W60 Milan, W20, Forster Systems

Weather Performance
Experience has demonstrated the suitability of steel windows for most sites and exposure conditions, where an exposure rating of 1200 Pascals satisfies most locations. Extensive testing has produced the typical results tabulated below. The weatherseals introduced with the Milan suite provide an external rainscreen, internal airseals and a pressure equalised cavity that has significantly improved resistance to air and weather penetration in severe exposure conditions. For the first time in New Zealand, steel window joinery can match the performance characteristics of aluminum joinery.

Thermal Performance
With a temperature differential from -5º outside to +20º inside, no ventilation air movement, and relative humidity above 33%, condensation will form on the internal frame surfaces. Although inconvenient, such condensation will not cause harm to the window. It is perhaps preferable that condensation should manifest itself on visible window surfaces rather than in concealed cupboard and wardrobe spaces. This should encourage people to seek greater ventilation as the recommended means of control.

Security
The inherent strength of steel ensures maximum rigidity once the window frames have been installed and glazed.

The most secure steel window is a regular, standard window divided into small panes of glass, with vertical and horizontal glazing welded into the frame. Even if the glass is broken, entry cannot be made though this window.
A high level of security can also be achieved with the Hollow Profile Systems; Bomb blast, Bullet resistant, and Anti-bandit steel-framed glazing systems are possible.

Corrosion Protection
An integral part of Crittall's production process is that all windows and doors are protected against corrosion by zinc metal spraying. During this process the fully fabricated steel units are thoroughly cleaned and steel grit blasted, in preparation for the arc metal spray process. In this process the raw pure zinc, in the form of a pair of metallic wires, is melted by an electric arc. This molten material is atomised by a cone of compressed air and propelled towards the steel surface. The molten spray solidifies on the surface to form a dense, strongly adherent coating that will not crack or peel. Unlike hot dip galvanising, this process does not warp or distort the steel.

Surface Finishes
We offer 2 surface finishes. The most popular and most economical is polyester powder coat. Alternatively, we also offer to supply the windows and doors pre primed with a 2 pot expoxy primer in readiness for site painting, with a compatible top coat system of your choice.

Installation
Fixing. Steel windows are suitable for fixing direct into brickwork, concrete, stone, or timber framing.

The size of the opening should overall, should be 10mm greater in length and height than the inside window dimension. Windows and doors must be installed in accordance with good building practice. No load shall be applied to the head of any window. Where direct fixing is not achievable, lugs are factory fitted. Steel windows are fitted without liners.

Glazing. Steel windows can be single glazed or fitted with insulating glass units. Bead glazing of W20 and Milan windows will allow glass thicknesses of up to 8.8mm. Glazing practice should always comply with NZBC F2 and NZS4223. Specific instructions about the use of dry glazing products and putty compounds are available.

Aftercare and Maintenance
The modern steel window is an extremely durable, high performance product. Its performance can be enhanced by observing good maintenance practices.

Frames should be cleaned at regular intervals, using a mild, non-alkaline detergent in warm water, applied with a soft cloth or sponge.

Glazing or perimeter sealants should be inspected on an annual basis and appropriate maintenance action taken.

Windows are manufactured with clearances set for the original applied finish. When re-coating, it is important that these clearances are maintained to ensure weathering and correct operation of fittings and hardware.

All hinges, handles, stays and other mechanical parts should be checked for operation, kept free of excessive paint build-up and lightly lubricated on an annual basis.

Fire Resisting Glazing
Crittall Arnold has developed a diverse portfolio of fire rated, steel framed, glazing systems; from single and double leaf doors, fixed and opening windows, to screens and curtain walling. We provide systems for integrity only, or integrity and insulation as required, from 15 minutes up to 2 hours.
For specific details, maximum sizes, or other advice please contact Crittall.