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Nick Morrison: Building a House of Straw Part 3

The oldest straw bale houses are around 130 years old, the oldest European house in France dates back to 1921.  When a brick dated to 3000 years old was broken apart the straw inside was as bright and golden as the day it went in. But is this a form of construction we can still use today – and in Orkney? 

In this series of columns I will touch on the history of straw construction, Tools and Skills, Planning, Building Warrant, Site, costs, Environment, and at least obliquely other green building systems.


Part 3

Advantages of Straw Bale Construction

The advantages to Orcadian residents of Straw bale construction are:-

1. The main building material can come straight off our farmers’ fields with no additional treatment required apart from being harvested and stored in the dry. This is a big cost saving.

2.You don’t need any cement at all! Also reducing costs and helping the Environment.

3.Can easily be built by a husband and wife team.

4.Insulation both thermal and acoustic is superb. Scottish Building regs now call for a mu value of 0.25 across the walls. It was 0.45 not so long ago. The builders will be familiar with this but mu is a measure of how good the insulation is and the lower the number the better. A Straw bale wall rendered on the outside and plastered on the inside is around a mu of 0.13. That makes it very cheap to run. Another factor contributing to cheap running costs is that the airtightness of a straw bale house is well superior to the “silver standard” of the Construction Industry, in a nutshell far fewer draughts. This makes it a very comfortable house.

5.As an extension to “comfortable” is that the renders and plasters used “Breathe” unlike cement and gypsum. So unless you go out of your way to introduce a lot of plastics etc. into the house it will not suffer from “Sick Building” syndrome.

6.Speed of construction. This is very fast so much so that the term ‘baling frenzy’ has been coined. This is where a work crew realises just how fast the walls can go up then push themselves to go faster. The walls of the Orphir house went to 1st floor stage in a week. Now this was also a training course so a lot of time was used in teaching.

Scientist’s Hat On

insulating-the-joint

Insulating the joint of myStraw Bale House

OK here is where I put my Scientist’s hat firmly back on plus that of a concerned grandfather. It is morally incumbent on us as residents of one of the areas in Europe potentially most affected by rising sea levels caused mainly by man-made CO2 to adopt those systems of construction which put the least CO2 into the atmosphere. In a worst case scenario I saw published in the Scientific press it showed a map of the UK when the ice at both poles had melted. The Orkney archipelago was unrecognisable. Some islands like Wyre and North Ronaldsay had virtually disappeared along with much of Sanday and Stronsay.

Global warming deals a double whammy here – as well as melting the worlds glaciers and ice caps it also causes the seas to expand significantly. The average UK house causes 50 tons of CO2 to be put into the atmosphere. Here in Orkney it’s more than that. Firstly we don’t have access to bricks or aerated concrete and have to use CO2 hungry alternates. Secondly there is the added CO2 due to the extended transport we have to use to get it all here. Estimates vary but globally the Construction Industry is a major polluter with cement being one of its biggest culprits.

Orkney weather!

You must keep the bales dry at all times especially from the top. So at cease of work in the evenings all work needs to be covered up with tarpaulins and uncovered the next morning.

That is the usual method used in the south. However there is an alternative and that is the “Roof First” technique. This was used in the construction of Europe’s biggest straw bale structure. Here the roof to a water shedding layer is built directly on top of the Straw bale wall plate. This has the advantage of the joiners building the roof do so from the ground which is quicker, easier plus saves scaffold hire costs.

The roof is then jacked up bit by bit to allow the bale walls to be built, then lowered onto the completed walls. You now have an umbrella to work under and are no way near so reliant on favourable weather.

In Part 4: What went wrong!


More information on Straw bale construction here: Straw Works

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