Heating your Growing Dome
Over the years, we at Growing Spaces®, have accumulated a lot of knowledge and experience on the topic of heating your Growing Dome. People often ask how much heat does it need to keep it warm on a cold winter night?
We have created a useful spreadsheet which calculates how much heat loss the dome experiences- as this needs to be balanced out by heat input.
Here’s where it gets a bit technical.
Heat loss from any structure = (inside temperature – outside temperature) x (surface area) x (u-value of the material).
Our spreadsheet calculates the heat loss from each size of Growing Dome® taking into account the area and insulating value of each of the components of the Growing Dome; foundation wall, north wall reflectix and polycarbonate.
The spreadsheet shows average interior and exterior temperatures on a cold winter night. If you want to play with this and insert your own value, go ahead using the EXCEL SPREADSHEET. You will need to download the XLS file in order to modify the inside/outside temperatures. In order to convert °C to °F, use this formula: (°C x 9/5) + 32 = °F
In mine, we inserted average temperatures over a twenty-four hour period, as obviously the temperature continuously varies throughout the night. You would end up with a number of BTU’s per hour of heat loss if you want to maintain the interior temperature at the value in the spreadsheet you would have to use a heater that gives out the amount of BTU’s shown in the column.
The column to the right shows an approximate amount of kilowatts if you were going to use an electric heater for the dome.
However, the Growing Dome in reality, stores a lot of heat on a sunny day. So the amount of heat needed can be reduced because of this effect. We have calculated that on a cold winter night, the water tank in the 22’ dome can give out as much as 30,000 BTU’s of heat. Also, we store heat in the soil, and even though it’s hard to quantify this, it nevertheless provides some free energy to keep the plants growing all winter long. We hope you will find the spreadsheet useful when thinking of heating your Growing Dome®.