Self Build BlogWall ties - going ‘eco’ starts small
Trying make your new build home more eco doesn't have to be a huge effort. The smallest improvements can make a big long term difference.
Ever since the original Architect labelled the house as an 'eco house', I've been trying to get some eco materials into the design. Their only contributions originally were the sedum roof and the large south-facing windows - which are really nice ideas and ones I would never have thought of myself - but there should really be a whole lot more involved to be able to confidentally call it 'eco'.
What does 'eco' mean?
Generally it means ecologically friendly and considerate. It can mean a way of life or a philosphy. It can define what raw materials are used to manufacture or build something. It can also mean how something is manufactured, in terms of the processes used and the amounts of energy consumed. It can relate to a physical object as well as a procedure, so there is no one element of building a house which could possibly define it as being 'eco'.
For example, you could consider any (or all) of the following things:
- Are the construction materials made from other recycled or reused materials?
- Where have materials come from? ie. How big is the carbon footprint caused by the transportation of these materials to an interim factory, retailer and then the site itself?
- What manufacturing methods have been used to make the materials? How much energy is used and what pollutants are created?
- What pollutants are released into the enviroment during the degradation of the materials and what happens at the end of their life?
- How much energy will the house use? How efficient will it be at retaining heat in the winter and keeping it cool in the summer?
There are literally hundreds of questions you could ask yourself before and during the build, which will determine how 'eco' your house is. To be honest, I could probably write a whole book on the subject - but I'm sure there are plenty out there already.
As Kevin McCloud has jokingly said on one of his TV programmes, "You can't make something out of leaves and dog spit!" ... so there will always be a carbon footprint involved. It's just a question of how big a footprint.
In my opinion, most of it is common sense. For example, if you're having slate roof tiles shipped in all the way from China, then they're going to be massively more environmentally damaging than using locally-sourced roof slates. But the question here is, "Would this have a smaller or greater carbon footprint than buying concrete roof tiles from this country - bearing in mind how polluting it is to manufacture concrete?" A tricky one.
To eco or not to eco?
So, one of the little features I wanted to incorporate into this build, were eco wall ties. I'd read about them on numerous occasions and had seen them in the flesh at the EcoBuild show in London.
Wall ties are used to join the inner skin, across the wall cavity, to the outer skin of blocks/bricks, at various intervals to make sure everything is strong and sturdy. The downside is that any heat from inside the house will bridge the cavity, along these wall ties and leak out into the outside world. This is known as "thermal bridging". Although the insulation requirements for building homes is much more stringent these days, there is still no requirement from Building Regs to use non-stainless steel wall ties.
One reason is probably due to the fact that in the grand scheme of things, the amount of heat lost through the wall ties is very small. Building a new house with cavity insulation sheets is a massive leap forward over previous practices, so requiring lower thermal conductive wall ties isn't going to make a massive difference on one house. However, if you looked at the country as a whole, I'm sure the total numbers would be quite staggering if all new houses used them. I wonder how much energy would be saved on an annual basis, from people not losing so much heat through their walls, if we all used eco wall ties?
The other downside (at the moment) is the price. Traditional stainless steel wall ties usually cost a few pence each. Whereas eco ones are usually about a Pound or so each. This adds up to a huge cost difference if you need 1000 or more to build your house. I'm sure as eco ones are manufactured in much greater quantities, the price should start to drop quite dramatically.
So the choice is to spend more, and be more eco in the long term (and therefore save more on your heating bills too) - or stick with the stainless steel ones and maybe spend the cost difference on more loft/cavity insulation. Hmmm, decisions, decisions.
Types of wall ties
So as I've mentioned, the traditional walls ties are made from stainless steel. They are quite flexible (physically speaking) which makes things easier for the builders to use (as I found out during this build).
The most popular mainstream eco wall ties are made from basalt and resin. These have a much lower thermal conductivity value but have a slightly larger cross section and are rigid. They are also a lot more expensive.
I was going to go for the basalt wall ties but decided to shop around, to see what other options were out there. I discovered a company in Ireland who manufacture wall ties made from fibre glass. They have a similarly low thermal conductivity but were slightly cheaper than the basalt ones. So the decision I had to make here, was whether to spend the money on something I knew I probably wouldn't benefit from in the short term - but feel good about making an 'eco' decision - or go for stainless steel wall ties and spend the money on something else. I opted for the feel-good factor and chose the glass fibre wall ties.
I ordered 1000 glass fibre wall ties from the Irish distributor and hoped the builders wouldn't have an issue with them. As it turns out they weren't convinced at first, and there were plenty of swear words being thrown around the building site (more than usual!) trying to get them to 'behave', but they managed it all okay in the end. Sometimes people don't like change.
Before ordering them, by the way, I also checked with our Building Regs officer and the house warranty provider, so find out whether they were satisfied with the spec. They got the green light no problem.
Thermal conductivity
These are some rough guidance thermal conductivity values for the different wall ties available:
- Stainless steel wall ties 17W/mK (approx)
- Basalt wall ties 0.7W/mK (approx)
- GFRP (glass fibre reinforced polymer) wall ties 0.19W/mK (approx)
Obvsiously the cross-sectional area of the wall ties will make a difference, as will the quantity used in the house.
On a mission to find insulation clips
It was almost a case of "game over" when the builders pointed out how the cavity wall insultation retaining clips wouldn't work with these new wall ties. The reason being that the wall ties have a much larger and unusally shaped cross-section, so the clips were buckling and not really doing their job. Unfortunately the wall ties distributor wasn't able to recommend a suitable clip either, so I started trawling the internet for some that would do the trick.
As you can see in the photos, the clips the builders were using, had too much plastic in the moulding so they weren't really able to open out properly to accommodate the size of the wall ties. Luckily I managed to find some suitable ones at Screwfix (would you believe?!) and saved the day.
Manufacturer and supplier
The GFRP wall ties are made by Qwik-Fix in Ireland.
http://www.qwikfixings.com/glass-fibre-wall-ties.aspx
We were able to buy them from a distributor, also in Ireland, called Killeshal.
​http://killeshal.com/building-components/gfrp-wall-ties/
Tell them I sent you.
