Water-Storing Underlay with Hydrophilic Storage Layer
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Solution Overview
Problem
Existing roof and wall underlays with hydrophobic bottom layers face issues with moisture condensation in cold weather, leading to droplet formation and potential mold growth due to inadequate water management.
Innovation Solution
Incorporating a hydrophilic inner storage layer capable of absorbing water, with a hydrophobic top layer and a microporous film functional layer that allows water vapor permeability, along with adhesive strips for enhanced sealing and water management, to prevent water accumulation and facilitate diffusion under changed environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bottom layer is made hydrophobic to provide water-repellent surface, then water resistance is improved, but moisture condensation accumulates on the underside in cold weather
Solution Approach 1:
The underlayment uses different hydrophobicity properties in different layers: the top layer is hydrophobic to repel rainwater, while the bottom layer is hydrophilic to absorb and store condensation moisture. This local differentiation of material properties resolves the contradiction by allowing each layer to perform its specific function optimally.
Solution Approach 2:
The underlayment combines multiple materials with different properties into a composite structure: a hydrophobic top layer (e.g., polypropylene fleece) and a hydrophilic bottom layer (e.g., cellulose or polyester nonwoven). This composite structure enables simultaneous water repellency at the surface and moisture absorption at the base.
2Object-generated harmful factors
If the inner layer absorbs water to store condensation moisture, then mold growth is prevented, but rainwater can penetrate through the structure
Solution Approach 1:
The top layer is specifically designed with hydrophobic properties to repel rainwater and prevent penetration, while the bottom layer is designed with hydrophilic properties to absorb condensation moisture. This local quality differentiation ensures that each layer addresses its specific functional requirement without compromising the other.
3Reliability
If adhesive strips are added to improve sealing and water management, then waterproofing is enhanced, but device complexity increases
Solution Approach 1:
Adhesive strips are introduced as an intermediary element to seal the overlapping edges of adjacent underlayment sheets. These strips provide a simple yet effective mechanism to ensure waterproof continuity at the joints without requiring complex sealing systems or additional structural elements.
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 solution effectively absorbs and stores condensation moisture, preventing droplet formation and runoff, thereby reducing the risk of mold growth and ensuring long-term durability and UV resistance.
Implementation Method 1
a microporous film, which consists in particular of polyolefin, preferably of polypropylene
Implementation Method 2
The film can have a thickness of 25 to 40 g/m 2 . The microporous film can consist of 40% to 60% calcium carbonate
Implementation Method 3
the inner layer be capable of absorbing water. The inner layer can thus form a storage layer that is able to temporarily store liquid water
Implementation Method 4
The absorbency of the bottom layer allows liquid water to be trapped in the tiny spaces between the fibers
Implementation Method 5
The water can remain stored in the inner layer until it can diffuse outwards through the underlayment after a change in the thermodynamic environmental properties
Implementation Method 6
While the inner layer is preferably hydrophilic, the outer layer can be hydrophobic. Because the top layer is preferably hydrophobic, the underlayment has a water-repellent surface that does not absorb water when it is sprinkled, but rather allows it to roll off
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to an underlayment (U) permeable to water vapor but impermeable to liquid water, comprising an outer layer (1) facing outwards when laid on a roof or wall and an inner layer (7) facing inwards. To prevent liquid water from accumulating on the inner layer (7) when the humidity is high indoors, the inner layer (7) is a water-absorbing storage layer (7) that can absorb liquid water during periods of high humidity and from which the liquid water can evaporate when the humidity decreases.