|The Alambique - timber frame and windows (from Jon and|
Mary in Scotland!). Shuttering below to hold the straw-clay.
We've been working on the walls, floors, roof, plumbing, drainage, power supply since May. Now we needed a front wall. We have a few choices for wall material: bricks and mortar, earth bricks, timber frame with plasterboard and insulation slabs, and so on.
|Nikita as Paulo's carpentry assistant, building the timber frame.|
Note the stone wall built below the timber, to keep straw and wood
well away from any water.
|The clay takes loads of time to soften up, at least 24 hours. Then it needs whisked, then then the slip decanted into another container. |
|Paulo, surrounded by clay slip buckets, showing our Galician|
friends the right mix of clay to straw, in Donald's old bath.
|Federico on clay stone crushing duty|
|Irena, Cesar and Jorge working the clay slip into|
Then you need to have at least 2 people fluffing up the straw in a container of some sort. On bigger projects people have all sorts of equipment to do this, but these are not available here in Portugal, and if they were they would cost a fortune to rent.
|Bugui, Galician yoga and meditation teacher, working with|
the Zen of Straw
|Cristina, recent Galician resident from Italy, adding her labours|
to the wall compaction.
Once the wall sections are done you can remove the shuttering right away. What you have is a damp walls of clay. Looks nice, it's straight and ready for plastering. But not for months! Here's another disadvantage: it takes up to three months to dry properly. It's been 6 weeks since we built this wall and it's been really hot, so it is almost dry inside. But in colder climates this could be a real problem, mould can occur and delays in the building process can cost a lot.
|Irena, great friend from Northern Galicia, and child (still at one with her)|
one of the hardest workers on site. Impressive.
|Me, driving ash stakes|
through the bales to keep
them stacked in place.
OK. What about thermal performance? Dhanya's research found that the U-value of a 40 cm straw-clay wall can be around 0.239 W/m2K (this refers to the U-value, which is a measure of energy conduction, in watts, per square meter, conducted through a material, for each degree difference on each side).
How does this compare with other types of walls? Well, here's a selection, taken from the Whole House Book:
Wall type U-value
Solid brick (225mm) 2.20
Timber frame with
50mm insulation 0.96
Timber with 100mm
Our straw-clay wall
with 250mm insulation 0.14
Straw bale wall 0.13
The latest UK building codes state that external walls must have a minimum U-value of 0.35 (W/m2K), which means straw clay/ light earth would be considered more than acceptable.
That said, now the wall is done and almost dry, I think it's going to perform well. But we'll have to see after plastering, and after a winter of rain and cold.
|Petrus, building up stone wall in front of the alambique where|
we plan to build a wooden structure for a veranda. More on this later.