The Perfect House with modern design & construction has a very, very, low energy requirement and the annual cost of energy (hot water and space heating) would be in the region of €150-200 using oil or gas.


This low cost is because the perfect house;

  1. a) has perfect insulation of attic and external walls plus energy saving windows,
  2. b) makes use of solar gain (heat from the sun) and utilises solar panels,
  3. c) makes use of Mechanical Heat Recovery Ventilation (heat exchange system that allows outgoing “used” warm air to heat incoming cold fresh air), and
  4. d) has a high efficiency heating system that is used in the Winter when solar heat is at a minimum.


The annual cost of energy for the average 3-4 bedroom is €1,750-2,000.


To bring the average 3-4 bedroom (30 yr old) house to a similar level of performance of the perfect house would require a “deep retrofit” which would cost up to €50,000-€60,000  which is not an attractive economic proposition.


To significantly reduce energy costs for the average 3-4 bedroom house the following 4 actions need to be carried out;

  1. a) insulate your attic with a minimum of 200mm but preferably 300mm of insulation. Make sure that your water tank is also insulated. (As only two SEAI grants are given, the €300 grant for attic insulation could be forfeited in favour of the higher grants referred to below).
  2. b) remedy “Air Tightness” issues such as closing off coal fire flue (purpose-made inflatable balloons can be used), reduce size of large wall-vents to smaller size by inserting a central 150mm open tube and packing the gap around the outside of the tube. Check that front & rear doors plus windows are sealed properly. Make sure that the attic hatch has a good seal. Block up any over-sized holes or gaps in hot-press ceiling.
  3. c) if your oil or gas boiler is old with only 60% efficiency then replace it asap as modern condensing boilers are far more efficient at 95%. (A new boiler costs circa €3,000 and SEAI grant of €800 is available).
  4. d) install 3 or 4-zone heating controls so that heating is only provided when, where and at a level that is needed, e.g. bedrooms may only need to be heated after 7 or 8pm. (This type of control usually costs circa €1,000 but an SEAI grant of €500 is available).


Finally, if all of the above a-c (4) items have not been addressed in your home then undertaking all 4 of them now would result in the energy bill for a 3 / 4 bedroom house being reduced from €1,750-2000 to €500-650.