NSBRC - Alan Muncaster

Could you tell us any interesting facts or remarkable features about your project?

Project Chafeys is like 10s of 1000s of other traditionally built properties with an EPC rating of D back in 2011. What is remarkable is that the EPC rating is now A with a score close to 118. The imported electricity is now very low even allowing for charging two EVs.

Alan’s Experience at National Self Build & Renovation Centre

How many times have you visited The National Self Build and Renovation Centre before?

Over the last few years I have visited the NSBRC three times attending a couple of courses covering renovation and heat pumps. Prior to this did visit around 2011.

What would you say is the most helpful feature or resource?

The NSBRC houses a host of displays and a wealth of knowledge that helps form the ideas and the project direction.

What did you enjoy most about your visit?
The staff at the NSBRC are very helpful and carry plenty of knowledge that people can tap into. There is no pressure or hard sell and I have found it a relaxing place to visit and contemplate the project.

Would you recommend the NSBRC to a friend, and if so, what aspects of the Centre would you recommend and why?

As part of the Dorset Greener Homes network I always recommend the NSBRC to all my visitors. Whether you are building a ‘Grand Design’, or like me retrofitting, there are many solutions to be found through the courses, staff and displays.

Floorplans:

Elevations:

The Garden Room was built and again a bit of an experiment, and was used as a home office during lockdown. This is timber framed with 100mm of insulation in the walls, 125mm in the roof and upcycled double glazing units. There is a small wood burner in there and a temperature of 46C has been reached. The hot tub was a bit of fun but works so well using our summer surplus.

Technologies:

Information compiled in November 2024. Energy Use grid added March 2025.

View Alan's presentation 'A Journey to an Efficient House' here.

View further details about 'Project Chafeys' here

Project Chafeys is part of Dorset Greener Homes and is available to visit throughout the year.

Project Chafeys – The figures.

1st October 2025 to 30th September 2026

Generation 8,342 KWh

Exported 5,508 KWh

PV to home 2,048 KWh

From the Grid

Peak Electricity 114 KWh

Off Peak Electricity 4,090 KWh

Of which Car Charging 2,536 KWh

Peak electricity to House 114 KWh

Off Peak electricity to House 1,395 KWh

Total electricity to house 3,557 KWh (682 KWh less than 2024/2025)

43.47 KWh / m2

The Costs for 2025 – 2026

Electricity cost £507.46 including standing charge, VAT & car charging

Transport cost 2536 KWh x £0.07 £177.52 (+share of SC and VAT)

Exported electricity 5508 KWh x £0.12 £665.52

Net cost -£507.46 +£665.52 = £158.06 in credit.

Solar Generation

East PV array, installed Nov 2011. Generated 49,500 KW c. 3297 KWh/year

West array, installed March 2021. Generated 20,700 KW c. 4577 KWh/year

Pre-works we used between 13,200 and 17,000 KWh of energy to run the house.

Reducing our energy footprint from 160 to 207 KWh/m2 down to 43.47 KWh/m2.

Passive Houses + 60 KWh/m2 of which 15 KWh /m2 for space heating/cooling.

Average UK house uses 140 KWh/ m2 for heating.

If you start to look at the figures used to run the house in terms of only what is imported from the grid then the figures look like this.

Pre-works 13,200 to 17,000 for gas and electric 160 to 207 KWh/m2

For 2025 / 2026 18.4 KWh/m2

Post works Project Chafeys has reduced its demand for nationally produced energy by around 85%.

The Combination.

Solar PV and a home battery enables you to generate electricity and store it for use later in the day.

When combined with a heat pump and suitable tariff from the energy supplier the costs reduce further.

Take this one step further and incorporate an EV into the mix and (currently) this enables you to further reduce costs by making full use of an overnight off peak charging tariff that can be used to power appliances and to charge the home battery.

Most energy suppliers have export tariffs where you get paid for the surplus PV generation which is exported to the grid. These can be a bit of hit and miss but just opting for a basic export tariff will offset the electricity purchased from the grid.

Project Chafeys | The EV Question

With fuel (Oct 2026 price) costing around £7.95 / gallon for petrol and £9.04 / gallon for diesel the question to be asked is does an EV make sense?

We have owned an EV since 2020 and now in 2026 both our cars are full electric and we are able to charge both at home. This is the cheapest way to run an EV.

When travelling away from home we just take the hit from the costs of commercial charging hubs.

Cost Comparison.

Taking 8,000 miles per year and 45 mpg (you can adjust to suit).

Petrol £1,413 £7.95/ gallon

Diesel £1,609 £9.04/ gallon

EV avg 4.2 miles/ KW 1,905 KWh @£0.07/KWh = £133.33

With proposed mileage tax @£0.03 £240

Total Annual £373.33 pa.

Naturally in the summer months you can fuel your EV for free from your solar PV.

Smart Charging.

Companies like Octopus can take full control of your EV’s charging at home. The overnight charge is straight forward but if there is surplus generation on the grid then your car gets charged anytime of the day but at the off-peak rate. On some days there have been free hours.

Please note this service is not available from your local petrol station.

Alan’s Retrofit Experience - Project Chafeys

What first inspired you to undertake your project – what did you hope to achieve?

I have had an interest in what used to be known as Alternative Technology since the early 1970s and when our children left home it was time to downsize from the 5 bed house into a 2 bed bungalow. This smaller property has enabled me to indulge my interest in reducing my carbon footprint and to also reduce the costs of powering the house. Being smaller, it made the various works cheaper.

How did you find the property for your retrofit project? And do you have any tips for others currently searching for something similar?

To start with there was not a real plan, just an idea. The first project was the installation of 4 KW of PV and at this stage being retired I was able to make full use of the electricity generated, but what was clear was that we were exporting more than we used.

At this stage I started to research just where I could take the house. At this time YouTube supported a number of interesting channels, Fully Charged being one. This in turn led me to other channels and to events such as ‘The National Self Build & Renovation Show’. Gradually the direction became clear and as I was going to be self managing the works I needed to be clear what I wanted to achieve.

What was the cost & size of your retrofit project?

The first 4 KW PV system attracts the highest Feed In Tariff (FiT) and I have been able to fund the works up front with a view to seeing the FiT as a return on investment.

Costs: First 4 KW PV - £13,000

Second 5 KW PV + one 8.2 KW battery - £13,000

MVHR - £2,500 self installation

2 more 8.2 KW batteries - £5,400

External wall insulation - £6,500

ASHP - £12,500

ASHP grant - £7,500

Plumbing - £4,500

What was your budget and were you able to stick to it?

There was a not a budget for the project but as money became available and the income from the FiT built up other works were carried out. I have looked on Project Chafeys as an experiment in producing a warm, comfortable and cheap house to run. Mistakes, there have been a few, but these have largely been a result of my ideas being ahead of the available tech.

At times it has felt like a journey into the unknown but I knew what I wanted to achieve and for the large part that goal has been met. Now there are companies who can assess and advise the best route to improve the efficiency of a house – I was ahead of the curve.

Now fully integrated battery, solar diverters and car chargers are available and integration of all these systems is key to a good result. Mine has been a 12-year project so I would recommend planning the whole of the works and gradually add the modules, keeping a close eye on the developments in the tech.

What aspects of the process did you find stressful – and do you have any tips on how to avoid the pitfalls you encountered?

I can’t say I have found it too stressful, my career in Civil Engineering helped with this, but there have been a few moments when I have asked myself if that was the right choice! Remember the 6 Ps!

What is one of your favourite features about your project?

The one feature that improved the house environment was the MVHR (Mechanical Ventilation and Heat Recovery) system and if you are sealing up a house you do need one.

The external wall insulation and ASHP were installed May / June 2024 so it’s too early to assess their benefits. What I have noticed is that the house temperature does not fall more than 2° overnight.

We now have a warm, comfortable and cheap to run house where the EPC has gone from a standard D to A at nearly 118.

Is there a possibility you would ever undertake another project in the future?

Would I do it again? The years are creeping up on me but with what I know now... YES.

If so, is there anything you would do differently?

Well, I did have a plan to demolish the house and build a chalet bungalow on the same footprint but that was just too much for the Planners.

What would your top tip be for other NSBRC Visitors about to embark on their first homebuilding project?

Have a plan, work the plan but be ready to adjust as new items become available. Sit down and work out what you want to achieve and don’t forget this plan can be a 10 year one. Go for the easy wins, insulate as much as you can as this one item has a real effect on the performance of the house. Basically, wrap it first. Fabric first. Ask yourself, once you have got it all sealed up how are you going to provide ventilation?

My top tip, in three words: RESEARCH – RESEARCH – RESEARCH.

Alan Muncaster