Heat in an Emergency
Where do you turn when the power has failed? Emergency generators won't start! The greenhouse is cooling! Panic! When all else fails, there is one last thing you can do to save your crop from freezing. Use "smudge balls" made of newspapers! Begin with a single crumpled sheet of newspaper. Wrap another sheet around it. Then another and another until you have a ball 15-20 inches in diameter, Place it and other balls like it in the walks of the greenhouse and light them.
Source: • Connecticut Greenhouse Newsletter #62