Greenhouse Condensation

[Ger-annie-um]

Oh wise ones - I have a gas heater in my greenhouse that I just keep on 'frost free'. Problem is there seems to be a fair bit of condensation building up. I know I should have some ventilation but need to know where is best to have it...........in the opening roof vents, or through the louvre vents at the back/side of the greenhouse and how wide should the ventilation gap be.
I do open the greenhouse everyday to allow some air through but couldn't today because I would probably have lost the house to the wind.

[VirginVegGrower]

A common problem with gas heaters. I would have thought lower down as in your louvres. But will that chill any plants you have overwintering? If so, open top.

[veggiechicken]

Can you water the plants less? Reduce the amount of moisture in the greenhouse overall.

[Ger-annie-um]

I only water when the plants are really dry and then just enough to dampen the capillary matting everything stands on. I was opening the overhead roof vents a little (about an inch) but then thought that just lets out any heat that might be in the greenhouse, whereas if I open the louvre windows at the back and side of the house then, because they are below the plants, it may be better.

I've got about 500 propagated rooted cuttings in there at the moment and I really don't want to lose them because they rotted/dampened off!

[rustylady]

How often is your heater on?

[hollychap]

theres an high water content in the gas you use in the portable gas heaters

[VirginVegGrower]

The heaters create water vapour and Carbon Dioxide, the latter you want. Just keep air circulating with a vent open somewhere.

[veggiechicken]

Can you line the glass with bubble wrap? I used to do this, but with an electric tube heater on frostfree. Don't remember condensation being a problem as any moisture was not hitting cold glass.

[Potstubsdustbins]

I presume you mean a proper flueless GH heater not a cabinet style radiant heater.

If so it will depend on the size of heater i.e. the output in kilowatts and the cubic area of the green house as to best advice.

However most GH gas heater manufactures require some amount of ventilation for the safe operation of their products. Full combustion of the fuel gas can only be achieved when the correct amount of oxygen is available, poor combustion leads to more water vapour and the production of carbon monoxide not carbon dioxide.

First thing is to check your flame picture if it is yellow/orange or floppy looking you have a problem open your green house door and again check your flame picture if there is an improvement low level ventilation is required. If there is no improvement you may have dirt in the injector or primary air ports. Also check for soot in the combustion chamber as this will slow down the airflow and again affect the combustion process.

Exactly how much water vapour your appliance will produce depends first on what fuel is being burnt methane, propane or butane. Butane being the worst offender.

Hope this helps Colin.

[Snadger]

I reckon your main problem is the capillary matting. This stuff is great during the summer when you need the moisture around the plants but is probably unecessary during the winter months when plants just need watering now and again.
Its like covering the bench with a damp warm blanket........nons the wonder you have condensation problems

You will always get condensation problems with gas/paraffin heaters but the capillary matting will surely exasperate the problem?

[VirginVegGrower]

I presume you mean a proper flueless GH heater not a cabinet style radiant heater.

If so it will depend on the size of heater i.e. the output in kilowatts and the cubic area of the green house as to best advice.

However most GH gas heater manufactures require some amount of ventilation for the safe operation of their products. Full combustion of the fuel gas can only be achieved when the correct amount of oxygen is available, poor combustion leads to more water vapour and the production of carbon monoxide not carbon dioxide.

First thing is to check your flame picture if it is yellow/orange or floppy looking you have a problem open your green house door and again check your flame picture if there is an improvement low level ventilation is required. If there is no improvement you may have dirt in the injector or primary air ports. Also check for soot in the combustion chamber as this will slow down the airflow and again affect the combustion process.

Exactly how much water vapour your appliance will produce depends first on what fuel is being burnt methane, propane or butane. Butane being the worst offender.

Hope this helps Colin.

But with ventilation, ie. oxygen you will get Carbon Dioxide, which is good for plant life. Think Colin is urging us all to be a bit more careful with our gas appliances, which is good advice.

[VirginVegGrower]

I reckon your main problem is the capillary matting. This stuff is great during the summer when you need the moisture around the plants but is probably unecessary during the winter months when plants just need watering now and again.
Its like covering the bench with a damp warm blanket........nons the wonder you have condensation problems

You will always get condensation problems with gas/paraffin heaters but the capillary matting will surely exasperate the problem?

We had a paraffin heater - nightmare! Pro GH growers use dirty great gas powered heating systems. Look next time you're in a nursery (not you Snadger - grapes in general). I've taken all heat out of mine and bring stuff indoors, utilizing the greenhouse come Spring. Mr VVG planning on putting power (electric) up to the GH - it's at home, not at the Lottie.

[Potstubsdustbins]

I don't think the problem lays with the matting, if we think about it the heater is only set on `frost free` hardly warm enough to cause excess evaporation from the matting.

However if we follow the formula for the combustion of propane gas C3H8+5 02 = 3CO2 + 4H20 we can see that for example for every cubic foot of gas burnt we produce 4 cubic feet of water vapour. As said before if we are burning butane the situation is much worse 1 cubic foot of gas burnt will produce 10 cubic feet of water vapour.


VC yes that is my advice I hate flueless gas appliances as they are in my opinion inherently dangerous.

The products of combustion are discharged into where the appliance is sited if the combustion process goes wrong and the appliance starts to produce carbon monoxide people have no idea how little is needed to cause serious problems or how quickly they can be affected.

To give you an idea at 0.4% by volume of CO in atmosphere 60% saturation of a person's haemoglobin will be achieved in a few minutes this will result in collapse, loss of conciousness and coma. The result is usually death.

Colin

[Snadger]

I don't think the problem lays with the matting, if we think about it the heater is only set on `frost free` hardly warm enough to cause excess evaporation from the matting.

However if we follow the formula for the combustion of propane gas C3H8+5 02 = 3CO2 + 4H20 we can see that for example for every cubic foot of gas burnt we produce 4 cubic feet of water vapour. As said before if we are burning butane the situation is much worse 1 cubic foot of gas burnt will produce 10 cubic feet of water vapour.


VC yes that is my advice I hate flueless gas appliances as they are in my opinion inherently dangerous.

The products of combustion are discharged into where the appliance is sited if the combustion process goes wrong and the appliance starts to produce carbon monoxide people have no idea how little is needed to cause serious problems or how quickly they can be affected.

To give you an idea at 0.4% by volume of CO in atmosphere 60% saturation of a person's haemoglobin will be achieved in a few minutes this will result in collapse, loss of conciousness and coma. The result is usually death.

Colin

Are we throwing a wet blanket on my theory then Colin..................

[Potstubsdustbins]

Me Snadger? No way, just pointing out how much water the bladdy gas heaters produce.

I would think without correct ventilation not only would the heater not work properly but the moist atmosphere could encourage all sorts of nasties. molds etc.

One manufacturer recommends a 3" to 4" drain pipe at low level for a 3Kw heater to combat the problem.

Colin