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Tips when constructing this model construction package.

Air Tightness

There are no real changes in how buildings are constructed apart from a wider cavity and the air tight barrier. The big difference is the introduction of the air tight barrier: plaster finish; membrane or spray foam. The builder has the option of following the recommendations on the drawings published on this web site or employing a specialist subcontractor who is familiar with the workmanship required to make the building air tight, the problematic are at the intermediate floor and at the eaves and gables.

The air permeability test should be carried out by the builder after the building is made air tight and before the plasterboard is fitted onto the rendered air barrier. Only when the design permeability outlined in the design specification is achieved should the plasterboard be fixed. If the recommendations for air tightness outlined in this section of the system are implemented then the 6.0 m3/m2/hr. 50 Pa is very achievable. The builder is encouraged to improve on the design air permeability and when completed the builder must forward this information to the Approved Verifier and the energy assessor who will record the result on the Foresite data base and then use the information to calculate the as constructed DER.

Thermal Continuity

The thermal continuity for the walls from the DPC to the eaves and gable barge levels are provided by the bonded bead / Rockwool/ Cellulose Insulation Contractor, the builder must ensure that the cavities are as per the design and are free of all debris at least once per half storey or use cavity boards which will reduce debris in the cavity. The areas that need most attention are the typical detail junctions but more importantly at the eaves.

When a building is registered on the Foresite building control system by the Designer, an e mail will be sent to the builder giving him a Project ID so that he has access to design information specific to the registered dwelling. The builder can download customised fabric compliance documents with typical details that will have reference numbers and details specific to the registered dwelling, this compliance document will prove the insulation has been installed correctly and should be made available to all the registered stakeholders for the project on request.

Thermal Bridge

The builder should familiarise himself with all the typical details that are needed to construct the project and this can be done by using the project ID to access the construction details and technical data for a particular project on the web based building control system. The builder can download customised fabric compliance documents from the building control system with typical details that will have accredited reference numbers and specific details of each element of the fabric, this compliance document will allow the design y factor to be used to calculate the as constructed DER.

Other practical considerations because of larger cavity

If a large cavity is being used, and the construction drawings have not allowed for the bigger cavity, the builder should ensure when setting out the building that the internal dimensions are not affected. Before commencement the builder should ensure that he has sourced the DPCs, wall ties, cavity trays and lintels and has made allowance for the extra width of the cavity, and that all the tradesmen are familiar with the detail and good workmanship required when constructing energy efficient buildings.


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