Actual energy savings from efficiency measures only half what is officially claimed

(This article provided some of the data for the Guardian’s article on energy efficiency on 18.01.14. I have put it at the top of this web site in order to make it easy to find. Chris Goodall)


Research published by DECC last month showed that home insulation measures deliver half the savings that are claimed. A study of homeowners installing a package of cavity and loft insulation and a new boiler in 2010 indicated a 19% reduction in energy use, and a likely saving of about £140 at current gas prices. The government’s Energy Saving Trust claims savings from these measures of twice this amount. The smaller than expected reductions in energy use mean that the typical UK householder will lose hundreds of pounds a year from taking out a Green Deal loan.

The research

The DECC study is part of a long running research project to track energy use in British homes. Actual gas and electricity use is logged for a large sample of households. Homes installing energy efficiency measures under government schemes can be compared to a control group of houses with initially identical gas and electricity consumption.

The results released on 21st November tracked those homes that had cavity wall insulation, loft insulation or a new boiler installed in 2010. The numbers showed the reductions in energy use in 2011 in these houses. Energy use in UK houses is tending to fall so the DECC survey  estimates the extra reduction in gas bills arising from the energy efficiency measures compared to the control group average.

The results

The table below gives DECC’s estimate of the cut in energy consumption arising from the individual reduction measures

Measure Percentage reduction in gas use Estimate of kilowatt hours of gas saved
New boiler 9.2% 1,800 kWh
Cavity wall insulation 7.8% 1,400 kWh
Loft insulation 1.7% 400 kWh



a)       Loft measures include full insulation where the house had none laid and also ‘top-up’ measures to take the depth to 270mm.

b)       The homes having, for example, new boilers would have had a different control group to the cavity wall houses. So the baseline energy consumption may well be different.

c)        The average (mean) gas consumption across all the houses in DECC database was 14,100 kWh in 2011.

d)       By coincidence, those homes installing all three measures together achieved a saving of 19.0%, almost exactly the same as the individual elements combined.


At today’s gas prices, what are these savings worth? (I have used the lowest Big Six energy company costs of 3.874p per kWh for an address in Oxford). And what does the government’s Energy Saving Trust say that the measures should save a householder?


Measure Annual value of savings EST estimate of savings
New boiler £69.73 ‘£105 to £310’ depending on the age of the replaced boiler
Cavity wall insulation £54.24 ‘up to £140’
Loft insulation £15.50 ‘up to £180’ when loft had no insulation otherwise ‘£25’.


The DECC survey also looks at homes that had all three measures installed in the same year. The typical saving was 3,600 kWh, producing a saving in 2013 prices of £139.46. This compares with the EST’s headline saving estimate of £270, almost as twice as much as actually achieved. (I have used the EST’s figure of ‘up to £140’ for cavity wall insulation.

What would this package of measures cost today? The EST web site gives a minimum figure of £3,050. In other words, the typical return to energy efficiency investment is less than 5% per annum. (£139.46/£3,050) It may still make sense financially in these times of low interest rates on savings but the benefits are not large in cash terms.

The DECC study also shows that many households saw an increase, not a decrease, in their gas consumption after installing cavity wall insulation. The report doesn’t provide a number but a chart (Figure 3.3) suggests that perhaps 40% of homes with new insulation experienced increased bills compared to the control group. This may be because the insulation was installed badly – a depressingly common phenomenon – or because the occupants decided to heat their house to a higher temperature as a result of the better insulation.

The implications for the Green Deal, the government’s main energy efficiency policy, are very troubling indeed. Unsurprisingly, the DECC statistical report doesn’t make this clear.  The Green Deal arranges for householders to get loans to improve their properties. The interest is charged at commercial rates and repayment is made through the electricity bill.

According to the EST figures, the typical householder installing loft and cavity insulation and a new boiler would need to take out a loan of about £3,050 to pay for the measures. At an interest rate of 8% and repayment over 20 years, the annual addition to the electricity bill would be £342.87, compared to the average savings on the gas bill of £139.46. In other words, a family taking out Green Deal finance would be over £200 a year worse off as a result of doing what the government suggests and improving the energy efficiency of their home.

Outside government, everybody knows the Green Deal is a disaster. The scheme is excessively complicated, over-bureaucratic and expensive. The initial assessments for the programme use software that is misleading, and often simply wrong, in its estimates of cost savings from energy efficiency. (I know; I had one done on my house).

More generally, I want to ask this question. If the research arm of DECC knows the true figure for the likely cost savings from energy efficiency  measures, why are other parts of government continuing to promulgate much larger figures in order to get householders to take out Green Deals? When is DECC going to get sued for not telling people trying their best to save money that the Green Deal will typically cost families hundreds of pounds a year?





  1. Roddy Campbell’s avatar


    Clearly, assuming your numbers are right, then this presents all sorts of problems for the Green Deal as you outline.

    But in the bigger picture it also presents problems for enviros claiming huge efficiency potential, and cuts in energy consumption versus whatever counterfactual from efficiency gains?

    I suffer from confirmation bias here as I’ve always thought efficiency potential overstated, so am I reading this right?

  2. Chris Goodall’s avatar


    Like you perhaps, I think (retro-fittted) energy efficiency is much more expensive than claimed. Last time I did the calculations, it seemed to me that the cost of some home energy efficiency measures – as currently implemented – exceeded the price of offshore wind.


  3. Michael Knowles’s avatar

    Chris – I’m not surprised by these figures. I too have done my bit getting over 70s free warm front insulation both roof and cavity wall with not much saving in gas use.

    In spite of this I am now putting in a new BGas gas-fired Worcester Bosch combi condensing boiler to replace the existng 78.6% Baxi Combi thus theoretically saving 14.6% max on my gas consumption. I’m only doing this because I’m fed up with my Lloyds Bank classic advantage account suddenly reducing my interest on saving from 1.5% to 0.75% just like that.

    As for the Green Deal with its 7% financing rate the BGas engineer says he dosen’t see anyone taking it up

    QED Mr Davey.

  4. Wookey’s avatar

    I am not surprised by the numbers you present, but ultimately, building energy usage has to be reduced, especially gas usage and the coresponding distributed emissions. The fact that it has some payback aspect, rather than being a simple cost, makes it better than most other home improvements the same money could be spent on (kitchens, floors, extensions). Too many peope still think exclusively in terms of ‘payback’ for energy measures, even though they don’t do this for other expenditures.

    Trying to get this done green-deal-style as something that will make commercial levels of profit has always been an implausible idea, and it’s becoming very clear that that is not going to work. People/govt are going to have to actually spend money.

    It has always been true that it’s more cost-effective to knock down houses than to retrofit them, especially beyond the first 40% or so of energy savings. But people don’t like doing that becuase it’s very inconvenient. I do feel that DIY is overlooked in all of this as it’s very cost-effective in comparison to commerical intervention costs – typically 1/3rd of the price. But most of the incentives in this area explicitly exclude such work, or even make it harder.

    You make an interesting point about it costing more than offshore wind (which is at the upper end of current acceptable energy costs), but until all heating is electrified that’s a false equivalence. More turbines don’t reduce emissions from gas boilers.

    The ultimate driver here is climate change, and failing to deal with that has very high costs. That probably more than covers the shortfall in the above estimates. The real issue here is that doing the easy stuff (boiler/loft/cavity), only gets you a 20% reduction in heat energy use (and thus emissions), when the sustainable target is more like a 90% reduction. Hardly anyone is doing 90% improvement retrofits. And those that are are generally finding that it costs serious money (maybe £70,000). That will improve over time, but however you look at it there is a huge amount of money/effort that needs to be found for rebuilds and/or retrofits. A carbon ration would be one way to really concentrate minds on these issues (heat your house or fly to thailand this year).

  5. Chris Goodall’s avatar

    Michael, Wookey.

    Thank you for the comments.

    I agree. We need to reduce household energy use (for CO2 emissions and fuel poverty reasons) by a huge percentage. But the cost of getting large percentage reductions looks as though it is enormous (and well beyond what people will do willingly, unless they are truly committed)


  6. Roddy Campbell’s avatar

    There is a cost level at which you are better off not doing it, from a climate change perspective. See William Nordhaus.

    So statements like ‘building energy usage has to be reduced’ can’t make sense, as they clearly don’t apply at any cost.

    Anyway, that’s slightly peripheral, although Chris always has an eye on cost effectiveness of abatement, because we clearly should be choosing the cheapest.

  7. Oliver Tickell’s avatar

    My own experience is that if you begin with a house with very poor thermal performance, in order to get serious benefits you have to achieve quite a good closure of the thermal envelope. You can carry out all the measures you describe, but if you have eg drafty doors and windows, still not achieve closure – and so still have high fuel burn.

    Of course the other question is that people will always take some of the benefit in increased comfort rather than lower bills. Which is fair enough as now the money they spend on fuel will yield more benefit per £ spent.

  8. Roddy Campbell’s avatar

    Good to see the rebound effect being clearly acknowledged.

  9. Michael Knowles’s avatar

    The insulation of old solid wall houses with many fuel poverty people living in them is evn worse perhaps with cladding insulation costing something like £5000 for a semi-detached or terraced property as has been found with the very expensive Eco cover scheme now transferred to taxes.

    One other problem with all the figure is that we tend to put the room thermostat temperature setting higher to give more comfort. 1 deg C increase adds 10% more gas consumption.

  10. Roger Anthony’s avatar

    Let me start by writing that in a previous home I had loft insulation fitted under the government scheme. After the fitters had left, I discovered they had covered the centre of my boarded loft with a layer of fibreglass. All of the insulation had been laid with gaps for my heat to escape through. I moved it all, re fitted it carefully (no gaps) and made the best of it. Packed in at the correct depth it covered about two thirds of the loft floor.

    If this was a typical example, its not surprising the BRE cannot understand why insulation doesn’t bring the expected reduction in power usage.

    A few months ago, I took a Sunday afternoon stroll round our local town. I was surprised to see a row of terraced houses in the throws of having external insulation fitted. I was appalled by the level of incompetence displayed, there were two inch wide gaps between the insulation panels.

    Somewhere/somehow the logic of insulating a property has been lost. Are all fitters untrained, unsupervised?

    The perfect insulated room, is a Thermos flask! Unfortunately Thermos flasks don’t come in room sizes or shapes. A Thermos keeps its contents warm for along time, because the heat is retained by a vacuum and the only heat loss, is though the neck and stopper.

    For a room to be insulated successfully, the insulation needs to be on the inside/room side of the walls, floor and ceiling, it needs to be continuous with no heat bridges.

    The cheapest way to do this, is to glue sheets of polystyrene to the walls, screw it to the ceiling and lay it floating on the floor.

    Placing insulation on the outside of a building, may stop some heat from escaping straight through the walls and ceiling, but it does not stop the heat from escaping down the wall into the ground and up the wall into the sky.

    Is our current ineffectual system down to the impact of lobbying by big business? Or What?

  11. martyn’s avatar

    Would be interested to hear what kind of households this applies to. The more as household struggles to pay bills, the more likely they are to simply put up with it being cold and underheat it. Once insulated these households could stay just as cold and enjoy lower bills, or spend the same amount but be warmer.

    Despite mildly snarky remarks above, many environmentalists have been making this point for years. It is why insulating fuel poor homes is predominantly a social/health programmer rather than an environmental one. I have frequently objected to this cost – which is the cost of as failed housing quality policy and of largely social benefit – being loaded onto the very small energy/climate change department and labelled ”green crap”.

    Also a bit concerned direct price comparisons to offshore wind are off beam. Many homes in the UK are currently unheatable in cold weather – if the temperature outside is 20 deg below the inside, heat is lost through the fabric faster than the heating system can generate it, even if the householder has no concern for the cost. Halving the price of that energy would not change this problem.

  12. Chris Goodall’s avatar

    Interesting data from a full refurbishment project in High Wycombe.

  13. Robert Wilson’s avatar


    This also came through in today’s report by the Committee on Climate Change. Their revisions on the potential savings from solid wall insulation are pretty significant. In fact you really have to wonder why this was so wrong in the first place.

    Previously the CCC said internal solid wall insulation would cost -£70 per tonne of CO2 saved, i.e. it would pay for itself. Incredibly they have revised this to £890 per tonne of CO2 (page 67 in link below). So, it has gone from being incredibly cheap to just about the most expensive carbon mitigation approach available. Basing policies on this kind of analysis is deeply misguided.

  14. Scott’s avatar


    “-£70 to £890″ seems to describe a range, not old and new values.

    seems intuitively right that there should be some homes for which these measures would be cost effective and others for which it’s a waste of time.

  15. Michael Knowles’s avatar

    One wonders when anyone will get to grips with all this and all the expensive mistakes that we consumers pay for? Also all the rising subsidies on renewable electricity to get more costly offshore wind at £155/MWh and large solar pv at £120/MWh for 15 years?

    Whatever happened to the Offshore Cost Reduction Programme – last report June 2012 – aiming to reduce cost to £100/MWh by 2020?

  16. Roddy Campbell’s avatar


    Re emissions, it seems most/all interventions are flawed and result in unnecessarily high £/tonne abatement, and fail to dent emissions anyway. We can see this now backfiring politically, so it doesn’t get proponents what they want.

    Stick to a carbon tax, and call the rest what they are, social programmes.

  17. Robert Wilson’s avatar


    You are probably correct, but it’s very ambiguous language from the CCC.

    But let’s assume your reading is correct. They are actually referring to a range for *average* abatement costs. How on earth can their estimate for average costs range from -£70/tCO2 to £890/tCO2? And for external solid wall insulation the average abatement cost is from £88 to £2,000 /tCO2.

    Therefore in essence the CCC is telling us that they have absolutely no idea how cost effective solid wall insulation is, but they are unwilling to make this clear.

  18. Chris Goodall’s avatar


    Thanks very much indeed for pointing this out. The CCC paragraph is certainly not very helpful.

    The DECC research that is the subject of the article does provide some evidence on the impact of solid wall insulation.(There is no distinction made between internal and external insulation). Through the use of some statistical sleight of hand (perhaps legitimate, perhaps not), the research suggests average yearly savings of 2,400 kWh. Very roughly, this equates to 0.5 tonnes a year of reduced emissions, if the fuel being used is gas. It would be more than a tonne if the fuel was electricity.

    If we assume that a) the insulation lasts 30 years and b) costs about £5,000 then the cost of per tonne of CO2 is about £300-£350 in the gas of gas fuelled homes and about £150 in an electrically heated house (with no heat pump).


  19. Robert Wilson’s avatar


    This is interesting. Yes, what the CCC has written here is rather troubling.

    One of the key problems with these debates is that numbers are tossed around with zero thought. As you’ve written before the CCC have not helped this at all by producing rather questionable numbers about the costs of policy. They frequently tell policy makers that the costs of policy are simply one number. This quite simply is bad advice. If the CCC actually has no idea how effective solid wall insulation is they should say so. This is a big problem with their latest report: summary figures showing narrow uncertainty bands for abatement costs of nukes etc., that simply supported by the text.

    We are also frequently told that the costs of climate policy will be close to zero through to 2020 because of insulation. The CCC has in the past fed this narrative, as has DECC. If as it appears to be the case that they have now massively lowered their expectations on what can be done with insulation, then it is time they said so. Otherwise policy is just being based on wishful thinking.


  20. Wookey’s avatar

    Roger. you are right that standards in existing (non-DIY) work are pretty low. I contend that DIY work is generally _much_ better as it’s not done with the same time constraints, and by people who will have to live with the results. On the other hand I have only (a lot) of anecdotal evidence for this.

    I would quibble with “For a room to be insulated successfully, the insulation needs to be on the inside/room side of the walls, floor and ceiling, it needs to be continuous with no heat bridges.”: Continuous, complete and no bridges are all important, but it doesn’t have to be on the inside, and it’s usually better for the building structure to have the insulation on the outside. This also provides more thermal mass, which is good for comfort, although not necessarily overall efficiency. The catch being that it also costs a lot more and is much less DIYable.

    Those DEC numbers are interesting – something else I ought to read…

    Roddy. I agree that there are limits on how much it is sensible to spend on retrofitting. At some point it becomes cheaper to do other things. I guess my point was that focussing on direct costs and benefits to individuals is not the complete picture – it’s actually the external costs (climate change) that is the big driver. Of course if those costs are not reflected anywhere then it’s very hard indeed to make sensible change happen.

  21. Roger Anthony’s avatar

    Roddy; lets get this into context, the idea that mass helps you save on energy is false.

    In real life, yes concrete, brick, blocks can hold a great deal of heat but, to get that energy out, you have to allow the temperature of the room/home to drop. Logically, most people try to keep their heating costs down, they do not overheat, to benefit later from released heat as the temperature drops. This is too expensive.
    This holds no benefit for most people, they do not benefit from heat released from a wall after they have turned their heating off and have gone to bed.

    The fact is, using mass as a means to gain heat from the sun during the early part of the day and to get the benefit of slow release as the evening temperature falls, is a figment of imagination on the part of the cement companies, who have seen the amount of cement use fall over recent years, as there has been a move to lightweight building.

    The only way mass is worth using is in glass fronted offices where, mass cooled overnight by opening windows or running ventilation systems, is used to absorb the sun’s heat during the morning. This delays the time when their air conditioning comes on. Air conditioning being very expensive to run.

    In our context all mass does for most people who turn their heating down or off at night etc; is raise their costs as the heat is absorbed into the walls. Making the room/home harder to heat and delaying the moment when the room/home becomes comfortable.

    I read so often in the press how poor people only turn their heating on for an hour in the morning – almost a total waste of money and time.

    The fact is, heat always moves to cold, heat input heads for the nearest cold surface, usually a window making it hard to gain much warmth in such a short time.

  22. Paul D’s avatar

    Google search on ‘u value solid wall insulation’ :-
    If you insulate a solid wall, you have to make sure it complies with the current Building Regulations. The main condition to meet is the thermal performance of the insulated wall – if you live in England or Wales then it must have a U-value of no more than 0.30 W/m2K. The U-value is a measure of how quickly heat will pass through the wall – as a rough guide you will need around 60mm to 120mm of insulation to achieve this, depending on what insulation material you use.

    My house is about 10mx6m around the base slab and 5m high to the loft. Total area of walls 2x(10+6)x5=160m^2
    Loft area 10×6=60m^2. Assume insulated to the same standard.
    Total area for heat transfer between internal(20C) and external(0C) temperatures = (160+60)x0.3x(20-0)=220×6=1320W heat loss
    Add in losses for doors and windows. Say double heat losses = 2640W

    Heat supply by one heat pump of 450W(electrical) at a COP of 4 at freezing = 1800W. Use two of these pumps for a heat supply of 3600W which allows the pumps to deal with a few degrees sub-zero. Rough design size of heat pump(s) required 900W, supplied as 2x450W.

    I have measured data for the night of 5 November with frost outside of 380W power (4×380=1520W(thermal)) for my heat pump to hold the house temperature at a set point of 21C 24/7. About half the rooms were shut off during this result and this lowers the heat demand of the house; these rooms are typically three to four degrees cooler than rooms that are open.

    The house is a five bed detached with Rockwool in the cavity, 400mm loft insulation and double glazing. All of this seems to tie together. Heat pump total consumption for November was 189kWh or about £27 at current prices.

    100mm of loft insulation and the cavity fill were supplied by the house builders. A £100 government deal increased the loft insulation to 400mm and we paid silly prices for full double glazing. Current projects are :-
    1: flooring the loft with additional 100mm joists, laid at right angles to the original and packing that with solid insulation;
    2: implementing ‘modern shutters’ for the windows. I stayed in a hotel room in Scotland with real wooden shutters; they work! I prefer two or three wall poly-carbonate sheeting for the material, not optically clear but certainly translucent. A sheet of three wall has the same insulation properties as double glazing and two sheets of that behind double glazing gives 8-wall glazing. Not a lot gets through that!
    3: trying to figure out if I can implement a ‘zero-energy wall’. These come in active and passive forms. Passive is original construction; active requires an air-to-air heat pump. Essentially, an external clad that is air-tight is required; it should not have insulating properties. Push cool air from the heat pump discharge into the bottom of the clad and send the warmer air from the top to the heat pump suction. If the interspace is a degree or two below ambient, then how much heat is lost from the wall? Nothing. The heat gain is known from the above calculation: 1320W. Power up the cable for a 450W(electrical) heat pump adds to the 1320W to give 1770W. The rest comes through the clad or the tiles because those spaces are a degree or two below ambient. Any solar gain on the clad and the tiles would be a big boost to performance. Can it be done? Ask me next year.

  23. Michael Knowles’s avatar

    Thanks for all these sensible and practical comments. It made me think a bit harder about my semi-bungalow that has a single storey with a 40 sq ms of boarded ceiling that I hope is insulated underneath the boards but only to the the depth of the joists. So as we don’t store anything up there, I went to B&Q and found they do a Homefit Insulation service. You can get a qualified tradesman to fit 200mm EKO rolls of insulation costing £35 for 8 sq ms roll less 10% senior citizen discount on Wednesdays. I could do it myself but much prefer a professional to do it!!!
    It is a pity that all these politicians & DECC officials don’t do a week’s course on such as this and then they might understand what they are spouting about!

    Today’s energy news – EDF Hinkley C up for EU anti-competitive investigation; blackouts forecast becasue old non LCPD coal-fired power stations are shutting down; continuing saga on consumers’s and industrial energy-intensive users’ energy costs etc., was tempered by commnon sense talks about getting cracking with fracking. Muddle upon muddle.

    Chris – you might like to read the competitor EU Energy Post article I have written about the UK Government being ‘over a barrel with the financiers on renewables>

    Pity the poor old consumer in all this with his meagre savingsattracting 1.5% before tax if he is lucky!!!.

  24. John Goldsbrough’s avatar

    I have recently spent approx £6,000 on insulation, membranes, tape and sealants plus hundreds of man hours to make my 1954 built sieve a heat able proposition.

    Before carrying out this work the energy used to heat my house was very low as I did not bother to heat it.

    Now I have nearly finished this work I am expecting my energy use to rise as I say goodbye to cold and sometimes freezing temperatures.
    Insulating my house results in an increase in energy use.

    On the question of thermal mass I agree that it does not save energy for heating, indeed it may result in higher energy use in a house that is unoccupied for long periods. However I think thermal mass in a house is good for these reasons:

    1. It acts as storage so you can heat the house totally on intermittent renewables.
    2. A low thermal mass house cools down rapidly resulting in condensation and unhealthy mould growth.
    3. Makes a more comfortable house in summer due to decrement delay when living with no air con.
    4. Having lived in both low and high thermal mass house, I prefer high thermal mass. I have spent my money on hemp, cellulose and high density wood fibre.

  25. Wookey’s avatar

    Michael – If you have money to invest/save, even individuals can get the good 7-10% returns available for renewable energy projects. Good energy and ecotricity have put out bonds. Energy4All and Abundance energy both facilitate community investment schemes.

    You don’t get the guarantees of bank savings, but the returns are correspondingly better.

  26. Jon Pepper’s avatar

    It’s a pity that this, and the Guardian’s article on energy efficiency, misrepresent the evidence to argue against one of the best investments a household can make to reduce their energy bills. Chris, can I suggest you are being somewhat (and I assume deliberately) disingenuous in your analysis. As some responders have already pointed out, the difference between the EST and DECC figures is the decision a householder takes to heat their home to a higher temperature following installation of energy efficient technology. The UK has some of the most energy inefficient homes in Europe but if we keep comparing the full costs of insulation against only partial benefits, it’s little wonder this situation persists.

  27. Chris Goodall’s avatar

    Dear Jon,

    Thanks for your comment. As I say in the article on this web site, although the Guardian may not have fully covered the point, the benefits of insulation may partly be taken in greater comfort. We all know this, and if the householder understands the point, everybody is happy.

    However, the whole basis of the Green Deal is that the householder takes out a large loan, carrying a high rate of interest to pay for the improvements. The loan is supposed to be paid for – in its entirety – by the savings on energy bills. These savings may well not actually occur. About 40% of households putting in insulation or a new boiler saw a rise in their gas consumption. Despite this, the documentation provided with the Green Deal assessments suggests fairly precise numbers for the savings that will be achieved by householders. These numbers simply aren’t accurate, even if the householder runs the house at the same temperature as before.

    Why the differences?

    a) Most cavity wall insulation is done badly. Gaps are left. (This is visible from infr-red photography). The reduction in U value is nothing like as much as the EST and other bodies project.
    b) New boilers don’t perform as well as suggested because of the failure to achieve proper condensing.
    c) Draughts are responsible for about a quarter of all heat loss in UK homes, and a higher percentage in homes with CWI. This fraction has been consistently under-estimated by UK agencies until the recent DECC research. The implication is that whatever one does to improve insulation, the heat loss will still be a higher base than the Green Deal software projects.

    We both agree that UK homes need to be radically improved. Goodness knows I bang on about this enough. But conning people into believing that poorly done CWI is going to save them significant sums does nobody any good. It is also dishonest and I’m glad that the EST says today it is going to reduce the estimated savings from insulation in light of the DECC research. And we also need a major national effort at draught-proofing, where the savings per pound invested are clearly highest.

    Lastly, the Green Deal assessment software (and perhaps the scheme itself) should be amended to stop pretending that people will be able to finance their worthwhile improvements when they are paying 7 or 8 per cent interest.

    Best wishes


  28. Jamie’s avatar

    Chris, I’m sceptical that the NEED analysis is giving us a valid picture of the energy savings achieved from installing these measures. As far as I can make out the behavioural choices of the comparator group are a major confounding variable in this analysis.

    In 2009 gas bills had increased by more than 50% over the space of four years and the unemployment rate had leapt from 5% to 8% in the space of one year (where it remained for four more years).

    In this context consider two homes: one (intervention) household looks at their bills and decides to install loft or cavity wall insulation. The other (comparator) household looks at their bills but for some reason is unable or unwilling to adopt the measure.

    It’s highly likely that the second household will instead adopt behavioural changes (reducing the thermostat setting, using their heating less, shutting off radiators in unused rooms etc) to manage their energy bills. And this is confirmed by the comparator group reductions seen in the NEED data. Doubtless those households are also less comfortable as a result.

    The first household doesn’t need to adopt the behavioural changes to such an extent (indeed will probably lose some of the potential saving in increased comfort) because they feel that the insulation will do that job for them. I wouldn’t expect them to turn the thermostat down or curtail their heating if they’d installed loft or cavity wall insulation because they don’t need to (although I would always encourage it to everyone).

    The insulation has done its job in the intervention house but also behavioural changes have done their job in the comparator household too.

    The next step is to move the comparator house on to adopting the insulation and to move the intervention house on to adopting behavioural changes. Then we’re starting to get somewhere.

  29. Jamie’s avatar

    Chris, I wondered if you had had a chance to consider my comment above?

    Given that the only way that we’re actually going to be able to bring down household energy bills in any meaningful way is through energy efficiency, it’s absolutely critical that there is confidence in the ability of the measures to do their job.

    I’m concerned that this blog post and the associated Guardian article are undermining this confidence.

  30. Chris Goodall’s avatar


    Sorry for delay in reply. As I understand your point – and to be honest, I’m not sure I have quite got it – intervention households may reduce their consumption by a small amount because they take greater comfort. I agree, and I hope I made that point in the article.

    We don’t know if this is actually the case. We’d need to measure temperatures in the two types of houses. (Overall, homes appear to be heated to lower temperatures now than they were five years ago).

    So we don’t know whether better insulation really improves energy efficiency by a larger amount than has been found in the NEED analysis. My personal hypothesis is that if your theory was correct we would see increasing differences between intervention and non-intervention homes over time. But actually the benefit of insulation seems to fall as the years pass, to almost negligible levels. Not something that was mentioned in the Guardian or my article but true nevertheless.

    I’m afraid I don’t think I have properly responded to your point. I do think that government has substantially inflated savings from insulation and boiler replacement and your hypothesis about differential behaviour change doesn’t invalidate a conclusion that efficiency savings are much smaller that projected. As I’ve said above, this is partly because of lamentable air leakage and poor quality workmanship.

  31. Jamie’s avatar

    Hi Chris. Many thanks for the response.

    My main point is that the comparator group are chosen because they are thought to have had no major energy efficiency work done on them over the time period in question and yet over this period we see that the median energy saving is a little over 6% for each of the three comparator groups.

    We know that this reduction in demand is not due to physical energy efficiency measures being installed. We know that it isn’t a temperature driven effect (the NEED is based on temperature corrected data). It can’t be demographic changes because the timeframe is too short. Gas cooking is negligible and won’t change significantly. Hot water is significant but I would argue wouldn’t change much year to year as well.

    Therefore the only explanation for this reduction in comparator demand that I can think of is behavioural change i.e. comparator houses making simple, zero cost changes to heating control settings in light of increasing fuel bills. By extension, if it is changes to the heating controls which are driving this and energy demand is going down then comfort must be reduced.

    Much like it wouldn’t be valid to calculate the savings for these measures on a difference in difference basis if the houses in the comparator group had been fitted with double glazing, I don’t believe that it is valid to calculate the savings in this way if the houses in the comparator group have adopted behavioural measures.

    It’s worth noting that we do have a pretty good idea that loft and cavity wall insulation and boiler replacement work pretty well as there have been field trials conducted in recent years and I can only assume that these inform the savings which are quoted by the government as DECC funded them (I can’t at the moment find links to the insulation field trials – I’m sure they used to be on the DECC website but I can’t find them on The boiler field trial report can be found at ).

    What is much harder to account for are substandard real world installations (which I suspect were not uncommon around the time of CERT subsidisation) but I don’t believe that the NEED research gives us a true picture of the savings achieved by installing these measures and that there is not enough certainty to use this analysis as the basis of communicating the savings.

    I would argue that the savings promoted by organisations such as EST should be based on the field trial savings and that it’s down to the insulation industry to bring their supply chain into line to make sure that that quality is maintained. There is no practical reason why the field trial savings shouldn’t be achieved as a matter of course as they were simply good practice installations.

    What I think would be interesting would be for DECC to commission research whereby households in the different quartiles are revisited to find out exactly why there has been such a range in savings both in the intervention and comparator houses.

    Finally, I completely agree with you that draught proofing is a key, low cost measure that needs to be tackled as a priority. My personal view is that a good standard of draught proofing can be achieved by the householder themselves if given access to the correct guidance, materials and tools. Currently this isn’t available though. It definitely needs to have its profile raised and I think your idea of a competition is an excellent one.

    Couple the widespread roll out of draught proofing with really great advice on the setting of heating controls and I think we could achieve some really effective reductions at quite low cost.

    But we’ll still need to insulate the housing stock and we have a long way to go on that.

  32. roddy campbell’s avatar

    Anecdotal. ie me.

    Bills very high. Feeling poor. First response cut down by lessening time heating and hot water are on. Consciously use tumble drier less. Turn thermostat down. Wear Jersey. Turn thermostat further down and spot heat the room being used with electric. Do some poor quality diy for draughts by visiting home base. Put up a curtain in open doorway. Use electric blanket and spot electric heating to mitigate cold bedroom.

    Very very last on this list is spend capital sums of money on insulation and a new boiler. Even further down would be to listen to a green deal man lying about likely savings and Payback period. I would also be aware of rebound …. That if bills fell I would become less careful in my behaviour.

    But overall the starting point to all this is that I’m feeling poor. I know I can get my bills down by behaving differently. I don’t know about the other. My house is 150? years old.

  33. Sofie Pelsmakers’s avatar

    Hi Chris, interesting article/blog and comments from readers. I agree with most; and like some other readers, it concerns me that the article perpetuates the assumption that:
    1. it is not worth pursuing fabric efficiency as no/not as much ‘money will be saved’. That might be in cases where people underheat; or cannot afford to or simply their boiler is undersized to provide heat in a leaky building. That is also more likely where installs are done badly – exactly what the Green Deal tries to avoid (see my third point).
    2. A main benefit of better fabric is also ofcourse increased thermal comfort – though while there is a hint of this in the GD Occupancy assessment, the implications of this could be made much clearer in the process.
    3. People DO NOT need to borrow for the Green Deal to take out a Green Deal, making it much more attractive financially. You can have a Green Deal and borrow elsewhere/extend mortgage or pay via savings, yet still benefit from the scheme. For example, we have taken out a Green Deal (EWI) without using the finance but still benefiting from ECO grants and – if they finish on time – £650 cashback. ECO covers 65% of the cost of the EWI, with a bill of just ~ £2400 (excl. cashback) for insulating the back of our Victorian Terrace. Originally we thought we’d need GD finance, but after the quote we realised we could fund it via other means and avoid the GD finance interest rates and complexity. The Green Deal is not by any means a perfect scheme but having gone through it ourselves, it is better than doing nothing for most people. We could not have afforded EWI otherwise and there definitely is quality control on site to avoid some of the horror stories about gaps in insulation etc. But I guess good story’s usually don’t make the front page do they?

  34. Sofie Pelsmakers’s avatar

    sorry, that should read ‘ stories’!

  35. Will Griffiths’s avatar

    I could comment on a number of things here, but I thought I would provide the link to the Green Deal in-use factor document, which specifies in-use factors for GD measures (if you have not seen it). Clearly, these downgrade the estimated savings from measures, adding safety to the GD, and therefore effect payback periods and the Golden Rule:

    These in-use factors are used by GDSAP software.

    I thought the recent finding of the UKGBC regarding GD finance is relevant to this discussion. It would seem that an interest rate of 7% really isn’t the sticking point most people think or a particularly unattractive rate:

    The report launch event was summarised on the Building 4 Change website:

  36. Adam Trickett’s avatar

    I’ve observed a lot of compensation behaviour. We are in the middle of upgrading our 1936 semi. Most of the big ticket items were forced on us: the boiler was 30 years old, the window frames were aluminium and deforming, many of the double glazed panels were blow and impossible to clean etc etc.

    We took advantage of locally free loft insulation to take the loft from about 100mm to more than 300mm. We put 170mm of loft insulation under the suspended floor, replaced the glazing with A-rated triple glazing and put in an A-rated condensing boiler, and replaced all the old light bulbs with a mixture of CFL and LED. Except for two rooms we could never actually get warm at all, the rest of the house is just as warm as it ever was, but it is costing a little less to heat.

    Anyway – what is surprising to me is that everyone we talk to says “The house should now be warmer!” – which is what it mostly isn’t… I’m pretty sure that when people get a newer boiler then just end up running the house hotter because they can!

    I know I wont get my money back on the doors and windows – but most people think I will. I’m pretty confident I will get my money back on the LED lights and the loft insulation but most people seem to want to cling to the old orange coloured tungsten incandescent units and can’t be bothered with loft insulation…

    Don’t even get me started on the sloppy installation that mostly happens – you get to see that if you borrow a thermal imaging camera and have a look round…

  37. Roger Anthony’s avatar

    The single most important thing to do is….draft proofing!

    If you have not eliminated every single draft, then you have no hope of having a warm, cheap to heat home.

    As I wrote earlier, the perfect room is a Thermos flask, it is totally draft proof and well insulated with an almost complete vacuum round it.

    You need to keep in mind that the wind blowing over and past a home, creates an area of low pressure above and to the lee of the building, this means that if there are holes in your home, the heat will be sucked out and replaced by cold air.

    Start at the bottom where the incoming air will be cold and easy to trace, then work upwards. Remember you need at least two holes, one for the warm air to escape through and one for the cold air to come in.

  38. Adam Trickett’s avatar

    @Roger, you are quite right, we’ve put a lot of effort into draught proofing as we have been working though the house. The two rooms that were unheatable were mostly the result of draughts which we have now blocked up and they are usable now.

    I’ve done thermal imaging quite a bit, and while I’m no expert leaking door, windows and buildings are a constant theme…


Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>