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;
- a) has perfect insulation of attic and external walls plus energy saving windows,
- b) makes use of solar gain (heat from the sun) and utilises solar panels,
- c) makes use of Mechanical Heat Recovery Ventilation (heat exchange system that allows outgoing “used” warm air to heat incoming cold fresh air), and
- 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;
- 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).
- 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.
- 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).
- 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.