Saturday, November 5, 2011

Want PV? Soon you will need an EPC!

5 Nov 2011: After April 12th 2012, it's likely that PV-hunting householders will have to get an Energy Performance Certificate (EPC) for their house to be eligible for the 21pence Feed in Tariff. The EPC should be grade 'C' or better. Without this, you may only be eligible for 9 pence/unit.
   This is going to need clarifying, because it seems to be bad news for people in historic buildings who are unable to bring the buildings up to grade C, or those who have to erect panels in the orchard, garage or uninsulated outbuildings because the house is historic, listed or is encrusted with chimneys and dormers. You need EPCs in order to sell a house, so there is now a small industry of EPC assessors. Google "EPC" and you will find loads, including some companies based in West Bridgford/ Rushcliffe. If your house does not yet meet grade C, then you will get advice from the assessor on how far it can be taken.

How do you get an EPC?
• EPCs are explained further on the DECC website,
• It costs between £30 and £70 to get an EPC evaluation, there are many companies offering to do one. See this page:
• Here's an example of a EPC for a house in 'AnyTown'

Does the Peveril Solar house have one? No, not yet, it wasn't required when we built it, but perhaps we should do so, if its only £30-£40 to get one. Although the PV makes the house Carbon Zero, the requirement is for the house itself without the PV. Our insulation is very good and the annual heating requirement is low, being about 100 kWh/Sqm/annum base requirement, but because we use an efficient heat pump, it is only requiring only 26 kWh/Sqm/annum to space-heat and provide hot water. On heating alone, it is only requires 20 kWh/Sqm/annum, which is better than the Passivhaus requirement for existing houses. So it should be A rated, but I will get it rated independently anyway.
    I've made a phone call to arrange to have one done in the next couple of weeks. The assessor says that PV is taken into account, and their rating includes recommendations for the 'potential' grading providing the basic house underneath gets improvements in insulation.


  1. David,

    I see you have a heating load of 100kWh/sqm/yr... have you calculated this from total floor area i.e. sum of both floors or just the ground floor?
    Note when comparing to passivhaus standards: the passivhaus standard is predicated on energy efficiency in terms of how the building fabric, orientation, glazing and ventilation performs. It does not include the benefit of using a heat pump. The load of 15kWh/sqm/yr (25kWh/sqm/yr for retrofit) of a passivhaus is the actual heat load, not the elctrical energy input. So a retrofit passivhaus may then use a heat pump in which case the input energy may be as low as 6 or kwh/sqm/yr!


  2. Hi Chris. Well theres the calculation of what we actually use, and that is easy because all inputs and outputs are metered. The starting position is to ask what the house would need if it had no 'systems'. Adding together Fabric Losses and Ventilation losses, the assumption is about 12,000 kWh/annum plus about 3,000 for DHW. With a 120 sqm house, thats easy to divide - 100 kWh/sqm/yr. Because we live frugally, we probably require a bit less. The actual heating for the house in terms of systems is about 2400 kWh (metered use of electricity) from which I get the 20 kWh/sqm/yr. I realise that if this was a Passivhaus, the insulation would have to be even better, but I have a developer-built house, so it has to be an Aktivhaus.

  3. Oh, and in calculating the base heat loss, I assumed worst case, just to be safe, i.e adding in a percentage of heat loss for thermal bridging, assuming some leakage of air etc. In reality we have good thermal mass in the inner leaf and centre partition which helps thermal performance.


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