# Building Membrane

## Weather Resistive Barriers & Vapor Retarders

### Weather Resistive Barrier (sd=0.1m)

Weather resistive barriers with sd=0.1m provide water resistance while allowing moderate vapor transmission. These membranes are designed for exterior wall assemblies where both water barrier and vapor management are critical. Typical applications include behind cladding systems and as secondary weather protection. Material must be installed with 1mm thickness in building models. Effective for climates requiring moisture control without restricting vapor drive.

#### Basic Information

| Property             | Value                                                        |
| -------------------- | ------------------------------------------------------------ |
| Type                 | Non-Woven Membrane                                           |
| Thickness (m)        | 0.001                                                        |
| Thickness (mm)       | 1.0                                                          |
| Thickness (inches)   | 0.039"                                                       |
| Colour               | Orange/White                                                 |
| Primary Applications | Weather barrier, secondary water protection, breathable wrap |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value         |
| -------------------------------------------- | ------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 100           |
| sd-value                                     | 0.1000 m      |
| Vapor Resistivity                            | 500.00 MNs/gm |
| Vapor Resistance                             | 0.50 MN.s/g   |
| Perm Rating                                  | 0.59 perms    |

***

### Weather Resistive Barrier (sd=0.2m)

Weather resistive barriers with sd=0.2m provide increased vapor resistance while maintaining breathability. These membranes are intermediate performance vapor barriers suitable for climate zones requiring enhanced moisture control. Allows slower vapor transmission compared to 0.1m equivalent but still permits drying. Used in moderate to cold climates where bulk water protection must balance with vapor management. Material must be installed with 1mm thickness in building models.

#### Basic Information

| Property             | Value                                                            |
| -------------------- | ---------------------------------------------------------------- |
| Type                 | Non-Woven Membrane                                               |
| Thickness (m)        | 0.001                                                            |
| Thickness (mm)       | 1.0                                                              |
| Thickness (inches)   | 0.039"                                                           |
| Colour               | Orange/White                                                     |
| Primary Applications | Weather barrier, moderate vapor control, cold climate protection |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value          |
| -------------------------------------------- | -------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 200            |
| sd-value                                     | 0.2000 m       |
| Vapor Resistivity                            | 1000.00 MNs/gm |
| Vapor Resistance                             | 1.00 MN.s/g    |
| Perm Rating                                  | 0.30 perms     |

***

### Weather Resistive Barrier (sd=0.5m)

Weather resistive barriers with sd=0.5m provide substantial vapor resistance while maintaining vapor-open classification. These membranes serve as enhanced water barriers with moderate vapor transmission control. Suitable for warm and humid climates where condensation control is essential. Prevents bulk water infiltration while allowing the building envelope to dry. Material must be installed with 1mm thickness in building models. Bridges between vapor-open and Class III retarder performance.

#### Basic Information

| Property             | Value                                                                       |
| -------------------- | --------------------------------------------------------------------------- |
| Type                 | Non-Woven Membrane                                                          |
| Thickness (m)        | 0.001                                                                       |
| Thickness (mm)       | 1.0                                                                         |
| Thickness (inches)   | 0.039"                                                                      |
| Colour               | Orange/White                                                                |
| Primary Applications | Weather barrier, humid climate protection, water control with breathability |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value          |
| -------------------------------------------- | -------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 500            |
| sd-value                                     | 0.5000 m       |
| Vapor Resistivity                            | 2500.00 MNs/gm |
| Vapor Resistance                             | 2.50 MN.s/g    |
| Perm Rating                                  | 0.12 perms     |

***

## Vapor Retarders

### Class I Vapor Retarder (≤0.1 perms)

Class I vapor retarders provide the highest level of vapor resistance with µ-values exceeding 10,000. These impermeable or nearly impermeable barriers are designed for applications requiring maximum condensation prevention. Typically used on warm-side (interior) of wall assemblies in cold climates or on vapor-open structures. Installation in conditioned spaces prevents warm, moist interior air from reaching cold surfaces where condensation occurs. Material must be installed with 1mm thickness in building models. Requires careful design to ensure building envelope remains vapor-open to exterior.

#### Basic Information

| Property             | Value                                                                    |
| -------------------- | ------------------------------------------------------------------------ |
| Type                 | Polyethylene/Foil Barrier                                                |
| Thickness (m)        | 0.001                                                                    |
| Thickness (mm)       | 1.0                                                                      |
| Thickness (inches)   | 0.039"                                                                   |
| Colour               | Grey/Clear                                                               |
| Primary Applications | Interior vapor barrier, cold climate protection, condensation prevention |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value            |
| -------------------------------------------- | ---------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 32800            |
| sd-value                                     | 32.8000 m        |
| Vapor Resistivity                            | 164000.00 MNs/gm |
| Vapor Resistance                             | 164.00 MN.s/g    |
| Perm Rating                                  | ≤0.1 perms       |

***

### Class II Vapor Retarder (0.1-1.0 perms)

Class II vapor retarders provide moderate vapor resistance with µ-values between 3,000 and 10,000. These semi-permeable barriers are designed for applications where vapor control is necessary but some vapor transmission is acceptable. Positioned typically between insulation and interior finishes. Used in mixed climates where both condensation prevention and potential emergency drying are important. Material must be installed with 1mm thickness in building models. Allows slow vapor movement while restricting bulk vapor drive.

#### Basic Information

| Property             | Value                                                       |
| -------------------- | ----------------------------------------------------------- |
| Type                 | Kraft Paper/Polyethylene Blend                              |
| Thickness (m)        | 0.001                                                       |
| Thickness (mm)       | 1.0                                                         |
| Thickness (inches)   | 0.039"                                                      |
| Colour               | Kraft/Tan                                                   |
| Primary Applications | Vapor retarder, mixed climate protection, insulation facing |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value           |
| -------------------------------------------- | --------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 3280            |
| sd-value                                     | 3.2800 m        |
| Vapor Resistivity                            | 16400.00 MNs/gm |
| Vapor Resistance                             | 16.40 MN.s/g    |
| Perm Rating                                  | 0.1-1.0 perms   |

***

### Class III Vapor Retarder (1.0-10 perms)

Class III vapor retarders provide light to moderate vapor resistance with µ-values between 300 and 3,000. These highly permeable barriers allow significant vapor transmission while still providing some condensation control. Used in climates where building envelopes must remain relatively vapor-open. Positioned typically on exterior side of insulation to allow drying. Material must be installed with 1mm thickness in building models. Allows emergency drying while providing minimal vapor barrier function.

#### Basic Information

| Property             | Value                                             |
| -------------------- | ------------------------------------------------- |
| Type                 | Latex/Vapor-Retarding Paint                       |
| Thickness (m)        | 0.001                                             |
| Thickness (mm)       | 1.0                                               |
| Thickness (inches)   | 0.039"                                            |
| Colour               | Various                                           |
| Primary Applications | Interior paint, vapor retarder, drying capability |

#### Thermal Properties

| Property                     | Metric        | Imperial                |
| ---------------------------- | ------------- | ----------------------- |
| Thermal Conductivity         | 2.3 W/(m·K)   | 13.27 BTU·in/(h·ft²·°F) |
| Specific Heat Capacity       | 2300 J/(kg·K) | 0.55 BTU/(lb·°F)        |
| Density                      | 130 kg/m³     | 8.12 lb/ft³             |
| Thermal Resistance (R-value) | 0.00 m²·K/W   | 0.00 ft²·°F·h/BTU       |

#### Vapour Properties

| Property                                     | Value          |
| -------------------------------------------- | -------------- |
| Water Vapour Diffusion Resistance Factor (µ) | 328            |
| sd-value                                     | 0.3280 m       |
| Vapor Resistivity                            | 1640.00 MNs/gm |
| Vapor Resistance                             | 1.64 MN.s/g    |
| Perm Rating                                  | 1.0-10 perms   |

***

## Vapor Permeance Classification Reference

### Classification Standards

| Classification | Permeance | µ-value Range    | Examples                              |
| -------------- | --------- | ---------------- | ------------------------------------- |
| Class I        | ≤ 0.1     | µ ≥ 10,000       | Polyethylene sheet, aluminum foil     |
| Class II       | 0.1-1.0   | 300 < µ < 10,000 | Kraft paper, polyethylene blend       |
| Class III      | 1.0-10    | 30 < µ < 300     | Latex paint, vapor-retarding paint    |
| Vapor-Open     | > 10      | µ < 30           | Non-woven membranes, weather barriers |

### Conversion Formulas

**Perm Rating to µ-value:**

* µ = 59 ÷ Perm Rating
* Example: 0.5 perms = 59 ÷ 0.5 = 118 µ-value

**µ-value to Perm Rating:**

* Perm Rating = 59 ÷ µ
* Example: µ=100 = 59 ÷ 100 = 0.59 perms

**sd-value Calculation:**

* sd = thickness (m) × µ-value
* Example: 1mm membrane with µ=500 = 0.001 × 500 = 0.5 m sd-value

**Thermal Resistance (R-value):**

* R-value = thickness / thermal conductivity
* Example: 1mm, 2.3 W/(m·K) = 0.001 / 2.3 = 0.0004 m²·K/W

### SI Unit Conversions

**Perm to SI (ng/Pa·s·m²):**

* 1 perm = 57.2 × 10⁻⁹ kg/(Pa·s·m²)
* 1 perm = 57.2 ng/(Pa·s·m²)

**µ-value to Vapor Resistance (MN.s/g):**

* Vapor Resistance = (sd × 1000) / 21.6
* Example: sd=0.1m = (0.1 × 1000) / 21.6 = 4.63 MN.s/g (approximate)