Design

Heat transfer through a building can occur via conduction through the building fabric or by radiation from sunlight. Heat conduction can be controlled using correctly designed Nirvana panels, but this does not apply to radiation heat from the Sun. Designing for sunlight exposure during Summer and Winter months greatly influences the ultimate energy performance of a building. Ideally, sunlight should be allowed inside the building during Winter and prevented during Summer to reduce heating and cooling loads.

This can be achieved through correct orientation of the entire structure, selective placement of windows, and the installation of eaves and shades above windows. The goal here is to block the Summer Sun (which is higher in the sky at this time of year), but allow the lower Winter Sun to warm the building.

All structures require correct design to ensure they will withstand the forces exerted during their service life. This includes the weight of the structure, wind loads (especially in cyclonic regions), seismic loads, and any other dynamic forces that could be experienced. The internal concrete face of a Nirvana panel forms the structural load bearing wall, and contains lifting anchors for moving into place, connection points for fixing, and steel reinforcing bar and mesh to support the structure throughout its life.

In addition to these typical applications, this internal section has a layer of insulation and an external concrete face attached to it through the Nirvana connector pin. These high tensile pins are embedded into the internal concrete layer during manufacture, and anchor the insulation and external concrete face tightly to the structure to prevent delamination and separation of the panel layers. Reid will design the spacings of the connector pins to safely hold the weight of these two external layers firmly in place. The design considers the weight of the external concrete to be supported, the thickness of the insulation and subsequent bending moment generated, and the dynamic loads exerted during lifting and placement of the panels.

Thermal mass or “heat capacity” refers to the amount of heat energy required to induce a change in temperature in a material. The structural wall of the Nirvana system provides a high thermal mass, where heat energy passing into or out of it is limited by the insulation component of the system. This mechanism allows the Nirvana system to be engineered such that the internal wall temperature will never rise excessively. This will maintain comfortable temperatures indoors, and greatly reduce heating and cooling requirements throughout the changing seasons.

The effectiveness of insulation is dependent on the type of material and its thickness. The Nirvana system can be used with many varieties of insulation, to suit your performance requirements and budget. Once selected, the R-value (thermal resistance) of the Nirvana panel can be varied by altering the thickness of the insulation. By doing so, the Nirvana panel can be designed to achieve a specific R-value to meet Building Code of Australia (BCA) requirements. However, as BCA guidelines are a minimum requirement only, higher R-values may be used if greater financial benefit can be realised.

Nirvana connector pins are manufactured from pultruded glass fibre/resin composite, providing exceptional tensile and flexural strengths, with low heat conductivity and high heat capacity. These heat transfer properties are particularly important, otherwise the pin will form a thermal bridge between concrete layers, greatly reducing the R-value. An important feature of connection pins is that they should possess a circular cross-section to provide maximum shear loading capacity, no matter how the pin is orientated. Non-unidirectional pins have load capacities which can vary by up to 70% according to their orientation. This results from the change in modulus of the cross-section against the shear load – a vital component in structural design.

Specification of connection pins must first consider their length, which must be sufficient to span the insulation layer and provide appropriate embedment within each concrete layer of the panel. Once the length is determined, the distance between connector pins can be calculated. The number of pins required to support the weight of the external concrete layer and resist the bending moments (“lever arm” formed over the distance between each layer of concrete) will determine the distance between individual pins. More pins will be required around edges and penetrations such as windows and doors.