The new ecoheater Slimline Greenhouse & Shed Heaters are one of the most energy efficient ways of providing low-cost ambient heating and frost protection and preventing dampness and condensation in a range of outbuildings, greenhouses, cold frames, sheds, garages and ...The new ecoheater Slimline Greenhouse & Shed Heaters are one of the most energy efficient ways of providing low-cost ambient heating and frost protection and preventing dampness and condensation in a range of outbuildings, greenhouses, cold frames, sheds, garages and conservatories. The heaters are designed to use far less electricity than fan heaters and are cleaner than paraffin heaters. Energy usage is kept to a minimum with a built-in thermostat which switches the heater off when the surrounding area gets too warm.