"Example calculations about the cost saving from external wall insulation."
This is a worked estimate where you can take the calculations and substitute your own numbers to match your property. If you have any queries about how these calculations were done please contact us.
Heat loss per year
To calculate how much can be saved by insulating the walls we need to start with an estimate of the total heat loss. In Ireland the best way to do this is by using the BER figures. BERs covers the total annual energy use for space heating, water heating, ventilation, lighting and associated pumps and fans. This is calculated on the basis of a notional standard family with a standard pattern of occupancy.
Most homes that we are asked to visit fall into one of these bands.
E1 = >300 kWh/m²/yr
D2 = >260 kWh/m²/yr
D1 = >225 kWh/m²/yr
C3 = >200 kWh/m²/yr
Each band as you can see has a annual energy usage figure. This is a calculation of the amount of energy that is required to heat a house. A BER does not cover electricity used for purposes other than heating, lighting, pumps and fans, i.e. does not include for cooking, refrigeration, laundry etc. This means that this energy is used to heat the home.
Note the energy emitted by light bulbs as visible light is mostly absorbed by surfaces within your home also contributes to heating your home. This is a very important element in Passive Haus design. Energy is neither created nor destroyed only converted from one form into another - first law of thermodynamicsSo we can take an average of 250 kWh/m2/yr as a starting point for a typical Irish home. Next let’s assume a 200 sq meter house to give an annual energy usage figure of 50 000 kWh/yr. In an uninsulated house around 1/3 will escape through the walls (according to SEI) or 16 666 kWh/yr. A typical uninsulated wall in Ireland will have a U value of 1.56 W/m2K, when that wall is insulated to current “Part L” building regulations the U value must drop to 0.27 or below. That works out as an 83% improvement in the insulating properties of the wall, which is a saving of 13 783 kWh/yr.
Cost saving from external insulation
Looking at the EU Energy portal http://www.energy.eu/#domestic we can see that the average price of Electricity for an Irish consumer in 2009 was 0.184 euro/kWh. The equivalent figure for gas is 0.107 euro/kWh.
For an electric home the cash saving is about 2536 euro a year and for a gas heated home the equivalent saving is 1500 euro per year.
Projecting forward, using a very simple 10% increase in energy prices per year we can estimate what the savings are to a householder. Over a 5 year period with a 10% increase per year, the savings for a gas heated home is just over 9 000 euro. For an electrically heated home the 5 year savings are over 15 000 euro.
To move away from cash and looking at CO2 emissions, a slightly different way of seeing the same problem! From the emissions angle the British Energy Saving Trust (A UK charity) suggest a saving of 2.1 tonnes of CO2 for a typical 3 bed semi-detached house, per year or 10.5 tonnes in a five year period.
Coupled with the 4000 euro grant, and the ever increasing price of energy it clear that most Irish homes will recoup the cost of External Wall Insulation in 5 years or less. The rumoured imminent arrival of BER related property taxes will just make the case for insulation even more stark.
Note this is a worked example just to give an indication of the savings for a certain house. For more specific figures for your existing home or new build please consult your Engineer or Architect. Each house is unique and give a definitive account on how much money will be saved by external insulation would require a study of the particular house (residual thermal bridges etc) and household behaviour.
Contact us now to learn how your home can benefit from External Wall Insulation.