Curtain walls

Advance Construction Materials

1. advance construction & materials A Short note on curtainwalls

2. What is Curtain wall ? A wall which encloses the space within a building but does not support the roof. Non-load-bearing exterior wall that hangs (like a curtain) from the face of floor slabs, regardless of construction or cladding material Glass curtain wall of the   BauhausDessau , 1926 Ford Metro.Inc Rochester, 1985

3. One of the oldest curtain-wall in the world, Bucharest Developers previously used steel to frame curtain walls. But this was problematic, as steels acts as a conductor and creates thermal bridges that contribute to heat loss in a system. Today, glass and aluminum curtain wall combinations are more popular for use as cladding and for exterior walls. The benefits of this combination include limited air leakage, prevention of rain penetration and limited excessive heat loss (or gain). The development and widespread use of structural steel and later reinforced concrete allowed relatively small columns to support large loads and the exterior walls of buildings were no longer required for structural support. The exterior walls could be non-load bearing and thus much lighter and more open than the masonry load bearing walls of the past. This gave way to increased use of glass as an exterior façade, and the modern day curtain wall was born.

4. Classification: Curtain walls can be classified by their method of fabrication and installation into the following general categories. Storefront Stick Wall I-Beam Wall Pressure Wall Unitized Wall Window Wall

5. Glazed systems that occur on the ground floor, and typically include aluminium entrances. Installed between floor slabs, or between a floor slab and building structure above Storefront “Storefronts” are non-load-bearing glazed systems that occur on the ground floor, which typically include commercial aluminium entrances. They are installed between floor slabs, or between a floor slab and building structure above. storefronts employ exterior glazing stops at one side only sometimes used as a low-cost alternative to for low-rise buildings, performance requirements for storefront are generally less stringent, and materials may require more frequent maintenance.

6. Stick Wall Stick systems are installed on site, component by component, after being prepared and machined in the factory and supplied in knock down form. They get their name from the fact that the vertical structural mullions (sticks) are fixed first. After the mullions are secure, the horizontal transoms are added and then the glazing panels, spandrels and vents installed in the completed grid; normally using a pressure plate and face cap. All stick curtainwalls are field-glazed stick systems are economical and, if correctly designed, detailed and installed, extremely reliable. They are, however, slow to assemble, which may not suit certain fast track projects.

7. Frame assembly requires the use of either, a) “shear blocks” to connect vertical and horizontal framing elements, or b) “screw-spline” construction, in which assembly fasteners feed through holes in interlocking vertical stacking mullions into extruded races in horizontals. Shear block

8. I-Beam Wall I” or “H” shaped, structural, vertical back members are set into openings in the field, with horizontals then clipped to verticals. After glazing, extruded aluminum interior trim is cut and snapped into place at vision areas. Since unexposed spandrel areas receive no interior trim, savings in material and finish (painting or anodizing) can result, partially offset by added field labour maintaining vapor retardant continuity at interior trim joints can be challenging if any positive building pressure is present. Interior trim at vision areas. No finish required at spandrel areas

9. Pressure Wall Many stick curtainwalls are called “pressure walls,” because exterior extruded aluminium plates are screw applied to compress glass between interior and exterior bedding gaskets. A Snap-On cover or “beauty cap” is then used to conceal pressure plate fasteners “Compartmentalization” of each lite is strongly recommended to isolate glazing pockets Performance of any field-assembled or field-glazed curtainwall is only as good as field workmanship allows, limited by variables such as weather, access, and job site dirt and dust. Pressure plates and snap-on covers at exterior, with joints allowing thermal expansion. Pressure plate and Snap-On cover

10. Unitized Wall Unitised curtain walling systems are installed as a series of factory-assembled frames, usually with interlocking mullions and transoms. The glazing panels and spandrels are usually factory-glazed and seals are also applied or prepared in the factory. Unitised systems are used where the movement or deflections in a building are such that a stick system is inappropriate Most unitized curtainwall systems are installed in a sequential manner around each floor level, moving from the bottom to the top of the building. Their principal benefits are speed of installation, minimal on site labour, and lower installation costs. However, these are obviated to an extent by the increased storage and shipping cost , the need for very careful site handling, and the requirement for expensive lifting equipment on site.

11. Unitised systems are popular because they eliminate, or reduce, the need for on site sealing, therefore making them less reliant on the standard of site workmanship. However, for unitised systems to perform to their full potential, it is critical that the brackets to which the components are fixed are accurately installed. Unitised systems do not require decanting during refurbishment contracts. In conclusion, unitised systems offer the benefits of factory fabrication in controlled environment, and very rapid assembly on site. However, they are generally more expensive than stick systems and require longer lead times.

12. Window Wall “Window wall” systems span from the top of one floor slab to the underside of the slab above. Window wall employs large, side stacking window units, contained in head and sill receptors, also called “starters,” which accommodate movement and drainage, but require field-applied perimeter sealants. Slab covers can be fabricated from aluminium extrusions, sheet, panels, or even glass. Window walls easily accept operable windows, and unlike curtainwall, can easily be installed non-sequentially. Hybrid” systems combine characteristics of multiple wall types. For example, some four-side silicone wall systems use stick wall grid frames, with factory glazed carrier frames Window Wall Head starter & two lines of perimeter sealant

13. Aluminium and sheet steel are durable colourfast cladding solutions. Skyline promotes the Rain screen Principle on all applicable projects and offers a variety of metal wall cladding systems. 20-year factory paint warranties back Skyline installs. In addition to sheet steel and aluminium, Skyline incorporates Aluminium Composite Material (ACM) into our proprietary panel systems. ACM is produced by bonding two thin sheets of aluminium on either side of an extruded thermoplastic core under tension. Surfaces are pre-finished and coil-coated in a variety of paint finished before bonding. ACM offers the following: • Rigidity of heavy-gauge sheet metal in a lightweight aluminium-faced composite material • Superior flatness, vibration dampening, durability and ease of maintenance • An alternative solution to sheet metal or heavy gauge plate for wall panels systems • Fabrication in a variety of types of panel systems Metal Wall Cladding

14. Basic Principles: Curtain wall systems must be designed to handle all loads imposed on it as well as keep air and water from penetrating the building envelope. The loads imposed on the curtain wall are transferred to the building structure through the anchors which attach the mullions to the building. The building structure design must account for Dead load Wind load Seismic loads   Snow load Thermal load Infiltration Deflection Smaller wall footprint = resulting in extra floor area available for occupants • Parallel scheduling = resulting in faster erection • Lighter structure = resulting in material and transportation savings • Structural flexibility= resulting in easier seismic engineering • Improved light access = resulting in a more flexible and economical architectural layout • Structural independency= resulting in a more flexible architectural layout

15. Dynamic water testing of a curtain wall in a laboratory. Only 5% of walls generally pass their first test. Horizontal movement of building structure. Frame is generally more flexible than walls Vertical movement of building structure. Note the difference between a rigid load bearing wall (upper left picture) and the flexible frame support Various modes of deflections

16. Advantages : Thermal performance (conduction, solar radiation, thermal break, comfort) Moisture protection (water penetration, condensation resistance) Visual (daylight, aesthetics) Sound (acoustics) Shadow boxes No falling ice and snow Maintenance access Health & indoor air quality Durability & service life expectancy Sustainability