Greenhouse temp in winter

[asaad]

Hii,
I live in the south of Iraq , I have about 300 tilapia (small ones ) , The winter is relatively cold over here ( may be the temp will as low as 5 degree centigrade , may be lower ) , I am thinking of building a home made greenhouse , I am asking about the temp this greenhouse will provide , and how efficient it will be , I mean if the temp is example 5 degree Centigrade , what will be the average temp inside the green house .
Best

[davidstcldfl]

Hi assad, I don't know alot about green houses. I live in a semi-tropical area, we just have shade houses.
I've heard of others talking about 'Chinese greenhouses'. I did a quick search...this is just 1 link of many...
http://www.energybulletin.net/stories/2 ... nese-style

[bsfman]

Hii,
I live in the south of Iraq , I have about 300 tilapia (small ones ) , The winter is relatively cold over here ( may be the temp will as low as 5 degree centigrade , may be lower ) , I am thinking of building a home made greenhouse , I am asking about the temp this greenhouse will provide , and how efficient it will be , I mean if the temp is example 5 degree Centigrade , what will be the average temp inside the green house .
Best

I use a plastic uninsulated greenhouse tent in south Florida during wintertime. Though our winter days average a high in January of 75F (24C) we do occasioinally have nights that drop into the 40's and rarely into the 30's. On sunny days, I had daytime temps inside the greenhouse of 120F to 130F. The thermal mass of my fish tank held the water temp in the low to mid 60's even during the coldest nights and the rare frosts were never an issue. I had to artificially heat my outdoor fish tanks on the coldest nights, but the tilapia thrived inside the greenhouse without any outside source of heating.

I would assume Iraq has LOTS of sunny winter days so a greenhouse might be just the thing to keep your tilapia happy and thriving, Asaad!

[asaad]

thank you davidstcldfl for the useful site .
thank you bsfman for the practical information , it clarified the issue to me very well . However i still have the problem of inadequate direct exposure to sun light , because my system is in a shade from the neighbors wall .I think I have to manage to solve this problem very soon or i will loss my tilapias .
thaaanx

[Lance_Green]

Just having a layer of plastic film will cut your heat loss about in half. Insulating the sides of your tank will help.

Reducing evaporation from the top of the tank is important. Evaporating a pound of water causes a heat loss of over 1000btu. The evaporation of 10lbs of water will lower the temperature of a 160 gallon tank by about 1 degree F. A dry climate would facilitate evaporation.

Being in a greenhouse helps somewhat with the evaporation, but not completely. The water vapor condenses on the inside of the greenhouse walls, losing the heat to the outside.

Having insulation floating on top of the tank would be the best way to reduce evaporation, but stops the oxygen exchange with the air. Maybe covering most with insulation and have some bubbling to make up for oxygen loss.

Even with indirect sunlight, your greenhouse will heat up a little in the daytime. Too bad you do not have direct sunlight to really heat a greenhouse.

Bsfman mentioned thermal mass (heat capacity). Water has a high heat capacity - takes a lot of heat to raise its temperature and gives up the same heat when cooling down again. Water in black coated containers will absorb the heat in the day time, reducing overheating in the greenhouse and then when the temperature drops at night, the heat given off reduces how cold it gets.

Hope your fish are surviving.