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The Simplicity of SIPs

Paul Newman of Kingspan Timber Solutions explains the simple and compelling concept behind SIPs (Structural Insulated Panels), and why you should consider them in the construction of your new home.

Masonry, SIPs, timber frame, ICF, straw bale, oak frame – the list of build systems available to those building a new home is long and making the choice can be daunting, even before one starts to consider the variants and hybrids that different manufacturers can offer.

In addition to the important considerations of aesthetics, construction cost and energy efficiency, design flexibility, speed of build and space efficiency should all be considered when selecting the build system for your new home as they all have a potentially lasting impact on its performance and desirability.

SIPs offer a simple and highly adaptable construction solution which can be used to create energy efficient homes with flexible open plan living spaces. They can also be used to build homes where the customer wishes to exceed the requirements of the Building Regulations or even to meet the highest levels of energy performance, including the demanding AECB Building Standard and Passivhaus.

What are SIPs?

SIPs are a genuinely modern method of construction, manufactured offsite in a quality controlled factory environment. SIPS consist of two sheets of oriented strand board (OSB) sandwiched around a rigid insulation core. The thickness and thermal performance of the core can be varied to achieve different panel performance levels. Thicker panels naturally achieve better U-values.

The overall thermal performance of the basic panel is easy to improve by the addition of extra insulation to either the internal or external face, and normally this is the best route to take when seeking lower U-values as it brings with it the additional benefit of reduced thermal bridging (the amount of solid timber or steel that crosses from outside to inside of the structure).

Thermal bridging is a significant component of heat loss in modern buildings, and systems that offer improved performance are preferable. As Building Regulations continue to improve in the future, thermal bridging will only ever become a more important component when it comes to heat loss.

The benefits

Despite the obvious energy efficiency benefits of reduced thermal bridging I often think that the major performance benefit of SIPs is the ease with which excellent levels of air-tightness can be achieved (<3 m3/m2/hr @Pa). For example, the Kingspan TEK Building System is manufactured with 15 mm OSB and a rigid urethane core of either 110 mm or 140 mm. The 15 mm OSB helps improve reduce air leakage and the high performance urethane insulation provides enhanced thermal performance. As a business we have constructed over 500 dwellings that achieve better than 1.5 m3/m2/hr @Pa.

Aside from low U-values, reduced thermal bridging and excellent air-tightness, one of the less obvious benefits of an energy-efficient building envelope constructed using high performance insulation products is the

larger floor area that results from thinner construction elements. On small sites, this can provide a significant increase in value of the completed build and arguably more importantly improve “livability”.

SIP structures are nearly always designed using 3D CAD systems. These help greatly when creating geometrically complex structures and invariably reduce the number of design errors in all buildings by enabling easier identification of potential ‘clashes’ in the construction. Once the design has been completed the panels for your home will be factory cut to its unique requirements and then delivered to site. If access to site is good then individual panels can be pre-fabricated in the factory into larger wall and roof elements to further reduce construction time – we do this with most of the SIP buildings we construct; only on the most difficult to access sites do we find it necessary to deliver individual panels direct to site.

The highly airtight nature of buildings constructed with a SIPs envelope makes mechanical ventilation essential in order to maintain a constant flow of fresh air within the property. MVHR (mechanical ventilation with heat recovery) units use the heat from the outgoing stale air to warm incoming fresh air, further reducing the property’s heating demand and creating a fresh and comfortable indoor environment. It is important that duct routes for MVHR systems are taken into account when the structure is designed.

Once the panels arrive onsite, the SIPs structure can usually be erected with no adjustment to individual panel elements, providing a highly predictable, dry build program which can be completed within a matter of weeks; typically structures will be handed over to customers in three to six weeks. Once the shell of the building has been erected, and windows fitted and tape- sealed, the property is weathertight and internal fit out work can begin at the same time as external works, reducing both the length and cost of the building process.

Self-building can be a daunting process, with so many important decisions to make at every stage. SIPs offer a tried and tested solution for creating homes which are not only meet your design requirements, but are also simple to construct and particularly energy efficient, giving you peace of mind both for the short and long-term.

Paul Newman is self build director at Kingspan Timber Solutions

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