Choosing the right house wrap is crucial for protecting your home from the elements, primarily water and air.
When selecting a house wrap, a key factor to consider is its ability to manage moisture. As a general rule, if you are deciding between different options, always choose the one that's the most water-resistant. In addition to making sure that the house wrap resists water, learn as much as you can about its ability to shed water. A good house wrap acts as a secondary layer of defense behind your siding, preventing bulk water (like rain) from getting into your wall assembly while allowing moisture vapor from inside to escape.
Here are the essential factors to consider when making your choice:
Key Factors for Choosing House Wrap
Beyond primary water resistance, several other properties contribute to a house wrap's effectiveness:
1. Water Resistance & Shedding
- Hydrostatic Head: This measures how much water pressure the wrap can withstand before water passes through. Higher numbers indicate better resistance to standing water or wind-driven rain.
- Water Shedding: Does the wrap effectively channel water downwards and away from the wall? Surface texture or integrated drainage gaps can improve this.
- Reference Insight: Prioritizing the wrap that is most water-resistant and understanding its ability to shed water are fundamental steps in the selection process.
2. Vapor Permeability
- What it means: This is the wrap's ability to allow water vapor to pass through it (measured in 'perms'). It's essential for letting moisture that might get into the wall cavity (from inside the house or minor leaks) dry out.
- Why it matters: Too low permeability can trap moisture, potentially leading to mold or rot. Too high in certain climates can allow too much outside humidity in.
- Considerations: Different climates require different permeability levels. Generally, house wraps are vapor-permeable, but confirming the specific perm rating is important.
3. Air Resistance
- What it means: The wrap's ability to prevent air leaks through the wall assembly.
- Why it matters: Air leaks waste energy and can transport moisture vapor into the wall cavity. A good air barrier improves energy efficiency and comfort.
4. Durability
- Tear Resistance: How well does the wrap withstand tearing during installation, especially around windows and doors or in windy conditions?
- UV Resistance: How long can the wrap be exposed to sunlight before siding is installed without degrading? This is important if there are construction delays.
5. Material Type
House wraps come in various materials and structures:
- Woven Polyolefin: Often coated for water resistance. Can sometimes have lower tear resistance.
- Non-woven Polyolefin: More common, generally good balance of properties.
- Drainable Wraps: Feature a crinkled surface or integrated strips to create a drainage gap behind the siding, significantly improving water shedding.
6. Climate Considerations
Your local climate heavily influences the ideal balance of water resistance, vapor permeability, and air resistance. In rainy or humid climates, robust water shedding and appropriate permeability are critical.
7. Building Codes
Always ensure the house wrap meets local building code requirements for weather barriers and air barriers.
Choosing the Right House Wrap: A Step-by-Step Approach
- Assess Your Climate: Understand the typical weather patterns (rain, humidity, wind).
- Prioritize Water Management: Focus on wraps with high water resistance and proven water-shedding capabilities, as highlighted in the reference.
- Check Permeability: Ensure the perm rating is suitable for your climate to allow drying.
- Verify Air Barrier Performance: Look for wraps tested for air resistance.
- Consider Durability: Choose a wrap that can handle the installation process and potential exposure time.
- Consult Building Codes: Confirm compliance with local standards.
- Review Manufacturer Specifications: Compare technical data sheets for potential options.
By carefully evaluating these factors, with a strong emphasis on water resistance and shedding, you can select a house wrap that provides effective long-term protection for your home's structure.
