"A+" class houses are carbon negative and sequester more CO2 within their wood fibre than is released during the production of the house. Loghouses belong to this class.
A-class houses are carbon neutral or carbon positive up to 500 kgCO2/t. Most wooden houses fall in this category.
B-class emissions range from 500 to 1000 kgCO2/t. A simple brick or concrete house would fall in this category.
C-class emissions range from 1000 to 1500 kgCO2/t. Most complex brick or concrete houses would fall in this category.
D-class emissions range from 1500 to 2000 kgCO2/t. Brick or concrete houses of this class contain a lot of glass, insulation and metal.
E-class emissions range from 2000 to 2500 kgCO2/t. A house built of plastic Lego bricks would fall in this category.
F-class emissions remain above 2500 kgCO2/t. A house built of stainless steel would fall in this category.