What is retrofitting? Who better to ask than Marion Baeli and Robert Prewett, architects who have spent the last 2 years retrofitting their 1960s family home in Sydenham, South London. Blue Patch’s Youth Blogger Phoebe is on the case…
“It’s all about comfort” says Robert, welcoming me in ‘Improvements in energy efficiency, through steps such as insulation (phase 1) and replacing windows (phase 2) are more of an added bonus than the main aim of the project. In a well retrofitted home, you don’t need to cautiously adjust the central heating throughout the day or keep alternating between dressing gowns and jumpers just to be comfortable. You don’t have to choose between having a natural air flow and being warm either– retrofitting your house will result in better air quality, consistent temperature and of course energy efficiency’ .
Immediately I notice is how light and airy the house is. “It’s about opening up the space”, Robert tells us. They have installed two skylights on either side of the house, which let natural light filter all the way down to the ground floor, helping to compensate for the deep floor plan of the house.
To make the house airtight, blue tape has been applied between the window frame and the wall material. A ventilation system with heat recovery is being installed, it’s basically a metal box with two fans which supplies fresh air and extracts stale air, recovering the heat through metal plates in the process, which means free energy! This allows for a constant flow of fresh air into the house without needing to open windows.
This house is being retrofitted to achieve PassivHaus certification – a building standard with a set of criteria which, when met, ensures that the house performs with low energy costs and very high comfort standards. Marion explains the key principles, which include insulation, installing triple glazed windows, ventilation, and building with airtightness details.
You’ll never find this family huddling around the radiator in winter. Thanks to the extensive insulation, the temperature inside remains constant: including all the floors, every type of internal and external walling; cavity and solid, the roof and finally the loft envelope. In fact insulation is the most efficient and effective thing you can do to your home to improve comfort and energy efficiency.
Installing loft insulation is straightforward – just make sure you insulate your loft hatch too.
You can check that you have cavity walls by drilling a small hole and putting a camera through it* – the cavity should be at least 40mm deep for insulation with blown rockwool; eco-beads are better for smaller cavities. *Cavity wall installers can check if your home is suitable.
Of course, we all know that replacing your windows with double glazing can have a huge impact on your energy bills. If you’re already planning on doing this, it may be worth looking into triple glazed windows, as the price gap is narrowing. Alternatively, secondary glazing, a cheaper option, can halve heat loss compared to single glazing and is particularly good for Victorian houses which still have their original charming windows.
So a quick recap. This architect power couple have done virtually everything they can to improve the energy efficiency of their home, from whole house insulation to a specialised ventilation system with heat recovery. Their triple glazed windows are on the way! Of course, you don’t have to do all this to cut down your energy bills – for anyone thinking about retrofitting it’s insulation, insulation, insulation!
On a budget? You can plan your retrofit over a longer period where works are undertaken piece by piece with an overall plan acting as a roadmap. Do consider using a designer experienced in retrofit, look out for qualifications such as Retrofit Coordinator or Passivhaus Designer. The most important thing is your designer has experience of doing the sort of thing you are looking for and is able to manage expectation, costs and build you a workable plan for your home retrofit.
If you want to see how to retrofit using primarily natural materials, take a look at my blog on retrofitting an Edwardian home.
Written by Phoebe Rowe a final year Psychology student at UCL, interested in behaviour change around sustainability and climate change mitigation. Linkedin
Blue Patch would like to thank Marion and Robert for welcoming Phoebe into their home and demonstrating a retrofit in action!
Marion Baeli is an architect and sits on the Board of Directors for the PassivHaus Trust. Marion is a Partner heading the Sustainable Design Group at PDP London and author of ‘Residential retrofits, 20 case studies’ ( 2013 RIBA Publishing) her passion is to spread knowledge and expertise on the fundamentals of retrofitting and to engage more people in how proper insulation will save as much as 80% of carbon loss from your home, creates a heathy and comfortable environment and save money too.
Robert Prewett heads the London office of Prewett Bizley Architects and has expertise in low-carbon construction, particularly in the field of retrofit. He is a certified Passivhaus designer and a member of the RIBA Sustainable Futures Group which advises the profession and government on the incorporation of sustainability in education, standards and policy. He is a founder member of the Passivhaus Trust and a technical advisor to the STBa (Sustainable Traditional Buildings Alliance). Prewett Bizley Architects were Sustainability Architect of the Year Award 2017 – Winner