Two families will have the opportunity to live rent free in one of two new eco homes in return for evaluating how well the properties function.

The United Welsh Housing Association is running a competition to find people to live in and assess two homes built on the site of a former steel works at Ebbw Vale in Blaenau Gwent, south Wales. The homes, built to showcase the “Passivhaus” concept, are in a group of state-of-the-art homes built for the 2010 National Eisteddfod.

In return, the families will not have to pay rent for 12 months. The average rent for a similar sized UWHA property is £74.03 a week.

The occupants of one of the two houses, the three-bed Larch House, will also avoid energy bills. The design and insulation of a so called Passivhaus, or “passive house”, means they need very little heating. Instead, body heat and heat from electrical appliances such as fridges and computers is enough to ward off the worst winter chills, and the house also has a mechanical heat recovery and ventilation system which extracts warmth from outgoing air and mixes it with incoming fresh air.

Passive houses are designed to be carbon neutral over the course of their lifetime, so provenance of materials is an important part of the equation. Larch House is built from local timber, and all the other components are sourced as locally as possible. Large, south-facing windows, closed-panel timber framing to minimise draught, high insulation, and photovoltaic panels all add to the zero-carbon footprint of the property.

The UWHA says monitoring of how the houses perform, most of which will be done remotely, will enable the innovative techniques used in building these homes to be shared and used in the future.

The Green House competition is open to anyone who either lives in Blaenau Gwent or has a connection to the area, and can include students as well as families. Applicants will be asked to write about themselves and their interest in environmental matters, as they must be prepared to adopt a green lifestyle. Research has shown that eco features alone will not reduce energy bills.

Richard Mann, head of development for the UWHA, says: “People have to change the way they use their home. Basic things like not opening windows when the heating is on make all the difference. In fact, if you don’t use an eco house properly it can end up costing more to run.”

However, the housing association advises that the winners may need access to a car. Although the properties are minutes from the Ysbyty Aneurin Bevan hospital, and the Ebbw Vale Parkway railway station is less than a mile from the site, the nearest school and supermarket are about 1.5 miles away. Finalists will be selected for interview by mid-February.

Mann adds: “These are groundbreaking buildings. This unique competition will deliver an environmental monitoring project which will help mould the future of social housing in the UK.

“Fuel bills can be a big financial drain for social housing tenants, so we want to make sure our homes are as energy efficient as possible.”