Polyurethane Foam Window Gap Filling for Thermal Insulation
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Solution Overview
Problem
Current window assemblies face challenges in achieving optimal thermal and structural performance due to the air gap between the glass unit and the frame, which compromises thermal insulation and structural integrity, and existing solutions are either complex, costly, or difficult to apply universally.
Innovation Solution
Filling the gap between the window frame and the glass unit with a polyurethane foam composition containing a propellant concentration of at least 5 wt%, which expands not more than 100% in volume, providing better insulation and structural strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the gap between the window frame and glass unit is left empty or filled with traditional materials, then the window assembly is simpler and easier to manufacture, but thermal insulation performance deteriorates
Solution Approach 1:
The polyurethane foam composition automatically expands to fill the gap between the window frame and glass unit without requiring manual positioning or additional structural support elements. The foam's self-expanding property eliminates the need for complex installation procedures while providing effective thermal insulation.
Solution Approach 2:
The foam composition undergoes a parameter change from liquid to expanded foam state, increasing in volume by a controlled factor (alpha) to fill the gap. This parameter change allows the material to adapt to varying gap sizes without requiring pre-measurement or custom fabrication.
2Strength
If the gap is filled with rigid structural materials to improve mechanical strength, then structural integrity improves, but thermal insulation deteriorates due to thermal bridges
Solution Approach 1:
The polyurethane foam creates a composite structure between the window frame and glass unit, combining the structural support function with thermal insulation. The foam's cellular structure provides both mechanical bonding and thermal resistance, eliminating thermal bridges while maintaining structural integrity.
3Reliability
If traditional sealants and adhesives are used to seal the gap, then water migration is prevented, but thermal bridges are created between the glass panes and frame
Solution Approach 1:
The polyurethane foam composition merges the functions of sealing and thermal insulation into a single material system. The foam continuously contacts both the window frame and glass unit, creating a water-tight seal while simultaneously providing thermal insulation, thereby eliminating thermal bridges that would otherwise be created by discrete sealant layers.
4Loss of energy
If triple glazing is used to improve thermal insulation, then U-value improves, but weight increases making it too heavy for certain applications
Solution Approach 1:
The foam filling extracts the thermal insulation function from the glass unit itself, allowing the use of lighter glass configurations. By providing thermal insulation through the gap filling rather than through additional glass layers, the system achieves comparable U-values without the weight penalty of triple glazing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The foam filling significantly improves thermal insulation, reduces air leaks, enhances acoustic insulation, and increases mechanical strength, allowing windows to meet stringent building standards and offering easier application and replacement compared to traditional methods.
Implementation Method 1
Filling the gap between the window frame and the glass unit with a polyurethane foam composition containing a propellant concentration of at least 5 wt%, which expands not more than 100% in volume
Implementation Method 2
The foam filling significantly improves thermal insulation
Implementation Method 3
enhances acoustic insulation
Data Source
Figure 1~2
AI summary
A PU foam forming composition, dispensed from a single pressurized container and comprising at least 5 %wt of a propellant, may be used for filling the gap between the window frame and the outer perimeter of the glass unit of the window assembly. The PU foam filling is preferably an OCF PU foam and may bring significant improvements to the window assembly, in particular in combination with multiple glazing and/or HR+ glazing, such as improved thermal and acoustic performance, improved air tightness, increased fire resistance, rigidity and burglar resistance. The foam forming composition brings user friendliness during its application as well as when the glass unit needs to be replaced. A corresponding window assembly is also disclosed, wherein the use of the foam filling may allow a smaller window frame for the same glass surface.