Hi I’m John Budworth, head gardender at Norton Priory Museum and gardens. On behalf of Sustainable Build.co.uk, I’ going to talk about the eco build at Norton Priory museum and gardens.
We were looking for indoor space at Norton Priory, we looked at three options, converting the existing buildings, introduction of a porta cabin but unfortunately the access was too small, and then someone suggested we use a straw bale as a building material.
As you can see it is a bit different from brick and block type constructions, very flexible and it is also your building material and your insulation all in one.
You may be wondering how you cut a bale, because of course it is held together by string,. If you were to saw it straight in half you’d go through the string and you’d just end up with a pile of string, so to avoid that, we are using a needle to thread it through. It is called a veiling needle and we will tie either side of that and that will turn this large bale into two smaller ones which will fit into the gaps.
Straws need to compress and that gives you your final height, and it is very important to allow for this in any kind of building design. As you can see the bales don’t always fit together perfectly, so you need to stuff loose straw inbetween the gaps and that makes sure that you don’t have any draughts or losses of insulation and also keeps the structure of the wall ready for plastering because in the end it will have a render on it so it is important to get a smooth surface and otherwise you would use a lot more of your line render and a lot more of your clay for the internal parts of the building.
Where the wall bulges out, sometimes that can be through various things, in this case we’ve got a bit of uneven settlement and John is using a mallet there and he’s just knocking the straw back so that it remains quite flexible until fairly late in the building stage right up to plastering which is one of its advantages, especially for self build.
We are using the same kind of building methods that you would do if you were doing a home build, but as we are a public site, we have to allow for adequate fire exits, wide enough entrance to take a large powered wheelchair or a baby buggy and we have to keep all our slopes for ramps and things like that to round about one in twenty.
Of course sustainability is something we are very keen on here at the Priory, and we have tried to use as much local materials as we can including wood from a local wood which is called “Big Wood” which is near to the main museum site. Unfortunately we can’t use this for load bearing timbers or stress timbers in any way because anything like that has to meet with a standard which is similar to C16 I believe its called and that is what the building inspector looks for so if it doesn’t have that stamp we can’t use it for structural pieces such as the roof trusses which we got pre fabricated and untreated so that we can do that ourselves and cut down on tanelisation of timber which most people are avoiding in public buildings now anyway.
The good thing about looking for recycled and re-use materials is that things that are difficult to dispose of. One such problem is old tyres, as you may know there is a mountain of old tyres in this country gradually building up and here we are using them to support the eco building for the main floor joists and they sit on these tyres and it is very useful it provides a damp course and a structural support all in one. You may be wondering how long this building is going to last, it’s a minimum of 25 years There have been some around in this country longer than that and it’s from a traditional method called the “Nebraska” method which was used by settlers in that area of the world and some of their similar buildings have been up for nearly 100 years.
For the roof we have used a fairly environmentally friendly we call it oncheline which is a fibre which is bitumen which provides the water proofing part of the sheet it is also self amalgamating so when you get a warm day, the bitumen goes soft and flows together and makes a really good water type seal. Obviously that is better than using plastics as far as your eco footprint goes. Of course it is important to insulate the building to keep the heat in. We have faced the windows south to make use of something called “passive solar gain” and in order to stop the heat escaping during the day or at night. It’s important to have the building as well insulated as possible. Obviously the straw does that but we give it a helping hand with some of this insulating as well. We try and use recylcled materials or things from sustainable sources. This is a material called warmasel and it’s actually made from shredded newspapers which is then treated to give it a bit of fire resistance and that’s packed into cavitiies like between the joists and in the roof cavity as well. We confer eco friendly wherever we can. Nothing goes to waste, the offcuts of wood and burnable material ic charcoaled and we’re hoping to sell them in the shop.