Case Study – Barn House – Great Busby


A modern barn converted to a PassivHaus (a PassivHaus is so well insulated and so well ventilated that very little space heating is required). The PassivHaus benefits from solar gain to provide space heat which is circulated by a mechanical ventilation and heat recovery system around the house, supplemented by a high efficiency wood burning stove for when the sun hasn’t shone. An air source heat pump provides hot water and could provide underfloor space heating but has never been necessary.

Watch the Film / Listen to the Radio Programme

This 18 minute video takes you on a guided tour of the barn conversion, explaining how a Passive House works and also showing how the carbon footprint of its construction was substantially reduced by using recycled materials.

CASaV tour of the Barn House on  January 25th 2020 filmed by Mike Newton

In winter 2022, Radio Leven Online visited and we had a wide ranging conversation about the house and the broader issues of low carbon housing. Richard Bradshaw turned our conversation a podcast – “The Green Man of Great Busby”.

Radio Leven Online – The Green Man of Great Busby with Richard Bradshaw

The Original Building

The outer fabric of the 16 metre by 9 metre building was erected in 2005 and permitted development rights were granted in 2014 for its conversion to a domestic dwelling.

The Conversion

The conversion essentially involved building a highly insulated, airtight box within the existing outer fabric. A 50mm ventilated void was left between the outer walls and roof.  A floating concrete and subsequently polished floor, in which was installed the under floor heating, was laid on top of the existing reinforced concrete floor pad.

A  Mitsubishi 2.8 KW input ASHP which was described as delivering up to 8.4 KW output provides domestic hot water and underfloor space heating. This year to date (15.06.2022) the ASHP has used 700 KW to deliver 1356KW i.e for 5 1/2 months This is a coefficient of performance of barely 2 for our very modest use of domestic hot water heated to 55 degrees C.

Since we moved in 4.5 years ago we have not used the underfloor space heating. Instead a very comfortable and draught free environment is maintained by the conservation of solar gain, the heat generated by electrical appliances and the occupants. This has been supplemented when necessary by the used of a modern super efficient wood burner with a catalytic converter and an external air supply and exposed 6 metre Poujoulat stainless flue. One ton of timber air dried to 15% moisture content or below is gathered from the 3 acres of woodland that we started to plant 33 years ago and that on my estimate now sequesters around 10 tons of carbon per year.

5kW high efficiency wood burning stove

The air supply into and out of the airtight building is supplied via ducting from a Paul mechanical ventilation heat recovery unit(MVHR) and this circulates the heat from the stove around the open plan house with its double height south-facing glazed area.

Paul mechanical ventilation and heat recovery system with ducting

How Does This Relate to Retrofitting

What relevance has this to those who are trying to improve the energy efficiency of their existing home? Not much unless you are prepared to gut the whole building you may be thinking, but the concept of a passive house does include standards you could apply in part even to a Victorian terrace, if you want to learn how look up EnerPhit.

Trying to retrofit to passive house standards is difficult, expensive and probably requires moving out while a skilled team of experienced retrofitters (if available) moves in.  Air flows carry heat out of and cold into a house, so a PassivHaus controls air flow, so burning anything that consumes the air in a passive house whether it is wood or solid fuel or gas for cooking is ruled out irrespective of the carbon emissions. In an airtight house with controlled ventilation you need to restrict the air supply to that needed for breathing and the comfort of the occupants.  The main plank of the government’s support for their replacement is to part fund heat pumps. (But you can’t cook the Sunday roast on a heat pump so you need to give up gas and go electric.)

How to Use this Approach on Your Home

My advice if you can’t afford the estimated £40,000 average cost of a full retrofit, is to work gradually towards those improvements which would ultimately make it possible to install a heat pump and go all electric by 2030. First improve airtightness  but still allow for the essential ventilation that will prevent poor air quality and moisture build up. After 42 years in a large draughty Victorian house the comfort of our new home is a joy and with one door or window fully open there are still no noticeable draughts and no need to constantly shout out “Shut that door!”

Research the different types of secondary glazing available and/ or work towards the replacement of single glazed windows, ideally with triple glazed, argon filled panels with thermally efficient frames.

There is a lot of advice around for insulating and draught proofing your home. Initially a worthwhile investment could be a new energy efficient and well-sealed front and /or back door. You could try a major DIY job on your existing doors and frames.

Burning Wood / Dealing with Humidity

If you live in a rural area without close neighbours and have an old wood-burning stove consider replacing it with a modern high efficiency model with an external air supply. This might involve running ducting from the back of the stove around a skirting board and through an external wall. Get a moisture meter and make sure the fuel is dry, below 15% moisture content, ideally below 12%. The jury is pretty well in on the serious dangers of wood particulates in an urban area though.

It is possible to swap an air extractor in the bathroom or kitchen for one that incorporates a heat exchanger, using the heat in the spent air to warm the incoming air.

In our passive house the air is very dry in the winter. This means that washing will dry very quickly indoors without the inconvenience of water dripping down your neck as you sit under the Sheila maid in the kitchen.  The drying washing also supplements the effects of the humidifier that we have in the bedroom. A tumble drier is a very heavy energy user as well as a contributor to the atmosphere of micro plastics. Any strategy you can devise for not using one, without endangering health in the home through excessive humidity, would make a significant annual saving.

Where Should You Start Your Own Retrofit Journey

Consider which aspects of a gradual retrofit process you could safely undertake yourself, depending on your knowledge and experience, agility, determination and ability to see a job through. Talk through what you regard as a possible DIY task with the growing band of retrofit advisers. Draught proofing and fitting secondary glazing may be within your compass but probably not external insulation and definitely not the plumbing for a heat pump.

Useful contacts.

  • The Green Building Store –
  • Seconds and Co for a wide range of Kingspan products.
  • Cleveland Timber
  • Bucklers Demolition for recycled building materials including reclaimed wire cut bricks usually sold cleaned individually but sometimes by the lorry load direct from the demolition site with the old lime mortar ready for you and the family to chip off.
  • Prosser’s Scrap yard for a range of treasures. In my case this included 500 feet of 6 by 12 inch reclaimed Welsh bridge timbers probably from Russia many years before I was born. (When visiting a yard always wear the right ppe and don’t wander around without permission or you will get shouted at in the Teesside vernacular).
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