Archive for materials

Dilemma – flooring

September 11, 2008 · Filed under Dilemmas, materials · Tagged , , ,

When we started this project we understood that at certain times the best environmental option and our meagre budget would clash and we would have to compromise. Well, this is one of those times. When we got planning permission for the extension, one of the conditions was that the floor of the kitchen would be concrete. Given that we were building down a level and the Perth area is liable to flooding, we conceded on this point but decided to make it feature. When the concrete was poured, we scattered recycled glass chuckies with a view to sanding them down and sealing to create a funky kitchen floor.

That was Plan A. Being, admittedly, novices at this we misjudged the timing and added the glass too late. As the concrete dried, the chuckies rose to the surface and our perfectly flat floor became pocked. We cleared the loose chuckies and held out hope that the remaining ones were deeper set and would shine up nicely when sanded. But we underestimated the power of glass. It wouldn’t be accurate to say that they broke the industrial strength sander but they certainly held their own. When we gave up on it as a bad job we were left with a green and grey lunar landscape.

One evening, while wilfing on the internet, I stumbled upon our Plan B - a clear resin floor covering with recycled glass screed in a choice of colours, pre-mixed and ready to pour. And then I lost it. We have wasted many hours online searching for this site (which I could have sworn I’d bookmarked) to no avail. If anyone out there knows of which I speak, please let us know and soon. We haven’t quite given up hope, but we’re close.

We started researching alternatives and came up with Plan C – marmoleum. Linoleum, marmoleum’s more industrial cousin, is often used as a generic term for vinyl but they couldn’t be more different. Vinyl is basically plastic so it uses petroleum products in its manufacture and will never biodegrade. While often used as a more allergy-friendly replacement for carpet, it is not recommended by the British Allergy Foundation because of the harmful chemicals it contains. Linoleum on the other hand is made from all natural materials – the word lino comes from linseed. It is everything that vinyl isn’t but to the casual observer there is no obvious difference once laid. This is where the budget comes in – the difference is in the price. Not only is marmoleum more expensive, it is much trickier to fit and requires specialist tools.

Now, Donald’s Dad is in the trade and he has very generously offered to provide our flooring – which makes a big difference to our budget. He was happy to source cork flooring for the kids’ rooms – cork being possibly the most sustainable floor covering there is (more on which later). He was able to source marmoleum (it is manufactured in Fife) but it was a big ask – he hadn’t fitted it before and didn’t have the tools. So we looked for Plan D – would the cork work in the kitchen? No, he said, not where it’s likely to get wet. Plan E was recycled plastic tiles but we couldn’t find them in anything other than bright industrial colours. As the floor was so uneven, before we could lay anything we had to use a self-levelling screed which raised the level of the floor. This meant we couldn’t consider local stone or tiles as it would make the floor too high. And then there was vinyl.

Even if someone out there comes good with the recycled glass resin, it’s too late now that the screed is laid. We have made our compromise, chosen a vinyl that looks vaguely like stone and Donald’s Dad has ordered it. We console ourselves with the thoughts that a/ this means we will finally be able to install our kitchen and b/ as easy to fit as it is, vinyl is also easy to remove should we find our dream floor in the future. There are now vinyl recycling schemes so it won’t end up in landfill or we could freecycle it.

We are very happy with the kids’ floors. Cork has a bad name due to the dodgy ’70s tiles we all grew up with but it has since undergone something of a reinvention. It is now available in a variety of natural shades and patterns and is laid in click-lock planks (like laminate). It is soft and bouncy underfoot, making it ideal for the rough and tumble of kids, and it has great sound insulation. Where cork stands out from other wood flooring is its sustainability. Our cork flooring comes from Portuguese Cork Oak. The trees are not harvested but coppiced which means that new growth is removed to make the cork while the tree is left to grow and absorb carbon – a bit ‘eating your cake and having it too’. We’ll post photos of the cork when its laid. Once the flooring is down it will really start to feel like home.

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The joys of hemp

September 5, 2008 · Filed under Eco tips, materials · Tagged ,

House building may not be the first thing that occurs to you when you think of hemp. Due to the fact that you can (apparently) smoke it, hemp has had a bad press so its commercial possibilities haven’t been fully explored. Hemp actually has a history of being really useful. Hemp ropes were used to scale mountains and to bind boats together until the early 20th century. It was the original material for artists’ canvas. It can be woven into fabric to make clothes. It also makes fantastic insulation.

Our first choice of wall insulation was straw. As a byproduct of farming, it is really low impact and incredibly cheap. Unfortunately it only comes in one size – bales. This would result in very thick walls and as our site is long and narrow would have reduced the living space of our rooms by about a metre. So we looked at other natural insulation material. Sheep’s wool, as a byproduct of the meat industry, wasn’t acceptable to the vegetarians in the family. It’s also relatively expensive – £9.50 per m2 compared to £6.50 for hemp. Warmcel is made from 100% recycled newspapers and is pumped into the walls but we couldn’t find a local supplier. British-grown hemp batts are supplied by Burden’s Builders Providers which made them the easiest option but the more we learnt about hemp, the more we loved it.

OK, there’s the ‘hur, hur’ value of having a house made of hemp but it really is an amazing resource. Commercial hemp crops are now grown in Britain and across Europe (but are still banned in the US) and are proving their eco credentials. They use far less water, fertiliser and pesticides than most crops, being unattractive to most insects and growing to 3-5 metres in a couple of months. As they grow they lock in carbon, creating a carbon sink even more efficient than trees. They are low impact in every sense. They may even hold the key to the biofuels issue.

From a building point of view, hemp has great thermal resistance and can be used in external and internal walls, floors, lofts and roofs. It also controls moisture, protects against fire, insects, fungus and vermin, and the strength of its structure means it doesn’t compress or slump once in place.  It has great acoustic properties – which means that once the kids are installed in their new rooms we shouldn’t hear them at all! The NBT hemp batts we used are available in different sizes and are designed to be compatible with the diffutherm system (see previous post). Hemp doesn’t have any of the nasties that trigger allergies and it has full lifecycle certification (see www.natureplus.org) which means that it is eco friendly from seed to disposal. And it smells good!

House full of hemp

House full of hemp

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Timber frame and the diffutherm system

September 3, 2008 · Filed under Eco tips, materials · Tagged , ,

When we moved onto this road in December last year, there were two extensions in progress. We broke ground in April and are nearly finished. The other two are still in progress. How did we get it done so quickly? Non-conventional construction methods. This does not mean that we employed dodgy practices or cut corners, we just didn’t opt for bricks and mortar. In fact, the old adage ‘it’s only bricks and mortar’ doesn’t apply to us at all. We’re going to have to invent a whole new lexicon for the eco builder – “well I know it’s just timber and hemp, but it’s home to me”.

The first and most important part of the house is the timber frame. This is the material of choice for most eco builders because a/ it’s sustainable and b/ it’s quick. Our joiner had 75% of the frame constructed and lying in the back garden within a week. Putting the whole thing together in place is like a giant flat-pack and takes more time than the actual construction but when it’s done you have the frame of your house – like a timber skeleton. The timber provides the structural integrity for the whole building. Even in conventional builds, where a timber frame is used with bricks, the bricks are only the facade, the timber is load-bearing. This probably comes as a surprise to many. We don’t tend to think of timber as strong and enduring the way we think of bricks and concrete. But there are many countries and cultures whose buildings are predominantly timber structures and there are timber buildings in Britain which are still standing after hundreds of years.

The key to timber’s longevity is making sure it’s weatherproof. This can be done with wood preserver, paint, charring – all of which require maintenance – or the aforementioned brick facade. We have chosen a relatively new method – the diffutherm system – which is supplied by Natural Building Technologies www.natural-building.co.uk and Burden’s Environmental Builders Merchants (nationwide). The system comprises Pavatex woodfibre boards, which are attached to the timber frame (after you have stuffed the walls with insulation – in our case hemp); Bayosan mineral render; reinforcing mesh and a finish coat of coarse grain render (similar to fine pebble dash).  When all the layers have been applied, the external walls are weatherproof, fire resistant, airtight and breathable. The system is also carbon-positive, meaning that the materials lock in more carbon than they use in construction – your very own carbon sink.

This system is a practical option for the self builder as it’s relatively fool-proof, cheaper than hiring a brickie and goes up quickly. Despite the rain hampering our efforts, we had it done in about two weeks. If you have two people on the job – one to mix the render while the other plasters – you’re laughing. You must allow a few days between each coat of render but by the time you’ve finished the other sides, your first side should be ready for the next coat. Here’s a step-by-step in pictures:

One hemp-stuffed wall, one with woodfibre boards

One hemp-stuffed wall, one with woodfibre boards

Boards in place

Boards in place

 

Applying the first layer of render

Applying the first layer of render

 

The mesh reinforcement goes on between layers of render

The mesh reinforcement goes on between layers of render

Team work - one mixer, one plasterer

Team work - one mixer, one plasterer

The coarse grain layer goes on over the render
The coarse grain layer goes on over the render

 

 

 

 

 

Wall showing the different stages of diffutherm method. Note the corner beads on the joint.

Wall showing the different stages of diffutherm method. Note the corner beads on the joint.

 

 

 

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High spec windows without the high cost

August 17, 2008 · Filed under Budget tips, Eco tips, materials · Tagged , , ,

Windows often work out as one of the biggest budget-blowers in an eco build. If you’re happy to go for standard uPVC double-glazing you may get off relatively lightly but if you’re eco-minded uPVC just isn’t an option. PVC is cheap and durable which is why it has become a favourite material of the building industry. [Note - none of the savings in production costs have translated into lower house prices.] Apart from encasing your home in plastic, the downside of PVC is that it is a source of phthalates and dioxins. Both are known to leach from PVC products and have been banned from children’s toys as a result. They also escape into the atmosphere when disposed of in landfill or incinerated. So that would be a no then. For more information see www.greenpeace.org/international/campaigns/toxics/.

The only sustainable type of window frame is timber but again, timber is only sustainable if it comes from well-managed forests (where trees are planted to replace the ones harvested) and hasn’t travelled half way round the world. So tropical hardwoods are obviously out but where do you reckon the cheap patio furniture on special offer at your local supermarket comes from? The only way to guarantee your timber is ethical is to buy only FSC-approved sources. And that is where things get expensive. Not every supplier stocks FSC timber and those that do often charge a premium for it.    

We managed to source windows from Rembrand Timber in Dundee (http://www.rembrandtimber.com/). They’re Swedish, which is almost local (Dundee is nearer to Scandanavia than to southern England) and come straight off the boat at Dundee. They are Traryd Fonster, FSC-certified and triple-glazed. They have a u-value of 1.5W / m2 oC – which means that they will make our house energy efficient to run.  These are top of the range windows. So what are they doing in a low cost project?

One thing you don’t skimp on in an eco build (or any build if you’ve got any sense) is windows. They are one of the most important factors in making your home warm so you don’t need to use as much energy to heat it. They also ensure the house is properly ventilated so you don’t get condensation or damp problems down the line. It wasn’t a difficult decision to make. It was, however, one of those rare occasions when it was actually cheaper to go for the greenest option.

The trick is to buy them ‘off-the-shelf’. Windows are manufactured in standard sizes. Unfortunately if you’re replacing windows, you’ll find that most houses don’t come in standard sizes. Which means the windows have to be custom made to fit. The big advantage for self-builders is that you can choose the sizes of your windows. Donald did his research before he drew up the plans so all the windows in the extension (and luckily, two in the existing house) are built to standard sizes. Even our very sexy triple panel back door was off-the-shelf. If you are working with an architect, make sure you are clear on this issue - it will save you a fortune.

The Segal Method of contruction works like this on a bigger scale – it plans the entire house around materials in standard sizes to keep costs down. Building an extension on to an existing house meant we were more constricted than someone building from scratch but it is an option to consider if you are self-building. Unfortunately, our front windows are enormous, non-standard sized, badly sealed, poorly vented, aluminium 1970s double glazing and will cost us a fortune to replace but it’s not an optional extra if we want the whole house to be energy efficient, not to mention warm this winter.

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