Post-Carbon Home One

Where we were in May 2008

Where we are today

Before...	After...

 

What was done, what it cost and when we did it

Item	Date	Cost	Comment
Double Glazing	n/a	none	Pre-installed. Probably the only eco-beneficial items the house had already!
Energy saving lightbulbs	May 2008	£400	Spotlight-type from Lightbulbs Direct
Pipe Insulation	June 2008	£39	From a DIY store - fitted ourselves
Attic Lighting	June 2008	£55	Not a true eco-feature but necessary in order to insulate the attic ourselves
Loft Tank insulation	June 2008	£37	Fitted ourselves
New Loft Hatch	June 2008	£63	Fitted ourselves
Sheep's wool loft insulation	June through October 2008	£999 + £618	We added 200mm (2 layers of 100mm) on top of existing mineral wool. Purchased about 100m2 of sheeps wool (100mm deep) which cost us £999. An additional £618 was required for tools, wood and boarding gave us the storage space and access for future solar panel & boiler work via attic.
Two new doors to garage	July 2008	£1300	Old wooden doors replaced with UPVc equivalents. These doors linked the garage to the kitchen and garden. They were hopelesly dated. These also improved security.
Garage Door	July 2008	£1905	Rollover Garage Door fitted by SWR. Not an essential eco-item but replaced the broken original. New roll-up door has a foam interior sandwiched between aluminium and plastic exterior walls. Helps keep the warmth inside the fabric of the building as the boiler is in the garage. It works too. High embodied energy but gave us good security.
New Gas Boiler, TRV's & controller	August 2008	£2480	Fitted by a local plumber. This boiler is now only a backup for the wood-pellet boiler
Chimney Balloon	August 2008	£30	Fitted ourselves
Solar powered security lights	October 2008	£122	Fitted ourselves but a big waste of money - later replaced by mains-powered versions that were much better
New Curtains	October 2008	£240	Thick lined curtains made to measure
Draught proofing & miscellanious insulation	October 2008	£80	Fitted ourselves
Energy saving security light	November 2008	£23	Fitted ourselves
Radiator Foil	November 2008	£65	Fitted ourselves. We overspent on this due to an attempt to use double-sided sticky tape rather than wallpaper paste.
Energy saving security light	December 2008	£99	Fitted ourselves
Cavity Wall Insulation	December 2008	£219	Inserted by Mark Group
Wood Burner Dovre 250	April 2009	£2720	Fitted by local company Nature's Warmth
A++ fridge/freezer	June 2009	£420	Fitted ourselves. Replaced built-in units
Water butts and fittings	August 2009	£70	Fitted ourselves
Kitchen LED lights	August 2009	£250 approx	Fitted by local electrician (ceiling units) & ourselves (undercupboard units). Supplied by Wattlite & Lightbulbs Direct.
Biomass Boiler KWB Easy Fire for Wood Pellets	September 2009	£15590	Fitted by Green Systems UK Ltd
Water Softener	September 2009	£1320	Not essential but we live in a hard water area
Barilla Solar Thermal hot water system & tank	April 2010	£3750	Fitted by British Eco
Photovoltaics 2.96kWp Mitsubishi panels & new consumer unit	April 2010	£13500	Fitted by British Eco. New Consumer Unit fitted by local electrician.
Removal of trees from rear garden	June 2010	£855	Local tree surgeon. These were mostly 18ft leylandiis that screened the home from the south blocking out the sun all year round. The house is far warmer in winter now. Replaced with fruit trees that will not shade the house even when fully mature and lose their leaves in Autumn.
Replace plumbing & toilets with lo-flush & lo-use options	August 2010	£800	Fitted by local plumbers
Replace all radiators	September 2010	£1450	Fitted by a local plumber. The originals had all rusted through so we opted for slightly larger units.
Fruit Trees	December 2010	£152	Planted ourselves. Replaced the leylandii removed earlier.

Note that the costs above exclude a lot of incidental expenses such as tools and materials. Some of the items (as indicated) were not entirely necessary solely for the eco-retrofit but also functioned as security improvements. We excluded other lifestyle costs and the LPG conversion on the car.

The Bottom-line

• Estimated reduction in Carbon Footprint: >90%

• Actual savings: >4.5tonnes pa

• Minimum expected lifetime of the retrofit: >25 years

• Total savings = 25 x 4.5 = 113 tonnes minimum resulting in a carbon cost of £424/tonne maximum

• Total home energy used per annum = 24,000kWh (includes heating, electrical & hot water)

• Total living-space floor area = 124m²

• Footprint now 193kWh/m² pa*

• We buy in about 4 to 5 tonnes of wood pellet pa at a cost of around £230/tonne delivered

• We import about 500kWh of electricity per year on a green tariff at a cost of about £0.13p/kWh

Much of this retrofit will last longer that 25 years and many of the actions taken may not have been essential for other retrofits. Some of the work would have little or no impact upon the carbon footprint (such as the toilet replacements and the new garage door). Other work was done for the educational purposes or added home security. Many items were essential replacements. Most homes in the UK should get similar results for an investment of between £15,000 and £30,000. This calculation ignores the Feed In Tariff and Renewable Heat Incentive that we factor-in below. The RHI and FIT alone will return a profit on the entire project over 25 years.

*For a Passivhaus the total primary energy use for all appliances, domestic hot water, and space heating/cooling must be less than 120kWh/m² pa.

Why we did it

This was never really an "eco-refit". It was modernisation meets future-proofing. However our definition of "modern" is "low-carbon" not the sort of energy profligacy that so dominates our culture today. The planting of the Fruit Trees marks only the end of the first phase. Our objective was not to have the maximum reduction in carbon footprint for the lowest possible cost. The objective was to upgrade an old home in serious need of improvements. This was all done with an eye on the carbon-footprint.

Having said that the most expensive single item was the wood-pellet boiler that was chosen because of research showing that it would have the lowest cost per carbon-tonne saved over its lifetime. We took a whole-house & whole lifestyle approach such that we did the things that would be the most resilient over the longest time. We also did things because they looked good and added convenience & security. Plus we had fun along the way and tried things that we knew might not work.

Payback

Do you calculate the payback of a new car or a refitted kitchen? No. You do those things because you want to live with those creature comforts. It was the same with this modernisation. We didn't want to live in a 1980's throwback. Even-so, this refit should pay for itself. The Feed In Tariff should pay for the Photovoltaics and return a profit of £17,000 by the end of the 25 years. IF we get the Renewable Heat Incentive (a big IF as I write these words in 2011) then the solar thermal will yield a profit of £1500 in 20 years. The biomass boiler should return the cost and then a profit of £8000 in 15 years. That SHOULD be a total profit of £26,000 more-or-less. This is in ADDITION to paying for the Biomass Boiler and Solar Panels (yielding around £33,000). That is total earnings of £59,000. Hence, if everything goes to plan the retrofit will have paid us £10,000. That is actually -£88/tonne of carbon to US.

This back-of-the-envelope calculation doesn't quite factor in the increased cost of wood fuel over gas. It ignores any savings in the heating bill derived from insulation. We'll assume that the small improvements are offset by the small increases in cost.

Insulation benefits are difficult to quantify as we had no baseline. We started insulating the moment we moved in. We estimated that the annual electricity usage of the house would have been around 4000kWh but this has dropped to under 2900kWh. Of this 2500kWh will be supplied by our own grid-tied PV. Gas usage may have been as high as 26000kWh per year but is now nothing. Equivalent wood-power estimated at 21,000kWh per year.

What we will do next

We plan a solar conservatory for the rear garden but it would prove to have a very high cost for very small benefit. It can't be justified for carbon footprint reasons so would have to be a lifestyle/comfort choice. We have considered putting an air-source heat pump on the conservatory - just to tick that box! That awful front door need insulating or replacing. There is a plan to remove the bathroom over the garage and convert the space to have a larger bedroom and smaller en suite. This would remove some pipework from the garage ceiling. Thus the garage ceiling can be insulated from below to keep the living space above somewhat warmer. As part of this project we are considering doing a super-professional-insulation job of the over-garage living space. This might include interior wall insulation. This space is a big problem as it is always the coldest space in the home acting as a reverse radiator sucking heat our of our home and dumping it into the garage and garden. It is a hole we wish to plug.

The loft is another area we can improve upon as some celotex can go between the rafters and we think we could purchase some sealed pads of insulation we could move around between storage items rather than having fixed insulation. However we would have to move the TV aerial out of the attic as the foil-covered insulation would rob us of our TV reception.

From there on we are into the fantasy-areas. If we could we would refit all the double-glazing with Passivhaus-standard wood framed triple glazed units (starting with the north-facing side of the building).

Summary of next stages:

1. Insulate/replace front door

2. More insulation in living space above garage

3. More insulation in attic

4. New conservatory

5. Triple glazing

Would we do it again?

Given a clean sheet of paper and the money all over again then: YES! Certainly. It was fun, but a lot of hard work. We think we'll take a bit easier going forward....

December 2011: full thermal imaging survey