HPH008 : Retrofitting a Victorian House to Passivhaus Standard #1 – with Tom Pakenham from Green Tomato Energy
Tom Pakenham from Green Tomato Energy describes the practical challenges of making a Victorian house energy efficient. Plus how passive house principles helped a Norwegian explorer in the 1890s.
Interview with Tom Pakenham
Tom explains that he wanted to do something about the way we treat the planet and he believed that the best way to do that was by setting up businesses in the environmental sector. It started with Green Tomato Cars, a minicab company which runs on low emission principles. Then the Green Tomato Kit was launched, a green starter kit for the home. The third business in the group is Green Tomato Energy which exists to help people reduce their environmental impact through their homes. They also offer a consultancy service for low energy building.
New Build Not an Option in London
Tom lives in West London where there are virtually no opportunities for new build and, as he had no intention of moving away from family and friends in the area, it was logical to renovate a property. Most of the building stock is from the late 19th century and early 20th century, and Tom wanted to create a low energy home that was also sympathetic to the cultural heritage and was a beautiful building. A lot of people tend to think of eco homes as looking like bomb shelters or nuclear bunkers. This project set out to dispel that myth.
The Passivhaus Standard is Flexible in Terms of its Application
Over a year and a half Tom was introduced to Passivhaus. The better acquainted he became with the options, the more attractive the Passivhaus standard became. He particularly liked the fact that it was not a prescriptive way of building and that the principles could be applied to the geometry of the existing structure in order to work out a way of making it perform to the low energy standard.
Attention to Detail is Important
After selecting your architect and energy engineer, Tom advises to spend time with your design team to make sure what they’re designing will work within your budget and within how you want to live in the property. Don't rush this planning stage because this is where a lot of time can be saved further down the line. When assembling your team, look for a builder who is not only technically competent but understands what is trying to be achieved and why. This must also filter down to all other workers. If you fail on the detail, then the whole project can come into jeopardy.
Be Prepared to Learn Along The Way
No matter how much planning is done upfront, when a period property is stripped back there may be some surprises. Tom thinks that as long as you approach the project with an open mind and the understanding that something might change and you might need to learn things as you go along, then you’ll be fine.
The Risk of the Project is More Psychological Than Real
When Ben expresses a concern about the potential for ruining an old building by carrying out this type of extensive work, Tom reminds him that there is a risk but this is not like jumping down a well! If the project has been designed well and the work has been carried out properly, then it's not an issue. Its structural behaviour and its energy behaviour is something that can be worked out and designed. Changing insulation or cutting off thermal bridges will have an impact on the joists or brickwork, etcetera, but it can be predicted.
Triple Glazed Sash Windows
Tom explains some of the challenges around finding windows. In the end he had to have his windows specially made. The top frame is fixed and the bottom pane opens on a tilt or turn mechanism, so you can open it like a door or tilt it inwards. So they’re not actually sash windows. Triple glazed sliding sashes look unlikely to be become popular due to their cost. The issues include the increased weights necessary to balance the extra weight and also how you create a proper airtight seal.
The big advantage of triple glazing in the city is it acts as a great sound insulator.
Payback in 35 Years
Although this project was one of the first of its kind, there would still be a straight-line payback in 35 years. That assumes no capital uplift in the cost of the house. Also as energy prices rise that payback gets shorter and shorter.
However, Tom doesn't believe it is helpful to look at it in these terms. He emphasises the comfort and improved air quality of the building: you are creating a great place to live. He gives another example of when you are installing something like a kitchen, you rarely look at the payback and that you really want the great environment it will give you.
Tom's Top 3 Tips for Renovating a House with Energy Efficiency in Mind
- Spend more time planning than you think you need. The work is much easier with a proper plan.
- Make sure you have a good team that understand the objectives and buy into the project.
- Have enough money to finish. The last thing you want is to be caught halfway through and unable to finish in a completely gutted house.
Watch a Video About This Project (Lena Gardens)
Tom Pakenham and his design team explain the work that was carried out to this Victorian terraced property.
Download a transcript of the interview with Tom Pakenham.
Energy Efficiency in the 19th Century
In the last session Ben Adam-Smith mentioned the eco houses from the Home World exhibition in 1981 and he thought that was incredible. However, after attending a talk by Mischa Hewitt from Earthwise Construction at the Retro Expo, Ben is now aware of an eco ship over a century ago.
‘The Fram' of Fridtjof Nansen was a ship built for polar exploration and had many pioneering designs, including in the cabin:
- Highly insulated cork and felt
- A triple glazed skylight
- An airtight layer of linoleum
- Good ventilation
According to the 1897 publication ‘Farthest North' the ship had a stove in the cabin but it was never lit because the temperature was warm and comfortable already. In fact they even thought of getting the stove removed!
Ben reads out an email from a listener, Dr James Shorrock, who is about to renovate his own house. He talks about ‘researching the usual heat pump options' but after listening to the podcast ‘thinks maximising the building fabric/insulation has got to be the best starting point'. Dr Shorrock has also requested a future episode on SIP panels.
The Construction Industry Podcast
If you like podcasts and you work in construction, Ben recommends checking out The Construction Industry Podcast with Cesar Abeid. There's relaxed chat with construction professionals, plus Cesar shares some great marketing strategies for your business.
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