The hole topic is very complex. I will only touch it here to give additional input and let people think about it.
log buildings are good, but …
Log buildings are great, they have a lot of advantages. Because they are of pure wood the statics are often not a big problem. It is possible to build them with very simple hand tools and you do not need a lot of nails or screws. You can even build them somewhere in wilderness without having anything besides the tools. They isolate pretty well for a simple structure and store heat in the logs.
But, if you want a building nowadays, which is rarely extreme remotely, you do not want a log building.
why not building a log building?
Log buildings need huge amount of timber. That is not a necessarily disadvantage as it is better to use timber then other materials. But you can use the same amount of timber much more useful! A log building is nowadays a waste of resources. And the second big reason is: pure wood is not isolating very good. So what is the alternative
timber frame
I only compare here timber frame with log buildings. All other kinds of buildings who do not share the big advantages of wood are not mentioned. A wood building is nearly always superior to a not wood building.
Timber frame, and all its different kinds, have mainly only advantages over log buildings. When you use the saw dust, chips or plane chips for insulation from the wood processing you also have a pure wood wall. The loose filling is sealing excellent and the strength of the structure, when done correctly, can be even higher then with a log building. Therefor I assume here to use wood chips/dust as insulating material.
I will describe some major advantages. This is not a complete list.
1. better insulation
One of the biggest advantages is that for the loose filling you need much less wood then for pure timber, because the density is much lower, allowing you to build a thicker wall or using less timber. Besides that the loose wood filling is insulating over 3 times better then a log wall with the same thickness. The λ-value (the lower the better) of pure wood is around 0,13 W/(mK) while a loose wood filling has around 0,04 W/(mK).
what is the λ and U-value
The λ and U-value of a material describes how fast it transmits heat to the outside. The value says how much energy gets transmitted when the temperature difference is 1°C (or 1°K). Most commercial insulation have around λ=0,04 W/(mK). The U-value is then the actual value of one square meter of a given wall W/(m²K).
comparison of insulation, log wall vs. timber frame
A 200mm thick timber frame wall with 150mm loose wood filling and 25mm boards on both sides has a U-value of 0,234 W/(m²K). A 200mm wall out of pure wood has 0,585 W/(m²K). Besides that a log building always has thinner parts where the logs lie on top of each other. Rarely logs building reach there 200mm thickness.
2. lower wood quality demands
For timber frame you can use overall lower wood quality. Of course for some parts you need also higher quality but for a log building you mainly need good and straight logs which have a proper thickness. If you harvest the trees for a log building yourself you will have a lot of wood you can’t use because it is a little bit too slim or too thick.
3. cheaper
Wood chips are often for free or do not cost anything as normally they just get burned. Because you need less wood the overall material costs are less.
4. more environmental friendly
For a timber frame building you can use all kind of wood qualities. Everything which is not usable for boards or planks you can use for insulation.
5. all structures and shapes possible
While you are practically limited to the length of the logs with a log building you can build all kind of shapes with timber frame. (Of course theoretically this is also possible with log buildings but it gets practically much more difficult)
6. loose wood fillings seal very well
Loose wood fillings seal the wall very well without any extra needs. Air can practically not pass through easily but the wall still breathes excellent. All gaps are filled when done correctly. If you use other modern insulation like some fiber wool it can happen that you get cold gaps, meaning gaps where the air can travel through. If you seal the wall in these cases with tarpaulin it can affect the breath-ability of the wall negatively. Breath-ability is a huge topic and I do not want to dive deeper into that here.
It requires very good craftsmanship or huge, expensive machines to make the logs of a log building sealing very well.
so why do we not have timber frame buildings everywhere?
Timber frame buildings were pretty common earlier. But in central Europe wood as a building material got unpopular because of fires in towns. In the north they stayed very common for longer times, but they were the cheapest way of building and stone buildings were often considered to be higher class buildings. That lead to, that our culture sees timber frame buildings not as something very valuable. A log building is also often romanticized and is therefor often favored by people who want to build with wood. Modern building regulations can also make it more difficult to build a natural timber frame building.
verdict
I do not want to say, that you shouldn’t build any log buildings at all. But the alternative timber frame has a lot of advantages which makes it hard to find any good reason to build a log building. A wood building in general is always a good idea compared to other building methods.
