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The Lean House

What is a Lean House?

Llan Adan Having spent eight years as web master for The Lean Enterprise Academy ( it was a “given” to apply some lean principles to the design, build and fabric of our new home. My concept of a “Lean House” is made up of three parts:

We set out to build a well-insulated, low-energy, sustainable home. Now we can start to see how well we met the objectives ...

Designed for Living

Llan Adan Llan Adan Llan Adan

For our lifestyle

Having both lived in New Zealand for some years we love the indoor / outdoor way of life. The sliding doors and French windows to most rooms allow us to use the whole house and outside areas to the full. The massive open plan kitchen dining areas make entertaining a joy, and having a ‘guest wing’ where our visitors have everything they need means we can have friends to stay as often as we like.

Natural light and air

It was important to have natural light in every room. With the large barn openings and sliding doors we have massive amounts of light in the main living rooms. French windows in the guest bedroom and snug give light and access to the garden. A wonderful by-product is the passive solar gain on sunny winter days where the sun heats the slate floor during the day and releases the heat during the evening.

A natural ventilation system is provided by the trickle vents in the windows, and this (plus the humidistat extractors in bathrooms and utility) seems to work very well without the need for a heat recovery system.

Process, Flow and Order

Without wanting to take the lean concept too far, we have managed to simplify and de-clutter pretty well. We have always enjoyed a pretty minimalist style in the home and have our own happy mix of new and old - a touch of wabi-sabi ( don't get confused with wasabi )

So the house flows from a central entrance hall - going one way for guest rooms, the other for living areas. There are places for boots and coats as you enter, a welsh dresser with phone and diary in the hall, and so it goes on.

There is just enough storage, but still the danger of storing things away when they should be destined for Freecycle or the tip.

Simply Smart

It is possible to spend a small fortune on smart homes and media systems, but we wanted to keep everything simple (and under budget). So we are using the Apple airplay system to play music anywhere in the house through our existing hi-fi systems (controlled with an iPad,iPhone or computer via Airport Express) plus Apple TV in the snug for music, videos, photos and TV.

Apple Airport Express

Apple Airport Express For good measure we installed a CAT5 network cable to all the main rooms. This has already been put to good use to solve a wi-fi blind spot.


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Insulation and Airtightness

There is no point using the latest eco systems if the house is badly insulated and “leaky”. So during the build we spent a lot of time ensuring that the insulation was fitted correctly with no gaps anywhere. We used a combination of Celotex, sheep wool and rockwool.

Careful attention was given to the join between the top of the wall / roof, and around windows and doors. Even though we were very hands-on during the insulation process we found quite a few spots where cold air managed to find a way through. Luckily these were fixed before final plastering and decorating took place.

Space Heating

In theory, we shouldn’t need to spend too much money on space heating. We have a combination of Ground Source Heat Pump (GSHP) to run the underfloor heating (UFH) to the ground floor, and a Charnwood Cove 2B wood burning stove which warms the snug and heats the hot water. As a by product the flue runs through the bathroom and give extra heat upstairs, which also has in-floor "trench" radiators in the master bedroom.

The GSHP needed 400 metres of piping laid over a meter deep in the grounds (it is surprising how much land is needed for this). We chose the Worcester-Bosch Greenstore System 9, and decided to use it for UFH only where it can efficiently raise the temperature of the ground loop from around 7° up to 40°. To use a GSHP for domestic hot water as well could see a serious drop in the COP rating. The GSHP has worked very effectively through our first winter in the barn. We will touch on running costs later ...

How water

Our hot water is heated by 4 Velux solar panels and the Charnwood Cove 2B wood burning stove. There is a back-up immersion heater for those times when the sun isn't strong enough, and we do not need to light the stove. Between October and March we have only had to use the immersion heater 4 times, so the system is working well for us.

A radiator loop from the hot water store provides space heating for upstairs via 2 trench radiators in the master bedroom and towel rail in the bathroom. The exposed flue also provides additional background heat to the bathroom.

Windows and Doors

copyright Shed22 We looked at a number of different window systems, but chose Velfac, mainly because of the design. They are excellent quality and designed to prevent thermal bridging between the outside and inside. At the time they only did a ‘push and slide’ sliding door of limited width, so we chose AJS Windows of Birmingham for our wide sliding doors in the sitting room.

Low energy consumption

We have used low energy lighting and A+ energy appliances wherever possible and only used pumps where really necessary. So our energy consumption is as low as practicable.

Generating our own energy

We planned to generate our own electricity but had to wait to see if there was any money left in the pot after the build.

Solar PV or Wind Turbine?

The economics for wind appear to work out better than solar, but you need an exposed, windy site. Even up here at 67m above sea level the wind speed is likely to be marginal (about 5mps). So when we heard that the Government had lost their appeal to reduce the Feed In Tariff rate (from 43p down to 21p) we decided to return to our original plan and install solar PV panels on the garage roof.

Because of the uncertainty caused by Government messing around, and the on / off nature of the FIT deal, there were only three companies that could install for us before the deadline of 3rd March 2012. It is still not certain that the 43p will prevail, but as this was something we wanted to do anyway we have gone ahead.

We chose Gwent Energy because they have installed quite a few systems locally (they are based in Chepstow), and they had given us a quote back in October 2011. They are supplying Suntech panels, and although I had really wanted all black panels (without all the silver diamonds and frames) I have had to go with the best on offer at the time.

Using local sustainable materials and trades

Stone, oak and slate

copyright Shed22 It was important to us to convert what started out as not much more than a “pile of stones” into a rural building that would quickly blend in with its surroundings.

All the stone on site has been re-used and additional stone was supplied from a quarry only 5 miles away. Probably the same quarry where the original stone came from. The roof is reclaimed Welsh slate and the oak is FSC registered from local sawmills.

It is difficult to carry this idyll through to every aspect of the build. Our slate floor came from Brazil, the windows and solar panels from Scandinavia. This can't really be helped, but we have managed to find some excellent local builders, craftsmen and trades people.


Sourcing materials and fittings and the right price, at the right time has proved to be a very time consuming activity. How was this done before internet search engines? Even our local builders merchants can supply the same product at widely different prices, so it is worth checking prices and choosing the best supplier for all major purchases.

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The Verdict

How does it all work?

It is very early days, but everything seems to be working as we hoped, and the barn is a simply wonderful place to live.

We have now installed the Solar PV, and are starting to monitor our energy generation and or consumption (using an OWL monitor).

We will post the results once we have enough data ...

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