NBT’s Pavawall used for affordable low energy homes

Natural Building Technologies’ Pavawall system has been used by social housing provider, Four Housing Group, to create 21 energy efficient and high quality affordable houses and bungalows for local people in Berwick-on-Tweed.

Designed by leading architects, Fitz Architects of Sunderland, the two and three bedroom homes are built to the Code for Sustainable Homes (CfSH) level 4 standard, delivering very low energy usage combined with a healthy living environment.

Principal architect, Craig Fitzakerley explained why Pavawall was specified for the development: “We’d already specified Pavawall on a previous CfSH level 6 house scheme and understood the benefits and how good it was. The system also won over the contractor on the project who hadn’t used it before, but was impressed by its ease of construction.”

The flexibility of the system accommodated two external finishes; render and cedar cladding, while ensuring the wall structures benefited from high levels of breathability.

The Pavawall system comprises a continuous layer of NBT’s high performance woodfibre boards, which are manufactured from 95% wood waste, installed on the outside of the houses’ timber frame structures. The woodfibre boards feature tongue and groove edges to enhance the wind and airtightness of the walls. Additional insulation was installed between the 140mm deep walls studs to deliver the required level of insulation.

Internally, the system is completed by the installation of OSB boards on the internal face of the timber panels. This provides racking strength and acts as an internal airtight layer.

The U-value for the walls is 0.24 W/m2K. Airtightness tests undertaken on the properties returned impressive figures well under the target value of 5.0m3/hr/m2@50Pa, greatly outperforming the Building Regulations’ requirement of under 10m3.

Pavawall’s breathability also means that the structure of the houses is able to self-regulate moisture levels to minimise the risk of interstitial condensation, thereby protecting both the building fabric and the internal environment, an unceasingly important need as houses become increasingly airtight.

In addition, the thermal mass of the Pavawall system means that the properties will benefit from effective protection against summertime overheating.

As well as benefiting from the ultra high insulation delivered by the building fabric, each home is equipped with photovoltaic panels to further reduce running costs and impact on the environment.