Ecomerchant

  • Design elements that help prevent overheating

    The current prolonged spell of hot weather will have highlighted to many of us the susceptibility of our buildings to overheating.

    The issue of overheating in buildings is a serious health risk, figures published on mortality rates during heatwaves make grim reading but still, our construction methods and building regulations fail to deliver buildings resilient to overheating.

    In this article, we look at why this is important, how we can design for cooler more comfortable buildings and what to look out for when planning building work.

    What is a heatwave?

    The World Meteorological Organisation definition of a heatwave is "when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5oC, the normal period being 1961-1990". They are most common in summer when high pressure develops across an area. High-pressure systems are slow moving and can persist over an area for a prolonged period of time such as days or weeks.

    They can occur in the UK due to the location of the jet stream, which is usually to the north of the UK in the summer. This can allow high pressure to develop over the UK resulting in persistent dry and settled weather.

    When was the hottest heatwave in UK history?

    The scorching summer of 1976 was the hottest summer since records began. It led to a severe drought owing to the exceptionally dry conditions, although it is thought that 1995 was drier. In the summer of 1976, Heathrow had 16 consecutive days over 30oC from June 23rd to July 8th, and for 15th consecutive days from June 23rd to July 7th temperatures reached 32.2oC somewhere in England. But the single hottest temperature of 38.5oC was set on August 10th, 2003, the heatwave of 2003 led to the government creating a Heatwave Plan for England in response to the increase of deaths directly attributed to the heatwave.

    You can read the Heatwave Plan here https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/711503/Heatwave_plan_for_England_2018.pdf

    The current 2018 summer heatwave has seen the hottest day of the year so far recorded on Sunday, July 8th  a temperature of 32.4oC (90F) recorded in Gosport, Hampshire.

    Outdoor Temperature Thresholds – the effects on health

    Statistical analysis shows that maximum daytime outdoor temperatures are a predictor of heat-related mortality.

    In London, mortality starts to rise when the maximum daily external air temperature goes above 24.7ºC and has been estimated to rise by approximately 3% for every further 1ºC increase in external temperature. In other regions, the thresholds at which mortality starts to rise are lower. For example, the threshold for the North East of England is 20.9ºC.

    Heatwave Plan Regional Threshold Temperatures for Heat-Health Watch Alert Levels 2-4.

    Design considerations to prevent overheating - decrement delay and thermal buffering.

    Anyone familiar with spending a hot summer's day in a caravan and then another in a stone house with closed shutters will appreciate the meaning of ‘Decrement delay’. The inside of the caravan closely maps the rise and fall in external temperature to provide the familiar stifling effect on the occupants. In contrast, the internal air temperature of the stone house stays well below the midday heat, barely varies throughout the day and so provides relative comfort to those sheltering from the sun.

    In the caravan, as soon as the outside cladding starts to heat up, output is detected within minutes on the inside face as most of the heat quickly transfers through the aluminium / lightweight insulation composite; whereas as the face of the stone wall heats up, the heat is absorbed by the stone and progresses slowly from the outside inwards. Hours later, some of that heat has arrived on the inside face of the wall whilst the remainder is released back into the cooler evening air.

    The interesting, and often baffling, aspect of this phenomena is that the two materials can have very similar u-values - so that in steady-state conditions where heat applied at a constant rate over a period of time to the external face of both materials, there is an equally constant flow of (diminished) heat from the inside surfaces. Crucially though, for the purposes of thermal design, one material will start delivering heat to the inside before the other.

    Heat transfer factors: Conductivity, Density and Specific Heat Capacity

    But let’s start with understanding how different materials cause different heat flow rates.  What’s actually happening within the materials? The answer relates to the dynamics acting between three variable characteristics whose values are unique to each material. The rate of heat transfer is determined by:

    And of course, a further factor is the quantity or thickness of the material the heat is transferred through.

    Thermal Diffusivity

    Thermal Diffusivity ties the above factors together into an equation that measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy.  In effect, it is a measure of thermal inertia or ‘buffering’.

    The equation is:

    Thermal diffusivity = thermal conductivity / specific heat capacity x density

    Examples:

    • Rigid polyurethane insulation has a thermal diffusivity of approximately 4.46 x 10-7 m2/s
    • Timber fibre insulation has a thermal diffusivity of approximately 1.07 x 10-7 m2/s
    • Copper has a thermal diffusivity of around 1.11 × 10−4 m2/s

    In a material with high thermal diffusivity, heat moves rapidly through it because the substance conducts heat quickly relative to its volumetric heat capacity or 'thermal bulk'.

    In the above three examples, we can see that heat races through copper while it moves more rapidly through rigid polyurethane than it does through timber fibre board.

    Introducing the variable heat source - Periodic heat flow

    ‘Thermal diffusivity’ then accounts for the different rates of heat transfer through the variety of materials from a constant heat source.

    However, when we look at the transference of the heat from the sun striking real-world roofs and walls, the heat source is not constant. The variability caused by such as the sun’s passage through the sky is known as ‘periodic heat flow’ and, because the sun behaves, in the same way, every day (‘diurnal’), its effects can be designed for.

    Decrement delay

    So, what is ‘Decrement delay’ and what can it do for us? In discussing its use we’re looking to take advantage of the fact that some materials are slower at transferring heat than others. In buildings, the benefits of decrement delay are only realised where the outside temperature fluctuates significantly higher and lower than the inside temperature. So, ideally, if the maximum heat delivery to the wall or roof is at around midday, and because we can achieve a delay in heat transfer, it should be possible for that heat to finally penetrate the wall or roof to the interior of the building some time later when the inside of the building is relatively cool and the outside temperature has fallen as the sun goes down. At this point, the heat ‘stored’ in the wall can be released from the wall in both directions without overheating the inside.

    The time it takes the peak temperature in the middle of the day on the outside of a wall or roof, to make its way to a peak temperature on the inside face, is called 'time lag'’ phase shift or, more commonly, 'Decrement delay'.

    By controlling decrement delay it is possible to control and prevent the overheating of a building.

    A delay of between 8 and 12 hours might be considered optimum in normal conditions during extended periods of hot weather and cloudless skies up to 16 hours may be required.

    It’s worth noting too at this point that in a construction element containing several layers, the sequence of the material layers that heat passes through is also a factor in determining decrement delay. For example, in masonry construction where insulation forms one layer, locating it on the exterior of the masonry can significantly enhance the decrement delay effect.

    The image below shows a roof make up with a variation in decrement delay (phase shift) achieved only by changing the insulation type, the overall section U value remains the same but the difference in phase shift is 8.8hours between the maximum at 16 hours and the minimum at 7.2 hours.

    Image courtesy of Steico


    How Decrement delay / Thermal buffering works on a rendered stone wall



     

    Amplitude damping and the ‘Decrement factor’

    A stable indoor temperature is an aspect of thermal comfort. In conditions where the outside temperature fluctuates relatively widely, a constant indoor temperature is desirable. For example, an outside temperature might vary between 10ºC and 30ºC while internally it might vary just 1ºC above or below 20ºC. The fabric of the building envelope has effectively dampened the degree of oscillation.

    The ability to attenuate the amplitude of the outside temperature to that of the inside is known as the 'decrement factor'.

    It is calculated as f (the decrement factor) = Ti (the maximum swing from the ambient temperature on the inside) / Te (the swing in external temperature)

    Example: From above, the peak to peak amplitude of the outside temperature is 20 degrees, and for the inside temperature it is 4 degrees.

    f = Ti / Te = 1 / 10 = 0.1

    Hence the closer the decrement factor approaches zero, the greater the effect the construction element has on attenuation. I.e. the smaller the decrement factor, the more effective the wall / roof at suppressing temperature swings.

    The decrement factor is determined by the type and thickness of the materials that make up the wall or roof that the heat passes through.

    (Confusingly, the same effect or 'amplitude suppression' is often expressed as a straight ratio. Taking the example above, the ratio would be 10:1 or 5:1 or more often just '10')

    For a construction element containing several layers, the sequence of the material layers that heat passes through is a factor in determining decrement delay. For example, in masonry construction where insulation forms one layer, locating it on the exterior of the masonry can significantly enhance the decrement delay effect.

    Calculating decrement delay

    The response of construction elements to periodic cycles in temperature and heat gain can be quantified by using the thermal admittance framework as described in EN ISO 13786:2007. The framework also provides the basis for the CIBSE 'Simple Dynamic Model' for calculating cooling loads and summertime space temperatures (CIBSE (2005) Guide A: Environmental design).

    Manually calculating thermal response simulations is not for the faint-hearted, but a number of programs are available to take the load - notably the freely available, Excel spreadsheet based 'Dynamic Thermal Properties Calculator' developed by Arup and distributed by the Concrete Centre.  https://www.concretecentre.com/Publications-Software/Publications/Dynamic-Thermal-Properties-Calculator.aspx

    The importance of decrement delay

    Decrement delay will nearly always be more important in hotter climes than in the UK. An exception though is in timber/steel frame construction. One of the more common criticisms directed at lightweight construction is the lack of thermal mass - which can lead to the familiar 'caravan effect' above. Whereas masonry construction has the obvious benefit of 'heavy' materials such as brick and block, framed structures are typified by combinations of a cavity and lightweight insulation - leading to low thermal diffusivity and so little in the way of decrement delay.


    Steico Special Dry Wood fibre insulation boards used on a pitched roof. Picture Courtesy Kithurst Builders Ltd

    Until recently, insulation products were chosen mostly on the basis of a combination of their u-value and their thickness. Since the most commonly used insulation materials such as polystyrene, polyurethane and mineral wool had broadly similar densities and heat capacities, their decrement capabilities were relatively insignificant. With the increasing availability of wood fibreboard insulation materials in the UK, boasting comparatively high levels of diffusivity, designers can look forward to realising thermal performances more closely mapped to traditional masonry construction.

    Some examples of materials

    Don’t building regulations already set a standard?

    Approved Document Part L1A is designed to drive the conservation of fuel and power, rather than set thermal comfort standards. It requires housebuilders to make “reasonable provision to limit heat gains” in dwellings in order to reduce the need for mechanical cooling. Specific criteria or thresholds are not specified. The overheating ‘check’ in SAP Appendix P provides a means of demonstrating that reasonable provision has been made, but the calculation is not integral to the SAP rating and it is unclear what happens if a development fails the test.

    The dwelling should have appropriate passive control measures to limit the effect of heat gains on indoor temperatures in summer, irrespective of whether the dwelling has mechanical cooling. The guidance given in paragraphs 2.38 to 2.42 of this approved document provides a way of demonstrating reasonable provision.” Criterion 3, Approved Document Part L1a

    The Standard Assessment Procedure (SAP) is the Government’s procedure for rating the energy performance of homes.

    Designers and developers in the UK need to show compliance with SAP for each of the domestic units they are designing. It is not a design tool, but rather a compliance tool intended to produce an energy rating.

    SAP Appendix P is a simplified check of whether the home could have an overheating problem. It uses regional average external air temperatures for the months of June, July and August, heat gains and fabric characteristics of the building in order to calculate monthly mean summer internal air temperatures. These are then compared to a table of threshold temperatures. For monthly mean internal temperatures below 20.5°C, overheating risk is predicted to be ‘not significant’, whereas for temperatures of 23.5°C and above, the risk is ‘high’.

    Issues with SAP

    The temperature inside a home depends on many variables and changes throughout the day. Overheating risk during severe hot weather events cannot be calculated using monthly average temperatures. Neither can the impact of the Urban Heat Island effect or future changes in climate.

    Housing Providers and experts consulted by the Zero Carbon Hub raised many concerns with SAP Appendix P. For example, it allows unrealistic assumptions to be included, such as that windows are constantly open, which make it too easy to pass.

    SAP 2012 (Appendix P): Levels of threshold temperature corresponding to a likelihood of high internal temperature during hot weather.

    To sum up

    We have to acknowledge that overheating is a problem to be avoided and that we don’t need a heatwave to prod us into action, buildings can overheat for a multitude of reasons but the use of materials that help buffer heat preventing rapid transfer through the building can be used to substantially mitigate the risk. Typical areas that will benefit from such design are timber frame and lightweight structures, on a brick or masonry house this will usually be the roof. This is an important area to factor in heat buffering as it combines the warmest part of the house (hot air rises) with the largest solar collector on the building – the roof itself. Wherever possible design with overheating in mind, the Building Regulations do not require minimum standards for decrement delay and SAP is currently under review regarding overheating, so the choice to design and build to prevent overheating is one that rests solely with you.

     Further reading

     BRE Overheating in Dwellings

    Tackling Overheating in Buildings

    Overheating - a growing threat that mustn't be ignored

     

     Our thanks to Sandy Patience Dip Arch RIBA editor of www.greenspec.co.uk for material used in this article

  • The Sustainable Self-Built Home in the Age of Consumerism

    Are we really getting what we want from the housing market?
  • Healthy buildings or toxic buildings?

    The Healthy Home

    In our view, a healthy home is   ‘one that incorporates healthy design elements, non-toxic building materials, and proper construction techniques. It "breathes", emits no toxic gasses, and is resistant to mould and decay.

    Indoor air quality can be worse than outdoor air quality

    Here are our top tips when designing a healthy building.

    • Choose a simple build system
    • Use natural and non-toxic materials
    • Make the best use of natural light
    • Ensure adequate ventilation
    • Ensure that all building elements are compatible
    • Use a breathable vapour open system
    • Make the structure do the work
    • Take a whole-house approach to design
    • Include the end user in the design and build process

     

    The toxicity of construction materials in our homes is a serious issue homes do not have to contain potentially damaging materials.mitigating this should be considered right at the start at the design stage.

    Without a doubt, it is the control of moisture and the ventilation of the building that sits at the root cause of most building decay. We also have a huge issue with applying healthy principles to the biggest issue of all refurbishing existing buildings.  Often in these cases, the prophylactic principle should be applied, where some anticipation of problems such as damp penetration can be mitigated by choosing materials that can hold onto moisture and let it go later (drying out) or at least minimise or contain the problem. The issue with a more synthetic and hermetic approach is that such problems can often remain hidden deep within the building structure for a long time and on discovery lead to costly and extensive repairs.

    To apply healthy principles to any building project you first need to appreciate that the standards by which most UK construction is governed (and built to) do not account for the ‘health’ of a building in all but the most basic ways. So don’t expect a building that meets Building Regulations to be healthy.

    Damp problems are often first seen as a 'bloom' of household mould often triggered by warm wet air coming into contact with a cold surface, one that is poorly or insufficiently insulated.

    To describe an unhealthy home can be more effective at persuading us to adopt healthy principles. We will all recognise the description of an unhealthy building as one that fails to control the internal environment leading to partial, then increasing, early decay of the building fabric in turn leading to mould growth, rot and a failure of the element(s) to physically perform, the description would further include the use of toxic chemicals in materials and the resulting expulsion into the air of these toxins over time, and it would include the use of materials that contain allergens.

    Now most of us will recognise (and probably have experienced) the symptoms of poor building health but it is surprising how many of the houses built today have this very low on the agenda of considerations. The consequences of damp and unhealthy buildings can mean the aggravation of conditions like asthma, in the UK this is a real problem where 1 in 6 people have asthma a massive increase since the stable base in the 1970s with almost 2000 deaths per annum and 75,000 hospital admissions the cost to the state runs into £billions; most of this is directly linked to dust mite faeces which in turn is directly linked to relative humidity in houses, (as you find in an unhealthy house) other moulds, bacteria and diseases present in the same conditions are also linked to asthma.

    The main contributors to poor building health are the following

    • Water ingress
    • Condensation
    • Failure to control internal moisture
    • Poor build quality
    • The use of toxic materials
    • Poor ventilation
    • Material degradation over time leading to performance failure (e.g. air leaks)
    • Poor design
    A combined use of roof lights to flood a room with daylight and allow natural ventilation

    You can see that it is not only the absence of harmful environmental characteristics but also the presence of beneficial ones that define a healthy building. Designers should begin by avoiding harmful elements and attempt to incorporate supportive beneficial ones. This is why the inclusion of items such as natural light, ventilation and acoustic insulation is as important as layout and functionality in the whole house approach.

    Real progress is only made when the builder and future occupants work closely with the building’s designer to ensure that all these issues are addressed within the context of how the building is intended to be used.

    Thankfully a lot of the approach to building healthy homes is common sense and can be summarised in a few simple principles

    • Choose simpler building systems they are more failsafe
    • Manage moisture by creating a breathable shell to provide a means for managing and buffering variations in moisture
    • Include natural materials in many applications these will outperform synthetic ones.
    • Be involved at every stage

    As highlighted by recent events the toxicity inherent in our building materials can be a lethal problem especially in the case of fire, one of the most important materials used in the construction of a building is insulation, but can your choice of insulation really affect your health?

    A well-insulated house or office will protect your health, comfort and lifestyle but how many of us know and understand how to achieve this?

    Ecomerchant and Steico UK have joined forces to launch a protection campaign. It aims to champion the benefits of using natural insulation products, see www.ecomerchant.co.uk/protexion  where you will find the wheel (illustrated below) which has dynamic segments (links) e.g. health, fire and acoustic which click through to more information on each subject, you can also download wood fibre insulation certifications and find toxicology reports and environmental product declarations, this is the type of clear unambiguous information that allows us to make informed and better design choices.

    The Protexion wheel, each segment links to the relevant role with supporting information, the wheel also links to accreditations, EPD's and toxicology reports. Click the image above to link to the Protexion site.

    How we select insulation needs to be about having a real choice and for specifiers to be equipped with the right knowledge to compare materials on a like-for-like basis.

    To design a well-insulated building, you need to make informed decisions throughout all phases of a construction project to ensure your building performs as you envisage as mentioned above.

    However, selecting the right insulation is about more than just reaching building regulation compliance or ‘keeping in the heat’. It’s about ensuring a building protects its occupants’ entire well-being and comfort in the following ways.

    How well does insulation keep the heat out?

    In the UK, thermal insulation to protect from the cold is essential, particularly given ever-increasing energy costs. However, as demand for usable square footage of buildings increases, basement and loft conversions are the routes many now take. However, these parts of a home or office, are the spaces most prone to extremes in temperature. They, therefore, need more thought – i.e. how do you keep a space warm in winter but, for a loft, how to keep it cool come summer.

    Compared with synthetic insulation materials, wood fibre insulation has a much higher density. This higher density means that natural insulation makes for a better heat buffer as the high midday temperature will only reach the internal side and be lost at night when the temperature is already cooler outside.

    How a building’s breathability is hurting our health

    A breathable structure is one that allows the passage of moisture.

    With 90 percent of all building construction problems associated with water in some way, breathability is essential in measuring a building’s performance and preventing the accumulation of harmful water within the building’s fabric.  These are fundamental in reducing health risks from mould, mites that those suffering from respiratory illnesses such as asthma and chronic obstructive pulmonary disease (COPD) are particularly susceptible to.

    For effective breathability, there are four essential components that need to be considered:

    • a moisture pathway
    • a driving force
    • a sorptive fabric
    • vapour control.

    Natural fibre insulation is most effective as it suppresses potentially harmful water by binding and releasing moisture which helps regulate humidity levels as the moisture moves.

    Easy-to-fit insulation

    A well-designed building takes into consideration how a material performs throughout the building’s entire life cycle. This includes ease of installation. Steico’s wood fibre insulation is simple and easy to fit (either packed or friction-fitted), eliminating installer error, keeping construction programmes, tight and costs, low.

    How sustainability will save you time and money

    While all insulation is helping the environment by limiting energy being burnt for heat, natural fibre insulation materials are comparatively more robust. This means that when it comes to disposal, they can be composted – i.e. no specialist waste facilities or landfill. Throughout their lifecycle, they will additionally have a much lower, and often, negative carbon footprint.

    More than just protecting your home from fire

    All insulations will meet fire safety standards, but this is a minimum rating. The key differentiator between natural and synthetic is that natural insulations will prevent the spread of fire and if burnt, will not give off toxic fumes such as cyanide as polyisocyanurates (PIR) might. See article link below to Alliance for Sustainable Building Products (ASBP) Healthy Buildings or Toxic Buildings?

    Will the house be standing in 100 years?

    Condensation is one of the costliest risks to buildings causing huge maintenance repairs and structural damage. Natural materials are better able to absorb and release water whilst remaining dry meaning it is better able to protect from and buffer moisture thereby becoming a key part of healthy living.

    Comfort for occupants

    When selecting insulation for a building, there are implications for the health of the occupants, the structure of the building, its impact on the environment, its acoustic properties, durability and carbon footprint.

    Cancelling out the noise for a peaceful night’s sleep

    The higher density of natural insulations - such as wood fibre - makes them better at reducing noise. Sounds external to the building, such as traffic or music, as well as those from within the building, through walls and ceilings are attenuated better by wood fibre than synthetic equivalents. In providing better protection from acoustic pollutants, occupants often report a building as being more restful and relaxing thereby encouraging better mental health.

    When a building is well-designed and well-built, occupants should be at their peak comfort. With the average person spending approximately 80% of their lives in enclosed rooms, an occupant’s well-being is imperative. Therefore, the products used to achieve this should cover all the issues affecting a building’s construction, its impact on both its occupants and nature.

    Further reading

    ASBP Healthy Buildings Conference summary of key points, https://asbp.org.uk/asbp-news/healthy-buildings-or-toxic-buildings

    Read the expert’s view on healthy buildings including Professor Stephen Holgate CBE, Clinical Professor of Immunopharmacology at the University of Southampton and co-author of The Royal College of Physicians ‘Every breath we take‘ report, who explains why poor quality air is a lethal problem that affects us all, Consultant, Clinical Psychologist at UCL, Dr Sarah Mackenzie Ross who looks at the rapid rise in new chemical entities in our day-to-day environments and the consequences on our health, CIBSE’s Head of Sustainability Development Julie Godefroy  who questions the role of Building Regulations in delivering healthy buildings and Professor Anna Stec, fire toxicity expert from University of Central Lancashire who looks at the potential fatal effects when plastics in the home burn.

    Visit

    www.asbp.org.uk for more on sustainable building products

    www.ecomerchant.co.uk/protexion to see how insulation can provide so much more than keeping the heat in

  • Insulation that doesn’t work shouldn’t be called insulation

    Ecomerchant explains why this matters

    For 20 years we (Ecomerchant) have focussed on sourcing the best materials to build energy efficient, healthy, and sustainable buildings. We want to reduce environmental impact be it pollution, waste, embodied energy or toxic ingredients in everything we do, its part of our DNA.

    We haven’t been around this long by accident, natural materials such as wood are as old as building itself, proven over centuries, renewable and robust many natural products are popular because they are proven to work. Some of the most modern low energy buildings are made from natural materials, these aren’t mud huts but cutting-edge contemporary designs fit for our modern age. The processes used turn natural raw materials into performance products like insulation are some of the most sophisticated technologies in construction today.

    A good example of modern design built using a timber frame and wood fibre insulation this home offers high levels of comfort and ultra-low running costs

    Building technology doesn’t need to find chemically engineered, synthetic solutions to most building problems, most of them are solved in simpler more practical ways by adapting the inherent features of naturally occurring raw materials.

    Human beings and trees were not born in space, and are not designed to live in alien surroundings. The materials which are the most natural and most ancient in our buildings are the materials which we have evolved with and which are the best for us and for construction. Nature works by building up and breaking down; these natural cycles, sometimes over millennia, include robust and long lasting materials like wood but nature eventually welcomes them back by providing a mechanism for them to be recycled back into the system without causing adverse impacts on the wider environment. In short, all natural products are a food of some description. The same is not true of man-made synthetic materials like plastic or petrochemical-derived products. Nature has not had time to develop a coping mechanism so they persist often with alarming consequences. These materials require their own closed-loop recycling system, the problem is that we haven’t created that either so they inevitably escape into the natural cycle where they cause harm.

    We are most comfortable in buildings that don’t adversely affect the environment (this also includes the consequences of production and disposal of the materials used) or our health and we can all measure a reduction in the need for fossil-based fuels through our energy bills.

    The UK home insulation market alone is huge worth over £800 million of this a staggeringly small amount is made up of natural insulation products– probably less than 1%. The rest is largely manmade and so sits outside the natural cycle of re-absorption and re-purposing by nature.

    Accurate figures are hard to come by but there is one common factor we observe, natural insulation products are growing their market share. Insulation is an eponymous term as it is by definition an insulator, typically viewed in this country as a protector against cold.

    As public understanding of environmental concerns has re-orientated how products are sold and marketed we have seen moves by manufacturers of synthetic insulation materials to ‘shoehorn’ in green claims about what their products contain and this has made people wonder what was in there before that was so bad for us.

    Building Regulations should be the start point for design, not the end

    All insulation products, no matter what they are made from, reduce greenhouse gas emissions by reducing demand for heat (or cold) so all have a form of inherent 'eco' credentials, but as this applies to all insulation the principle difference between types of insulation boil down to suitability for the intended application, stated efficiency in terms of capacity, embodied energy and toxicity, and this is what has made manufacturers re-align their marketing to reflect these concerns into a new way of re-describing existing products.

    When choosing insulation its worth remembering that there is a significant difference between being 'designed' and being 'compliant', within UK domestic construction there is a tendency to focus on the latter especially when it comes to the building shell, this leads to a 'lowest common denominator' effect, a subject on which we have written about many times. A tendency to deliver only compliance can exclude beneficial features and expose us to unwelcome consequential problems. This also assumes that the level of compliance achieved will deliver the required performance and levels of comfort, which it can fail to do,  for example, we have all experienced over hot 'rooms in the roof', compliant yes, but comfortable no, an overhot room can be unusable. Designing and specifying materials should take into account all possible features and benefits not simply compliance, this also helps mitigate cost differences as you only end up paying for delivered performance.

    Insulation is capable of offering 10 key features – all of which are valuable in terms of building performance, installation and occupant comfort. perhaps you should be asking how many of these things your insulation can do.

    1. Insulates against cold or heat – these are the thermal benefits needed to create a comfortable internal environment and reduce energy bills
    2. Reduces sound – has acoustic properties – this helps create a better living environment. Some products are better than others.
    3. Buffers moisture – helps protect against structural damage, mould, fungal growth etc. This is a key part of healthy living, plus it protects your most expensive asset against repair and maintenance costs and keeping its value
    4. Reduces heat transfer by its mass (how much of it there is) especially true for ‘room in the roof’ and timber frame or lightweight construction, stopping excessive heat transfer requires more stuff in the insulation something that is inherent in all wood fibre products.
    5. Is simple and easy to fit – better fit equals less air movement equals higher efficiency. Badly fitted insulation doesn’t work, really badly fitted insulation is near useless, in other words badly fitted insulation is not insulation it’s just ‘stuff in a building’
    6. Fire: - almost all insulation has a similar fire rating, the key difference is that natural insulation is better at resisting the spread of fire than many synthetic options it also does not give off toxic fumes when burnt.
    7. Does not pollute or have the potential to pollute – no off-gassing- no toxic emissions – no concerns for asthmatics, or sensitised people and no health issues for installers
    8. No waste issues; can be recycled or reused without specialist mechanisms which carry a cost.
    9. Works at the same level over many years – doesn’t crumble, collapse, degrade or deteriorate and so lose its performance we have all encountered insulation that has failed in lofts walls and floors when we renovate or buy a property that needs updating, natural insulation is long lasting and doesn’t degrade.
    10. Meet or exceed the requirements of the Building Regulations. Remember Building Regulations are a minimum standard and do not require many of the above benefits to be met, except U value as a measure of conductivity – point 1. - be careful you don’t just choose an insulation that passes Regs, pick one that meets your needs, after all, they ALL have to meet the minimum standard so anything else is a bonus!

     

    1. Bonus Point. Choosing natural insulation can often eliminate the use of other materials such as membranes or boards so saving money and simplifying construction, after all, why take two products on to a building site when you can take one.

    Most natural insulation will deliver all the above.

    It’s a short step from this list to consider a genuinely natural product as long as it does the same job and is more or less the same price as a synthetic option. Never forget that bad insulation (insulation that is not fit-for-purpose usually cheaper, entry-level products made to a price) or badly chosen insulation is ‘not insulation at all’ if it doesn’t work reliably over many years it's just a waste of money.

    Our customers have shown us that they ‘get it’ they know that natural insulation can do everything a synthetic one can do but with more benefits and fewer unwelcome associated issues such as waste, embodied energy or giving off toxic fumes when burnt.

    Wood fibre boards can be safely left exposed to the elements for up to 6 weeks with no loss of performance. They may also remove the need for a roofing membrane.

    This change in the market explains why natural insulation is being specified and used more and more in areas previously the sole domain of the big insulation manufacturers, it works, this is a trend that we only see increasing.

    Most of the market growth is driven by customers wanting healthier products that function on a number of levels and compliment the higher performance being designed into modern buildings.

    Terms such as breathable and airtight have created awareness that natural products have multiple and consequential benefits plus they do not degrade or pollute the environment. Our modern-day focus on well-being and health have caused many to question the provenance of materials they have to live with, manufacturers claims are under scrutiny and viewed less plausibly than before and the consequential effects on our environment made by our choices now form a key part of the decision making process.

    It appears that the time for natural insulation materials is now and rather ironically the main driver is not the fact that they are natural it is often a performance and health-driven choice reinforced by the additional benefits they bring.

    How we help you

    Every home and every installation will be different but the methodology for calculating how much insulation is required, how it will perform and what type you need is a well-trodden path for our experts.

    If you are unsure or need a hand figuring out what you want, just call us and ask for help. This is what we do day in day out. Our manufacturer partners and our team will always be able to help you to work out what is the best available option for your particular job.

    If you know what you need then why not buy online you can shop when you want, all our products are delivered directly to you from stock.

    Our commitment to you is to only sell natural insulation products.

    How we can save you money. We are the only supplier of Steico insulation products to sell by the individual board or pack meaning we can keep unnecessary waste to a minimum. All our Steico products are priced individually by the board or pack (for Flex), buying online couldn’t be easier, just one click and the goods are on their way, just when you need them and no need to waste or store any surplus.

    If you need help please call and ask, we are here to help just call 01793 847 444 or email info@ecomerchant.co.uk  and we will do the work for you.

    Wood fibre boards - product links

    Download our installation guide

    Steico Sarking and Sheathing boards Installation Instructions

  • Why would you incorporate a gaping hole the size of an ATM in your building shell?

    The answer to the question is 'because that's what the regulations allow and as many people regard the building regulations as a target standard that's what most people do.' 

    Current building regulations stipulate a minimum air leakage rate to be no more than 10m3/hr/m2, in the example below you can see that by comparison to Passive standard this equates to leaving an open hole in the building fabric equivalent in size to a typical a cash machine, whereas the Passive standard this hole size would be reduced to the size of a credit card.

    Obviously, people do not leave a single gaping hole but the equivalent size will be distributed over the whole building which means that the energy efficiency is stripped away by the movement of air through the building fabric especially the insulation. This is why airtightness matters and sits at the core of improved energy efficiency.

    What is Airtightness?

    Often we are asked what the term airtightness means.   Airtightness primarily focuses on the elimination of all unintended gaps and cracks on the external envelope of the building.  Airtightness is an essential part of creating a healthy, comfortable, energy-efficient living environment.  In contrast, air leakage is where leaks occur due to gaps and cracks that should not be there in the first place.  This can account for up to 50% of all heat losses through the external envelope of a building.  There are many factors which can cause air leakage such as poor build design, poor workmanship, or indeed the inappropriate use of materials.   It is important to remember that an airtight building does not mean it is hermetically sealed, rather it means that the air leakage has been reduced to a minimum.

    What role does ventilation play in airtightness?

    Ventilation is crucial in all buildings, not just airtight ones.  It is key to construct buildings which are both airtight and gap-free and then introduce a designed and controlled ventilation system which ensures that adequate fresh air is supplied to meet the needs of the occupants.

    Can I not just add more Insulation?

    Insulation requires high levels of airtightness to perform.  This can be explained by the "woolly jumper" effect.  Imagine going hill walking and you only wear a single layer then the wind blows through the woolly jumper quite easily.  However, if you apply a light windshield over the single layer it has a dramatic impact as it reduces air movement through the jumper and consequently, the woolly jumper insulates much better

    Therefore, for insulation in a building to perform it needs to be protected against air movement on both sides

    1 - on the outside protecting against wind by using a windtight external membrane

     

     

     

    2 - On the inside protecting against the hot air penetrating through it creating air movement through the insulation by using an airtight membrane

    Short Video -  Intelligent Airtightness Explained

    What are the benefits of airtightness?

    1. Reduced heating costs
    2. Improved health - substances which can provoke allergies can be carried into a building via air leakage - air coming from outside in or from within the building fabric itself
    3. Improved building durability - Airtightness protects the building fabric against damage due to moisture-laden air leaking into the building envelope and condensing
    4. Reduced callbacks - Airtightness focuses on build quality and quality workmanship
    5. Improved comfort levels - Airtightness is a key component in reducing overheating in summer and insulating better in winter
    6. Improved Acoustics - Air is a very effective medium for transporting sound.  Higher levels of airtightness means more effective reduction of sound transfer

    What steps can I follow to achieve high levels of airtightness?

    1. Design for airtightness - ensure the architect designs the building with key airtightness details in mind.  Keep it simple with the details
    2. Build for airtightness - Now that it is designed correctly, ensure all personnel who interact with the airtightness layer are trained and install products correctly.  Workmanship can be validated with a WINCON test.
    3. Test for airtightness - We can only understand how something is performing by attaching a metric to it, airtightness is no different.  Blower door test should be carried out to measure the airtightness.

     

    Airtightness - The Facts

    On average we spend up to 90% of our time indoors - it makes sense to make this environment as stable and comfortable as possible, free from any draught and cold spots.

    Based on the envelope area of a 1,900 square foot certified Passive House If built just to building regulations (a leakage rate 10m3/hr/m2) the equivalent size hole in the building once everything has been sealed up would be approximately 440 x 440mm.  Whereas what was achieved on this Passivhaus was a leakage area that is 10 times smaller at just 44 x 44mm

    To put this leakage area into perspective, if a building was built to the backstop allowable leakage rate for building regulations, a hole in the wall the size of a typical ATM machine would still be an allowable leakage area whereas for an extremely airtight would only have a leakage area equivalent to that of a credit card.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    This article is an abridged version of an original article published by By Niall Crosson, Senior Engineer, MEng Sc, BTECH, MIEI, CEPHC  in June 2017

  • Is lime a forgotten building wonder product?

    Lime; a building wonder material...we think so and here's why
  • Effective natural landscaping

    Erosion of the landscape can be a serious problem whether it is caused by wind, water (nature) or human activity. For many years the solution  has been to pile quantities of stone, concrete or plastic membranes, nets or matts into the ground to try and control the degradation of soil
  • Should tradespeople know about airtightness?

    Achieving a reasonable level of airtightness is important for the energy efficiency of dwellings and the comfort of occupants. The benefits of improved insulation levels and more energy efficient heating systems are lost if warm air can leak out of a building and cold air can leak in energy, leaking energy is leaking money.
  • U values for Dummies

    In the course of our day to day business we encounter plenty of customers, builders and trades who find U values a little confusing especially when it comes to understanding what the U value actually means and how it will affect or benefit the performance of a building, so we have compiled a brief 'U-Value for dummies' style explanation to help.
  • Paint: Human health and the environment

    This is guidance we give to specifiers and architects on how to choose environmentally sound performance paint. Read on to find out why:

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