Glazing DesignHerman Kwok

Daver BolbolanMatthew Vong

Glazing Design G.K Garden Canadian Building Digest 55, 1964

• Introduction • Types of Glazing • Glazing Material • Glass Properties • Frames Used for glazing

Types of Glazing

• Single Pane of Glass• Double glazed• Gas Filled Window • Low-e Coating • Heat Mirror• Super Window • Canadian Fiberglas Triple glazed

Glazing Materials

• “Glass”, frame, inert gas fill, coating, spacer, gaskets, seals, structural attachment

“Glass”

• Regular transparent glass• Double / triple glazing• Absorbing glass• Reflective glass• Polycarbonate• Corrugated fibre glass• Acrylic sheets• Float glass• Annealed, tempered, heat-strengthened, laminated

Properties

• Visible transmittance• Visible Reflectance• Solar heat gain coefficient• U / R Values• Ultraviolet transmittance• Spectral selectivity• Fire resistance• Sound transmission• Colour

Frame

• Wood– High maintenance– Moisture problem

• Vinyl– Low maintenance– Thick

• Aluminum / Steel– Strong– High thermal conductivity

• Fiberglass– Best but expensive, colour may fade

Inert gas fill

• Lower thermal conductivity than air• Argon, Krypton, Xenon• Reduce sound transmission• Sulphur hexafluoride (SF6) , Carbon dioxide• 0.44 times of velocity of sound in air

Coating

• Low-e• Metal Oxide or

Semiconductor Films• Blocks heat while

allowing solar energy to pass through

• Tinting

Spacer

• Sufficient resilience and thickness• Aluminum Stainless Steel Silicone Foam• Insulated – foam, desiccant• Silicone warm edge spacer– Thermal conductivity 950x less than Aluminum

Spacers in IGU

Sealant

• Substrate compatibility• Adhesion strength• Resistance to UV degradation• Curing time• Movement capability• Modulus• Blast resistance

Gasket

• Vinyl• EPDM rubber (Ethylene Propylene Diene

Monomer)

Gasket

• All components work together• Movement allowance• Waterproof• Air tight

Differential Movement

• 3 common types– Vertical– Lateral in plane– Lateral normal

• Factors: Wind, Thermal Expansion, Warpage of Wood, Seismic Events

Thermal Edge Breaking

Differential Movement• Require damping and/or spacing • Compressed gaskets– Relieve shear stress through glass slippage

• Structural Silicone• Non-hardening glazing compound– 3M Bedding & Glazing Compound

Water Penetration

• Water penetration occurs due to inside-outside pressure gradients, gravity

• Affected by:– ‘Time of wetness’: frequency and duration that a window

is wet– Wind driven rain– Presence of overhangs

Waterproofing

• Determined by glazing method (wet vs dry) and glazing method

• Wet glazing: gunable sealant installed over a preformed tape or gasket

• Dry glazing: extruded rubber gaskets as glazing seal (relies on compression to seal)

Moisture Protection

• Need to control forces moving water inward on face of joints and glazing

• Prevent by having a deterrent to water entry at wetted face, making air seal at dry side of joint, which equalizes air pressure in glazing cavity

Moisture Protection

• Rainscreen windows: air path between water shedding surface and exterior moisture barrier forms capillary break and drainage path

Strategies to Control Moisture

• Limit condensation with low U-value glazing and supplemental heat to increase glazing surface temperatures

• Flashings at sill, jambs, and head integrated with waterproofing at adjacent walls

• Sill and head flashings sloped to exterior for prompt drainage

Design considerations

• Many windows leak at sash corners and sill to jamb frame corners

• Miter corners and stiffen with spline inserts

Design considerations

• Vulcanized rubber continuous gaskets and weather-strips (not very economical)

• Sill flashings with end dams to collect leakage and drain to exterior (lower quality windows)

Moisture Control

• CSA-A440-M “Windows”– Standard for evaluating and categorizing rain penetration

control performance for windows– Tests new windows– Uses historical rainfall and wind records to establish ratings

for municipalities– Neglects micro climate effects (building form, overhangs,

local terrain) that impact water penetration due to wind driven rain

Durability

• Sealant – UV resistance, de-bonding• Frames – painting, anodizing, coating• Glass – heat-strengthened, NiS impurities,

edge & surface damage• Maintenance – cleaning, inspection, repair or

replace