Facade Performance Requirements: A Specifier's Guide (2026)

What a performance-based facade brief actually is

A defensible facade specification separates performance requirements (what the envelope must achieve) from prescriptive requirements (named systems, finishes, warranties). Lead with performance so bidders compete on engineering, not merely on price, and so any substitution can be judged against a number rather than a marketing claim. A prescriptive-only spec locks you into one supplier and gives you no objective way to reject a poor alternative; a performance-only spec can drift on aesthetics and warranty. Almost every good real-world facade uses a hybrid - hard performance numbers plus a few prescriptive constraints on finish, warranty period and named-equal products.

At minimum, your requirement schedule should fix targets in six categories:

• Thermal: assembly U-value (W/m2K) for vision and spandrel zones, plus a mandatory thermal-break requirement and condensation resistance.
• Solar and daylight: SHGC (Solar Heat Gain Coefficient) and VLT (Visible Light Transmittance), ideally with a target light-to-solar-gain (LSG) ratio.
• Acoustic: weighted sound reduction index Rw, and Rw+Ctr for road-, rail- or airport-facing facades.
• Structural: design wind pressure, deflection limits and the dead-load support strategy.
• Air and water: air infiltration rate and static/dynamic water penetration test pressures.
• Interfaces and tolerances: movement joints, slab-edge tolerance and structural deflection allowance.

Get these six categories onto a single requirement schedule and most disputes evaporate before tender. If you want early input while the schedule is still open, get a free quote and involve a fabricator in design-assist mode.

Thermal, solar and daylight criteria for Hyderabad

For Hyderabad, Secunderabad and the wider Telangana region, SHGC is the dominant energy driver - controlling solar gain cuts cooling load far more than chasing marginal U-value gains. Specify SHGC and VLT together so the glass selection is not accidentally pushed toward a dark, daylight-killing product just to hit a solar number.

• Reference the ECBC (Energy Conservation Building Code) envelope requirements and any IGBC, GRIHA or LEED target the project is pursuing; let those set the ceiling values, then tighten if the energy model demands it.
• Typical high-performance double-glazed vision targets: U-value around 1.6-2.0 W/m2K, SHGC around 0.25-0.35, VLT around 40-60% - always confirm against your project's energy model rather than adopting blindly.
• Require a thermally broken aluminium system wherever the U-value target cannot be met by glass alone; state clearly whether the quoted U-value is centre-of-glass or whole-assembly (Uw), because the two figures differ materially.
• Ask for SHGC at the assembly level - including frame and any external shading fins or projections - not just the centre-of-glass figure lifted from the coated-glass datasheet.

As a rough commercial benchmark for Hyderabad projects, a good double-glazed unit (DGU) with a soft-coat low-E and argon fill runs roughly INR 900-1,600 per sq ft supplied, before the aluminium system. A high-selectivity coating that buys you a lower SHGC without dropping VLT sits at the upper end of that range but usually pays back through downsized HVAC. You can see how these glass choices play out on real buildings in our recent projects.

Structural and wind performance under IS 875

Wind governs the structural design of most facades in Telangana and Andhra Pradesh. Derive design wind pressure from IS 875 (Part 3) using the correct basic wind speed for the region, terrain category, building height and local pressure coefficients - and remember that corners, parapets and canopy soffits see far higher local suction than the field of the wall.

• Deflection: limit framing member deflection to the lesser of L/175 or roughly 19 mm for single spans under design wind (structural sealant glazing practice per IS 2553 and relevant ASTM methods); tighten to L/240 where finishes or interfaces are movement-sensitive.
• Glass strength: verify glass thickness and heat-treatment (annealed, heat-strengthened or fully toughened) against the design wind pressure and the human-impact safety requirements of NBC 2016.
• Dead load: define exactly how self-weight transfers to the structure - stack joints, bracketry, embeds - and the vertical live-load movement the system must absorb.
• Seismic and inter-storey drift: state the drift the facade must accommodate without glass-to-frame contact or sealant failure, particularly on taller Hyderabad towers.

The connection back to the building frame is as critical as the glass itself. On a structural glazing facade, the spider fittings, brackets and structural sealant must be selected against the actual design suction, not a generic catalogue rating - a fitting rated for the field of the wall can be badly under-specified at a corner mullion carrying two to three times the suction.

Air, water and acoustic tightness - write numbers, not adjectives

These are the criteria most often lost to vague language. Replace words like 'weatherproof' and 'well-sealed' with pass/fail test pressures the fabricator and lab can act on.

• Air infiltration: specify a maximum leakage rate at a stated test pressure (commonly measured to ASTM E283 methodology); lower rates protect both energy performance and cooling comfort during Hyderabad's dusty pre-monsoon months.
• Water penetration: require static water tightness (ASTM E331) and, on exposed or tall facades, dynamic water tightness under simulated wind-driven rain (ASTM E547 / AAMA dynamic method) at a pressure tied to your design wind.
• Acoustic: set Rw (and Rw+Ctr for traffic noise) per room type - a higher Rw for facades facing arterial roads such as the Outer Ring Road or the airport approach. The glazing make-up (asymmetric panes, wider cavity, laminated PVB interlayer) then follows from the target rather than the other way around.
• Mock-up and testing: state whether a project-specific performance mock-up (PMU) and field water testing (for example AAMA field spray) are required, and who witnesses them.

Air and water tightness also depend on hardware discipline at the openings. Doors and openable vents within a glass facade need reliable, correctly rated door hardware so gaskets compress evenly and the tested performance is actually delivered in the field - a curtain wall that passes in the lab still leaks if the entrance door alongside it is under-specified.

Cost breakdown: what facade performance costs in INR

Performance costs money, but under-specifying costs more once a leaking or overheating facade has to be reworked. Use these indicative Hyderabad ranges to sanity-check bids and to write a spec that is ambitious yet fundable.

• Glass (supplied): plain toughened INR 120-250 per sq ft; high-performance DGU with soft-coat low-E and argon INR 900-1,600 per sq ft; premium high-selectivity or acoustic laminated DGUs above that.
• Complete curtain walling (aluminium system, glass, sealant, install): roughly INR 1,600-3,500 per sq ft depending on system depth, performance class and glass.
• Structural / spider glazing: typically INR 1,400-3,000 per sq ft, driven by fitting quality and glass thickness.
• Standard aluminium composite / ACP cladding: roughly INR 350-750 per sq ft installed, for opaque zones and spandrels.
• Performance mock-up (PMU): INR 8-25 lakh depending on size and test scope - a rounding error against a seven-figure facade package, and cheap insurance against a systemic air, water or structural failure discovered after mass fabrication.

The single biggest cost lever is the glass and coating, so resolve SHGC and VLT before you fix a budget. The second is system depth, which is set by your wind pressure and deflection limits - over-tight deflection on a tall, exposed Andhra Pradesh site can push you into a deeper, costlier mullion, so specify what performance genuinely requires, no more and no less.

Tolerances, interfaces and buildability

Most facade failures live at interfaces - the slab edge, the parapet, the window-to-wall junction - not in the middle of a panel. Assign ownership of every joint on the drawings so nobody decides on site who owns the leak.

• State the structural tolerances the facade must absorb: slab-edge deviation, floor-to-floor variation and long-term structural deflection or creep, especially at cantilevers and transfer levels.
• Define movement joints for thermal expansion of long aluminium runs and for building movement; do not let them default to the fabricator's convenience.
• Fix the datum and setting-out responsibility, and require shop drawings to be checked against a surveyed structure before fabrication begins.
• Coordinate air- and water-barrier continuity across trades - where the facade meets RCC, blockwork, roofing and waterproofing - and show the continuous seal line on section.

A performance number is only as good as the interface that carries it. Coordinating these junctions early, ideally with the facade contractor engaged in design-assist through our services, is what turns a clean specification into a facade that actually holds water on site.

Common mistakes to avoid

The same avoidable errors recur across projects in Hyderabad and beyond. Design them out at the specification stage, not during snagging.

• Quoting centre-of-glass U-value and SHGC as if they were whole-assembly figures - the frame and edge effects always make the real assembly value worse.
• Using adjectives ('weatherproof', 'robust', 'premium') instead of tested pressures and rates; they are unenforceable at handover.
• Ignoring corner and parapet suction and designing the whole facade to the field-of-wall wind coefficient.
• Chasing a low SHGC with dark glass and destroying daylight and views - always pair SHGC with a VLT floor.
• Omitting a performance mock-up on a tall or complex facade to save a few lakh, then discovering a systemic water path after fabrication.
• Leaving interface ownership undefined, so the curtain wall, RCC and waterproofing trades each assume another owns the critical seal.
• Specifying performance for the fixed glazing but not for the balcony doors, terrace access and entrances - usually the leakiest, most abused elements of the whole envelope.

Writing the spec so it holds up

Turn the criteria above into a requirement schedule and reference the governing standards by name rather than describing them loosely. Ambiguity is precisely what gets value-engineered away.

• Tabulate every zone (typical vision, corner, spandrel, entrance) with its own U-value, SHGC, VLT, Rw, wind pressure and deflection target.
• Cite the standard for each test: IS 875 Part 3 (wind), IS 2553 (glass and glazing), NBC 2016 (safety and human impact), ECBC (energy), and the relevant ASTM air/water methods.
• Require submittals: structural calculations, thermal/energy compliance, glass processing certificates, test reports and stamped shop drawings.
• Name the acceptance route: performance mock-up, factory checks and field testing, with a defined remedial and retest procedure.

A schedule written this way is self-policing - every clause maps to a test, and every test maps to a pass/fail line the contractor priced. That is what makes the built facade defensible if it is ever challenged.

Local support: specifying with a Hyderabad facade partner

Hakimi Aluminium and Glass offers design-assist, shop drawings, fabrication and installation for architects across Hyderabad, Secunderabad, Telangana and Andhra Pradesh - useful when you want early buildability and testing input while the performance spec is still open.

• Engaging a specialist during design, not just at tender, lets you pressure-test your U-value, SHGC and wind targets against what is actually buildable and available in the local supply chain.
• A local partner can advise on realistic INR budgets - curtain walling in Hyderabad broadly ranges from roughly INR 1,600-3,500 per sq ft depending on glass, system depth and performance class - so your spec is ambitious but fundable.
• Coastal Andhra Pradesh sites need higher corrosion resistance on fixings and hardware than inland Hyderabad; a partner who knows the region specifies for it from the start rather than discovering it in year two.

When you are ready to convert a performance schedule into a costed, buildable structural glazing or curtain-wall proposal, get a free quote and share your drawings, energy model and standards references.