The SPARC greenhouse has been in use for several weeks and it seems that it is working far too well. The attached greenhouse was designed to collect heat during the day and then transfer the heat to the rest of the home when needed. However, this created a very uncomfortable greenhouse with temperatures reaching over 100 degrees.
With this design we are able to heat the house at a very low cost. We installed a 24V 4amp fan that would be able to circulate the heat through the house. When comparing costs of heating a 1300 sq ft house, a very reasonable cost of $1.50/month might be considered a bargain.
However, the system is working too well. We had to cut in a chimney to vent the excess heat. Now, we didn't want to hobble the system from working in the winter when heat is at a premium here in central MN. We added a removable sliding insulation board to ensure that heat would not be lost when needed.