cost

Cost of zero carbon house in comparison to social housing

The cost of building zero carbon house as a whole can be compared to the cost of social housing. The cost per square foot of building:

  • an average housing association home in 2009 was around £120
  • zero carbon house, including the cost of the new construction and retrofit, was around £150

However, figures collated in 2014, show the cost of building zero carbon homes has fallen.  The added cost for building a new home to zero carbon standards is estimated to be around £5,000.

 Savings from renewables

There are no fuel bills at zero carbon house as it’s so well insulated.  The solar panels generate more hot water and electricity than the house needs each year. The energy provider pays more than £1,800 each year for the renewable energy generated by zero carbon house,some of which is used in the house with surplus exported to the National Grid through the Feed-in Tariff scheme.

In a case study in his book Designing Zero Carbon Buildings Using Dynamic Simulation MethodsProfessor Ljubomir Jankovic focusses on costs of the retrofit part of the house.  He calculates the cost of upgrading the original house to zero carbon standards will be paid for by the income from electricity generation and the savings in fuel bills within 8.6 years.

Cost of new walls in comparison to retrofit walls

We compared the cost of our new build walls with our retrofit walls.  (Remember these are to zero carbon standards with thermal insulation of the walls = 0.11 w/sqmdegC.  Thanks to Matthew Bailey at Speller Metcalfe who kindly supplied these figures.)
  • New build (insulated render over clay blockwork finished internally with wet lime plaster) cost £165.50/sqm of wall.
  • Retrofit (plasterboard and Intello airtight membrane on timber frame dry lining, filled with Warmcel insulation and breather membrane, all fitted inside the existing nine inch brickwork front wall of the old house) cost £78.82/sqm of wall.
 It is interesting that of that £78.82, only £17.05 is the insulation cost – so if you were to halve the insulation you would only save £8.50/sqm.  Therefore it seems sensible, if you are retrofitting, to encourage people to go the whole way and insulate to a very high standard.

 

Improving insulation on a budget

Even without much money it’s possible to make worthwhile savings. Sealing all gaps to the outside in walls, ceilings, floors, windows, doors, electrical sockets and skirting boards can make a big difference.

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