Sunday, 22 November 2009

A radical renovation

Welcome to my blog! I hope it will be informative and entertaining. If you are planning any changes to your home, whether or not motivated by environmental concerns, there should be something of interest here for you.

We are about to embark on a very challenging journey to convert our leaky, draughty, unrenovated 1970s home into a certified Passivhaus: a house that needs no active heating or cooling systems to maintain a comfortable indoor temperature and a healthy indoor air quality, all year round.

The project and this blog are intended to be about more than just eco-renovation. In fact, I want to avoid using the "E" word and the "C" word (carbon) as much as possible, as they have both become clich├ęd. Even if you are one of those who apparently doesn't "believe" in climate change or peak oil - both of which are significant motivators for me to take on this project - most of you would still want to live in a comfortable, cheap to run home, so read on. That said, implicit in this project is an understanding that we are moving into an era where energy is much more expensive and increasingly less freely available than most of us have been used to.

In the blog, there will inevitably be a certain amount of jargon. I'll try to make sure I explain any technical terms when I first use them.

What do we want to achieve?
Put simply, we want to create a comfortable home that is very cheap to live in and to maintain; a house that will meet our needs for the whole of our lives. It will also be a house with a low environmental impact.

Why a renovation and not a new build?
Here in the UK, building plots, particularly where we live, are scarce and expensive. It is a practical choice for us, given our other constraints. Renovations are important because most of the buildings we will be using in 2050 already exist today; renovating our existing housing stock is inevitable. Each renovation is an opportunity to reduce the building's future running costs by reducing its energy use.

What is a renovation?
The word renovation covers a wide spectrum of repair and modernisation work. It could just mean fitting new cupboards and appliances in your kitchen, re-painting inside and out and re-fitting the bathroom with a new suite from the DIY centre. All superficial changes intended to make the property more attractive. Here we are looking at a much deeper renewal, replacing and augmenting elements of the building that many renovations leave untouched. In our house, the roof, windows, external walls, doors and all services need replacement or repair.

Where have we got to so far?
I guess the project started a couple of years ago, when we started looking for a house or a plot. We chose with a keen eye on what type of property we thought would lend itself to Passivhaus renovation. We decided to live in the house as is, partly to get to know it before making any changes. There is quite a lot about the house that we like and it often takes a while to tease out what changes really are needed.

A Passivhaus is different from most building projects, as a lot of thought must go into some detailed design considerations at the beginning of the design stage. Because of this, it is very hard to convert a non-Passivhaus design into a Passivhaus one later on in the design process. We have been working with our architect on these: the two areas that are most challenging are the floor and exterior walls.

The construction of our house is typical of many built in the early 1970s. It has two leaves of dense concrete blockwork and a concrete slab of concrete (reinforced?) covered by about 70mm of screed. The ceiling heights are not particularly generous, so we cannot increase the finished floor height significantly. The 50mm wall cavity is filled with mineral wool. We will be cladding the walls with external insulation and a rendered finish to match what we currently have. This is because the house is on an estate of similar properties and we want our house to retain its "group identity", as will the local planning officers!

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