Building an ICF home with standard windows is like buying a sports car and putting on economy tires. The wall assembly can only perform as well as its weakest link.
Understanding Window Ratings
U-Factor: Measures heat transfer. Lower is better. Standard windows: 0.30-0.50. High-performance: 0.15-0.25.
SHGC (Solar Heat Gain Coefficient): Measures how much solar heat passes through. In Texas, lower is generally better (0.20-0.30) to reduce cooling loads. However, strategic south-facing windows might benefit from higher SHGC for passive solar heating in winter.
VT (Visible Transmittance): How much light passes through. Higher means more natural light. Balance with SHGC for optimal performance.
For Texas ICF Homes: Look for U-Factor ≤ 0.25 and SHGC ≤ 0.25 for most windows. This combination minimizes both heat loss and solar gain while maintaining good visibility.
Double vs Triple Pane
Double Pane: Standard for quality construction. U-Factor typically 0.25-0.30 with low-E coating and argon fill.
Triple Pane: Superior performance with U-Factor 0.15-0.20. Additional benefits include better sound isolation and reduced condensation. Premium cost but increasingly justified as energy prices rise.
For high-performance ICF homes targeting net-zero, we typically recommend triple pane windows.
Low-E Coatings
Low-emissivity coatings reflect infrared heat while allowing visible light to pass. For Texas:
- Low-E 366: Blocks solar heat gain, ideal for west and south exposures
- Low-E 340: Balanced performance for all orientations
- Passive low-E: May be appropriate for strategic solar gain on south windows
Frame Materials
Fiberglass: Our top recommendation. Excellent thermal performance, doesn't expand/contract like vinyl, paintable, durable. Brands: Marvin, Pella, Andersen.
Vinyl: Budget-friendly option with good thermal performance. Can warp in Texas heat. Quality varies widely by manufacturer.
Wood: Beautiful but requires maintenance. Clad exteriors reduce upkeep. Premium cost.
Aluminum: Avoid for thermal performance unless using thermal breaks. Common in commercial, less suitable for high-performance residential.
Installation Matters
Even the best windows fail if poorly installed. Critical details:
- Proper flashing and waterproofing at ICF interface
- Continuous air sealing around frames
- Shimming that doesn't create thermal bridges
- Insulated bucks in ICF openings
We work with window installers who understand high-performance construction requirements.
Complete the System
Let's discuss windows that match your ICF home's performance level.
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