Frameless double glazing with stainless steel channels, an internal glass floor with secondary steel ring beam structure and framed glass balustrades: area 60 m2.

This project is bespoke solutions to a private dwelling house bring together a minimalist frameless façade with an internal glass floor and an external glass balustrade.

The façade is located to the rear of a Georgian dwelling.
The glass double glazing is two edges supported ie sitting into a concealed 316 stainless steel channel. 316 stainless steel was chosen over aluminium as it had better insulating properties over aluminium, therefore reducing the risk of thermal bridging at critical construction interfaces.

The architectural intent was to minimalize the external appearance and every effort was made to detail the interfaces between adjacent surfaces and finishes.

The two storey façade extends into lower courtyard located beneath the basement and the concept of a private balcony gallery looking from the kitchen into the living space was realized as a glass floor for additional space thus allowing the light to penetrate deeper into the dwelling.

The glass has some interesting characteristics. The double glazed units comprise of 44mm, consisting of 10mm toughened outer, 16mm warn edge spacer and 15 toughened k glasse inner.

Fritting to face two and face four was a very important design feature. Consultation with the glass supplier enabled the frit to be painted to a light grey ral colour which was visually inspected along its perimeter to ensure satisfactory aesthetic appearance. As the internal pane is hard coated, the inside pane could also be fritted as the glass could be edge deleted to receive the ceramic paint.

Fritting is an important feature of flush glazing. In this instance its width has been determined by the width of the warm edge spacer and the size of the joint (10mm). The architectural intent was to line up the glazing joints vertically.

The fenestration incorporates internal and external overlap glass details.

A growing trend in recent times has been to incorporate aluminium opening sashes and doors. The projects used in this project are from the APA range of high thermal performance casement and door sections.

Glass floors have become a personal speciality.

The internal glass floor is single glazed 46mm thick consisting of 4 no 10mm toughened panes laminated together using an ionoplast interlayer. This type of interlayer has high strength and high temperature stiffness (55-66 0C) which gives it a greater resistance to delamination. The unit sits on a secondary steel ring support and spans across the opening with butt joints pointed in dow corning.

This type of solution is typically on a longer procurement route as the glass manufacturing process is more harder as the glass is more difficult to laminate, there are a limited number of processors and this technique is relatively new technology.

The façade incorporates standard casement sashes and rebated doors for general access. These are the only passive measures that enable the client to naturally ventilate the interior. The internal environment is regulated by mechanical measures.

Solar gain is managed by internal blinds which when fully open are concealed within the roof space at each level. This allows the occupant the opportunity to manage the solar gain and regulated the level of discomfort glare.
Internal surfaces are painted white to allow the natural daylight penetrate deeper into the room.

The client’s objective was to have a minimalist façade. Various options were explored initially as the client did not want to see the black frit at the glass to glass joint. The sight line buildup read as 60mm which initially because of the black fritting appeared excessive and beam an issue as the client wanted unobstructed vision to and from the courtyard space. As a result a number of options were explored.

• The concept of one large single glazed pane of approx. size 2800 mm by 6450mm was investigated but because of the additional requirement for mechanical ventilation and the risk of internal condensation it was eliminated.
• The concept of one large double glazed unit was also considered but was eliminated because of cost and practicality.
• The end result was a compromise that made best practise of fritting to ral 7037 matt. This reduced the tone of the broad sightline and gave the fenestration a much larger visual transparent impression.

Each glass unit was inspected at the glass factory to ensure that the internal black silicon mix did not penetrate or foul the external finish.

The internal pane was a hard coated glass which enabled the coating to be edge deleted and fritted leading to a sharper and more consistent visual line. The use of K glass, warm edge technology and zenith gas within the cavity of the Insulated glazed unit (IGU) gave an overall u-value of 1.1 W/M2/K.

The façade aspect has a southerly orientation which means that the use of annealed toughened glass allows sufficient solar gain to naturally heat the internal spaces for most months of the year. Mechanical measures are employed to cool in the summer months.