Everyone wants an energy efficient home but what is practical for you
depends on your budget. In general there are two approaches to be energy efficiency.
Firstly there is efficiency through the building fabric. Concentrating
on this aspect of a building is commonly called the "Fabric First" approach. If a building
is well insulated and free of draughts with south facing glass to catch
the sun then it will not require much energy to keep it warm. This approach is taken to its reasonable limit in the passive house standard. The sustainable energy authority of Ireland has some good introductory guidance here.
The key requirement for a new passive house is that it takes a maximum
of 15 kWhr/m2 a year to maintain a 20 degree temperature 24 hours a day.
This would mean that if you were heating a 200 m2 house with an
efficient oil boiler it would cost less than €300-00 euro a year to
heat - 24 hours a day for the entire year !
The other way to be energy efficient is in how the energy a building requires is produced. Solar water heating andPhotovoltaic power or heat pump systems are all examples. Under the Irish system for assessing energy efficiency (DEAP) a buildings total energy use is what matters and this can mean a poor standard of building with enough renewable power attached will get a high rating. As an extreme example a stone cottage with single glazed draughty windows and no insulation could be an A1 rated home if it had a hydro electric dam attached that produced all the power it needed.
When looking at upgrading
the energy efficiency of an existing house it can be difficult to know how far to go and measures have to be consistent. For example it would be a crazy waste of money to build an extension to passive house standards while not doing any work to existing uninsulated walls. For most typical houses there are some basic measures that are very effective and I
would recommend the following as a starting point. 1. Replace an old boiler
with a new efficient condensing boiler and upgrade the heating controls with a programmable
timer and temperature sat control and thermostatic radiator valves. Older
boilers may be only around 80% efficient (or worse) whereas a condensing boiler
might be 95% efficient and improved controls mean you will waste less energy.
2 Insulate the attic with around 300mm depth of mineral fibre insulation. This
is very easy to do and cheap. Make sure you do not block the necessary
ventilation of the roof space otherwise you could cause damp and rot. 3. If the
house has cavity walls investigate having them pumped with blown (grey)
bead insulation. The sustainable energy authority of Ireland has a grant system which you can find here.