Energy-efficient glass in Berwick & South East Melbourne.

U-value — how much heat the window leaks.

U-value (W/m²K) measures thermal transmittance — how much heat flows through a square metre of window per degree of temperature difference. Lower is better.

• Single-glazed clear: U ~5.8 (terrible)
• Standard double glazed clear-clear air-filled: U ~2.7
• Standard double glazed clear-clear argon-filled: U ~2.4
• Double glazed Low-E argon-filled: U ~1.6 (our standard)
• Triple glazed Low-E argon: U ~1.0–1.2 (passive-house spec)

SHGC — how much solar heat the window lets in.

SHGC (Solar Heat Gain Coefficient) is a 0–1 number measuring what fraction of solar radiation hitting the window passes through into the room. The right number depends on orientation:

• North (winter sun): SHGC 0.55+ — let winter sun warm the room. Clear Low-E.
• East (morning sun): SHGC 0.45–0.55 — mild morning sun useful in winter, not problematic in summer.
• South (no direct sun, just diffuse): SHGC 0.45–0.55 — doesn't matter much. Low-E for U-value.
• West (summer afternoon heat): SHGC 0.30–0.35 — block summer heat. Tinted or strong reflective Low-E.

Blanket-spec the same SHGC everywhere — which the discount end of the market does — and you lose ~10% of available solar heating on north windows and gain ~15% of unwanted summer heat on west windows. A per-orientation spec costs the same in materials and delivers a measurably better NatHERS rating.

VIC Climate Zone 6 — what we design for.

South East Melbourne is NCC Climate Zone 6 (cool temperate). Heating-dominated (we use more energy heating than cooling). The right glass spec is U-value ~1.6 with north-tuned SHGC. We never under-spec on U-value, we tune SHGC per orientation, and we always specify Low-E coating on surface #3 (inside face of inner pane) for the cool-climate optimum.

VEU rebate — what's included.

The VIC Energy Upgrades window activity rebate is the single biggest financial driver for SEM glazing upgrades right now. It's paid on the change from single to double glazing with documented improvement. We do the lodgement paperwork as an Accredited Provider so you don't have to. Rebate per window $200–$800 depending on size, climate zone factor (Zone 6 multiplier is favourable) and the rated U-value/SHGC achieved. On a typical 16-window full-house retrofit, expect $4,000–$6,500 in rebate value netted off the invoice.