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QUESTIONS AND ANSWERS
We live in a traditionally built old stone-built houseand are currently planning a new extension to it. Keeping the existinghome warm in the winter is becoming increasingly difficult. What options are available to us in terms of insulating our home walls? And what materials should we consider for the new extension?
When thinking of your stone-built home, consider it your second skin. Your skin is breathable and carries out several functions so why your walls shouldn’t be doing the same for you? In permeable, traditionally built dwellings this can be translated into the right choice of materials. In the UK, moisture is one of the biggest features of our climate so let's embrace it instead of fighting it. Old buildings are great teachers for learning about naturally breathable and moisture-regulating permeable materials.
In the case of your stone house, it is important to remove any impermeable materials such as cement concrete on the walls to allow moisture to pass through freely. Cement, gypsum boards, plastic membranes and EPS, XPS, PUR, PIR insulation boardsor other impermeable materials have no place here. Bauwer insulation render and plaster regulate room humidity levels, absorbing and releasing moisture readily. Expanded Perlite is not only a great insulator it is also hygroscopic and able to purify the air in a room, for example removingodours. Bauwer insulation carries out multiple functions and creates healthy living environments, whilst also being ecologically sustainable and cost efficient product.
You can also use the same approach - treating your house as a living, breathing structure - in the new extension to your home by using similar natural materials which have been improved by modern technologies. An example for a masonry wall is the monolithic clay Porotherm block with a light weight structure, which has breathability and thermal mass attributes. It eliminates the need for the onerous cavity, ties and fixing of impermeable EPS insulations as used in the ubiquitous cement concrete block walls.
It is important to remember that traditionally built homes require breathable permeable insulation materials which performs numerous functions and benefits you most by creating a long-lasting healthy living environment.
Can I use impermeable insulation materials like EPS, XPS or Celotex boards for my stone wall cottage?
Practical experience of the repair and insulation of older buildings shows that the introduction of materials and systems that do not maintain permeability can seriously exacerbate existing moisture related problems and or create new ones. Examples of impermeable materials and systems which could give rise to problems include EPS, XPS, phenolic boards insulation, plastic vapour barriers, cement or acrylic based renders, cement pointing, non-permeable external wall paints.
Any of these used on an external wall can trap moisture within the wall and lead to damp and decay, as well as making the walls feel cold and ‘clammy’. Installed on the inside, they may do less damage to the building fabric itself, but will negate its ability to buffer moisture levels in the internal air. Both of these can significantly reduce comfort for people using the building, who tend to try to compensate by turning the heating up, thus wasting energy.
Clearly, if the walls are already damp beforeinstalling impermeable insulation these effects will beexacerbated. Under these circumstances it isparticularly important to allow walls to ‘breathe’in order to dry to the outside as effectively aspossible. Drying to the inside is significantly lesseffective, and may be unpleasant for users ofthe building.
Why it is critical to use permeable insulation materials in the solid wall insulation of older buildings?
Traditional solid walled buildings are often referred to as ‘breathing’ structures, meaning that they exchange moisture readily with the indoor and outdoor environment. Where insulation is introduced it is important that this characteristic is taken fully into consideration.
It is important to understand that moisture in solid walls comes from several possible sources:
•Water from rainfall: This obviously affects solid walls but not all internal damp is a result of penetrating rain. With the exception of extremely exposed locations such as on the coast or high ground, it is unusual for driving rain to pass through most solid walls in good condition. Normally it will only saturate the outer part of the wall, which will then dry out when the rain stops
•Rising ground moisture: This can be present in any solid wall which does not have a physical damp proof course. In such situations the moisture level is generally controlled by the ‘breathability’ of the material, which limits total moisture by allowing the excess to evaporate harmlessly away
•Moisture generated in the building: It is often underestimated how much moisture can be generated by people using a building, simply through breathing but also from cooking and washing. The permeability of external solid walls also significantly helps to buffer and control excess moisture and condensation from these sources.
Materials used in repair and maintenance must be selected with care to preserve this permeability. Impermeable materials can significantly impair the performance and trap moisture. Often this will also increase problems of damp and associated decay of the building fabric.
Could you please explain the differences in insulation of older homes vs more modern dwellings (with a cavity) insulation?
Most traditional buildings are made of permeable materials and do not incorporate the barriers to external moisture such as cavities, rain-screens, damp-proof courses, vapour barriers and membranes which are standard in modern construction. As a result, the permeable fabric in older buildings tends to absorb more moisture, which is then released by internal and external evaporation. When traditional buildings are working as they were designed to, the evaporation will keep dampness levels in the building fabric below the levels at which decay can start to develop. This is often referred to as a ‘breathing’ building.
If properly maintained a ‘breathing’ building has definite advantages over a modern impermeable building. Permeable materials such as lime based Bauwer insulation renders, plasters and limewash act as a buffer for environmental moisture, absorbing it from the air when humidity is high, and releasing it when the air is dry. Modern construction relies on mechanical extraction to remove water vapour formed by the activities of occupants.
As traditional buildings need to ‘breathe’ the use of vapour barriers and other impermeable materials commonly found in modern buildings must be avoided when making improvements to energy efficiency, as these materials can trap and hold moisture and create problems for the building.
How Bauwer is finished?
Using Bauwer Finish which can be ordered through us.
Is Bauwer insulated plaster applied instead of insulation boards and basecoats?
Yes, Bauwer Light is insulated plaster render. Similar to backing render plaster but with many more benefits, like thermal value, acoustic value, dehumidifying effects and fire resistance performances.
Can I use Bauwer Light internally?
Yes, Bauwer Light can be used internally and externally. Furthermore dependent on the project we can advise the best course of action to help you in the process.
Internally is it ok to use gypsum over the top?
Yes, but Bauwer Finish is a preferred skimming option.
I believe Bauwer finish is similar to other products I could use however it is not pre mixed? Can it be Spayed once mixed?
Yes, it is premixed and can be sprayed on (Mtec, PFT friendly), it is also cheaper and it has thermal and sound insulation effects.
We are based in Kent, do u have anyone spraying the product in our area?
Yes, at the moment we expand to all areas of the UK. We have many house owners’ requests that we direct to our partnersplastering companies.
How do the thermal properties compare to insulation boards and other insulated renders?
Bauwer Light insulation value is about 50% better vs our next rival Cecil EcoCork available from Mike Wye. Thanks to a monolithic structure even in difficult or curved areas, no thermal losseson cold bridges which you would find on insulation boards.Bauwer Light's true thermal value is 0.068 which is a bit lessvs impermeable petroleum based EPS, Celotex, Kingspan insulation boards....but it is vapour permeable and Eco-friendly. Also insulation boards might lead to humidity issues where as Bauwer has dehumidifying properties.
Is it breathable?
Bauwer is highly breathable as it is a light weightonly 280kg/m3 hardened density. Vapour permeability coefficient of Bauwer Light is a benchmark at µ = 4.
Do u have specialist beads to allow for 40-50 mm thickness?
Could be delivered on a request from our partners at Likov Ltd.
I should be thinking BauwerLight is direct replacement for insulation boards? Yet a thin coat system still needs to be applied over the top with mesh and the decorative finish?
Yes, that’s correct, Bauwer is the two layer insulation system. Bauwer Light is insulation layer and Bauwer Finish is finishing layer. With regards to external application, yes, mesh is required within the Bauwer Finish layer. Internally no need, unless difficult area, like window areas. After two weeks Bauwer Finish layer could be painted with a vapour permeable paint.
Are you the UK rep?
We are based at Liverpool but we also have branches in Cheltenham, Evesham, Bournmouth and Jersey. Bauwer Group Limited is a UK based and registered company.
But the product is made in Europe right?
Bauwer material is imported from Europe, made on the modern German built line for light weight mixes which we have overseen and hence brought the product to the UK. We are hoping to open a manufacturing line in the UK after market development and growth within the country.
Is the finish a gypsum product?
Bauwer finish is Lime, Cement and Perlite based.
Do I have to use Bauwer Finish or can I use something else?
Bauwer Finish is required as a finish layer over Bauwer Light. Any permeable decorative finish could be used on the top of Bauwer Finish. Bauwer Finish, like Bauwer Light, 'firm-up' quickly after application and don't like to be troweled much. It is possible to achieve a reasonably smooth and flat finish, better than Lime-Putty based render.
Is it more environmentally friendly compared to other products? I ask because in some cases people prefer it.
Eco-friendly Bauwer Insulation is based on naturally occurring volcanic mineral called perlite and therefore has excellent environmental and health credentials.Perlite do not emit any odours and are resistant to chemical and biological effects of environment. You could find perlite sustainability fact sheet as well as health aspects on Bauwer website at: