SuperHome Database

London, Balham, Cornford Grove

House Summary

Susan Venner
House Type:
Victorian 6-bedroom semi-detached 3-storey house
Carbon saving:
60%+ - SuperHomes Assessed  
Reported saving on bills:
The bills are now a third of what they were, so we have saved two thirds
Total invested:
approx. £27,500

Measures installed:

  • Condensing boiler
  • Double Glazing
  • Draught-proofing
  • External Wall Insulation
  • Floor Insulation
  • Internal Wall Insulation
  • Loft Insulation
  • Low Energy Appliances
  • Low Energy Lighting
  • Solar Water Heating
  • Triple Glazing
  • Water Saving Devices
  • Wood Stove

  • Balham SuperHome
  • ext_Insulation_London_Balham_Venner
  • Wood stove_Cornford Grove

Upcoming events

Early interest in Open Days encourages SuperHome owners to host more events. If you'd like to visit this property please contact the owner and let them know. SuperHomers are often happy to respond to questions about their refurbishment project by email between times. Please read ‘more on contacting this SuperHomer’ before you make contact.

What visitors are saying

"Impressive how much difference insulation makes."

"A practical/hands on visit like this is invaluable for "real life" knowledge compared with the theory we know."

“Really interesting to see how someone has pragmatically managed to achieve sustainable carbon reductions on a budget- not just another sales pitch.”

"Very informative and useful about what to do on a budget and what is the most important."

"Useful to see things in situ. Great project, I liked the cork exposed - brilliant!"

"I think it is very good of people to open their homes like this. It is useful to hear what works in reality… A very rewarding visit"

"Impressed by the carbon footprint reduction. Very friendly and knowledgable host. Statistics/graphs were impressive!"

"Very inspiring to see what can be done and successfully implemented. Loved the exposed cork insulation - it looks very good, insulating without losing the aesthetic quality of the house."

"It was an eye opener of how to improve your home on a budget."

Personal story:

I am director of VennerLucas architects, a practice specialising in sustainable buildings, eco retrofits and passivhaus new builds. I have had a keen interest in the environmental building sector since I was a teenager and throughout my career.


We set ourselves the task to reduce our carbon emissions by 80%, in line with the government’s targets for 2050. Our aim was to test the feasibility of a nationwide strategy of retrofitting to reduce carbon emissions, on a limited budget, while also realistically assuming that people won’t be able to move out for the duration of the works.

We undertook the refurbishment over a three-year period, starting in July 2010, while living in the house.  The majority of the works were undertaken during the summer months. Prior to commencing any of the works we produced a detailed programme, which set out the sequencing of work, the specification of materials and an estimated cost, over the 3-yr period in order to avoid any unnecessary abortive work while also allowing us to spread the financial burden.

Property background:

This Victorian, semi-detached, 6-bedroom house was built in 1876.  I have lived here with my family (husband and 2 children) for just over 15 years. Before the retrofit the house was cold and draughty, and very much a classic hard -to-heat house.

Key changes made:

The key change was installing insulation, although we did change the boiler as well, which has made a big impact on reducing our carbon emissions.

Measures installed in detail:

• New 92% efficient condensing boiler
• New double glazing fitted into existing old sash windows from Slimlite with Low E glass, Krypton & Zenon in the gap – U-value 1.9.
• Rationel double glazing to rear windows – U-value 1.12. (Cost £300 – £400 per window)
• Draught stripped all windows and front door
• External wall insulation using 180mm cork insulation (in 2 layers)
• Floor insulation using 100 mm Rockwool and 100mm Celotex
• Internal wall insulation using 120mm cork
• Loft insulation using 300mm Rockwool
• Low energy appliances include an A-rated dish washer and washing machine
• 90% Compact fluorescent lights, we are slowly replacing the remaining halogen lights with LEDs
• Solar Thermal System – 8 sqm panels (Ferroli Ecotop VB), providing hot water through late spring to late summer/early autumn (depending on levels of sunshine) we usually turn the boiler off during this time. During the winter months the panels provide some pre warming of water going to the boiler (again depending on levels of sunshine)
• Triple glazed sash window to one bedroom – Danrose Vrogum  (U-value 0.9)
• Water saving devices include 2 low flush loos, a flush reducer, low volume showers and spray taps
• Wood burning stove in living room. Wood is collected from friends and neighbours gardens and from street prunings.

Benefits of work carried out:

Before the retrofit it was too costly to regularly heat the house in the winter to level where we felt comfortable. However, following the improvement works we now have a house where the internal temperature is very comfortable and where the house is significantly warmer and draught free throughout the winter months, our energy bills are significantly lower (approximately a third of what they were before) and most importantly with a 65% reduction in our carbon emissions.

One unexpected benefit has been that as a consequence of installing internal wall insulation, we now have window sills. This is an added bonus because you don’t normally have window sills with sash windows.

We are still monitoring our energy consumption on a monthly basis and it’s become very apparent that lifestyle has a significant impact on energy consumption even in a well-insulated house. If you take your eye off the ball and don’t turn radiators down or off when you’re not in the room it can significantly increase your gas consumption. So, to a certain extent, you cannot just install energy saving measures and forget about them, you have to be thinking about changing your behaviour as well.

Favourite feature:

It is difficult to chose just one because they are all interrelated and all work together to improve the thermal comfort of the house.

Project update:

We are continuing to replace the remaining halogen lights, with LEDs.

One thing that we are currently working on is dealing with the cellar door. This is a bit of a tricky issue in all buildings with a cellar and requires finding an appropriate way to draught strip it.

Common questions and answers for this SuperHome

How do I install double glazing panels into the weighted sash windows of my house?+

If you replace the single glass in your sash windows with double glazing you will have to adjust the sash weights as the double glazing is twice the weight of the single. I suggest you look in the sash pockets and see how much depth you have below the existing sash weights. You will need to calculate the additional weight you require and either add to the existing weights – which are most probably cast iron. If you cannot get the additional length of cast iron into the existing pocket you will then have to see if you can fit lead weights in – these are heavier than cast iron – so you need less depth for the weight. Lead weights are however more expensive. In our windows we ended up replacing all the cast iron weights with new lead ones.

Do you get condensation with the Slimlite double glazed units?+

We don’t get any.

Will external wall insulation help clear up damp? Or could it make it worse?+

If there is damp you should deal with it before covering it up.

Which company did the cork external wall insulation work for you?+

We installed the cork insulation ourselves. It wasn’t difficult, but you do need some basic building skills and scaffolding. The cork insulation has been really effective in reducing heat loss and improving internal comfort of our house.

However, I must state that our use of this cork is experimental as it is supposed to be rendered. We didn’t render it because it would have been to stark a contrast with the rest of the house. Our cork is also on a very sheltered wall.

Which supplier/ products did you use - for both the cork and fixings?+

We got our cork from Environomix. The fixings we used were from ejot.

Did you check for interstitial condensation?+

I did have an interstitial condensation calculation done to check the dew point would be on the right side of the wall.

What we did with the cork on the north side of house was experimental as it is supposed to be rendered. It is essential to get an interstitial condensation risk analysis done for any walls that you are intending to insulate to ensure you are not going to get a dew point on the inside of the walls. The company selling the cork should be able to do this for you. We fitted the cork ourselves.

Note that if your current walls are damp you really need to understand why this is happening before you cover them up. And then let them dry out before installing any insulation.

Did you use any sort of moisture barrier under the cork?+

We did not use any vapour barrier – but we did have a condensation risk analysis done of the make up of the proposed insulation.

How did you fix cork to the internal walls - adhesive or screw/nail?+

We fixed the cork using proprietary external wall fixings from Ejoit – which are thermally broken and expanding.

I like the idea of avoiding render and adhesives - just mechanical fixing, with the external cork insulation. Has this worked well for you?+

The recommendation from the cork people is that if used externally the cork is rendered. We chose not to because our external wall faces due north (thus very little UV degradation) and is very sheltered by the neighbouring building which is only 1000mm away. Our cork installation is effectively an experiment and so far it is performing very well, but we cannot and do not recommend our approach for any other building. So please, if you choose not to render, be aware that it is at your own risk.

Did you fit it in one 120mm layer or a couple of layers to stagger joins?+

Internally we fitted either 120mm in two layers (70mm and 50mm) with staggered joints and in some places it was 150mm thick in just one layer (this is because we had cork left over from the external wall to use up).

Did you remove plaster and attach to bare brickwork or just attach it straight onto the plaster?+

We did not remove the existing plaster from the walls. We fixed the cork directly to the inside plaster.

Would you still recommend cork for wall insulation...vs say wood fibre or insulated plasterboard?+

I can’t really say I would recommend cork over wood fibre or insulated plasterboard as they all have a slightly different properties – eg thermal conductivity, embodied energy, easy of fixing etc. but I can say that we are very happy with our internal and external cork wall insulation and I would use it again.

But please note that the way we installed our cork insulation was rather experimental (I.e. No vapour barrier internally , no render on external cork). It is not what the manufacturers recommend/suggest. So we cannot and do not recommend our approach, if you decide to follow our approach please be aware that it will be at your own risk.

Contact this homeowner

Assessment types

SuperHomes Assessed

A home that has been visited and assessed by us and confirmed as reaching the SuperHome standard, which demonstrates a 60% carbon saving.

Homeowner Reported

Information has been provided by the homeowner about their home and energy use prior to the installation of measures and following their installation which demonstrates a carbon saving. This information has not been verified.

Remote Assessed

The homeowner has provided information on their home including what measures have been installed which has enables an assessor working on our behalf to assess their carbon savings. This home has not been visited to verify the measures installed.


This home has not been assessed, but the homeowner has reported what measures have been installed. It may be that this home is awaiting assessment.