Tag Archives: building regulations

  • 2019 'must have' retrofit materials

    In this article, we pick three standout retrofit products from 2019 and ask if their popularity could be linked to current and proposed regulations.
  • Are housebuilders selling us a lie?

    The planet faces an unprecedented series of environmental crises including climate change and the collapse of bio-diversity, yet for our construction industry and particularly the carbon-emitting housing sector it’s ‘business as usual’. Ecomerchant asked Sandy Patience, architect and editor at GreenSpec for his take on the paradox.

    People don't buy, and the Government doesn't legislate for, future-proofed homes: Why not?

    Why are we set on building houses that will cost owners and the rest of us dearly in the future? What follows, explores the complex reasons that have resulted in a perfect storm and the failure of the Government to provide adequate legislation.

    Why are housebuilders selling us a lie?

    My current walk to school alongside the new 'St. Michael's Fold' housing development provides me with an example of just how far volume housebuilders have travelled towards sustainable construction. The news is that it's not very far.

    Some 30 houses are under construction. Brick and block with minimum cavities; lofts are waiting for the contractor to unroll the insulation; dummy chimneys and PVC windows surrounded by gaps through which you could slice a ping-pong ball. Each house is fiercely independent of its neighbours even if they are only a metre away - detached properties, of course, fetch premium prices. It's hard to detect evidence that the developer, or buyers, or planners, realise that we have a climate crisis and that new homes will be quickly rendered unfit for purpose.

    Building new houses is a business designed to maximise profits and deliver shareholder value; customers play their part buy buying into this model, often due to there being too few viable alternatives. So begins the downward pressure on quality, as Dame Judith Hackett observed in her review of the UK housing market we are in 'a race to the bottom'.

    The maximum wall area, using conventional materials, provided by detached houses ensures that they will lose heat in winter and badly overheat in summer. Given too, the rock bottom prices in the PV market and cheap hot-water collectors, it's surprising that the developer has declined to offer his customers their benefit. The on-site sales centre confirms that the houses are 'fully compliant' with building regulations. "Our buyers don't ask for any more than that." says the sales assistant looking sheepish.

    For this particular estate, it gets worse. Sitting next to drainage ditches that criss-cross the landscape, this is essentially marshland incapable of sustaining much more than frogs. The site is so low that it's hard to see its survival much beyond a couple of floods from the nearby river as water levels rise. It's enough for an insurance man to break into a sweat.

    Why are so many environmentally ill-equipped properties sold even before they're built? As in so many similar developments, the clue is in the hoarding size graphics at the entrance. 'Welcome to St. Michael's Fold'. St Michael is a local saint. A fold is where sheep are kept. The image is bucolic. Desirable.  In the show house, the sales assistant shows us the 'period' features we can expect with our homes. It's another slice of ubiquitous 'Ye Olde England' signified by stick-on half-timbering, hanging tiles and 'leaded' lights. These are the bastard grandchildren of the Arts and Crafts movement.

    Everything about how this development appears is fake. Fake history. Fake houses. Also fake too are the developer's claims that they have built homes for the future. No one is born to like country cottages or loathe terrace houses. The homes sell like hotcakes.

    Why do we buy into Ye Olde England myth?

    A typical bucolic English scene from which many new developments draw inspiration for their names, e.g. 'Bluebell Wood' or 'Meadow View' marketing terms designed to sell the lifestyle they have paradoxically helped to obliterate.

    Status anxiety

    In contrast to most of the Continent, there's an association between Anglo Saxons and the detached house. Go to any suburb in the English-speaking world, be it Vancouver, Boston, Melbourne or Birmingham and you'll find detached housing built as default. Debate still runs about the origin of this, formerly English, phenomena. It derives at least from both the classic 'Englishman's Home is his Castle' icon and the need for differential from collective housing. Above all, it is a status symbol. For most people, it is the single most crucial signifier. Irrespective of the cost, the size and fitness for the purpose of being a home - it is the sign of having 'made it'. The Range Rover, another status asset, should have enough room to park in front.

    The flight from industry

    The Industrial Revolution gave us Blake's 'Dark satanic mills' - islands set in seas of Victorian industrial housing. Housing in an environment that we would describe today as toxic: Child mortality hit new peaks in the nineteenth century and in 1860s Liverpool, life expectancy sank to 25 years. No wonder then that a newly wealthy middle class chose to evacuate the city in search of AE Houseman's 'blue remembered hills' and the 'land of lost content'. There they built what they dreamed they'd lost. The pastoral fantasy reached its peak in 'Garden Cities' such as Letchworth, Welwyn Garden City, Bournville and New Earswick.

    The 'Estate.'

    For many, the collective memory of row upon row of straight Victorian 'two-up, two-down' terrace housing still haunts. Now relatively wealthy, we build the opposite. We cherish the cosy curves of the avenues (note: not 'streets'), closes, meadows, ways, rises and drives. The price we pay is a needlessly low-density sprawl of housing estates. From a conservation view it's a losing strategy - not only is it an inefficient use of land, but many of the houses will be ill-aligned to make the best use of the sun and provide protection from the elements.

    A modern estate development typical of many across the UK

    Will the Building Regulations protect us?

    Expecting Building Regulations to set the standard for tackling Climate change would be a category error - the Regulations are not designed for engineering environmental policy.

    Part L owes its origins, not to an environmental crisis, but an economic one. It wasn't until the 1960s that the Building Regulations expanded from protecting life and limb from bad construction to protecting our wealth. The introduction of statutory U-values for building envelopes in 1965 was only a gesture towards minimising energy wastage.

    Come the 'Oil Crisis' of 1973; energy policy was revolutionised. Previously taken for granted, energy became a weapon in world politics. Dependence on oil turned into a liability - cutting off the flow could ruin a nation's economy. Nearly all Western governments introduced ranges of inhibitions on oil's use. The UK Government began requiring a U-value of 1.0 for external walls. Over subsequent years the U-value screw has tightened in line with oil and gas prices. Consequently, energy efficiency has significantly improved over the last 50 years, but it still falls far short of being a useful tool sufficient to realise any environmentally relevant standard.

    Part L stands in an odd place. There's still the commercial imperative for fuel efficiency, but shouldn't it be the first legislative measure by which we prepare our building stock for global warming? If the industry was serious about climate change, wouldn't we have the appropriate regulation by now?

    That, of course, would depend on Government policy.

    The independent Committee on climate change (CCC) published the 'UK Housing: Fit for the Future?' in 2019. It condemns 'The way new homes are built (and that they) fall short of design standards. This is unacceptable.' The report calls for 'Immediate Government action … to ensure the new homes planned across the UK are fit for purpose, integrating the highest possible levels of emissions reduction' and that 'This will require an ambitious trajectory of standards, regulations and targets for new homes…'

    So here's the problem: since concerns about global warming became public in the 1990s, fossil fuel-funded think tanks have framed it and other environmental issues as liberal and radical ideology designed to undermine capitalism. Pushing this agenda is a right-wing doctrine that claims that global warming is a hoax; that we shouldn't abandon coal, oil and gas.

    The Conservative party already has form. The most crucial casualty of ideology was the plan to make new housing 'Zero Carbon' from 2016 onwards. Introduced by the Labour Government in 2007, it required new-build housing to be net-zero carbon through day-to-day running. Early in his premiership, Conservative Prime Minister David Cameron claimed that his was going to be the 'greenest Government ever'. It wasn't to be. That same Government, funded by the oil and gas sector, retreated from the 'Zero Carbon' commitment only months before it came into play. George Osbourne, the Chancellor, cited that constructing Zero Carbon Homes would be 'too expensive'. The Home Builders Federation added, helpfully, that '… new homes were already energy efficient under existing regulations'.

    Of course, the 'extra expense' argument was nonsense. The building industry had a decade to bring construction up to scratch. Non-legislative standards such as the widely adopted Passivhaus showed that getting too demanding levels of energy efficiency added perhaps 1-2% to the cost price of a new home. Contemporary researchers at Cardiff University demonstrated that a zero-carbon house could even be built within the cost margins of social housing.

    However, the door had been slammed shut. Other Conservatives expressed similar fears to the Chancellor:

    '…we should not sacrifice Britain's economic recovery on the altar of climate  change.' David Davis MP

    'If you assume the worst then there is absolutely no point in spending any money trying to prevent inevitable climate  change.' John Redwood MP

    'People will die this winter because of the environmentalist obsession with the end of the world' Jacob Rees-Mogg MP

    '…global leaders (are) driven by a primitive fear that the present ambient warm weather is somehow caused by humanity; and that fear – as far as I understand the science – is equally without foundation.' Boris Johnson MP

    Beyond these shores are fellow travellers including one notorious conspiracy-monger who 'tweeted':

    'The concept of global warming was created by and for the Chinese in order to make US manufacturing non-competitive.'


    'This very expensive GLOBAL WARMING bullshit has got to stop.' President Donald Trump

    Eccentric and irrational views are, of course, held by many people, but where climate change scepticism happens in Government, it becomes a weapon to thwart environmental protection.

    Other measures withdrawn during this same period include 'The Code for Sustainable Homes; subsidies to onshore wind and solar energies; the 'Green Bank' as well as the 'Green Deal' designed to cut the energy loads in existing homes.

    All across the board ministries rowed back on environmental initiatives - including the Department of the Environment which cut funding for climate change adaptation by 40%. Owen Patterson DEFRA's then-Secretary of State is a climate change denier.

    With a policy environment this toxic, it is little wonder that any serious climate change legislation failed to appear.

    After a brief hiatus, housebuilders could breathe again. It was business as usual.

    Planning? What Planning?

    The relationship between housebuilders and the Government is symbiotic. Both profit from their relationship with each other. A commitment to building homes has been the pledge of governments for over a century. Homeownership is a central plank in most election manifestos, and delivery of such is a key barometer of overall performance; Housebuilders, the other half of the association, have to do what they say on the tin. Their need to build houses correlates almost precisely with Government need to fulfil its promise to the nation. The whole is maintained through a balance applied through the Planning Acts. Local and central governments allow housing and the housebuilders build them. All is fine and dandy just so long as this judicious transaction continues.

    A developed parcel of land with high density detached housing, typical of many developer-led projects, focus for the provider is to maximise land use and profit.

    Government isn't a commercial enterprise, and housebuilders are not elected institutions. Difficulties occur when the Planning balance is upset by one or other of the parties. It might be on the one hand the need for unusually large numbers (as now) of homes and on the other the Government's need to satisfy the voting public. They see poor quality housing appearing on their green belts and cherished orchards. Added to the mix is the climate crisis as well as other acute environmental issues needing of robust policy to tackle.

    Understandably, volume housebuilders resent change and 'unnecessary' legislation. Profit depends on construction efficiency and tight supply margins. Rather like other industrial products, houses are designed as commodities to be sold 'off the shelf'. Template-based rather than custom-built, each is designed to be easily constructed employing simple techniques and conventional materials. Imposed variations including changing legislation and Local Authority requirements invariably threaten the profit margins: new design templates are required, employees need training and the materials supply chain requires adjustment.

    The climate crisis has been managed by successive governments according to respective views of the future and associated ideologies. The Labour governments of 1997 - 2010, responding to scientific advice, introduced the Climate  Act in 2008. In 2006 they introduced the 'Code for Sustainable Homes' aka the 'Code' or 'CSH' and subsequently committed to the 'Zero Carbon Homes' initiative to be introduced through the Building Regulations in 2016.

    The Code evolved from the excellent BRE-developed non-governmental Ecohomes standard. It was designed to encourage an ongoing improvement in performance across a range of environmental issues including energy, materials' impact, water efficiency, waste and pollution.

    Use of the Code at Local Authority scale was wholly voluntary. It was implemented using Local Planning to impose aspects of the Code as planning conditions to achieve higher standards in new housing.

    Regardless, in response to housebuilders' objections to 'obstructive' planning legislation and 'green taxation,' the Conservative Government progressively cut back Local Authority planning powers to control and direct new housing developments. Included as part of the 'bonfire of red tape' was the Code for Sustainable Homes, withdrawn in 2015.


    Don't wait for Whitehall.

    However, we try to ignore/deny/avoid it; the elephant in the room is that the climate emergency has been politicised. To an innocent bystander, denial of the threat of climate change is right up there with the 'Flat Earthers' - incomprehensible. However, spend a little time in research, and it's easy to find how the fossil fuel industry and the anti-science movement fund climate denial lobbyists in both the US and the UK. Vested interests on both sides of the Atlantic, bend the debate to a point where progressive policy initiatives are stultified. In the UK, the PM talks in public of combatting shrinking bio-diversity as well as reiterating his predecessors call for de-carbonisation by 2050. Actual action on the ground: policy, legislation, workgroups even, there is none. Government is far the more useful tool in the box when it comes to tackling climate change; It's particularly painful then, to become aware that the current Johnson administration is blunted by ideology and compromised by its sponsors.

    Leopards and spots.

    Most volume housebuilders have no moral aspirations, so put-away your expectations. They build for profit in the here and now - there is no money to be made from anticipating the future. The only way they change is through legislation or by market forces.

    Collective nostalgia throttles design for sustainability.

    Developers will continue to build miniature fantasy houses just so long as we buy them. We are complicit in a self-deluding circle of marketing and buying. If the housing sector was the car industry, the lines would still be turning out Morris 1000s and Austin Allegros. Frightened about an uncertain future we hide in nostalgia. Breaking free is difficult.

    Now what?

    Generally, we find ourselves in strange times. We’re facing an existential threat more significant and more certain than anything humanity has faced before. In addition to climate change, we simultaneously confront reduced bio-diversity, diminishing resources and environmental pollution. It’s the perfect storm, and we’re still scrambling around to find some way of grappling with it. Ideologues disrupt science; The few technical developments making progress are piecemeal and uncoordinated; Our industries, including construction, are unprepared; Our political systems are ineffective vestiges from a time before environmental crises.

    Never have we faced a crisis where lack of effective action by one generation can so completely screw-up the prospects of succeeding generations.

    Inaction and prevarication over commitment to real change has brought public protest onto the streets as witnessed by the Extinction Rebellion protests.

     So, what to do?

    It’s apposite that one way forward comes from the determination of one Swedish schoolgirl. Frustrated by the lack of political or popular will to confront the climate crisis, Greta Thunberg sat outside the Swedish parliament alongside a sign pronouncing that it was pointless for her to continue her education for a world that she wasn’t going to inherit.

    Stripped of the institutions we usually look to for action and reassurance; responsibility falls upon the individual. We must organise ourselves. “Since our leaders are behaving like children, we will have to take the responsibility they should have taken long ago.” (Greta Thunberg addressing COP24, 2018)

    We all have roles in the construction industry.  Let’s carry out those roles as if our children’s futures depend on them.

    About the author

    Sandy Patience  Dip Arch RIBA is an architect, journalist and speaker. He is the editor of GreenSpec at www.greenspec.co.uk - a site dedicated to delivering information about the design and building of Green Buildings and the Green Self Builder www.thegreenselfbuilder.co.uk  a website specifically designed to educate and inform the self-build and custom-build market.

    Editor's note: 

    Disclaimer: The views, thoughts, and opinions expressed in the text are solely those of the author and do not necessarily reflect the official policy or position of Ecomerchant, its employee’s or associates. This material is subject to copyright. Reproduction of the material may be made only with the written permission of the author.

  • 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.


    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

  • A brief history of Building Regulation U-Values – with examples

    In this post, we look at how U-Values within Building Regulations have changed over that last 50 years and how that has affected the thermal efficiency of a new build.

    The theme of Building Regulations and U-Values is something we have commented on for many years, the Regulations, especially Part L1A is designed to set minimum standards for the conservation of fuel and power, but they are just that. For those who are looking to build energy efficient homes with good indoor air quality, the Regulations are simply part of the process as the design of such buildings will necessarily far exceed these minimum standards. We have looked at this subject many times in our blog, one of the most popular was an article that described ‘The worst building you can build by law’ subtitled Building Regulations are no guarantee of quality. However it is a fact that the Building Regulations do influence behaviour across the sector and can act as a lowest legal common denominator for any building, exceeding them for many developers has to be a considered choice, one that carries the certainty of return on investment so many still default to ‘Regs compliant’ only building. For this reason, we thought it interesting to look at how the regulations have changed over the past 50 years and how this has affected the baseline performance of our housing stock.

    The theme for this article came from a piece originally written by Jon Davies and published on www.great-home.co.uk  in this post we look at his observations and examples with comment and opinion by Paul Kalbskopf MRICS Senior Building Control Surveyor Wiltshire County Council and ATTMA Level 2 Airtightness Tester Paul Jennings of Aldas.

    In his original article Jon Davies points out that the age of your house is a fairly reliable indicator of its likely thermal efficiency especially if no upgrades have been made to the fabric of the building – although many houses have been extended or otherwise significantly modified over the years. Over the last 50 years, the level of insulation required in Building Regulations has changed drastically to reflect both the need to reduce heating bills and increasing demand for comfort from homeowners. Below we consider how insulation levels have changed and what difference it has made to energy use.

     Determining Factors on Space Heating Demand
    When heating any space there are two critical factors that help determine how efficiently it can be done.  The two factors also interact, typically in a detrimental way, and this has been a major cause of the “performance gap”, about which so much has been written in recent years.

    The first factor is the thermal efficiency of the structure, and within Building Regulations this is largely defined by U-Values for which there are target ‘pass’ values for the key elements: walls, floors, roofs & windows and doors. U-values are arrived at by calculating the combined individual lambda values of all the section components to arrive at an overall number, the number given in the Regulations will be the minimum required.  It is generally accepted that the lower the U-value of an element of a building's fabric, the more slowly heat can pass through it, and so the better it performs as an insulator. The u-value is measured in W/m²K (Watts per square metre per Kelvin) the figure tells you how much energy is lost for every 1°C difference between the two sides of the material. Very broadly, the better (i.e. lower) the U-value of a buildings’ fabric, the less energy is required to maintain comfortable conditions inside the building. If you have a material with a poor u-value then you can generally improve it with insulation - broadly speaking the more insulation you put in the lower the u-value although it’s important to note that thermal bridging can ruin the performance of any installed insulation, make sure these are checked.

    The second factor is air leakage, whether uncontrolled draughts or ventilation heat losses. Heating an insulated space may keep it warm but (and possibly more importantly) if the building leaks then the heat will be lost and the efficiency plummets. Too much air leakage and we lose our expensively heated air much faster than we need to, resulting in bigger heating bills and colder rooms. The circulation of fresh air to maintain good indoor air quality is essential,  so the elimination of leaks coupled with controlled ventilation is one factor in determining an associated requirement within Building Regulations for a certain number of air changes per hour as houses get better insulated to reduce heat loss through the fabric then the heat lost through air leakage starts to become more significant.

    Changes in u-values over the years

    The table below shows the u-values required by Building Regulations for each building component in each decade. Building Regulations actually change more frequently than that (about every 5 years or so and each part of the regulations may be updated at a different time) but it gives a good guide to what has happened over the last 50 years. Highlighted cells indicate the first time the U-Value requirement for a component was strengthened.[1]

    Building Regulations U-Value minimum standards 1970 – present*

    New Build Regulations Part L1A https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/540326/BR_PDF_AD__L1A__2013_with_2016_amendments.pd 

    See also Appendix 1. Below on ‘Limiting fabric parameters’

    Typical 1970s built terraced houses, despite the small size of the house they have front and back gardens with ample parking bays nearby. many of the houses on this estate also have separate garages.

    The oil crisis of the 1970s forced the government to think seriously for the first time about reducing energy usage through regulation. The crisis drove changes in the 1976 Building Regulations which set minimum insulation levels for the first time. Before 1976 the standard cavity wall had not changed much since the end of the 19th Century, although solid, thermally less efficient, walls were still being built into the 1930s. Walls and ceilings were the first target areas with floors and windows following on later. Until 1994 you could still put a single glazed window in a house (u-value 4.8). When double glazing became a requirement the standard was set at 3.1 (what the double glazing industry could achieve at the time). In 2002 stricter regulations were introduced for windows for both new houses and also for replacement windows in existing houses.[2]

     In his article ‘Building Regulations and U-values: How have they changed?’ Jon Davies gives a good example of the impact of the changes in u-values over the years, he provides the following example for a house built in each decade. He uses, in this example, a simplified 3-bedroomed two storey house, a rectangular box 10 metres long x 5 metres wide x 5 metres high (the pitched roof is not counted as part of the house as the floor of the loft is insulated).

    Jon’s example works through the consequences and comparative outcomes for each decade when building to prevailing Building Regulations, he also takes into account air leakage as described in the Regulations as this has an effect on the overall performance and subsequent heating cost. Needless to say, this is an ‘on paper’ exercise and as both he and Paul Kalbskopf points out later ‘as built’ will generally provide poorer results.

    Jon assumes that the occupants try to keep all the rooms at 20°C for 15 hours per day whilst the outside temperature is at zero (0°C); that the floor is a suspended timber floor with clay underneath. The house is constructed with a cavity wall construction insulated to the standard prevailing at the time of build; he also assumes that air leakage is equivalent to an optimistic 1.5 air changes per hour (using this figure to compare ventilation heat loss with fabric heat loss).

    Using the dimensions above gives the following for the simplified 3-bedroomed house:

    • Ground Floor Area: 50m²
    • Upstairs Ceiling Area:50m²
    • External wall area: 125m² (excluding windows/doors)
    • Windows/doors area: 25m²
    • House volume: 250m³

    This simplified house is not that different to a house built today; today’s average house has shrunk a little over the years in length to be 8.6m with a 5.2m width.

    So what is the impact of improving u-values on the heat loss from this house? 

    Building Fabric Heat Loss by Decade Built To Building Regulations

    Jon Davies makes the calculations in the table below in order to show the comparative difference that each change in building regulation has made. The calculations he uses are necessarily simplified based on pure fabric heat loss with no additional factors included.

    He assumes the gas cost at 4p per kWh which means the occupants of the simplified 3-bedroomed house built to today’s Building Regulations would be spending around 16% of what someone living in an unmodified 1970s built house would spend to mitigate fabric heat loss when the outside temperature was a constant 0°C.

    A small terrace of 3 houses part of a 1980s development note how the front garden is now a parking space.

    Jon's figure ignores the cost of heat loss due to air leakage which is worth briefly mentioning. The ventilation heat loss (air leakage) of a 1970’s house would be about 2,475 Watts when the temperature outside was 0°C. That would add about 37kWh and £1.49 to the day’s demand, taking the total heating cost from £5.46 to £6.95.

    Moreover, the air leakage and insulation choices interact to give rise to a significant part of the performance gap mentioned earlier.  Put simply, most of our bulk insulants (mineral fibre, glass fibre and more recently recycled plastic bottles or cellulose fibre) rely upon trapped air for the majority of the insulation they provide. If air is whistling through the insulation in a leaky house, most of the heat we expect to be retained by the insulation is actually being blown away!  Especially in a loft with rolled out batts of fibrous insulation and warm air rising through it, the insulation might only be 1/3rd as effective as theoretically calculated.

    A 2016-built house is expected to have less air leakage but it will not be dramatically better.  A requirement to restrict air leakage was only introduced in the Building Regulations issued in 2002 (see updated 2016 edition, Approved Document L1A: Conservation of Fuel and Power in New Dwellings) - and even now Building Regulations airtightness requirements are sadly weak. Airtightness is checked by an air leakage test when portable fan equipment is used to apply a pressure difference of at least 50Pa relative to atmospheric pressure and the amount of air required to maintain this pressure is measured. But sample testing is still the norm when large developments are being tested, and the whole industry is well aware that those houses chosen for testing tend to get finished to a significantly better standard – draw your own conclusions!

    For this example calculation, the Building Regulations airtightness target is 5m3/(h.m2) and the maximum allowable is 10m3/(h.m2) when tested at 50 pascals, roughly equal to the pressure of an external wind of 20mph.  If you compare this with a Passivhouse air leakage is an order of magnitude lower at less than 0.6 ac/hr, which equates to approximately 0.5 m3/(m2.h) this being one-tenth of the standard target (or 10 times better than it) and one-twentieth of the maximum allowable (or 20 times better than it).

    In a 2016 built house, it is likely that air leakage is a bigger cost than heat loss through the fabric. This is the big opportunity for future improvements in energy efficiency in Building Regulations. However, once you go much below 3.5m³/ (hr per m²) then other features should be added to the house design such as Mechanical Ventilation and Heat Recovery Systems (MVHR systems).

    Jon continues to provide a little more detail about how the heat loss figures are calculated, below are his fabric heat loss workings for the 1970’s house.

    U-value and Fabric Heat Loss for a 1970s Built House

    This tells us that ignoring air leakage, on a cold day 9,100 Watts or 9.1kW will be required to maintain a 20°C temperature. For a 15 hour period, this figure is multiplied by 15 to give 136,500 Watt-hours which is best expressed as 136.5kWh or kilowatt hours. Paying 4p per kWh for gas equates to about £5.46 uplift on the gas bill per day.

    A modern mixed development from 2016. Note the small strip as a front garden compared to previous decades plus the houses have parking for one car or offroad parking.

    Jon calculates the heat loss because of air leakage (ventilation heat loss) by multiplying the volume of the house (250 m³) by the air changes per hour (1.5) by the temperature difference (20°C) by 0.33 (energy required to heat 1m³ of air). This gives 2,475 Watts of heat loss that converts to an extra 37.12kWh of energy and £1.49 per day. Air leakage probably reduced as construction standards have generally improved between 1970 and 2016 but it is hard to quantify without air leakage testing on individual houses

    Paul Kalbskopf adds that Jon Davies’ excellent example has set out the theoretical requirements and costings for work carried out perfectly (as Jon notes).  As we are all too well aware, the practical outcomes in this fallen world are very different.  Practically all our buildings are prototypes, and, what is erected even in the controlled conditions of a test centre is rarely reproduced in the mucky reality of building sites affected by the daily changes of the UK climate.

    This has been recently confirmed by work carried out by Colin King and his colleagues from the BRE (Building Research Establishment) who, by performing in-situ U-value tests on a range of buildings of all ages across the country, have revealed some startling results[i].  (The pre-1900’s solid walled homes are performing twice as efficiently as we had assumed and the more recent, so-called low U-value elemental homes being compromised by poor construction standards; the 1940’s/50’s cavity-walled homes being worst of all!) Moreover, re-evaluation of condensation risk analysis methods, thermal storage capacity (and hence thermal inertia), microclimatology and air handling/air movement, should be causing us to consider buildings in a different light.

    While a combination of materials in any given thermal element will result in virtually the same U-value irrespective of the order of the layers in the ‘sandwich’, it will have a dramatic effect on thermal capacity, interstitial condensation risk and ultimately, comfort and health factors.

    The requirement for higher air-tightness requirements is a double-edged sword: whilst it reduces the energy loss due to uncontrolled ex- and infiltration, without addressing air quality, an increase of house dust mites, condensation, mould growth and ultimately rot can increase.  While there are four different systems that may be used to comply with the performance specification requirements, the blinkered view of most designers and builders is to stay secure and comfortable in the old ways of doing things.  Changing the way we do anything in our industry is akin to changing the direction of a fully laden supertanker!

    Therefore, the suggestion in Building Regulations Part F section 5 of employing something other than locally operated isolated extract fans is just that – a suggestion.  SAP calculations do not often allow for an air leakage rate of <3m3/(h.m2) at 50Pa, as most assessors will try to achieve design compliance at levels above that due to construction vagaries and quality.  However, on pre-completion testing, if a figure of <3m3/(h.m2) is achieved and an MVHR (mechanical ventilation with heat recovery) system has not been installed, there is huge potential for problems as outlined above, as a retro installation will be inordinately expensive and disruptive.

    Passive stack ventilation (PSV) only works if there is constant air input at a low level.  Any visible openings are often closed as the occupier views the incoming air as a cold nuisance.

    Mechanical extract ventilation (MEV) systems without heat recovery would appear to be literally missing the point if the priority is to maximise thermal efficiency, however, the fundamental reason to ventilate a building is moisture management (including odours) a critical factor in accelerated building decay.

    The other major factor is that the standards set out in the Approved Documents are only minimum standards.  Sadly most people – developers, builders, homeowners, see this as a maximum to be built up to, rather than a minimum to be built from. This attitude has sadly been disseminated throughout the industry by virtue of the major house builders who, in the name of maximising profit, build down to the minimum provisions required by Building Regulations, at minimal quality standards.  Paul Kalbskopf comments that in his 40 years in the industry, he has rarely seen a multi-house developer do anything more than the (Criminal) law requires.  The attitude is one of immediate expediency for short-term gain (profit for the shareholders) and for the foreseeable future, this looks set to remain unchanged


    Here's another statistic that affects our comfort and our pockets, we are building smaller and smaller houses, smaller houses you would think will require less heat (not necessarily the case as we have set out above) but the size of the building and plot does have a direct bearing on occupant comfort and well being, according to research published by www.onthemarket.com new build homes today are often 20% smaller than homes built in the 1970s. Forty years ago there was room for a garage and two cars on the drive of most semis commonly built 12 to the acre. Today, buyers are lucky to get one parking space outside a terrace, built up to 24 to the acre.


    Appendix 1.

    Paul Kalbskopf notes, within the current Building Regulations[ii] there is now a requirement to insulate/ seal party walls to achieve U-values as set out in Table 3 of L1A, which vary from 0.0 to 0.5, depending on whether solid, filled or unfilled or sealed or unsealed. See Building Regulations Part L1A Online Version pages 14/15

    Introduced in L1a 2014 is a requirement for swimming pool basins, if one is so fortunate, max. U-value 0.25.

    Paragraph 2.33 alludes to Table 2, which gives the ‘Limiting fabric parameters’.  The vital sentence is the third: The shame is that the word ‘likely’ is used, rather than ‘should’ or ‘must’.

    Table 3 does give values to which we try to achieve, but, given we are dealing in area-weighted averages, there will still be scope for variations to be at the (poorest performing) limit.

    Windows are a case in point where, for example, the insertion of an unsealed trickle vent into a hollow profile frame will make a mockery of the profile U-value and hence the ‘whole window U-value’ as given in Table 4.

    The original article can be found at http://great-home.co.uk/building-regulations-u-values-how-have-they-changed/ January 19, 2016 Jon Davies

    [1] http://great-home.co.uk/building-regulations-u-values-how-have-they-changed/ January 19, 2016 Jon Davies

    [2] http://great-home.co.uk/building-regulations-u-values-how-have-they-changed/ January 19, 2016 Jon Davies

    [i] https://www.bre.co.uk/filelibrary/pdf/projects/swi/UnintendedConsequencesRoutemap_v4.0_160316_final.pdf

    [ii] Building Regulations 2013 Edition Incorporating 2016 Amendments for Use in England.  Approved Document Building Regulations Part L1A the Conservation of Fuel and Power. Online Version.

    Further reading.

    LABC Warranty Survey 2018 ‘What is the average house size in the UK?’















    New build homes today are often 20% smaller than homes built in the 1970s. Forty years ago there was room for a garage and two cars on the drive of most semis, commonly built 12 to the acre. Today, buyers are lucky to get one parking space outside a terrace, built up to 24 to the acre.

    Source www.onthemarket.com


    Interesting article


    LABC Warranty Survey 2018 ‘What is the average house size in the UK?’




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