Tag Archives: Pro Clima

  • The worst building you can build by law

    "We live in an era when our homes have the potential to be energy efficient, comfortable and affordable places to live, despite ever-increasing fuel prices. In the past, it could be argued that we didn't know how to achieve this but today we have no excuses. Yet, on the whole, we continue to build new houses to a pathetic standard, and our refurbishments commonly concentrate on kitchens and bathrooms, rather than investing to provide warm and pleasant places to live without ruinously high fuel bills." this is an extract from the blog of Ben Adam-Smith a campaigning documentary filmmaker and creator of a film about poor quality building called 'The Future of Housing ' there is a short  clip below to help illustrate how poor quality construction can directly affect us all.

    There is mounting evidence to suggest that buildings that are being designed to achieve thermal performance standards, including standards set out within the current UK Building Regulations, are in some cases consuming in excess of 70-100% more energy than the predicted values.[1]

    Plus, some would say more worryingly, that the Building Regulations do not set an adequate base level of performance and facilitate the delivery of many buildings of poor quality into the UK housing market.

    But….don’t blame the Building Regulations they are not designed to deliver quality they are a set of minimum standards, all too often they are described, used and promoted as a benchmark; something to aim for:  we must remove the presumption prevalent in the UK that they provide some form of performance guarantee……….they don’t.

    The Building Regulations contain 14 individual sections that, in their own words, ‘contain the rules for building work in new and altered buildings to make them safe and accessible and limit waste and environmental damage’[2] nothing there about quality or performance then.

    airtight-house-diagramWithin the Building Regulations, Part L is the section on ‘Conservation of Fuel and Power’ which relates to the thermal efficiency/performance of buildings. This is important because it covers the building's potential (target) level of efficiency and therefore comfort, it also has implications for running costs and is linked to (largely erstwhile) carbon reduction targets.

    In particular section 43 of Part L deals specifically with a buildings air permeability, or airtightness, recognising this as a major factor in a buildings energy performance Interestingly the word “airtightness” wasn’t even a word used in connection with domestic buildings, until it was introduced and formalised (through building regulations in the early 2000s) and has now become a key part of Part L, section 43 goes on to describe how this the means by which a buildings efficiency can be measured. Compliance with Part L is mandatory throughout the UK[3] it applies to new buildings and certain types of work in existing buildings and is there to enforce minimum standards of energy efficiency.

    air-test-graphicAirtightness is measured as m3/ (h.m2)@50Pa given as the flow of air (m3/hour) in or out of the building, per square metre of the building internal envelope at a reference pressure of 50 Pascal’s between the inside and outside of the building.  Current Building Regulations require 10 m3/ (h.m2)@50Pa, for a new build property, that’s 10 cubic metres of exchanged air per hour at 50 Pascal’s. This is a low standard by anyone’s reckoning, examples of just how bad this is, in reality, are easily found. A new build terraced house with a tested result of 9.1 m3/ (h.m2)@50Pa passes Building Regulations but the tester pointed out (see clip below) that with external wind at an average of 20mph it would take just 6 and a half minutes to exchange all the heated air from within the building resulting in an expected increase in annual heating bills of around 50%.[4]

    The short video below is an extract from The Future of Housing which clearly illustrates the point made above, it's well worth a watch, most people who watch this have exactly the same astonished and angry reaction as the owner of the house.

    future-of-housing-clip

    So how do you reduce wastage and increase the energy efficiency of a building, in simple terms insulate well and prevent leakage..... and that sits right at the heart of what needs doing.

    In order to arrive at some basic elements that would apply to most building situations, we asked the technical team at Pro Clima if they could come up with a simple list of the “workhorses” of airtightness? Could they find six to eight products that would cover most eventualities? The answer came back as a resounding yes.

    First two very pared down observations about airtightness.

    • Airtightness is effected on the inside of a building, on the warm or internal side of the insulation; the function is to prevent leakage. Variously called vapour check, vapour barrier, vapour control, or airtight membrane
    • Wind and weatherproofing is effected on the outside of a building the function is to prevent adverse weather penetrating the building fabric and reducing the insulation's capacity to perform and prevent deterioration in the building fabric. Variously called vapour control, breather membrane, vapour open membrane, vapour permeable membrane, vapour open underlay and sometimes additionally described as being diffusion open.

    air-movment-and-insulationTogether this ‘wrap’ for the insulated layer allows moisture control geared to our climate with protection from the elements on the outside and leakage prevention on the inside. The airtightness won’t increase the U value of the insulation but it does ensure that the insulation functions to its optimum performance and more likely to achieve designed U Value. It cannot be overemphasised that airtightness and vapour control go hand in hand they work together to solve different problems.

    Airtightness means designing and installing a continuous seal around the internal fabric of the external envelope to eliminate unwanted draughts. Once the airtightness layer is in place and sealed with flexible and durable tapes, seals and glues, it ensures that the insulation functions to its optimum performance, saving energy and drastically reducing carbon emissions for the lifetime of the building. The airtight layer also ensures that interstitial condensation risk is minimised, ensuring no structural damage from moisture, mould, rot and damp.

    Here is the workhorse list

    1. Internal airtightness membrane Intello Plus
    2. External roofing membrane Solitex Plus
    3. External wall membrane for use with timber frame Solitex Fronta
    4. Universal jointing tape Tescon Vana
    5. Sealing tape for windows Tescon Profil
    6. Sealing tape for masonry and integrating into plaster Contega Solido

    Six products that cover pretty much all the basic requirements, there are various accessories such as grommets, stoppers and glue that will be required but the bulk of the work is done with these six products.

    How to use these products is neatly described in our “Making Airtightness Simple” [sic] guide available to download here

    If you start with the basic principles and keep the products to a proven few then you will be less susceptible to industry ‘noise’ creating confusion or quandary over what product to choose. It would be disingenuous to say the there won’t be times when technical advice is be needed and that is easily available through our technical support team. What it does mean is that for those manufacturers who do it well and make it look simple, take them on trust you are benefiting from years of robust and thorough testing and R&D arriving at a proven and purpose specific product. Their expertise should be your comfort.

    Our thanks to Ben Adam-Smith at Regen Media for his quotes and permission to use a clip from the programme see the whole film by clicking here

    [1] Lessons from Stamford Brook, Understanding the Gap between Designed and Real Performance, Evaluating The Impact Of An Enhanced Energy Performance Standard On Load-Bearing Masonry Domestic Construction, Partners in Innovation Project: CI 39/3/663, Report Number 8 – Final Report, Leeds Metropolitan University

    [2] DCLG Policy paper 2010 to 2015 government policy: building regulation

    [3] Check local variations for Scotland, Wales & Northern Ireland

    [4] The Future of Housing Paul Jennings 2016

  • Adhesive tapes: how do they work, what should they be able to do, and what can they do?

    Why do adhesives stick?

    Considerable lengths of various adhesive tapes are used when sealing buildings. A typical application is seen in the photo where tapes are being used to seal and connect an internal airtight membrane.

    Adhesive tapes are used as bonding aids in a wide range of applications in the creation of airtight building envelopes. Several hundred metres of tape is often used on a single building! Adhesive tapes have become established as bonding agents for these applications (just as nails are the standard solution for timber structures). They have to fulfil their functions for a number of decades to ensure that the building in question fulfils the standards expected by the energy consultant and by the building client. This article provides an overview of adhesive technology and the key properties of adhesive tapes typically used in construction.

    Aren’t all adhesive tapes the same?

    This illustration shows the various forces that act in an adhesive bonded joint. Cohesion refers to the internal strength of the adhesive. Adhesion refers to the sticking force to the subsurface. As a rule: the higher the adhesion, the lower the cohesion. An optimal balance between cohesion and adhesion is crucial for permanent adhesion. (See information box 1 with regard to adhesive tape tests on construction sites)

    Adhesive tapes might appear similar or even identical at first glance: when you compare different products, they all have a backing material. Depending on the planned application for the adhesive tape in question, this backing material may consist of paper, plastic film or fleece. An adhesive substance has been applied to the backing, and this adhesive substance is covered by a protective sheet or protective paper on the underside of the tape. The various types of backing facilitate different areas of application. For example, a tape that can be used both indoors and outdoors must have a UV-stabilised backing; an adhesive window-sealing tape must have a fleece backing that can be plastered over. The difference is easy to recognise. However, if you consider the adhesive substance itself, the difference is not so easy to identify. A review of data sheets is often of little help in this regard, as they generally only specify limited technical data – and this data is also difficult to compare.

    Adhesive tapes for the creation of air-tightness are generally manufactured using two main production methods. The majority (around 80 – 85%) are produced as dispersion adhesives. In this process, acrylates dissolved in water are applied to the backing material in a liquid state. Emulsifiers are added to the dispersion to ensure that the dispersion remains homogeneous and that the acrylates dissolve in water in the first place. The function of these emulsifiers is to attract water. The water is then evaporated in long drying tunnels later in the production process. The dissolved acrylates bond with one another, form long chains of molecules and become »sticky« as a result. The emulsifiers remain in the adhesive film, but no longer serve any purpose.

    A more exclusive group of adhesive tapes is manufactured using a solids-based adhesive containing pure acrylate. This production technology is relatively new and more laborious from an engineering viewpoint compared to the process used for adhesive tapes with acrylate dispersions. The adhesive is applied to the backing material in the form of a viscous mass and the individual acrylate molecules are cross-linked by the controlled addition of energy in such a way that the desired adhesive properties are created.

    Honey and stone, or adhesion and cohesion

    Honey has high adhesion – it sticks immediately to every surface. However, its cohesion is low, which means that honey drops off the surface under the action of its own weight. Stone is the exact opposite: it has high inner strength, i.e. cohesion, but has no adhesion and therefore does not stick to surfaces.

    Adhesion and cohesion can be demonstrated very well by comparing runny honey with a stone. Honey exhibits good adhesion and sticks to surfaces very well as a result. However, its inner strength (cohesion) is so bad that it runs off in drops under the action of its own weight. A stone has high inner strength, i.e. cohesion, but very low adhesion. Good adhesion is generally associated with poor cohesion and vice versa. A good adhesive tape results from an ideal balance between cohesion and adhesion.

    Why do adhesives stick? Sloths, squirrels and geckos

    These photos show how strength builds up over the course of contact time. An adhesive tape was employed here that can be used for interior air sealing and exterior wind sealing. The initial adhesion – after 20 minutes – can be seen on the left; the significantly stronger adhesive bond after 24 hours can be seen on the right.

    Let us consider the interesting question of how and why an adhesive tape is able to stick things together. The bond with the substrate is achieved using various mechanisms. Sheeting or a pane of glass may appear smooth at first glance, but their surfaces actually look very different – with hills and valleys – when viewed under magnification. The adhesive flows around these structures and claws to the surface like a squirrel on a tree or grips the surface like a sloth wrapped around a branch.

    If the adhesive is in direct contact with the surface, attractive forces – so-called Van der Waals forces – will result between the two elements at a molecular level. The closer the adhesive comes to the surface, the more these forces will come into play and increase the strength of adhesion to the substrate. A similar principle applies with the gecko, which is able to walk upside-down on smooth surfaces such as panes of glass. This is made possible by a large number of very fine setae (hairs) on the feet of geckos, which increase the contact surface and thus facilitate sufficiently strong adhesive forces.

    Take your time: the build-up of adhesive force

    It can take some time before an adhesive has flowed into a subsurface fully and established a strong bond with it. Adhesive strength is generally built up over a period of hours. The reason that all manufacturers recommend that their adhesive tapes should be pressed into place can be explained by the mechanisms described above: an adhesive must be brought into close contact with a subsurface to be able to flow around and surround it.

    A drop of water brings clarity – The influence of surface tension

    There is a commonly held myth that an adhesive should be able to stick to every surface. And if an adhesive bond doesn’t hold as desired, then it’s always the adhesive agent’s fault! However, this assumption is false. Nobody would think of taking two pieces of sawn timber, applying wood glue to them, pressing them together briefly and then pulling them apart again immediately, and then saying that the glue was responsible for the fact that the bond didn’t hold.

    Surface tension of foils: the low-energy surface has few attachment points and a low surface tension. It is not able to pull the water drop out of its shape. The more attachment points there are, the more energy the surface has and the more the water drop will be pulled out of its round shape as a result. High-energy surface: The liquid spreads across the material.

    The quality of a given bond is always dependent on the bonding agent, the subsurface and the method of applying the bond. The release films used are evidence that not all foils are suitable for adhesion: some adhesive tapes can be easily removed from their release films. On the other hand, there are films that tapes bond well too, but which then become detached under tension. Finally, there are also films that adhesive tapes cannot be removed from at all. The surface tension of membranes is responsible for all of this. This tension describes how well a given membrane can be ‘wetted’ by an adhesive – in other words, how well the adhesive can get close to the surface of the membrane to be stuck. The surface tension of a membrane cannot be seen, and this value is specified in data sheets by a few limited number of manufacturers.

    Water drop test

    Silicone paper: Surface tension: < 30 N/mm. Very poor surface wetting. Very hard to stick for this reason.

    Weak wetting and a poor adhesive ability for this PE airtightness membrane: approx. 35 N/mm

    Double-layered airtightness membrane: Very good wetting and good adhesive ability, as the surface tension is greater than 45 N/mm.

    How can one estimate surface tension on a construction site? One possible method here is the water drop test: a drop of water is placed on the surface of the membrane and it is observed how well the drop of water spontaneously wets the surface. The greater the surface tension (surface energy) of the membrane, the greater the likelihood that the water drop will be pulled out of its “drop” shape. This indicates a stronger and more reliable adhesive bond with an airtight membrane.

    Of course, this test does not provide precise information, but it has proven useful in practice over a long period. Membranes with a surface tension of > 40 N/mm are recommended for permanent airtight adhesive bonds. Membranes with surface tensions significantly below this value are often used in building practice. In order to supply the market with adhesive tapes that can still stick to these lower-quality surfaces, large quantities of resins are added to acrylate dispersion adhesive tapes, in particular. These resins stick aggressively to poor surfaces. However, the problem here is that resins can oxidise with oxygen, become brittle over their service lives and lose their adhesive strength. To prevent this from happening, it is recommended to ensure that adhesive tapes that only contain pure acrylates are selected.

    As well as being used for adhesive bonds for membrane overlaps, acrylate adhesive tapes can also be used on joints to adjacent building components consisting of timber, stone, wood fibreboards, plaster and concrete. This is possible as long as the surface is generally even, free of dust and resistant to abrasion. If all three of these prerequisites are not fulfilled by a given surface, it can be pre-treated with a primer. Primers for acrylate tapes are applied in liquid form and differ from undercoats in terms of their mechanism. An undercoat penetrates deep into the surface and strengthens it. A primer for an acrylate adhesive tape is designed to penetrate into the subsurface and also to form a film on the surface that levels out any unevenness. These primers have proven themselves in practice. It is critical that the primer is suitable for the adhesive tape: i.e. one should always think in terms of overall systems.

    Resistance to moisture – why are there differences?

    Adhesive tape after storage in water for 24 hours: Top: a conventional acrylate dispersion adhesive tape, re-emulsified with water; the adhesive has lost its strength. Bottom: pure acrylate on a solid basis is absolutely water-resistant.

    Nobody wants moisture on a building site, but regrettably the reality often very different! Adhesive tapes have to be able to reliably withstand the challenges of moisture after they are installed. The first protective layer is the backing material that is used. A film is clearly more resistant to water than paper. However, moisture does not always come only from the outside, but often from the subsurface too. In this case, the advantage of the external protective effect of the film is reversed, as the moisture cannot escape through the film and builds up instead between the adhesive and the film.

    As already described, acrylate dispersion adhesives contain emulsifiers in their adhesive film after production. A characteristic of emulsifiers is that they store water, and they are still capable of doing this years later. If an acrylate dispersion adhesive comes into contact with water again, the adhesive re-emulsifies often assumes a white colouring and can lose adhesive strength. Pure acrylates are fully water-resistant, as they do not react with water – in this way, their adhesive strength is preserved.

    See yee, who join in endless union – Durability: experience and laboratory tests

    Cohesion adhesion test with 47 adhesive tapes: 40 adhesive tapes failed within two years in a long-term test with low loading.

    Reference is often made to the positive experience observed over the last 20 years with regard to the durability of adhesive tapes. When we plan and build a house nowadays, clients expect the built structures and the materials used to have a service life of 50 years or longer. As a result, it is even more important when selecting adhesive tapes to take into account long experience in the marketplace alongside ageing tests that confirm the high durability of bonding agents.

    Consistent rules are coming: a new standard for bonding agents will create a basis for comparison

    The forthcoming standard DIN 4108-11 will specify laboratory tests that have to be carried out for all adhesive tapes. This will create consistent quality standards and provide a basis for users to compare products.

    Presently, adhesive tapes are not regulated by standards and there are no uniform minimum requirements that have to be fulfilled by-products. The draft of DIN 4108 Part 11 that is soon to be published will fill this gap and specify uniform and comparable minimum requirements for adhesive tapes. This standard contains various tensile strength tests on standardised subsurfaces such as wood and membranes, as well as the possibility of having systems (membranes and adhesive tape) tested by manufacturers.

    Many of the requirements demanded from adhesive tapes described above are formulated in this standard. For example, the tapes are pressed into place in a defined manner before conducting a pull-off test, and the test is carried out with a low pull-off speed so as to simulate the long-acting, low tensile stresses that occur in real applications in this test. Ageing will also form part of the scope of the standard. It is not yet possible to state exactly whether and when the standard will be introduced and become part of construction law. However, the standard will form a good basis for comparing adhesive tapes with one another and will help installers and project planners to make informed decisions.

    Summary: permanent adhesive joints are only possible with good systems and the right handling

    Soft adhesives perform better in the ‘finger adhesion’ test, as they are better able to wet the surface of the thumb. This can lead to problems in practical construction applications, as soft adhesives generally have low cohesion forces.

    Actual loading in practice on site: the adhesive joint is subjected to low forces over a period
    of years, so sufficient cohesive strength is important.

    Permanent adhesive joints on construction projects are feasible and can achieve reliable performance; nonetheless, damage to structures often occurs when joints become detached. Knowledge about the fundamentals of adhesion technology and about the loads that will actually be acting in practice is crucial in order to be able to carry out reliable project planning and testing too. An optimal end result can only be achieved with good handling, a high-quality subsurface and a suitable adhesive tape. All three of these criteria should be carefully considered by the specifier and the energy consultant on site. Manufacturers who make statements about the surface quality of their membranes and about the production technology used in their adhesive tapes (solid acrylate or acrylate dispersion) and who offer long market experience, 3 rd party accreditation by reputable bodies (i.e. PHI, BBA, NSAI, BRANZ etc.) appropriate ageing testing and engineering support should be preferred over suppliers who provide little or no information about their products.

    See the Pro Clima range of airtight tapes here

     

    This article was written by Jens Lüder Herms, Dipl.-Ing. (FH), Jens trained as a carpenter and then studied construction engineering. He develops practical solutions for sealing buildings as part of research and development at Pro Clima.

2 Item(s)