Passive House Construction

Foard Panel is committed to helping out customers reaching their performance goals.

Our Panels are well suited to meeting high performance standards because our default joinery meets the extremely strict air tightness requirements for Passive House. Our default joinery often measures well under the 0.6 ACH50 required by Passive House. Even in cases where no high performance detailing was used by the other contractors we have not exceeded 3.0 ACH50.

Our panels are also particularly well suited to eliminating thermal bridging. In studies by Oak Ridge National Laboratory, a nominally R-23 6.5″ EPS Panel wall had a measured R-value of 22, while a 2×6 stud wall nominally R-19 was tested at R-14, and an advanced framing 2×4 wall nominally R-13 was tested at R-9.7. These numbers show that a SIP wall preforms at about 96% of its center of cavity number while a stick framed wall preforms at 75% of its center of cavity number.

We can help reach even the highest of R-value goals with the thinnest wall/roof profiles, and have the shell of your building built in much shorter time frame than other methods. For designers and builders considering Passive-House-level construction, we are showcasing many of our custom details with the thicker panel specifications required to meet the high performance goals. These details are intended to further minimize thermal bridging, but for us structural considerations always come before thermal goals, so not all of these details will be applicable to every building situation. We are also sharing what we’ve learned over the past 20 years about building science, construction, and repairs.
Spline #1_3in-doubleSpline #5_I-joist


Notes: From a durability standpoint, spline joints are preferable to solid lumber joints because they are easier to air seal, provide no thermal bridge and are much less vulnerable to water condensation damage. However, spline joints are not enough to hold up large point loads on a vertical wall and I-Joists or solid lumber can add significantly to the spans and transverse loads a panel is capable of supporting. It is preferable structurally for a solid spline to go all the way through the panel so it can be connected to both skins. It can be done as shown in #3, but it makes the post bigger.

#1 3″ Double Splines pdf
#2 6″ Double Splines pdf
#3 Structural Splines pdf
#5 I-Joist Splines pdf
#6 Double 2x Material Spline pdf

Corner #3_angledCorner #2_with-holdown


Notes: Corners must have solid lumber to fasten to, in order to be structural. The best way to eliminate thermal bridging in corners is to put a post interior to the panels to which they can fasten. In high winds zones, especially in walls with a large proportion of windows, Panels can become shear walls by use of Hold downs and higher specification top and bottom plates. Shearwall detailing increases the framing factor, so Passive House designers in high wind zones should consider options for internal shear walls.

#1 Structural Corner pdf
#2 Corner With Hold Down pdf
#3 Angled Corner pdf

2nd Floor

Notes: The second floor deck is an unavoidable thermal bridge in structural panel construction, we would be happy to provide psi values for Passive House modeling so designers can check to see if it will make a significant difference. If the design is close enough to the limits this small thermal bridge is a problem designers should consider having and interior frame to hold up the floor decks. Construction order becomes much more complicated with a separate structural system for floor decks, but it does eliminate the thermal bridge.

#1 2nd Floor pdf
#2 2nd Floor pdf

2nd Floor #2Foundation #2a_rim-panel-ICF

Foundation #3_lower-slab-NB-floorFoundation #6_floating-slab


Notes: Foundation connections are a key part of the structural system, therefore some thermal bridging is inevitable. The connections below are all reasonable options, but our preferred systems are the rim panel system(#’s 1-2), floating slab(#6) or lower slab with nailbase panel floor(#3). The SIP panel floor system can be very effective for a pillar based foundation system, but the key to its durability is having lots of space for air flow below the panels. Sometimes it is suggested that one use spray foam around the end of floor joists and at Sill plates to help air seal and minimize thermal bridging, we do NOT recommend this as we have seen far to many examples of the wood rotting under the spray foam.

#1 Rim Panel Foundation pdf
#2a & #2b Rim Panel With Insulated Foundation 2a pdf-apdf-b
#3 Lower Slab Foundation pdf
#4 Insulated Slab Foundation pdf
#5 SIP Panel Floor pdf
#6 Floating Slab Foundation pdf
#7 Stepped Foundation pdf
#8 Stepped Foundation pdf

Eave #11_15in-plumb-overhang

Building Eaves

Notes: Large eave overhangs are an important aspect of Passive House building. SIP panels can create very large overhangs. Overhang length is most commonly limited by backspan, in general a 2:1 ratio of back span to overhang is required. This means that if the panels are running ridge to eave the rake overhang can be no more than 32″ (1/3rd of an 8′ wide panel), while the eave overhang is only limited by the length of its panel and the inherent span (e.g. 45psf snow load, 12.25″ panel, max span 12′, largest potential overhang is 6′ and the panel must have 12′ of backspan). Foard Panel is aware that most designers prefer not to have massively thick overhangs, we have two options for dealing with that. One is to cut the panel at the edge of the building and ladder frame an overhang on. These overhangs are often limited by the uplift and the amount of fasteners one can get into the panel edge blocking. The other is our custom pentalam panels. Pentalam panels are expensive and they still require the same backspan as normal panels, but they can give you significantly thinner overhangs.

#3 Plumb-Cut Eave Structural No Overhang pdf
#4 Plumb-Cut Eave Structural With Overhang pdf
#5 Plumb-Cut Eave Non-Structural Interior Cavity No Overhang pdf
#6 Plumb-Cut Eave Non-Structural Interior Cavity With Overhang pdf
#3 Square-Cut Eave Structural No Overhang With Floor Deck pdf
#4 Square-Cut Eave Structural With Overhang pdf
#5 Square-Cut Eave Non-Structural Interior Cavity No Overhang pdf
#6 Square-Cut Eave Non-Structural Interior Cavity With Overhang pdf
#7 Square-Cut Eave Non-Structural Interior Cavity With Overhang and Floor Deck pdf
#2 Pentalam Eave Structual Under 16″ Thick pdf
#3 Pentalam Eave Structural Over 16″ Thick pdf

Rake #1_15in-overhang

Building Rakes

Notes: Rake overhangs are often less critical to passive solar performance. However, a larger overhang can protect a portion of the wall from weathering. Structurally rake overhangs face the same backspan requirements as eave overhangs, and the same options apply for thinner profiles. Ladder framed eaves and rakes require either an additional layer of sheathing or strapping and re-sheathing to provide the required backspan support.

#2 Rake Structural No Overhang pdf
#3 Rake Structural With Overhang pdf
#4 Rake Structural With Ladder Rake pdf
#5 Rake Non-Structural Interior Cavity No Overhang pdf
#6 Rake Non-Structural Interior Cavity With Overhang pdf
#2 Pentalam Rake Structural Under 16″ Thick pdf
#3 Pentalam Rake Structural Over 16″ Thick pdf

Valley #4_15in-structural

Ridges & Valleys

Notes: A non-structural ridge or valley is generally the better option: easier to air seal, no thermal bridging, and more durable. However, when a beam below the panels is not an option the structural valley or ridge is necessary. Structural ridges must be continuous, meaning panels sections must be assembled on the ground and raised by crane, so longer spans are hard to assemble and require bigger cranes.

#1 Ridge Timberframe pdf
#2 Ridge Ridgebeam Below pdf
#3 Ridge Ridgebeam Embedded pdf
#4 Ridge Pentalam Over 16″ Thick pdf
#5 Ridge Non Sturctural Interior Cavity Ridgebeam Below pdf
#6 Ridge Non-Structural Interior Cavity Ridgebeam Embedded pdf
#1 Valley Beam Below pdf
#2 Valley Beam Embedded pdf
#3 Valley Non-Structural Interior Cavity Beam Below pdf
#4 Valley Non-Structural Interior Cavity Beam Embedded pdf

Truss #3_dropped-heel
Truss #7_panel-to-truss

Hybrid Panel & Truss Roofs

Notes: Trusses can be an ideal roof system for long spans and large open plans. The trusses can be the roof insulation system or they can have panels on top to be the thermal and air barrier. We have used both Energy heel trusses and a variant of the energy heel, called a dropped heel truss.

#1 Truss Top of Wall pdf
#2 Truss With Energy Heel pdf
#3 Truss With Dropped Heel pdf
#4 Truss Connection at Gable pdf
#5 Truss Panel to Top of Truss pdf
#6 Panel Butt Joint to Top of Truss pdf
#7 Panel Truss at Eave pdf