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  • lizdarley

Douglas Road energy strategy

[Criteria 1; SADIM, Holmgren Principles, PMI, Zones/sectors, microclimates, patterns, incremental design, mind maps, ethics. Criteria 2: permaculture in my own home. Criteria 3: site development. Criteria 4; dissemination (Open Homes). Criteria 6; symmetry (Open Homes and thermal imaging parties), Criteria 7: evaluation and costings]


The story is set in an end of terrace 3 bed house in suburbia, not been touched for 60 years resplendent with 1940s wiring, 2 pin plugs and an asbestos roofed shed.  The house is solidly built, but nonetheless draughty, there’s daylight seeping in round the edges of the front door, the aluminium framed double glazed windows are both leaking heat through the metal and because they are so old they no longer close properly and there are some really weirdly placed air bricks throughout the house which simply blow cold air directly into a couple of the bedrooms.  This was an opportunity not to be missed.  The chance for me to put into action all of the knowledge I had gleaned over my career to date working as a sustainability consultant and a civil engineer.  Plus the time for me to step away from desk bound activities to learn some new highly practical skills.  (PROBLEM IS SOLUTION)

We have a number of overall decision making criteria for the house project – the 3 most important ones are:

  1. Can the design choice save energy – are we adopting a system that will save the most energy in use? (EARTH CARE)

  2. Re-use of materials, closing the loop and preventing call off of new materials.  Can we use renewable materials as much as possible – sustainable timber, sheeps wool insulation, etc?  And also in what ways can we re-use materials that come out of the build on site – and or re-useable materials that are widely available in this part of suburbia (pallets!) (EARTH CARE)

  3. Our wallet is our weapon. (PEOPLE CARE AND FAIR SHARES)

The ‘energy strategy’ – grand title!  The overall plan to reduce energy in the building is to wrap the house in a woolly jumper.  We want to make sure that as much of the heat that is generated inside from ourselves, the cats, cooking and of course the gas central heating system stays in the house for as long as possible keeping us toasty warm.  Obviously it will all leak out at some point – but we want the house to ‘catch and store’ as much energy as possible.

  1. Keep our bodies warm – invest in thermal underwear before next winter

  2. Keep any heat generated in the house – draught strip, insulate, double glazing, thermal curtains

  3. Focus heat retention in zone 1

  4. Minimise hot water use – aerators, low flow taps, A rated appliances, small bath

  5. Generate heat renewably – wood burning stove, solar hot water

  6. Generate electricity from the sun – solar PV panels (plus a financial yield from the government!)


The survey phase for this design included the following:

  1. I had done some small retrofit works on my previous flat and through this process learned what else I could have done

  2. Work at BioRegional, running sustainability consultancy for 4 years – knowledge about sustainable energy and sustainable building materials

  3. Interview every trades person I could think of who would come round and give me a quote – asking lots of detailed questions (plumbers, electricians, architects, sustainability consultants, builders, solar installers etc)

  4. Feel where cold is in the house, assess possible materials from house – i.e. look at house!

  5. Other people’s retrofits (visits, blogs/websites)

  6. Other sources of info on building design – AECB, passivhaus etc

  7. Research specific products and product combinations; Green Building Store, Ecomerchant, Greenspec, and specific product manufacturers websites.

Decision Making and Targets

The plan was to upgrade the house and ensure our electricity and gas bills be as low as possible.  In keeping with the Climate Change Act 2008 I set myself a target of 80% reduction in bills.  But quickly came unstuck – 80% compared to what?  National averages?  But I know from monitoring our bills data in our old 2 bedroom flat (the ground floor of a leaky Victorian terrace) we are already 60% better than benchmark data for that house type.  Granted we had some energy efficiency measures installed, plus our normal behaviour – multiple jumper wearing and keeping the thermostat at 19.  So our personal benchmark isn’t the national average.  When I set out on this project I felt a target was important otherwise how else would we ever achieve our goals – the engineer in me!  But as time went on I realised that not only do I not know what to compare the reductions to I also don’t have a simple way of measuring the impact of individual design choices.  There are software and tools out there that could do this – but they are not available to me.  Plus the ultimate reductions will always be influenced by behaviour – so the high level target went out the window.  (APPLY SELF REGULATION AND ACCEPT FEEDBACK, original design concept was not appropriate to this design)

Over time I found The Association of Environmentally Conscious Builders (AECB) ratings which is a set of criteria for new builds and retrofit setting out good practice thermal performance for elements (walls, floor, roof etc).  The silver standard seemed good to me – better than Building Regs but not as far reaching as Passivhaus (German standard for houses requiring zero heating).


  1. Previous consumption data from our old flat

  2. Possible targets, decision making criteria and design parameters, pros and cons]


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So I have insulated with 140mm of sheeps wool insulation (Thermafleece), a renewable material (USE AND VALUE RENEWABLE RESOURCES) under the ground floor to prevent draughts from the floor void under the floorboards from coming up to cool our feet.  In addition I have draught stripped between the floorboards – yes this is belt and braces approach – but using the permaculture principle of multiple elements with the same function – if one of the systems fails we should still be ok.  One final element of the floor design has been to seal the draughts around the skirting boards with my trusty tube of decorators caulk – this plastic/toothpaste-like material squeezes into the small gaps and stops the draughts coming into the room.  The acid test was with the back of my hand on a cold windy day – pre-caulking there was some serious cold air blowing into the rooms… and now with caulk installed it is no more.  Draught stripping has been a low cost option and once the draughts are no longer coming through it’s possible to keep the temperature inside the house lower and still feel comfortable.

Insulation u value calcs

Insulation u value calcs


The loft is where most of the heat in the building is lost (maybe 35 – 40%), so making sure that the house has a very good hat on is vital.  We are undertaking a loft conversion so the loft insulation is going into the pitched roof and into our new box dormer.  My original design decision was to use Pavatex products from Natural Building Technologies – these are woodfibre boards and batts, using waste wood from industrial processes and converting it into a useable insulation product (PRODUCE NO WASTE).  These insulation materials are breathable, don’t release nasty chemicals into the air and lock up carbon (due to being made from wood) as well as closing a loop by using waste materials win win win win.  However – with a builder coming on board to build the loft conversion I’ve had a slight re-think (CREATIVELY USE AND RESPOND TO CHANGE).

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There is a downside to using woodfibre board – which is the thickness of materials (120mm above the rafters + 175mm between and below rafters) required to achieve a good u-value (0.15W/m2K) coupled with the (100mm) air space needed to ventilate the material to allow it to do it’s breathing thing making for a pretty thick roof.  To save space to gain more headroom in the loft we have decided to reach a compromise, we have decided to use a highly manufactured but super thin material called Tri-iso (Actis Super 10+) – like a space blanket coupled with some Pavatex to get the u-values to approx 0.16W/m2K – which I’m happy with and we get a roomy loft – brill compromise and keeping the heat inside the house.


  1. U-value/cost/company manufacturing ethics comparison of different products]


The windows were a difficult choice… PVC windows are widely available, cheap and do the job – but many PVC windows degrade


There remain some decisions to be made about the front door – with light and therefore cold air pouring in around the sides.  (SMALL AND SLOW – focus on the big areas first and prioritise)


The final piece of the woolly jumper on the house puzzle was to install insulation onto the external walls.  There are two possible ways to do it – (1) on the inside in which case you lose space in the rooms (not great if you want to sell the house in the future) and there are all sorts of issues with thermal bridging and damp that arise when doing the inside so we decided against this option – or (2) on the outside.  Outside is simpler you just get big sheets of insulation and fix them to the walls in long runs much less fiddly than the inside… so we opted for external.  However the prices we were quoted tripled during the project.  I tried to look in detail at the potential savings – but found it hard to find real and accurate data.  Based on our behaviour I estimated it would take 60 years to payback, and also considered how much thermal underwear could be bought for £10k! (the approx cost of the works). We have put the walls on hold for now.

We thought seriously about our zones when making the wall insulation decision – the zone 1 of our house where we spend most our time will be our new kitchen/dining room – which will be super warm because of the newly built highly thermally efficient walls.  Our zone 2 – the bedrooms – only need to be warm at night and when we get up, they’ve been draught proofed and only have 1 external wall each so heat loss from each room is not too bad.  The coldest part of the house is our zone 3 – the stairs and hall – which has the largest expanse of exposed external wall on the north side.  If we keep the internal doors closed and draught proofed, therefore preventing the colder air leaking into the warm rooms – then the hall being a little colder shouldn’t make too much of a difference.  We need the warmth of the house in our zone 1 – where we have also installed a wood burning stove to provide us with free heat from renewable sources.

But it is not a closed book now that we have two very thermally efficient rooms (our zone 1 kitchen and our bedroom in the loft) I can really notice the affect, thermal comfort is an important factor and to be in a space that requires little heating and still feel comfortable is great (RESPOND TO CHANGE, OBSERVE AND INTERACT).  I have been investigating the use of cork as an insulation material, I could do it myself, it would cost less, and it would support the very troubled Portuguese cork industry. (SMALL AND SLOW, VALUE THE MARGINAL – cork is an edge product in insulation terms).


The hot water plan is to make sure that all showers and taps are aerated and low flow to reduce the water coming out of the tap (VALUE RENEWABLE RESOURCES).  And then we are going to try and install some solar hot water panels into the twin coil cylinder (INTEGRATE RATHER THAN SEGREGATE) (which was required to replace the very old, very leaky hot water cylinder which currently doesn’t hold heat in the tank for very long and mainly heats the airing cupboard – great for germinating plants but a bit of a waste of fossil fuel energy I think!)  The location of the panels is proving to be a bit tricksy.



So to summarise the design and implementation of this project:

  1. Keep our bodies warm – invest in thermal underwear before next winter

  2. Keep any heat generated in the house – draught strip, insulate, double glazing, thermal curtains

  3. Focus heat retention in zone 1

  4. Minimise hot water use – aerators, low flow taps, A rated appliances, small bath

  5. Generate heat renewably – wood burning stove, solar hot water

  6. Generate electricity from the sun – solar PV panels (plus a financial yield from the government!)


The only way to identify the success of the strategies implemented will be to monitor our performance over the coming winter (the works were mostly completed by Feb 2013 so the 2013-14 winter will provide a complete winter’s worth of monitoring).

The monitoring plan is as follows:

  1. Weekly meter readings for gas, electricity and water

  2. Use imeasure website to record meter readings and assess against degree day analysis

  3. Observe how we use the house once it is no longer a building site and actually a place to live and assess if the analysis is appropriate to our useage patterns, tweak as appropriate

  4. Analyse meter readings quarterly to identify design tweaks and improvements

  5. Consider implementing the ‘next steps’ identified below

  6. Thermal imaging of the house to assess what is and isn’t working, work with Transition Town Kingston to implement a thermal imaging party in my street to include my hous

  7. Update this blog post with actual energy usage as I get the data


  1. Make final design decisions on solar thermal, wall insulation and front door

  2. Share my knowledge with others:

  3. web article,

  4. use this design as a teaching aid on my intro to permaculture courses

  5. contribute to the newly formed Kingston green building group

  6. thermal imaging party (as above)

  7. perhaps consultancy – I have already done this informally through friends and formally through a consultancy report on another house


  1. I had a very long survey phase through my previous work, previous flat project and through the first few months of owning the house and not doing anything but interviewing trade which allowed me to get to know the building.  No ‘design as we do’ on this project!

  2. A lot of the analysis took place as and when I needed to do it for the design of a particular element, there were a number of analysis/design cycles that I went through as the pattern was developed into detail.  There was a lot of analysis on this project – particularly numerical data analysis of consumption, u-values etc.  It feels like analysis was a bigger element of this project than some of the other designs I’ve done, I wonder if this is because I had the knowledge built up over years working in this sector to know what and how to analyse, compared to some of my other projects which have not had so much analysis because I was working in technical areas that are newer to me.

  3. The timing of the project (house purchase just as I was doing my PDC) was perfect for being able to see how permaculture integrates into the engineers approach.

  4. I could have tried to use a few more design tools in the early phases e.g. PMI, an adapted form of PASE – but this was really my very first attempt at integrating permaculture into my work (even though it’s one of my later write ups!) and I don’t think I fully appreciated the usefulness of some of the permaculture tools at the time.

  5. The biggest lesson from this project overall has been developing my skills and the confidence to use those skills – I am now reasonably confident carpenter and tiler and I can have a go at plumbing and electrics, these skills I gained through observation first and then working up slowly in my competence as I developed my skills.  These are really important and valuable life skills that I am pleased to have confidence to do now.

  6. I understand how houses work!

  7. Time was another key factor in my personal people care.  Allowing myself time to think through the problem, developing the solution and then implementing (even if it required some time to learn the skill) without strict deadlines has made it a period of abundance and learning for me.

  8. Costs – this is an extract from the costs spreadsheet, overall for the total retrofit project we came in at our budget with some elements costing more than anticipated but savings being made elsewhere. 1Windows£15,745.002Insulation – side + back walls (internal) tbd3Insulation – front (internal) tbd4Insulation – ground floor£761.665Bathrooms and plumbing – total£5,566.046Woodburner£1,958.007Hot water tank Incl in plumbing8Solar thermal tbd9Solar PV£6,127.09

  9. Time – the overall project took approximately 6 months longer than I had anticipated at the start, this was due in part to my naive time planning having never programmed a project like this before and in part due to stopping for 6 months to wait for the long wet winter to pass and finish off the final external elements.

September 2014 update

Following the monitoring plan I have been taking weekly meter readings.  Using 2 years worth of data I have worked out the total annual consumption and the % improvement from typical similar houses shown in the table below.  I have put a range of figures for improvement because there are a variety of different sources quoting different typical UK average figures (the problem I highlighted in the beginning).  Our electricity consumption is almost entirely offset by the solar panels so we are close to net zero on electricity.  In addition to the numbers the thermal comfort levels of the house are now SO much better we have plesant and warm spaces to live in.

We have joined the Superhomes network and have been assessed to have a 62% carbon reduction in the building fabric, the property was open for our first Superhomes open day on 13 September and 12 people came round.  We are planning a thermal imaging party based at our house and including others on the street in January 2015.Ave June – June% improvement on UK average for similar house/useage patternsElec, kWh/yr165050 -75%Gas, kWh/yr                   10,95030 – 65%

#building #design #energy

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