architecture design

Building of the week: RenovActive

I’ve been exploring the Active House idea over the last couple of weeks, explaining what it is and then looking at the first building to receive the certification. I’ve got two more posts on the subject, and today I want to look at renovating to Active House standard. This is really important, because we can’t tear everything down and build a whole new housing stock in response to climate change. It’s too expensive, slow, wasteful, and too disruptive. Buildings last a long time, and 9 out of 10 buildings in Europe today will still be in use in 2050. So renovation matters.

Generally speaking, it is very hard to renovate to zero carbon standard. To make a home with low or no heating requirements, you have to have a level of insulation and air-tightness that’s almost impossible to add afterwards. Orienting a building correctly is a big part of sustainable design, and there’s not much you can do if it faces the wrong way. That’s why there’s only one true zero carbon renovation in the whole of Britain. I profiled it last year.

That one example proves that ‘almost impossible’ is not the same thing as impossible though. Radical renovation can be done. The real challenge is to make it affordable, and that’s where Belgium’s RenovActive project is interesting.

The challenge was to take a rather run down 1920s semi-detached home and transform it into a bright and efficient modern home, keeping within the budget of an average housing association renovation. The project would be a learning exercise and a demonstration from Velux, and it had to be reproducible.

There are a number of elements to the redesign. The house was extended upwards into the loft and out at the back. Extra windows were added to the side and the roof, bringing more daylight and better ventilation. Solar shades were added to the windows to keep the house cool in summer, and a layer of external cladding creates a new thermal envelope to improve its energy performance. The stairs inside were re-configured to create a central stairwell.

The whole project has been carefully documented so that developers can learn from it and apply the principles, and you can find all the details here. The house was open for visits last year for those interested in seeing it for themselves. This spring a ‘test’ family moves in for two years to document its performance under real living conditions. So far the response has been positive, and the reproducibility proven – Over 80 homes in the area will be renovated in a similar way. I’ve got a 1920s house myself, and I’ve picked up a few ideas for things we could do with it.

This isn’t the only trial project in radical and affordable retrofitting. The Energiesprong campaign in the Netherlands has also demonstrated that zero carbon homes are possible without building them from scratch. That’s coming to the UK for the first time this year, and I’ll write about that another time.


  1. These UK projects may be of interest?

    Tim Nicholson’s Green House
    Web site
    Case study article
    Links to various other UK Passivhaus retrofits

    George Marshall’s Yellow House (George founded Climate Outreach)
    Rather old BBC article

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: