Perfect Wall Assemblies
for Healthy, Durable & Budget-Friendly Buildings
Overview
- Standard wood-frame construction
- NO insulation between studs
- Sheathing Membrane as water resistive barrier, air barrier & vapor barrier; protected by
- 100% Continuous Korolite® Insulation on the exterior
- Rainscreen behind the cladding
For New Construction & Retrofits
Benefits
All wood-framing, sheathing & rim-joists stay at indoor temperature levels
- Nearly NO risk of condensation, rot and mold means far fewer health & durability problems and costly repairs
- NO thermal bridging from studs, headers, rim-joists, electrical boxes etc.
Superior control of moisture details
- The rainscreen behind the cladding lets water drain, prevents capillary rise, and promotes outwards drying
- Korolite® Expanded Polystyrene (EPS) insulation resists liquid water while allowing some vapor diffusion for outwards drying
- LOWER COST, relatively vapor-impermeable sheathing membrane stops liquid water & controls water vapor
- NO additional vapor barrier needed, NO risk of vapor bypass at drywall penetrations, and NO split-insulation ratio worries
- You can humidify indoor air even in cold periods due to minimal condensation risk
Insulation installation only needed on the exterior details
- LOWER COST 2x4 wood-framing with no need for thick cavity insulation
- Other trades can simultaneously work on the interior with wall cavities 100% open for utilities
- NO costs for cavity insulation or rim-joist insulation
- NO batt compression, sagging & moisture-damage problems
- Ease of access for repairs & alterations of services (wires, pipes, ducts)
- Adaptability to future interior modifications
Easily optimize buildings for your Climate Zone & Energy Targets details
- Insulation thickness can be customized for value-engineering
- Korolite® Insulation provides the highest R-value¹ per dollar spent on rigid insulation, backed by a 30-year Limited Warranty to retain 100% R-value
Durable, proven components that are easy to install with no or minimal training
Cozy, Healthy & Durable Buildings with lower environmental impacts
Ideal for BC Step Codes 3, 4, 5, Net-Zero , IECC & More
Energy Model Example - B.C. Step Codes:
Step 5, Net-Zero Ready in Surrey, BC
TEDI of 27 kWh/(m²·year), 57.8% better than Reference TEDI for:
- R-20 FoamShield® Walls above-grade with 4" exterior Korolite® 160 EPS over uninsulated 2x4 framing & sheathing.
- Building Type: Single Family Residence with 4,775 sqft conditioned space incl. finished walkout basement
- Climate Zone 4 with 2750 Heating Degree Days (HDD)
- Airtightness: 1.0 ACH50
- Fenestration & Doors to Wall Ratio (FDWR): 15.7%
- Window & Door U-factors: 1.2 W/(m²·°K) [R-4.7]
- Roof: R-40 insulated standard truss assembly
- Basement Walls: R-26½ insulated w/
Quad-Lock Insulated Concrete Forms - Basement Slab: R-5 insulated heated floor w/ thermal breaks along edges
- Garage Floor over living area: R-20 insulated w/
Quad-Deck ICF - Ventilation: with Heat Recovery Ventilator efficiency 60% @ 0°C, 55% @ -25°C
No Basement? Skip the frost walls with Frost Protected Shallow Foundations.
Section View
Plan View
Introduction Video
FoamShield® Perfect Wall Assembly Details
The FoamShield® perfect wall assembly consists of rigid Korolite® EPS insulation placed on the exterior of a conventional above-grade, uninsulated, 2x4 or 2x6 wood-frame wall with sheathing membrane. The 100% continuous Korolite® Insulation on the exterior:
- provides high effective assembly R-values¹ per Table 1,
- protects the sheathing membrane,
- is not sensitive to moisture so it can be exposed to periodic wetting, and
- keeps the temperature of the moisture-sensitive wood structure near indoor levels, all but eliminating the potential for condensation and associated moisture damage. This mitigates the risks to indoor environmental quality from mold and mildew while also improving the durability of the assembly.
In most cases cladding can be supported by furring (a.k.a. strapping) that's fastened through the rigid insulation to the wood framing.
Key Considerations:
- Relatively vapor-impermeable sheathing membrane (e.g. < 0.2 perm) serves as the water resistive barrier, air barrier, and vapor barrier.
- Additional interior or exterior vapor barriers should NOT be installed.
- The cladding-attachment method needs to adequately support the exterior cladding while minimizing thermal bridging.
Table 1: Effective Assembly Insulation Values for 2x4 or 2x6 Exterior Insulation Stud Wall (No Batts)*
| Thickness of Exterior Insulation | Insulation Value/inch** of Korolite® 160 Exterior Insulation | |
|---|---|---|
| R-4.04 ft²·°F·hr/BTU | RSI-0.7115 m²·°K/W | |
| 3" | R-16 | RSI 2.78 |
| 3½" | R-18 | RSI 3.14 |
| 4" | R-20 | RSI 3.50 |
| 4½" | R-22 | RSI 3.85 |
| 5" | R-24 | RSI 4.21 |
| 5½" | R-26 | RSI 4.56 |
| 6" | R-28 | RSI 4.92 |
| 7" | R-32 | RSI 5.63 |
| 8" | R-36 | RSI 6.34 |
* incl. at least R-3.69 ft²·°F·hr/BTU for interior & exterior air films, cladding, sheathing, studs, airspaces and GWB. ** minimum @ 24°C [75°F] mean temp. R-values of Korolite® Insulation increase at lower temperatures.
Rainscreen & Cladding
The furring strips create a ventilated drainage space and capillary break behind the cladding (a.k.a. rainscreen or air gap) with numerous functions: 1. prevent hydrostatic pressure and 2. capillary rise, 3. promote outwards drying, 4. reduce the pressure of wind-driven rain, and 5. reduce overheating in warm periods with the "chimney effect" inside the rainscreen cavity. Continuous ventilation and drainage of the rainscreen cavity must be assured with water & air outlets at the walls' base and air outlets at their top and various products are available to also serve as insect screens. The rainscreen and cladding serve as the primary layer of weather protection.
Water Resistive Barrier
A sheathing membrane installed on the exterior of the wall sheathing and rim-joists serves as the water resistive barrier (WRB) - or "second plane of protection" - for this assembly. Self-adhered or mechanically fastened sheet products using shingled laps are suitable for this application, as are some liquid applied products.
In addition, insulation joints and transitions can be taped and sealed so the insulation layer fully sheds any liquid water that gets behind the cladding.
Air Barrier
The easiest air barrier solution for this assembly is to use the sheathing membrane. Ensure continuity of the air barrier at seams, transitions and penetrations with appropriate taping and sealing.
If a mechanically fastened sheathing membrane is used as air barrier, it
- must be taped and sealed,
- is structurally supported and protected by sandwiching between the fastened insulation and sheathing, and
- is best stapled where furring fasteners will be located to minimize air leakage at the holes.
Sealed Sheathing Membrane
Sealed Insulation Layer as additional WRB
Vapor Barrier
The 100% exterior continuous insulation of the FoamShield® assembly keeps all the framing, sheathing and rim-joists near indoor temperature and humidity levels, slashing the potential for condensation on these moisture-sensitive wood components. The FoamShield® Wall Thermal Profile illustrates how the temperature gradient occurs almost exclusively within the external insulation:
FoamShield® Wall Thermal Profile
At most thicknesses the Korolite® 160 Insulation is a "Class II" semi-impermeable vapor retarder of 0.1-1 perm [ 5.7-57 ng/(Pa•s•m²) ], see Table 2. Vapor Barriers are "Class I" with ≤ 0.1 perm in the USA although in Canada the term "vapour barrier" is also used for vapor retarders of roughly 1 perm and less.
Sheathing membrane with lower vapor permeance (e.g. < 0.2 perm) than the insulation's minimum vapor permeance should be used as the vapor barrier in this assembly. The relatively higher vapor permeance of the Korolite® Insulation then permits drying to the exterior of any moisture that's to the outside of the sheathing membrane.
This wall assembly will dry inwards and outwards from the sheathing membrane. Therefore this assembly should NOT include an additional vapor barrier (i.e. polyethylene sheet, vapor barrier paint, etc.) on the interior in colder climates, nor on the exterior in warmer climates.
Table 2: Approx. Vapor Permeance of Korolite® 160 Insulation [perm]
| Thickness of Exterior Insulation | Vapor Permeance @ 1" thick | |
|---|---|---|
| 1.51 perm·in Minimum |
3.5 perm·in Maximum |
|
| 3" | 0.50 | 1.17 |
| 3½" | 0.43 | 1.00 |
| 4" | 0.38 | 0.88 |
| 4½" | 0.34 | 0.78 |
| 5" | 0.30 | 0.70 |
| 5½" | 0.27 | 0.64 |
| 6" | 0.25 | 0.58 |
| 7" | 0.21 | 0.50 |
| 8" | 0.19 | 0.44 |
Typical Details
PDF Details DWG Details Korolite® 160 Specifications Korolite® Code Evaluation Report
Roof Transition
Foundation Wall Transition
Window Opening
Service Penetration
Install either insulation boards with ship-lap edges or two layers of insulation boards with offset joints. One installation approach uses dabs of compatible (e.g. polyurethane) adhesive or fasteners with large washers to temporarily hold the insulation boards in place before the furring is installed.
Boards should be installed in as large as possible pieces over the wall area. Butt all edges and ends tightly to adjacent boards. Stagger joints.
Exterior insulation should only be interrupted by necessary service penetrations, sealing / flashing, and structural elements. Seal insulation gaps and joints that have been cut or damaged (e.g. at corners, edges or penetrations) using suitable materials such as foam‐in‐place polyurethane. If required, the joints between insulation boards may be sealed with approved, compatible sealing/sheathing tape in shingled fashion, offsetting the tape and the furring to avoid fasteners through tape. Refer to the Korolite® Installation Guide for further details.
Cladding
Any type of cladding can be used with the FoamShield® wall assembly as long as it doesn't absorb solar radiation excessively. Taking into account that the rainscreen's convective "chimney effect" reduces overheating, claddings with a sufficient Solar Reflectance Index (SRI) may be required to not exceed the Korolite® Insulation's max. service temperature of 75°C [167°F] during the hottest conditions. An SRI ≥ 20 for the cladding material should limit its temperature sufficiently in most areas. SRI Calculator
The cladding attachment method depends on the weight of the cladding as well as wind and seismic loads.
Fasteners Through Insulation: In most cases the cladding can be attached to vertical furring strips which in turn are fastened through the exterior insulation into the studs of the backup wall. Since thermal bridging is limited to the thin fasteners through the insulation, this is one of the most thermally efficient cladding support options. In this arrangement, the furring, rigid insulation and fasteners will act together to carry the loads. For further details refer to the Illustrated Guide - R22+ Effective Walls in Residential Construction in British Columbia (incl. Fastener Tables on page 27), in the USA to IRC R703.15.2 or DrJ Report DRR 1303-04, or your engineer.
Furring: Borate-treated plywood is usually the most suitable material because the multiple fasteners at relatively close spacing could split furring made from dimension lumber. The required furring thickness and width is a function of the cladding weight and the insulation's compressive resistance of at least 16 psi [110 kPa] at 10% deformation for Korolite® 160.
Fasteners for the furring attachment through the insulation should be stainless steel or galvanized steel rated to 2000 hour salt spray per ASTM B117 because they will be exposed to the exterior environment. In highly corrosive environments higher resistance might be required. Ensure compatibility of the fastener type with both the furring material (i.e. wood pressure treatment) and the cladding material. Use screws with a countersunk head so the screw head can be embedded into the face of the furring and out of the way of the cladding. Do not remove any fasteners once installed because that would leave holes in the sheathing membrane.
Installing the fasteners at an upward angle of about 15 degrees increases the strength of the support system by benefiting from the truss action of the fastener tension and insulation compression, rather than relying more on fastener bending resistance. Note that fasteners installed at an angle of 15-17° need to be 5% longer than those used horizontally to achieve the same embedment into the backup wall.
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¹ R means resistance to heat flow. The higher the R-value, the greater the insulating power.