Friday 30 September 2016

Can you upgrade to a 'passive house' standard?

John Cradden

Published 31/05/2015 | 02:30

Although a conventional oil or gas heating system is not needed, you will still need a 'back-up' heating system for the winter, which can be provided by a ground source heat pump or solar thermal panels
Although a conventional oil or gas heating system is not needed, you will still need a 'back-up' heating system for the winter, which can be provided by a ground source heat pump or solar thermal panels

It's even more trendy in eco-building circles than renewable technologies and makes a lot of sense, but how feasible is it to do an energy retrofit to the 'passive house' standard?

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Based on a set of principles devised in Germany back in the 1990s, the 'Passivhaus' concept is about building houses to be so energy efficient that they don't need conventional heating systems.

Although it is mostly applied to new buildings, it is possible to retrofit an existing building to this standard, but it's more difficult to achieve.

The main principles are that the house is extremely well-insulated and very air-tight with triple-glazed windows. Because of this, good ventilation is critical; this usually involves installing low-energy electric fans. No open fires or hole-in-the-wall vents allowed here.

Although a conventional oil or gas heating system is not needed, you will still need a 'back-up' heating system for the winter, which can be provided by a ground source heat pump or solar thermal panels.

All of this means that the running costs of a passive house are estimated to be up to 90pc less than a conventional building. Jeff Colley, editor of construction trade magazine Passive House Plus, cites a 142 sqm 1970s semi-detached house in Galway that was retrofitted to the standard, and which now costs less than €200 a year to heat, including the water.

The house required a complete overhaul, so it made the ideal base for a passive house retrofit, he said.

The final cost of the project was just under €140,000, but it would be far more difficult to 'deep' retrofit a house to a passive house or 'near-passive' standard on a low budget because of the number of modifications and attention to detail required.

It is generally estimated that the costs are currently about 10-15pc higher than for a conventional retrofit, but this margin may close as the standard becomes more popular.

Besides greatly reduced running costs, a passive house is said to be much more comfortable to live in because temperatures remain more constant throughout the year, making it a 'healthy building'.

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