Building a Solar Passive Greenhouse With No Energy Inputs Other Than the Sun

Harnessing the power of the sun can look like many different things. For HeatSpring instructor Chris LaForge, solar energy means so much more than photovoltaics. In this short video, Chris shows us the beginning phases of his passive solar greenhouse build. Can you believe this structure stays totally warm in snowy Wisconsin winters and pleasant in the middle of the summer with nothing but the sun? Tune into the video or read the transcript below. 

To hear the full conversation, you can enroll for free in Unconventional Solar Applications, where Chris and other panelists share their outside the box solar projects. 

The beauty of this building is this is a pet project of my partner Amy and mine for years in design to try and get a building that would heat itself all year round without any input at all other than the sun and this is quite an interesting task in In northern Wisconsin. 

So with this kind of design, you start from the ground up. We call our little place SunFarm, and so we wanted to do a high-mass, indoor radiant solar greenhouse so that it could hold enough heat to get through the tough months. 

The soil type we have is a very hard clay, so you had to start by getting a sand lift to get some drainage, but then we put a large insulated box on top of the sand lift in which we put all this heat tubing that we were going to attach the solar array to. 

And so once the entire building’s mass was put together and insulated and the tubing was in it, then we laid in a bunch of sand on top of that. Then poured a five inch slab with a very, very substantial grade beam and center beam to hold a lot of mass.

Because what we’ve done is we’ve built a stone wall up 10 and a half feet high, one foot thick. Running east and west here through the middle of the building. People familiar with passive solar design that’s known as a trombe wall. And the trombe wall is a big element of the passive part of the design.