WUFI Analysis Assumptions

WUFI Pro 5.1 (1-d)

Orientation:  Each assembly was modeled facing the direction of prevailing wind-driven rain and maximum solar exposure as follows, for a vertical wall and building height up to 10m tall

Location: Vancouver (east), Edmonton (west), Toronto (east), Montreal (south-west), St. John’s (south-east)

Rain load: R1 (0), R2 (0.07 s/m) default settings

Surface Transfer Coefficients:

Exterior surface
Heat resistance: 0.0588 (m2K/W), external wall, wind dependant
Sd value: No coating
Short wave radiation absorptivity: 0.68 (red brick)
Long wave radiation emissivity: 0.90
Adhering factor of rain: 0.7 according to inclination and construction type

Interior surface
Heat resistance (m2K/W): 0.125 (External wall)
Sd value: User defined 0.3 (approximates two coats of latex paint)

Initial Conditions:

Initial moisture in component: Constant across component
Initial temperature in component: Constant across component
Initial relative humidity: 0.80
Initial temperature: 20ºC

Numerics: Each wall modeled for a simulation period of 5-9 years

Mode of calculation:
Heat transport calculation, moisture transport calculation
For thermal conductivity use temperature and moisture dependency

No hygrothermal special options

Numerical parameters
Increased accuracy
Adapted convergences

No adaptive time step control


Outdoor climate: Cold year when an option, from map/file, (using analysis function for choosing worst case orientation)

Indoor climate:
User defined sine curve parameters
Temperature, mean 210C with +/- 20C (day of maximum 06/03)
Relative humidity, mean 45% with +/- 15% (day of maximum 08/16)

Material assumptions:

Generic materials (WUFI 5.3 Material Database):
Red matt clay brick
Fibre cement sheathing board
Spruce (for wood siding)
Acrylic Stucco
Air layer, without additional moisture capacity
Asphalt impregnated paper (30 min paper)
Oriented strand board (650 kg/m3)
Plywood (USA)
Vapour retarder (0.1 perm)
Gypsum board (USA)
Sprayed Polyurethane Foam; closed cell
Polyisocyanurate Insulation
Metall-Foile (for foil facing on Polyisocyanurate)
Roxul RockBoard
Spun Bonded Polyolefin Membrane (SBP)

Modified generic materials:
R19, R21 and R24 Fibre glass batt
Fibre Glass Batt (WUFI 5.3 North American Material Database) modified density and k-value according to manufacturer data to represent R-21 and R-24

3/4lb spray foam
Spray polyurethane foam; Open cell (WUFI 5.3 North American Material Database) modified bulk density, thermal conductivity, water vapour diffusion resistance factor according to manufacturer data from Icynene

Smart vapour retarder
Material data from CertainTEED uploaded into WUFI 5.3 database

Liquid applied water resistive barrier
Vinyl Wallpaper modified with manufacturer material properties for the EIFS air and moisture barrier

Vinyl siding
PVC Roof Membrane modified properties

Note on WUFI Assumptions for Low Permeance Sheathings:
Building Codes have air barrier and rain intrusion requirements that are assumed to be complied with.  Failure to meet code requirements can result in walls that are not durable.

It is important to note that all the assemblies were simulated assuming no air leakage and no water intrusion/leakage.  As a result, the WUFI durability simulations do not consider the limited drying potential associated with the use of low permeance sheathing materials when combined with poor air barrier installation and flashing details.