•  very low levels of air leakage;

•  and the use of ventilation with heat recovery.

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The Passivhaus standard has consistently shown the true potential of a fabric-first construction approach. This approach can lead to the creation of highly energy efficient properties that don’t have to rely on expensive renewable technologies.

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Structural insulated panels (SIPs) offer a well-established alternative to traditional building techniques. The system provides inherently excellent fabric performance and airtightness, with a simple, streamlined construction programme.

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SIPs make it possible to build standards such as Passivhaus without the need for excessively thick walls.  An example of a typical SIP construction would be two OSB3 (oriented strand board) facings with a rigid thermoset insulation core. The demanding thermal performance requirements of the Passivhaus standard can then be easily met with the addition of an insulated lining.

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As well as providing excellent levels of insulation, the jointing arrangements inherent in SIPs can provide extremely airtight structures.

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Common construction techniques can be susceptible to air-leakage at a number of points, including :-

 

• through poorly sealed sockets or switches;

• at floor zones through masonry cavity walls;

• under skirting boards;

• through poorly sealed loft hatches and top storey ceiling light fittings.

 

Using SIPs can help to alleviate these issues.

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The demanding airtightness requirements of the Passivhaus approach makes mechanical ventilation essential in order to maintain a constant flow of fresh air within a property. In most cases, it will make sense to add a heat recovery element to the system.

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MVHR (mechanical ventilation with heat recovery) units use the heat from outgoing stale air to warm incoming fresh air, further reducing the property’s heating demand and creating a fresh and comfortable indoor environment.

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The jointing arrangements in SIPs mean that the insulation layer is typically interrupted by less repeating studwork than in a timber frame, greatly reducing repeating thermal bridging.

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In addition, the panels’ factory engineered design ensures very low levels of linear thermal bridging at junctions and openings.

Once onsite, SIPs can usually be fitted with virtually no adjustments, providing a highly predictable, dry build programme which can typically be completed within a matter of weeks.

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As soon as the shell of the building is erected and a breather membrane is applied to the outer face of the SIPs, the property is weather tight and internal fit-out work can begin, reducing programme length and costs.

 

The design is proven by carrying out energy modelling PHPP calculations, ensuring that the building will operate as expected and will not overheat. This also allows the opportunity to review implications on specification changes, ensuring the design is as cost effective as possible.