is small.

[kmarch]

I would thoroughly investigate the whole gas heating thing before going that route. I seem to recall hearing of problems with gas fumes harming plants. I'm afraid I just don't remember the details as it was some time ago. But I'd check it out with people who have them, even commercial nuseries. I'll ask my friends who have heated GHs to see how they do it.

[Anton]

ALL contributions gratefully accepted.

I didn't realise how hard it was going to be.

The gas heaters I have been looking at are designed for caravans, therefore low fume emission for obvious reasons.

They have powered flues to draw the fumes away, which also aids combustion.

[robb]

you mentioned you have an "M" restriction... but have you looked into a combination solar panel/electric heater? aus. must get enough sunlight! it would be a one time investment only, which is helpful i suppose. just some ideas i've picked up from electrician school...

[tom499]

How about better insulation? i dont know on price, but having some thicker glass and such to keep the wind out. more environmentally friendly

http://www.rhs.org.uk/advice/profile...greenhouse.asp

theres a few ideas to start off with

[Anton]

I am investing in a solar powered fan for next summer which is $300 for the panels and $250 for the fan.

Solar heating, I am looking at close on to $1,000 for what I need, if not over ! Already look at that option.

Long term it becomes finacially feasable but it is still a bit hit in the hip pocket to set up.

That techology is still quite expensive to date

[Anton]

Getting aircell insulation tomorrow to line it, you can see it on the Web.

It is 7mm thick material, that is similar to bubble wrap covered with a insulating metallic material like a sandwich. I intend on double layering it around the GH for more insulation.

The GH doesn't have glass as it would become too hot in summer. I have double layer thick plastic covering the window areas for winter.

If you look at the thread "Building a Green House" you'll see it there before I set it upo for winter.

[jerrymeola]

Insulation will give you the best results for the 'm' with all solutions. Two or three layers of plastic on 1x2 wood spacers will reduce heat loss greatly for little money. It can easily be removed in the spring. It is a common Florida solution (only one layer is necessary here to protect 10 degrees or more without a heater) The air cell you are looking at is for permenant use and not meant to be removed. It may get too hot for such a small area in summer. It is certainly not worth the extra money if you intend to remove it every year.

I would avoid kerosene the fumes will be to much for you to enter the greenhouse. Propane would be safer, but your greenhouse is small and it will be hard to control overheating with either of these. Their controls are not very acurate.

Gas powered infrared is the best heat but probably out of your budget. It uses gas to heat infrared elements and the heater is pointed down onto the ground. You can walk through it and hot feel anything, but the ground heats and the heat rises naturally and mild.

Electric may be your safest course. Use a timer for a few hours each night and with good insullation you should be OK.

I am constructing 4 new greenhouse 20x60 each and air cooling one if you want to drop by and help. It may surprise you that each (except the cooler) will not cost me any more than yours.

[Anton]

Thanks Jerry.

My son is com ing over tomorrow (Saturday) to build a proper roof for the GH with insulating in mind. Won't double thickness plastic with a gap cut the light levels down ?

[pikevi]

LOL, sorry, Anton.

I misread your post.

I was talking about indoor portable GH.

Good luck with yours.

[tom499]

From my physics lessons thick glass refract the glass more, but as long as its good clear glass it wont make much of a difference

I think its great you trying solar powered energy sources and plenty of insulation I know not everyone can have a greenhouse, so we need people who can to help save the environment like you

And as jerrymeola says, fossil fueled heaters are going to make a mess and probably cost more in the long run

[BillC]

Jerry, "Two or three layers of plastic on 1x2 wood spacers will reduce heat loss greatly for little money. It can easily be removed in the spring."
Please explain 'plastic'. I take it that you refer to sheet plastic but what grade of thickness ? And I am lost on '1x2 wood spacers ' Is that feet or inches and how does it support the plastic. Being an animal of very small brain I could not figure it out and hope you will excuse the questions.
Bill

[robb]

anton: the major concern for thickness, is clarity, as tom499 mentioned. the light will bend as it comes in, the only thing that will block or reflect light is impurities. probably best to keep the layers to a minimum required for efficiency. not sure your particulars, but i would think that making it airtight, or controlling the air exchange would be the keys to making it efficient.

[Lucinda Brown]

Anton,if you look around you can find propane heaters with built in thermostats.I saw one at Walmart here,don't know if you have walmarts there.I need to replace one of mine this coming winter and that's what I'm going to get.Already have one,but it's not thermostatically controlled.I have to run in and out to adjust temp.No fun!So this winter I'm buying one w/thermostat.Keeping the other,too for extreme cold.Mine is a free standing,front flame,cool to the touch outer surface with a protective grill on front.The only major pain,is refilling tanks.I have a 100 lb. and a 40 lb. tank,so I don't ever run out at a bad time again.The type I have does not require venting.

[Anton]

Lucinda, we don't have winters like yours, we have only had snow 3 times in my 55 years and that was on Mt Lofty behind Adelaide and the biggest dump was 2". People from all aroun d the state came to see it.

As a result we don't have Walmart type shops selling that type of heater, that is why I am having so many problems sourcing a heating source for my GH.

The ones that are available are for large commercial applications and overkill for me. Last night I was looking up heaters for caravans and came across some interesting units both 12v and propane gas which I am going to be looking in to.

At present our overnight lows are in the mid to low 40s, so still have a little time to sort it out. Usually the end of june through July are our coldest months. Frost is the worse that it gets here because we have a Mediterranian climate.