Acoustic Insulation

Having blogged previously about the many attributes of our natural insulation products beyond just thermal insulation I thought I’d elaborate more on each attribute. Because of the types of materials we use and the ways in which they are produced many of them have excellent acoustic absorption properties which make them ideal to use in areas where acoustics are important.

Our primary focus is on thermal insulation and reducing heat loss to a minimum is always at the top of list of requirements. However, with the increasing focus on much more open plan living we are encountering more and more problems with acoustics. Large open spaces inside buildings with hard surfaces can cause long reverberation times which can make speaking and listening difficult and make these spaces quite uncomfortable to spend time in.

Our Unger-Diffutherm wood fibre boards have an excellent capacity to absorb sound, so much so that they can be used between rooms or within walls and ceilings to keep buildings quiet. They can also be used on the surface of walls and ceilings to absorb sound as a retrofit measure.

Our UdiTOP and UdiFLEX wood fibre insulation systems are used in roof constructions, especially where the living space is partly or wholly within the roof structure, to keep the sound of the wind and rain out. It’s one thing to hear the gentle sound of the wind and rain outside and another to hear every drop of rain pounding on your roof tiles like buckets of ball bearings hammering down!! One thing that people often notice inside wood fibre insulated buildings is how quiet it is even when the rain is pouring down or the wind blowing a gale. Bizarrely, you can hear birds quite well through it so you actually create quite a relaxing sound profile inside!!

Although not a thermal insulation product, our EBB clay boards are phenomenally good at absorbing sound and are used (probably surprisingly) in between bathrooms and adjacent rooms and also to keep bedrooms quiet. They are a relatively lightweight way of ensuring an excellent sound break between adjacent rooms and also between floors. In terms of numbers, a 100mm stud partition, filled with UdiFLEX wood fibre wool, with a layer of 22mm EBB clay board on either side has around 4 times as much sound absorption as a solid concrete block wall (-63dB reduction), nearly 4 times what is required by Building Control for party walls.

Finally, for floors, we have our Cemwood products. This material can be laid at around 50mm thick and in conjunction with a 20mm layer of UdiTHERM and a floating timber floor on top provides a very effective sound break. Because this is a ‘loose’ material it absorbs vibration very well and so impact noise from walking is prevented as well as airborne sound. It can also be ‘poured’ in to timber stud walls, again absorbing vibration and sound very effectively.

So, when designing buildings where acoustics are important (which is basically anywhere you have people trying to talk to one another) it useful to consider whether your insulation materials can keep the building quiet as well as warm. If you’d like to discuss this more and see how we can help you please contact us.

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Why use natural fibre insulation if it is more expensive?

This is a question we are asked pretty regularly. Understandably, if you think that insulation is a one-dimensional issue then why indeed would you spend extra on anything but the cheapest, highest performing insulations available?

As with everything in life it is not that simple. There are several areas to consider in addition to the thermal performance and they are the heat capacity (thermal mass), the ability to store and transport moisture, acoustic performance and finally ease of construction. Natural fibre materials, such as wood fibre insulation perform well in all these areas creating a much more pleasant environment within buildings. They also tend to perform at or beyond the target levels of insulation because they are simple to use, they can be installed simply without barriers or ventilated cavities and they use moisture to actually improve their thermal performance.

Heat capacity or thermal mass is a property which is continually being shown to be beneficial. In the winter months it creates a much more stable environment and so heating systems can work at much steadier (and therefore more efficient) rates. In the summer the mass can not only absorb excess heat but it can delay penetration into the building, again creating much more stable and comfortable conditions inside. This can reduce the amount of heating required by up to 20% in buildings with high thermal mass.

Moisture storage and transport is an increasingly important topic as we begin to internally and externally insulate our existing buildings. We live (in the UK) in a maritime climate with some extreme rainfall but we also produce huge amounts of moisture inside our houses from bathing/showering, cooking and just breathing! In addition to this we generally have poor ventilation rates which combine to allow lots of moisture to flow into our walls. Without insulations that can store and transport moisture mould can grow, timber can rot and structures can decay. Again, natural fibres are used to store and transport moisture in plants and do so as insulation without affecting their thermal performance. In some cases the performance is enhanced by this low level humidity.

As more lightweight buildings are built and more super lightweight insulation is used acoustics get worse. Sound transmission (or lack of it) makes a big difference to our sense of privacy and comfort within our homes and noise is a major source of stress. Wood fibre insulation is one of the densest forms of insulation available and is excellent at absorbing sound, creating a quiet, warm inside space. This is ideal for high density housing or attic spaces. Interestingly, the lower frequency sounds are absorbed more readily than some of the higher ones, meaning you can still hear the birds sing outside!

Finally, ease of installation is vital so that what is designed is actually what is built. The biggest problem with very low conductivity foam insulations is that they are rigid and are very difficult to install correctly on a building site. Unless they are in complete contact with the surface they are insulating they do not work as expected. So much so that studies have shown with a 3mm gap between the board and the insulated surface (inner blockwork leaf or interior of timber frame panel) you can have 150% more heat loss and with a 10mm gap you can have more like 400% heat loss. Looking in to many cavity walls it is rare to see less than a 10mm gap between the inner leaf and the insulation hence the very poor performance of most cavity walled buildings.

With many natural fibre systems the walls are designed to be solid, with no cavities as there is no likelihood of condensation forming (one of the purposes of ventilated cavities is to remove the condensation which forms). Even systems which are used in exposed locations are solid walled but use the correct combination of vapour control and vapour permeable renders to prevent rain penetrating but allow moisture to be released from the structures. Because of the simplicity with which these structures are built the performance of the finished buildings is normally at or beyond required targets.

If you want to see how walls can be insulated with natural fibre insulations like wood fibre see the details on our Resources page or get in Contact.

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Beyond Ecobuild

Ecobuild 2014 was great for us!! We had 3-400 people visit the stand over the three days and some of these people had very exciting projects that they want us to get involved with. They range from small extensions up to housing schemes of several hundred houses so a real spread.

Once again our unique range of products proved interesting to visitors and even though we had a small stand in amongst some giant ones, we had lots of interest (you can feel somewhat inferior next to the likes of Dulux who spend over £100,000 on their stand!!). We had lots of enquiries about the clay PCM boards, the Cemwood fill material, the Lithotherm and the innovative wood fibre insulation systems from Unger-Diffutherm, all of which will hopefully lead to some great projects.

The show itself had shrunk from the heady days of 2011 when the whole of ExCeL was used for the exhibition. That being said about 50% of that was solar panel suppliers from the far east so having it a bit smaller is much better and allows you to more easily see what is on show. However, it is still so big that you really can’t see it all in a day and several of our customers actually stayed in hotels over night to be able to see the whole exhibition over 2 days and also catch the seminars that were going on.

All in all we were really pleased with how it went but I am glad to be sat behind my desk again, in comfy shoes, on a soft carpeted floor, in a chair, not talking that much and not standing for 10 hours a day!! I also have to say a big ‘thank you’ to Sabine Groeneveld from Unger and Christian Nialki from EBB for all their hard work on the stand. I couldn’t have managed it without them!!

If you want to see our products click here to go to our product page.

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This year we will be attending the Ecobuild exhibition at ExCeL in London. It is, according to the organisers, the worlds largest sustainability exhibition and is also the UK largest building exhibition. We’ll be at stand S212/3 if you want to come and see us face to face!!

We have some new wood fibre products to show plus a new material called Cemwood. This product is made from mineralised wood chips and comes completely dry in 50 litre bags or in bulk bags. It can be used for cavity wall insulation where EWI is going to be added, it can be used as a levelling fill under flooring or Lithotherm systems and it can be used as floor insulation as it is load bearing.

In years gone by we were great promoters of Tradical Hemcrete and although it is a great material the drying of the walls can be an issue. Cemwood is dry, has as good thermal conductivity (0.07 W/mK), it has higher heat capacity (2100kJ/kg) than Hemcrete and it also has higher density (300kg/m3) making it a very exciting product to use. We’ll have a few examples of how to use it on the stand.

This year I notice that the overall size within ExCeL has been reduced by at least 25% which is partly a sign of the reduction in exhibitor numbers (probably due to the recession cutting people’s budgets) but it will make it less daunting for visitors. The show is better zoned this year with similar types of exhibitors encouraged to stay in their suggested areas. This will help those interested in any specific topic more able to see all the relevant companies in that sector rather than having to navigate the vast arena trying to find individual companies.

For those of you who come along, I look forward to seeing you. For those of you who don’t, you can still share our excitement by getting a 10% discount from purchases through our online store via the Ecobuild page on our website.

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We are ‘Go’ with ECO

Finally we have got the go-ahead to supply our first ECO scheme in Manchester that Carbon Co-Op have been involved in creating. They have canvassed local householders and created a group of 13 home owners whom will now have insulation retrofitted to their Victorian brick homes. Carbon Co-Op have also been offering the 200mm UdiFRONT system from Unger-Diffutherm as one of the options and 10 of the 13 houses will be using this system. A great boost for us!!

The 200mm UdiFRONT system will bring U-values down below 0.2 W/m2K and in conjunction with airtightness work, internal insulation, replacement windows, loft insulation, etc. will massively reduce the energy consumption of these refurbished homes.

The design for the systems was carried out by UrBED who have had a challenge on their hands. When undertaking these schemes, it is important not to underestimate how much work there is on detailing!! Basically each of the 13 houses has had to have it’s own detail for almost every junction and section due to the differing shapes and sizes and restriction on each house. This is why the bigger, commercial schemes so far have been on houses or flats, all of which are essentially the same.

Training on site starts in mid February with the work due for completion by the end of March. Hopefully we’ll have some nice photos to follow!!

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Passivhaus carbon emissions

There is a perception that Passivhaus buildings use hardly any energy because of all of the insulation they contain. Whilst this construction standard provides unrivalled comfort and massively reduces the heat load required it does not necessarily mean the house uses much less energy for anything else.

In a conventional house the heat losses during the winter months are such that you need a significant amount of heat input to maintain a sensible temperature internally. Even when it’s not that cold outside the strong winds that we’ve been having mean that lots of heat is lost from drafts. Additional gains from the sun and waste heat from appliances are relatively insignificant and so are mostly ignored.

At Passivhaus levels of insulation and airtightness the amount of additional heat energy required is minimal (so far this winter the Silverton Passivhaus has used 260kWh of heat or about £13 worth of gas). However, this is not to say that no heating is required at all as you do still need to heat and you still need energy for appliances. It is simply that everything else done inside a building that produces heat becomes the heating instead.

From one angle this is obviously a big benefit as the carbon emissions from each dwelling can be reduced enormously but with a large caveat. Gas is widely used for heating and, in a modern condensing boiler, has the lowest carbon emissions per unit of heat produced of any of the fuels.

In the move towards ever more energy efficient buildings we are becoming more and more dependent on electricity as an energy source. Modern homes are ever more packed with electrical devices for security, ventilation and environmental controls, all of which demand ever more electricity and create a much higher base load for the building. We are at risk of substituting low carbon heating energy for much ‘dirtier’ (from a carbon perspective) electricity in the drive to lower our heating bills.

Grid electricity currently produces around 0.55kg of CO2 per kWh and natural gas produces around 0.185kg per kWh. To illustrate the point, the average UK home consumes 16,900 kWh of gas and 4000 kWh for electricity. This would give a combined CO2 production of 5326 kg. Whilst me and my family may not represent an ‘average’ household our gas usage has reduced to around 7000 kWh but our electricity is around 10,000 kWh. This means that our energy usage produces 6795 kg of CO2.

Our heating/water heating requirement now costs about 75% less than our old cob house (which was also 1/3 the size of the new Passivhaus) but our electricity bill is slightly higher, even though we have LED lights everywhere and A+++ rated appliances. I assume this to be because of the higher base load from ventilation and control gear which we hadn’t anticipated.

To summarise, Passivhaus and other low energy standards provide un-rivalled levels of comfort and vast reductions in heating requirement but they do not necessarily provide the reductions in CO2 emissions that one might expect.  Unless the design is kept simple and the temptation to install the (often vast) array of controls and systems that are stuffed into ‘Low Energy Buildings’ is resisted we may not be reducing our impact as much as we think. Until grid electricity becomes cleaner and lower carbon we should rely on it rather less to achieve our goals.


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Unger Licensing Course

Today (4th December) we’ve finished another very successful Unger licensing course. This is a two day course on all of our Unger-Diffutherm wood fibre insulation systems and was the first time we’ve used our new office for these events. Amazingly, it all seemed to work very well with everyone well fed and watered in between each theory and practical session.

The course is fairly intensive for our participants and is a mixture of learning the theory behind the products and the practical installation of them. Sabine Groeneveld from Unger (and NaturePlus) in Germany came over and discussed in depth how the systems work, how it is so important to be able to manage moisture in buildings (especially in our maritime climate) and also the importance of correct detailing with all of the systems (again, because of our maritime climate!!).

Each time we run the courses I am amazed by the level of detail that Unger use to ensure that the systems work correctly and do not get damaged or cause damage to the building to which they are fitted. The thoroughness with which each component has been selected and how it is used is very reassuring, both for the installers and for me as a retailer. After all, we selected Unger a a supplier from the various manufacturers on the market because of this. They also innovate and put their money where their mouth is by offering their own 15 year warranty on some of the systems.

All of our participants came away excited and enthused about what systems they can use on current and future projects. They now have a realistic understanding of the complexities of installing insulation and how it completely changes the dynamics of buildings. These installers realise that you cannot just ‘slap it on’ and hope to achieve a decent, long lasting result and now have the skills to create high quality installations and can offer the Unger 15 year warranty.

Now that we have the new offices set up we will aim to run these installers courses as often as possible for those keen to understand these amazing systems and how to install them. If you are interested get in touch here and let us know. We try and keep the sessions to 5-6 people at a time so as everyone gets very hands on training and fully understands it all. We look forward to seeing you.

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As an addendum to my last post I wanted to add a few things. The first being that the whilst the Silverton Passivhaus is an exceptionally well performing building the occupants are still consuming fairly large quantities of energy. This appears mainly to be because of their 3 children who create large quantities of laundry and struggle with the concept of energy and water saving. The washing machine, tumble drier (yes, you can use one in a passivhaus so long as it is a condensing one) and dishwasher are in almost constant use which consumes a lot of energy.

The second point was pointed out to me by Christian Nialki from Clay UK. Passivhaus’s PHPP can still produce energy consumption estimates which are wildly different from the actual consumption. However, in all of the German examples monitored (there hasn’t been a large UK study yet) even the worst performing households are still excellent compared to existing housing stock. As he says, Passivhaus not only gives you exceptional comfort and low energy consumption but it gives you choice. You can set the thermostat to 18 in the winter and keep the windows closed or set it to 25 and open them. Even in the latter example you’ll still not be using as much energy as anyone else.

For more info see or contact us to discuss it more.

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Mind the Gap/SAP – Go for Passivhaus

There is a gap between real energy consumption and consumption calculated by SAP (standard assessment procedure), known as the performance gap. In spite of this sometimes enormous gap it still used by the majority of engineers to size heating loads for homes, boiler sizes and everything else related. The savings made by adding Solar thermal and solar electric are then put forward to show what massive reduction in energy use is going to be delivered.

In the paper cited in the last blog (A Comparative Study of the Effects of Thermal Mass in New Dwellings in Scotland by Janice Foster) two identical dwellings, one of high mass and one of low mass had their energy consumption monitored and then compared to their SAP calculations. Both buildings had identical architectural designs (design layout, U-values, etc.) and were in the same location and orientation and so SAP predicted the boiler heating load for both would be 20 kWh/m2/annum. The actual consumption was 67 kWh/m2/annum for the high mass building and 89 kWh/m2/annum for the low mass.

Apart from showing how thermal mass can benefit modern, highly insulated buildings by reducing heating requirements by up to 20% it showed the monumental discrepancy between calculated and simulated energy consumption. This is very worrying given that the output of SAP is pivotal in a lot of domestic scale decisions regarding heating and lighting and also policy decisions from government.

I recently looked at the SAP (2009) calculation for the Silverton Passivhaus building and again found a very significant difference between the actual and calculated energy performance of the building. However, this time the building was using at least 30% less energy than calculated rather than the norm of using significantly more. I say at least 30% less as SAP doesn’t include cooking in it’s calculations whereas the total energy figures for the house do.

Maybe it’s time we switched over to using rather more complex modelling tools, such as PHPP (the spreadsheet used to model Passivhaus buildings) which will actually reflect the real performance of a building in most cases. The situation we are currently in appears to be that in most cases SAP does not represent the energy consumption likely.

Admittedly the reasons for this are largely due to the generally poor build quality of UK housing combined with massively variable occupant behaviour. The build quality of Passivhaus certified buildings is much higher than the norm as without this they will not achieve the levels of airtightness required. Also, the simplicity and attention to detail with which they are designed makes building them much easier from the outset.

If we are to really push our 21st century housing in to the 21st century we need to design it, model it and build it properly. It is time we stopped being apathetic about the way our housing is built and demand houses that perform as designed and don’t waste energy. Afterall, it is as important to make the volume house builders build homes that don’t waste energy as it is to demand that the energy used to heat and light them is not exorbitant.

If you’d like to read more about (including the SAP calculations) the Silverton Passivhaus then see the case study here.

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Thermal Mass

I was sent a very interesting thesis entitled ‘A Comparative Study of the Effects of Thermal Mass in New Dwellings in Scotland’ by Janice Foster. The paper researches how thermal mass affects overheating in buildings.

Most people would intuitively say that thermal mass would prevent buildings from overheating by absorbing the excess heat from either solar gains or internal gains and in some cases this is true. However, as with all things related to buildings and people, it is not that simple.

First and foremost there needs to be adequate night time cooling to dissipate the heat stored from the day. If this is not present then the thermal mass will exacerbate the overheating by radiating heat in addition to the other gains. Secondly, to actually work the mass need to be thermally coupled with the interior of the building. Simply, this means that the mass is in direct contact with the interior of the building and not hidden under carpets, behind service voids or in the case of ICF, not behind a layer of insulation.

The thesis also discusses how thermal mass, used correctly, is more useful in the South and East of the country where there is more sunshine and the average temperature is higher. High mass buildings typically have an internal temperature around 2 degrees lower than lightweight buildings and so as the climate changes developers and homebuyers should be looking for heavier-weight constructions.

There were two surprising points within the document, both around the cooler end of the year. One was that high mass buildings can reduce heating requirements by a staggering 20% by simply reducing the fluctuations in internal temperatures and storing heat gains from the day. The second was the gap between real energy consumption data and that calculated by modelling software such as IES and SAP. On one building SAP calculated the energy consumption to be 20kWh/m2, IES was 35kWh/m2 whereas the actual consumption of the building was 89 kWh/m2. Such staggeringly inaccurate assessments, especially by a tool which is a mandatory requirement of building control, beggars belief. How on earth can we pretend to be able to model buildings and make informed decisions on how to reduce heat loss when the output of such programs is so monumentally wrong?

The final point to make is about orientation and the difference it makes to heating and cooling requirements. South really is by far the best orientation from an overheating and a heating requirement point of view. To see a copy of the thesis contact Janice Foster at

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