End of week five

I promised you walls and here they are:

The massive windows are because this is the south-facing wall and the sun will be one of the major sources of heating for the building. We will have electronic blinds on the outside of the windows on this wall for the summer time, to stop the rooms overheating. Presumably we will eventually tire of playing with the electronic blinds, but I expect it will take a while....

The walls are all made with blocks of recycled concrete. If you look at them close-up you can see they are flecked with black stuff that looks like charcoal, although it's not soft. 

They are made of about 90% recycled material and, according to the WRAP website (http://www.wrap.org.uk/), they are "sourced from a variety of material: arising from construction and demolition (concrete, bricks, tiles), highway maintenance (asphalt planings), excavation and utility operations".

Apparently the bricks have got an A+ environmental rating (similar to the energy ratings of white goods) and I think they're produced in this country so that helps their carbon footprint.Sadly, like energy efficient white goods, they are also more expensive than their non-eco counterparts... sigh.

I know it's obvious when you think about it, but bricks in a wall have to be strong enough to support the bricks above them without crumbling so here's a bit of physics for you. The pressure that something can withstand is calculated by the force of the weight from above divided by the object's area and is measured in Pascals or N/m². These bricks have a strength of about 9 N/mm² (or 9 megapascals). Whenever I've had to read about pressure in physics I'm always reminded of the time the lady from Weightwatchers left tiny pits all over the newly-restored parquet school hall floor with her stilettos.