Currently, only class 5 boilers are available for sale. This means that you can not buy a lower class furnace. They are definitely more environmentally friendly than their predecessors.
What are the characteristics of a Class 5 boiler?
The Class 5 boiler is currently the only model available for sale. In accordance with regulations, as of July 1, 2018 all previous versions have been withdrawn from sale. These are environmentally friendly and definitely more economical versions of stoves, which are expected to completely replace the once popular "dug-outs" in some time. These are boilers with feeders that generate far less pollution, and are therefore environmentally friendly. These types of stoves primarily burn eco-pea or pellets.