I have not however, I have the ground open to the soil, and the foundation (with French drains) dips down 6 feet into the ground, as I have trees planted in the soil. They way it is constructed right now, I believe that the soil keeps the greenhouse a bit warmer (I know this as when the fuel runs out, solar heat and/or radiant heat from the ground keeps the temperatures at around 25 deg. F. But here in Worcester, the ground in most winters freezes at a depth of about 1 -2 feet. The single pane glass also is not efficient at all, so that doesn't help.

I see, but from what I see on the pictures, this is just wow. Love it.. I have planted some vegetables indoor. But seeing these pictures, I want to do flowers now. I think it depends all on the nourishing.. Do you have any recommendation which flowers to go for?

It's funny that you ask. For a few years after building the greenhouse, we decided not to have houseplants – to only bring in plants as specimen plants when they look good. Well, that only lasted a few years. Now, the house is full of plants again. Mostly begonias, palms and plants which require warmer winter temperatures. There is no escape!!!

Even though they have many downsides, I have never regretted building one. There will be a day when I cannot heat it, and then, I can convert it into a winter garden, I suppose.