3. Fuel - wood bulk densities

Another big variation to be aware of is the varying bulk-density that occurs between different species of timber. As we have seen, spruce and other softwoods can deliver the same amount of heat weight for weight as oak when they are both fully seasoned. But the chart below shows that if you are burning mainly spruce, you will need around 49% more fuel by volume than if you are burning oak or beech.
XXThis extra volume needs to be taken into account not just when you are storing your wood, but also when you are burning it. So if your principal fuel is likely to be softwood and you are still at the point of choosing a stove, give some thought to going up to the next biggest model above the one indicate by your heat requirement. That way you'll get the output you want without suffering unduly short stoking intervals.