Cob Blog

In what has turned out to be a phenomenally dry year so far there has been excellent progress made on the construction of our little house. During the ground works around 1500T of topsoil and subsoil have been moved around to make way for the office and basement rafts which normally means acres of mud at this time of year but, so far, we have been extremely lucky. If fact the only water that caused any puddles on site came from the drilling of the borehole!!

This is a little time-lapse video of what has happened so far. Unfortunately, due to my technical ineptness, I missed a few bits, but you’ll get the general idea.

The existing bungalow was put through a concrete crusher and made around 300T of hardcore which was then put under the office and basement. For the insulation we used Isoquick, a polystyrene insulation designed with Passivhaus requirements in mind which actually worked really well and made the construction of the rafts very easy. Because of the amount of steel that was designed in to the floor construction for both the office and the basement rafts we had to use a heavier gauge of membrane and went for Fosroc membranes.

Whilst the Fosroc radon barrier worked well in the office, the Fosroc Proofex Engage was a disappointment in the basement. It is a very robust system but has the drawback that it expands and contracts uncontrollably, making confident waterproofing of the slab very difficult in our case. We had around 150mm movement over 10m between daytime and nighttime which was unacceptable for such an expensive system.

However, the basement slab went in, as you can see above, and we now move on to building the walls up and getting the ground floor raft in. Fingers crossed for more good weather!!

We’ll be having a few open days in May once the timber frame is up so anyone who wants to visit and see first hand what we’ve been doing let me know.

And from the nice green and leafy picture below to this:-

This is however great!! After 15 months tinkering around with the design of the house we have finally demolished the old house and started the digging process. Apparently we are going to be digging around 2000 tonnes of soil out to make way for the basement and the floor rafts for the house and office, all of which are intended to stay on site. We’re fortunate in that the subsoil is very gritty and well drained so is ideal for non-structural fill.

The Isoquick flooring insulation is on order now and should be arriving around mid-March ready for us to pour the basement  and office slabs first.

Theoretically we should have a feed from the site webcam soon and so should be able to post time-lapse video of the progress. I do however suspect this will be largely dependent on my technical ability and how I get on with the software so don’t hold your breath.

Again, just a quick post to say that we will be exhibiting at the REGEN SW show above on the 8th of March at Westpoint in Exeter. The tickets to enter are normally £25 + VAT each but if you quote ExhibitorGuest as the discount code then you’ll be entitled to a ticket for £10 + VAT.

You can see more info HERE

If you follow the link and click the book now link then enter the discount code ‘ExhibitorGuest’ you’ll get the cheap tickets.

See you there.

This is probably going to be one of my shorter blogs as the video says it all for me really. Kevin McCloud talks about the project he was involved with in Swindon called ‘The Triangle’ (for obvious reasons when you see the site plan). 

Kevin recently presented a Channel 4 documentary about the scheme which was, I thought, remarkably honest about how the scheme ran. It was not an easy build and was hampered by the weather, the main contractor and the attitudes of some of the construction site workers which could be described as negative at the best of times. Unfortunately, the attitude of the construction industry is still the biggest barrier to environmental change.

However, it is rather handy when you have industry celeb’s like him singing the praises of materials like hemp. Keep singing Kevin!!!

We are now embarking on what is turning out to be an interesting and enlightening project. We’re building a Passiv Haus certified bungalow (although 40% of the house has a basement). This may not sound like much but as I am finding out, Passiv Haus works much better on two storey buildings as the surface area to volume ratio is far more favourable.

Some people think Passiv Haus is a very extreme level of construction (in terms of thermal performance and detailing) and not really necessary. Whilst on some levels this may be true for mass housing, the benefits of going through the process for a bespoke project are numerous. Because of the level of detail required by PHPP (Passiv Haus Planning Package) it encourages the designer to ensure that virtually every element of the build is designed and thoroughly considered prior to the project going to site. This is very important for the person paying the bills as it enables the contractors involved to price very accurately.

To get our building to achieve the estimated 15kWh or less required by PH we have had to bring the U-values of the walls down to just under 0.1 W/m2K. This has resulted in walls just over 500mm thick in total, which actually suits us as we have lived in a Cob house for the last 11 years and so we are used to very thick walls.

The original idea was to use Tradical Hemcrete with a layer of Unger-Diffutherm wood fibre insulation on the outer face to give the building a good level of thermal mass. However, as the design was progressing WARM Associates (our Passiv Haus assessors) were indicating the likely U-values would be below 0.1 W/m2K meaning that the initial design would end up being around 700mm thick and costly too. In the end we settled on using 300mm of UdiFLEX flexible wood fibre insulation in between the studs of a timber frame and then 140mm of UdiSPEED and Diffutherm over the top of the studs. This will be externally rendered with the UdiPERL self-coloured render.The roof will be much the same make-up as the walls but with UdiTOP sarking board over the top of the joists.

To counteract the loss of thermal mass by not using Tradical Hemcrete we have opted to use 22mm clay boards on the ceilings throughout and also in all of the internal partition walls. The clay boards are good thermally but also extremely good acoustically, between 4 and 8 times better than a solid 100mm concrete block wall.

In a slight break from using our own products we are using Logixx Polystyrene ICF blocks (Insulated Concrete Formwork) to construct the walls of the basement and also the whole floor slab will be on 300mm of Isoquick Polystyrene insulation. Before anyone asks, No, we can’t do it on LECA or on ‘something more natural’.

Sadly, the existing bungalow on the site is not practical for us and so will be demolished shortly after Christmas when the main works start. Anyone wanting some exercise with a sledge hammer is more than welcome to contact us!!!!

Over the last few years we have seen most of our sales going in to new build projects which has been very exciting and rewarding to watch. However, this year there has been a marked change in the type of projects we are involved with. This is partly due to a greater focus in the media and from government on retrofit and possibly because the recession changes peoples desire (and ability) to build new properties. We have also been quietly moving more in this direction too, with help from Unger-Diffutherm and their comprehensive understanding of how wood-fibre insulation can help improve existing buildings in a major way.

The UdiRECO product enables wood-fibre to be installed directly on to masonry substrates without (normally) the need to flatten them out to create a surface that these fairly rigid boards can be fixed to. This is often done with expensive plasters, creating quite a high system cost. We have seen great traction in the market this year for this product and since the TSB Retrofit project in Yorkshire, we have now got some very exciting projects on site.

There are several projects underway around London using the UdiINRECO system (the internal version) to thermally upgrade existing Victorian housing as part of an overall refurbishment. We also have great interest from those involved with barn conversions, of which there seem to be many in Wales. The UdiINRECO system is very effective when used in this situation as, with the use of Unger’s UdiMultigrund VCL plaster, it deals extremely effectively with any moisture in the walls of the building but also ensures that the building maintains good levels of thermal mass/inertia due to the high density wood-fibre boards used on the surface of the product.

Lets all get retrofitting the easy way!!

We have had a very exciting year with some excellent projects coming through. Somerset House in London has been a great project to be involved with as it has been interesting working with BDP architects on the design and then working with the contractor, Simplicity Mouldings from Dartford, helping them to design practical ways to install the systems.

As with all old buildings, Somerset House has been added to and altered a great deal over it’s lifetime and so the structures within the building in to which the Unger-Diffutherm wood fibre products had to be installed were extremely awkward. The roof structures are made from timber of no particular dimension or position and so every piece of UdiTOP and UdiFLEX has had to be cut individually and with around 1000m2 of roof, that is no mean feat. Simplicity Mouldings have been a pleasure to work with as not only are they open-minded about the materials they are using but they are also diligent and thorough in the way they installed the products. Consequently, the finishes they are achieving on the clay boards is excellent and the interior of the building is looking better than ever.

We have also supplied large quantities of Unger-Diffutherm systems to the UK’s largest Passiv Haus scheme in Dorset. Perryfields is a mixed tenure scheme consisting of 72 flats in 13 blocks, which will all be certified Passiv Haus and are a mixture of render and Portland Stone finishes. Again, it has been a very interesting process working with the architects and contractors in creating the correct detailing for openings, ensuring that a robust solution is found for what is a fairly exposed site overlooking the sea. So far four of the five blocks constructed to date have all used the Unger range with great effect.

This project has also enabled us to gain approval for the some of the Unger-Diffutherm systems from Premier Guarantee, one of the UK’s largest New Home Warranty providers. This was a simple process as all that was required was translation of existing European documentation along with an examination of the very thorough detailing provided by Unger.

This is a site that would be very worthwhile visiting for anyone involved in sustainable construction. The way these buildings are designed has meant that they are quick to build but more importantly, very cost effective. The costs for this project are in the region of £1050 per square metre, less than many conventionally built properties. Most people are used to seeing prices almost double that figure for Passiv Haus, so it is quite refreshing to see a scheme that enables everyone to live in a low energy home.

Finally, we have our seasonal crop of Tradical Hemcrete projects. Cornwall Air Ambulance are building the charity wing of their new hangar with Hemcrete and we have 6 other individual house building projects around the South West and as this is the South West we do not tend to get too many bog-standard buildings. We have some very interesting designs, some with oak timber frames, some with local stone cladding and some very contemporary designs.

Although my blogging has been rather sparse of late there has been a lot of activity over the last 4 months since. We have become involved in some fantastic and very interesting schemes where we are supplying Unger-Diffutherm wood fibre insulation.

The East wing of Somerset House in London is being completely refurbished with BDP as the architects and Wates as the main contractor and us/Unger-Diffutherm providing the insulation solutions. The brief was to provide roof insulation to this Grade 1 listed building without removing the exterior covering and without any possible detriment to the structure. It has been a very interesting process working towards finding a solution that satisfied the client, the architect, TRADA and the contractors involved but with a lot of work and site visits from Sabine Groeneveld et al from Unger (and us of course) we have finally achieved it.

The historic status of this enormous landmark on the Embankment meant that removing the original roof covering was not an option and so a solution applied from the interior was the only answer. The fact that the roof has no felt/membrane and that it occasionally leaks made a realistic solution all the harder. But, after a few changes in design and many condensation risk calculations a working solution was found.

Those involved with historic buildings will be aware that whilst a building has no insulation all of the heat that is lost through the walls keeps them dry. As soon as you insulate you have be careful of how moisture moves through the structure and prevent it from causing any damage. Through the unique properties of wood fibre insulation this is achieved along with high levels of insulation, resulting in a 95% reduction in heat loss.

This project demonstrates well how simply selling an insulation system with basic understanding is not enough. You need to be able to rely on a whole team of people with the experience, understanding and technical knowhow to ensure that what is proposed is the best solution without the risk of damage to the building. As they invented wood fibre ETICS, Unger-Diffutherm have this in spades!!

If all of the above wasn’t good enough we are also supplying 850 m2 of EBB clay boards to line the inside of the roof structure, 600 m2 of which are their amazing Phase Change Material (PCM) boards. These boards will be fixed to the interior of the Unger system above and drastically reduce the effects of solar gain during the summer months, preventing the building from going over 23 celcius. This is going to be finished with a lime plaster by Simplicity Mouldings, a company specialising in this type of high-end refurbishment project.

Well done to all!!!

This year we seem to have broken from the tradition of awful, wet, mild weather driving on into December being followed by a sudden plunge in temperatures with lots of frost. It is November the 26th and it is now, definitely, cold!! The up side is that it is now dry and the projects that we have supplied large quantities of Unger-Diffutherm Wood Fibre Insulation Systems to can push on without getting so wet.

Once again we have had another very busy year with turnover in the last 8 months 10% higher than for the whole of last year. I say this not to boast (as our turnover is barely a drop in the ocean of the construction industry) but to highlight the shift towards the very high performance and ecologically sound systems that we are supplying. It also highlights the realisation from the professionals within the industry that these products enable us to simply and economically achieve the high levels of performance now required for new construction.

Much of the Unger-Diffutherm we are supplying is going in to Certified Passiv Haus schemes which are now beginning to pop up far more regularly, which brings me on to my next point, the disparity between what is required and what is affordable. Passiv Haus as a standard has gained far more credibility than high levels of the CSH, mainly because it is a very well defined and established standard, but it is being promoted as a premium product that only the wealthy or those with a lot of foresight can afford.

Whilst the design side of Passiv Haus is rather more rigourous than for a standard build, the construction side is actually, potentially, very simple. The build can consist of a simple timber frame filled with UdiFLEX with an OSB inner face with the UdiFRONT system fixed to the outside. No vapour barriers, no airtightness membranes, no complex detailing. Schemes that we are supply the UdiFRONT and UdiTOP systems to are managing to build at a cost comparable to normal construction at around £950 sq.m of floor area.

Occasionally, it takes these times of austerity to change. Applying a bit of thought to a situation can create far better solutions without the need to throw vast sums of money at it. Those involved in these projects are true pioneers, showing that it is possible to change that way we build for the better and that it can be done within the confines of a normal budget. There really are people out there, doing large scale construction, who are conscientious and diligent enough to do it.

Change is good!!!! Honest.

The first HEARTH housing scheme is under way. The scheme uses Tradical Hemcrete as the walling material and a very adaptable, forward thinking design to create code 5 housing.

HEARTH started as a philosophical idea in April 2009 and with some technical input from Back To Earth, it is now a fully-fledged programme, with a pilot in construction in Swindon, and other projects in the pipeline at locations across the UK.

The first scheme in Swindon consists of two terraces of 6 and 7 units built to CSH level 5. Each unit has an Air Source Heat Pump supplying heat to underfloor heating. There is also MVHR and triple glazing to ensure the lowest energy usage possible.

The scheme has generated enormous amounts of interest from future tenants, Swindon Borough Council, architects, developers and other RSL’s interested in reproducing the scheme elsewhere in the country. Back to Earth, Lime Technology and various other companies involved in the scheme have held many site visits to show off the Tradical Hemcrete, the systems within the development and also the development as a whole.

Due to the size of the scheme all of the Hemcrete was mixed off site in a concrete lorry and trucked to site in 6 cubic metre loads. This was tipped into bulk bags on site and then lifted to the point of placement with a Telehandler. This allowed the team to regularly install around 18 cubic metres of Hemcrete in a day, equivalent to around 60 square metres of walling.

The Hemcrete has all been installed now and the renders are being applied as I write this. The project is due for completion by the end of the year.

This is one of many schemes under way at this time, totalling around 300 houses. Next year is set to be busier again!!!