energy analysis

power down

insulation and heat loss analysis

  • comparison with the Fabric Energy Efficiency Standard for the government’s Zero Carbon Homes Policy (figures are in W/m2K) for a detached home and current Building Regulations
  • roof: FEES 0.11 / estimated 0.18installed 200mm Warmcell insulation currently classified under Building Regulation as ‘worst acceptable’ 0.20 W/m2K – ‘super-insulated’ 300-400mm 0.12 W/m2K
  • walls: FEES 0.18 / estimated 0.22installed 150mm Warmcell insulation, 0.22 W/m2K, 0.30 W/m2K currently classified as ‘worst acceptable’ – ‘super-insulated’ 250-350mm or 0.14W/m2K
  • floor: FEES 0.14 / estimated 0.25installed 50+75mm Rockwool – 150mm insulation, 0.25 W/m2K currently classified as ‘worst acceptable’ – ‘super-insulated’ 250mm or 0.15W/m2K
  • windows: 1.33 in line with FEES and ‘super-insulated’ standards
  • the breathing wall construction needs research as the higher heat loss values may in fact produce a more energy efficient building – air permeability: FEES 3 m3/m2/hr@50Pa / thermal bridging: FEES 0.04?
  • insulation is not ‘super’ but adequate and not a priority


  • needs checking thoroughly: loft hatches, electrical fittings, cracks in external walls, air cavities in external walls and behind plasterboard, gaps around skirting boards, rotting timbers around windows and doors, junctions around windows, doors and walls, suspended floor joints where they butt up against walls, windows and openings, malfunctioning or uncontrollable air vents, pipes through walls and ceilings


  • breathing wall construction: needs monitoring for energy efficiency
  • need to check functioning of air vents, lobby, if there are window trickle vents

space heating

  • underfloor heating (from CAT’s information service):
    • It gives a very even temperature over the floor area, with very few cold spots.
    • Because the floor temperature is much lower than a conventional radiator, convection currents are minimised and there are less draughts.
    • Efficiently installed, it should run at 35 degrees Celsius, compared to radiators which run at 75 degrees. This makes it a good match for alternative heating systems such as heat pumps.
    • Underfloor heating works well with a condensing boiler, because the boiler runs more efficiently with low return temperatures.
    • The radiant heat given off by the floor results in very high comfort levels. In our experience this means that, in practice, you can run it at lower temperatures – so saving energy. It should be possible to have the house at a temperature 2 or 3 degrees lower than with conventional radiator use.
    • There will be no radiators taking up wall space.
    • It’s very good for rooms with high ceilings: heat from an underfloor system goes up the centre of the room giving the occupants a greater sense of warmth for much less energy input than with radiators (where heat tends to go up the walls and collect in the roof space)
    • Comfort conditions are improved as we are sensitive to radiant heat, so it is possible to have the house at a 2 or 3 degrees lower temperature than with conventional radiator use.
    • The main disadvantage of underfloor heating is that it is slow to respond and can take a long time to heat up. So it is best used in homes or buildings that will be in use for fairly long periods, rather than (for example) in flats that are only occupied for short period of time in the evening.


  • potential for savings


  • controls for the heating are present but no instructions on how to use


  • currently a kettle and a fridge with unknown rating


power up

renewable energy potential

  • possible to change electricity supplier to 100% renewable energy supply currently Good Energy or Ecotricity
  • quick investigation solar pv and solar thermal potential from Solar Century’s website:

Solarcentury estimate