Low-E Glass Calculator

Compare Low-E glass types and their cost impact. Soft-coat vs hard-coat, high-gain vs low-gain, single and dual coatings — with U-value and SHGC outputs.

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The Low-E Trade-Off, Calculated

Every Low-E coating buys thermal performance — and changes solar gain, light transmittance, and cost.

1

Soft-Coat vs Hard-Coat Pricing

Hard-coat Low-E (pyrolytic) is durable, can be used on outer surfaces, and runs ~€3-5/m² uplift. Soft-coat Low-E (magnetron-sputtered) delivers better U-values but must be protected inside a DGU — runs ~€6-10/m² uplift. The calculator shows both with their performance outputs.

2

High-Gain vs Low-Gain Coatings

High solar gain (HSG) Low-E passes 60%+ of solar energy — good for cold climates where winter sun is useful. Low solar gain (LSG) passes 35-45% — essential for warm climates to prevent overheating. Calculator recommends by climate zone.

3

Dual Low-E Configurations

For triple-glazed units, coating both inner panes (position 2 and position 5) pushes Ug below 0.5 W/m²K. Adds ~€8-12/m² to the glass cost. Standard for passive house and high-performance new build — the calculator configures this correctly.

4

Visible Light Transmittance

Low-E coatings reduce VLT to 70-80% (vs 89% for uncoated). For commercial work where daylight counts (WELL, LEED credits), high-VLT Low-E (Pilkington K Glass N, Saint-Gobain SGG Planitherm) are the pick — the calculator flags these by name.

Frequently Asked Questions

Which Low-E coating should I pick for a UK residential window?
For UK residential (mixed climate, heating-dominated): high solar gain soft-coat Low-E on position #3 delivers the best balance. Typical product: Pilkington Optitherm S3, Saint-Gobain SGG Planitherm One, or Guardian ClimaGuard. Uw values of 1.2-1.4 W/m²K with meaningful passive solar gain in winter.
What's the cost difference between Low-E and standard glass?
Standard 4mm float glass runs ~€20-25/m². Hard-coat Low-E 4mm runs ~€26-32/m². Soft-coat Low-E 4mm runs ~€30-40/m². In a complete DGU, Low-E adds about 8-15% to glass cost, for 30-40% improvement in U-value — one of the best value upgrades in the window industry.
Can Low-E coatings damage over time?
Soft-coat Low-E is protected inside the DGU cavity and has a projected life of 25+ years. Hard-coat Low-E exposed to weather can develop minor cosmetic issues in coastal or industrial environments after 15-20 years. Both outlive the sealant system of the DGU itself, which typically fails first (15-20 years).
Does Low-E affect window cleaning?
Only for self-cleaning Low-E products (Pilkington Activ, Saint-Gobain Bioclean), which have a photocatalytic outer coating that breaks down organic dirt under UV light. These are different products from standard Low-E — which is protected inside the DGU and doesn't affect cleaning.

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Compare Low-E Options in Seconds

Soft vs hard. High-gain vs low-gain. Single vs dual. Doorwin has every combination priced.

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