Demonstration House

We recently undertook a wholesale refurbishment of a period property in Peckham, South East London – its award winning and a Superhome. It’s owned by our Commercial Director and most of the work to the main property was carried out by him and his family. It’s now our demonstration house. As you will see below, it has not only been a stunning success in what it has achieved outright but most importantly in terms of the cost effectiveness of the renovation compared to the savings.

If you want to view the project as a Prezi then click here.

The property needed a bit of care and attention, and essentially needed gutting, so they weren’t able to live in it during the major works.  Here is an overview and some pictures of how it was to begin with:


  • Victorian, built 1875
  • Semi-semi detached
  • Solid walled
  • Difficult to treat alley
  • Rubbish insulation throughout
  • Electric storage heaters as primary heating
  • <65% efficient hot water boiler
  • Room gas fires
  • Blown plaster throughout
  • Leaky (unattractive) PVC windows



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Here are some before plans. 
On one side it is detached with the main entrance down an alley.  On the other it is attached on two storeys. The rear projection is also over three floors, although the top floor was added in the early 1990s and is aerated concrete block



The main roof is pitched and had the remnants of mineral wool insulation but not huge amounts.  The rear projection flat roof had some foam board insulation between the joists but expected to be only around 50mm.

The main ground floor is uninsulated and timber suspended and the rear projection solid with just a 10-20mm screed over bare soil!

All the windows other than the ground floor bay single sashes were older double glazed PVC windows which were leaky around the frames.

Heating was a mixture of electric storage heaters and room gas fires.  Hot water was provided by a very inefficient gas boiler.

Project Philosophy

At Parity Projects, whilst we agree with the general principles of Passiv Haus, our experience has shown us that in most renovation circumstances, similar levels of performance can be achieved for a fraction of the cost, and hence much more cost effectively, using simple good quality products and techniques supported by a detailed and holistic plan such as our Home Energy Masterplan….more on our results later.

As such, these were the guiding principles of our projects:

  • Cost effective – for most people there is very little point doing energy works otherwise.
  • Scalable – we wanted to use materials and systems that were available to anyone
  • DIY where possible – like most people we were working to a tight budget
  • Finish with a house that looks normal – it doesn’t make for a blow your mind tour, but it does show that this can be mainstream and make our houses still look really comfortable.
  • Aim for an 80% Carbon Dioxide reduction

So overall we wanted to show that anyone can do all or some of this – and it shouldn’t just be a pipe dream.

Standard Renovation Aspects

As the house needed a lot of work to just get it habitable there were quite a few aspects that had to be done anyway. We split the cost of these out so that we can present a final ‘eco renovation’ cost uplift.

  • Gutting – all the curtains, wall coverings, floor coverings, kitchen and bathroom suites were not in a usable condition and so needed throwing away and replacing.
  • Re-wiring – from a safety aspect it was deemed best to start again.
  • Replumbing – the limited amount of plumbing and changing of the bathroom meant that total re-plumbing was the best option. A central heating system would also be required and considered something that would be done as part of a normal renovation.
  • Damp-proofing was stipulated by the mortgage company
  • Re-plastering / dryling – much of the plaster on the walls and ceilings was blown and starting to fall off. In most circumstances, one you pulled some down the rest came tumbling after.
  • Kitchen and bathroom – these hadn’t been replaced for many decades and had reached the end of their useful life.
  • Re-pointing – especially at the front, the pointing was crumbling and a small knock with a hammer caused it to fall out.
  • Extension – how we use a house has changed and the proportions of the rooms no longer suite modern living.  We therefore took the opportunity to add a kitchen and alley extensions. We have considered these new build aspects and so have not included their basic construction in the ‘eco renovation’ figures.

What did we do?

First of all we carried out a Home Energy Masterplan assessment to work out what were the most cost effective and appropriate solutions.  Once we had a plan for each aspect we set off…

Walls – the main building front walls were internally insulated to 50% better than current Building Regulations.  The rear projection walls were externally insulated to a similar standard.  This cut the heat losses by a factor of around 10.

Almost done








P1050591Roof Areas – the main roof area was insulated with mineral wool over 300mm, the flat roof are the rear had an extra 100mm of foam board insulation installed and the bay roof was insulated with a mixture of mineral wool and foam board insulation.


Windows – All the windows other than the original sashes, were replaced with new Building Regulations compliant windows – a mixture of sash and casement.  Analysis showed that it wasn’t cost effective to install triple glazing. The sash windows in the bay were overhauled and had thin double glazing installed. New windows in the kitchen extension were triple glazing.








IMG_2591Floors – the ground floor of the main building had the floorboards raised, ventilation increased and insulation added between the joists. The thin screed over the kitchen floor was removed, soil excavated and 100mm of insulation added before a new screed was laid.




Heating System – gas central heating was decided upon as the best option. Its efficacy was improved by installing  four heating zones to minimise unnecessary heating. Because of the super insulation each room only needs a small radiator. A wood burner was also installed in the living room.

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Hot Water – this is provided by a mixture of the gas boiler and a solar hot water system.


Lighting and Appliances – High efficiency LEDs are installed in virtually all light fittings and top specification appliances were chosen

The Alley – this posed a serious problem. It couldn’t be insulated on the alley side, i.e. externally as the alley would become prohibitively small. It couldn’t be insulated on the inside as that was were the staircase was.  The solution was to enclose it with a side extension which would become an unheated buffer zone. In reality we also knocked into this extension on the first and second floors to create an ensuite and a large wardrobe respectively.

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Ventilation and Draughts – sensible draughtproofing of doors and windows was carried out, and a thoughtful approach taken when installing insulation etc. Ventilation in the form of through the wall heat exchange extractor fans were installed in the bathrooms and kitchen.

What was achieved?

  • Modelled CO2 savings around 78% (SAP) to 83% (Parity Home Energy Masterplan)
  • Total spend (excluding renting somewhere else, stamp duty, legal):   ~£100,00 although this includes building extensions, new kitchen, bathrooms etc
Marginal additional spend on eco stuff < £35,000
  • £10,000 PV (bolt on)
  • £3,000 Solar thermal (mainly for fun)
  • £8,000 windows (were they really for Eco reasons?)
  • £5,000 external insulation
  • £6,500 insulation, additional heating controls, lighting, thin double glazing (i.e. less than my kitchen)
Increase in value estimated at around 60%
Running costs – negative (thanks in part to the UK public!)


The Bills

Gas – we used 6,000kWh in the 12 months to end March 2014.  This means it’s been an overwhelming success.

Electricity – Generated – we are generating around 2,100 kWh a year and importing a similar amount.

CarbonBuzz Graphs IIIThe usage is now being input into CarbonBuzz, to give some graphs comparing modelled data with actual bills.



All in all that will be a net of under 2 tonnes of CO2 a year.  It’s worth comparing that with a similar sized award winning Passiv Haus property (albeit a terrace) which I’ve estimated has a net CO2 emissions as 2.6 tonnes per annum based on information published for 2011 to 2012. Even if we take our unfinished house and the coldest winter in 50 years we only used 2.5 tonnes CO2.  We also suspect our renovation was significantly less that the cost of achieving the Passiv Haus standard.

Finally some pictures of our project:

1 Front Elevation 2 Front Door 3 Hope Villa 4 Rear Elevation7 Sitting Room B6 Sitting Room A8 Kitchen9 Master Bedroom
13 Ralph's Room10 Ned's Room14 Guest Bedroom12 Main bathroom 16 Enclosed Alley11 Stairs15 Extension roof18 Garden B 17 Garden A