Here is a cute little prefab "portable home" from Spanish architects ÁBATON The 290 square foot one-bedroom unit is built from CNC cut timber and clad in wood fiber cement board.
It seals up nicely for shipping and security; you can barely tell where the windows and doors are. The architects write:
The use of wood throughout the building not only adds calmness and balance but it is also hypoallergenic. The sourced wood comes from regulated forests (will regrow to provide a wide range of other benefits such as further carbon storage, oxygen generation and forest habitat).
It is a simple yet sturdy construction made of materials chosen to provide both comfort and balance. ÁPH80 embodies the principles and objectives of ÁBATON: wellbeing, environmental balance, and simplicity.
I have a bit of worry about the detailing, the lack of roof overhangs and the use of cement board as roofing, but it has a childishly simple design that is seductive. The architects mention that it has a " Ventilated façade with 12cm thermal insulation around the building."
It looks like it was dropped in the field here for the photo shoot; there don't appear to be water and electrical connections. Cost is 32,000 Euros, which is pretty cheap for modern prefab. More at ÁBATON, found on Small House Bliss