I built my first heated shelter for my most cold sensitive bonsais. I used treated wood, concrete blocks, rigid insulation boards and an STC-1000 thermostat. Two light bulbs and two seedling heating mats serve as the heat source. The outer dimensions are 7’ large by 8’ deep and 5’ high.
Requirements
The shelter had the following requirements :
- Protect cold sensitive species (Japanese maples, magnolias, prunus, JBP)
- Be relatively modular in case I need to take it apart.
- The temperature must be set from inside the house.
- Being high enough to accommodate taller trees (up to 4 feet).
Everything starts with a plan.
11 insulation sheets were required.
Foundation
The wooden walls rest on top of the concrete blocks. That will protect the wood from the ground humidity. The blocks also act as a solid wall preventing rodents to enter the shelter. A foam insulation strip is added on the bottom.
Assembly
Wooden structure.
View from the backyard for perspective.
The top insulation board is cut to match the roof slope.
All gaps between the insulation and the wood are sealed with roofing asphalt tape.
Electricity
The thermostat is located inside the house in the basement and controls a quad electrical outlet located inside the shelter. The circuit is protected with a GFCI outlet. This way the STC-1000 controls both lights and heating mat.
More roofing tape is added on top of the electrical boxes.
I check the wiring using a circuit tester.
Modular structure
The roof beams can be easily removed to enable full access when storing the trees in the shelter.
Roof and front insulation
The remaining insulation panels are installed.
The front panels are secured with long wood screws and washers.
Under the snow.
STC-1000 thermostat
The STC-1000 thermostat is cheap (20$) and is frequently used for home-made projects where both heating and cooling is required, such as brewing beer. I only used the heating circuit to power the light bulbs and heat mats. As an improvement I could add a fan to extract heat in spring. All I would need is to wire the 120VAC from the fan to the STC-1000 terminals.
I will not explain how to configure the STC-1000 in this article as it can easily be found on the internet. One can set many parameters such as the minimum and maximum allowed temperature, trigger thresholds and delays.
Wiring schematics:
Does it work ?
Minus 8 degrees C outside and plus 1.8C inside.
