Passive Housing – The ultimate BER rating

It is almost a year now since BER certification became compulsory for all homes being sold or rented in Ireland. While an A1 rating is the top level achievable from your BER Assessor, why stop there?  A passive house is not only highly efficient (A1 BER) but in some cases can achieve a level where it is a net supplier of energy.

The aim of the passive house concept is to construct a house that comes as close as possible to heating and cooling itself in a passive manner, thus removing the need for a conventional heating/cooling system.

A passive house should anly require a small back-up heat source which may be required in extremely cold weather. This can result in a massive energy saving considering that up to 70% of a typical home’s energy cost will be spent on heating the space within the home.

The aim of Passive Housing is to minimise energy loss while maximising the amount of energy used from natural and renewable sources. The key element is achieving this is the design ofthe passive houseto combine the principles of passive solar building with a well insulated and air tight building perimiter.

Heating for cold days is provided by raising the temperature of the ventilation air using an efficient heat recovery ventilation system, through which the warm moist air exiting the house will pre-heat the incoming cold fresh air.

The concept of the Passive House originated in Germany in the early 1990s. and aims to provide comfortable living conditions while ensuring greatly reduced energy consumption. The ultimate Passive House design seeks to achieve ‘zero carbon’ output.

Based on current oil prices and on a 1100 square foot house, a Passive House will have an annual heating bill of between €100 and €200 which is a saving of almost 80% versus what you would expect to pay for heating a typical newly built home.

Enormous energy savings like this are achieved through the two main pillars of Passive House design;

1. super insulation of the building fabric to minimise heat loss, and 2. maximising free heat gains through passive solar techniques and optimal orientation of the house as a whole.

The overall effect of a Passive House will be to greatly reduce energy consumption and thus carbon emissions and in doing so will lead to your home achieving the best possible’ A’ rating on its BER certificate. Any additional costs incurred during the construction of the house in providing a superinsulated and airtight home with adequate heat recovery ventilation is likely to be rapidly paid back through energy savings especially as oil prices rise.

To meet the performance standards required to be considered a passive house, the annual net heating requirement must be less than 15 kilowatt hours per square meter of living space per year. To put this in perspective a standard house built in accordance with the 2007 building regulations in Ireland would typically have an energy consumption value of 100kWh/m2 per annum or even more. This figure is more than six times the passive house standard of just 15kWh/m2 per annum.

The maximum annual energy input for a passive house is set at 42 kWh/m2/yr. The typical; nonpassive house built under the 2007 regulation would be expected to have an annual total energy consumption of about 150 kWh/nl/yr, which is over three and a half times the total energy consumption of the passive house.

It can thus be seen that Passive Houses are extremely efficient in terms of energy consumption and, assuming quality design and workmanship, are still capable of providing high levels of comfort.

In addition to meeting the standards required to be considered “passive”, further investment in wind/solar or geothermal technology has seen examples where the energy consumption of a house can be negative with a net energy output.

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