For years we've tried to maintain our 20x48 foot
greenhouse above freezing throughout the winter but lose this battle every year by single degrees. We live near the junction of NY, MA and VT so it can get pretty cold. We do grow salad greens, onions and herbs through the winter but have not succeeded in keeping tomatoes, sweet potatoes, cukes and squash alive. Our fig tree does lose its leaves but it grows stronger every year and produces amazing quantities of fruit. I rushed fabricating a batch
rocket mass heater this fall but some -20 degree nights in December killed tender plants before I finished it. I did finish it in January and it performed well during another -20F high wind period and this time temperatures inside did not go below 38F but the plants did not perk up!
For four decades we've heated our home exclusively by burning
wood in our kitchen stove that has an
ash bin that we empty once a week. A decade ago we also had to replace the iron grate above the ash bin because it burned away. I replaced it with stainless steel pipes that are very easy to keep open to enable ash to fall through so I incorporated pipes above an ash bin in the
greenhouse batch
rocket mass heater. In both our kitchen stove and in the greenhouse heater, the stainless pipes admit secondary air (p-channel) that both warms the air and cools the metal. Since we have been using many dozen eight foot tall by one foot diameter fiberglass tanks in our greenhouse for the sun to warm up during the day we incorporated lots of these as thermal mass of the rocket heater. Those surrounding the barrels around the riser get pretty warm during an hour burn and do a pretty good job keeping the greenhouse warm overnight.
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