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 have also done a considerable amount of Therm Modeling to understand the actual impact of various construction details. See Herefor a visual aid to of the thermal bridging data.

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.

Splines

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, but it is not necessary an all cases.

#14 Spline Detail
#15 Structural Spline Detail
#23 I-joist Spline
#17 R.O. Header & Sill detail
#18 R.O. Side Detail
#19 R.O. Side Detail

Corners

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.

#16 Corner structural
#31 Corner with Timber Post
#32 Corner with 2x Interior Wall

2nd Floor

Notes: The second floor deck is often 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. Balloon Framing the 2nd floor deck is possible, but it has a very limited capacity and requires a lot of screws, you can not just nail the ledger to the inside skin of the panel.

#20 2nd Floor Deck
#21 2nd Floor Deck Ledger
#22 2nd Floor Deck Balloon Framed
#33 2nd Floor Deck with Interior Wall

Foundations

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 we prefer systems with the panels fully supported not cantilevered out over exterior foam. 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.

#1 Floating Slab
#2 Floating Slab With Cantilever
#3 Frost wall with Nailbase
#4 Frost wall with Thickened Slab
#5 Basement with Interior Wall
#6 ICF wall
#7 Tapered ICF
#8 Basement with Deck
#9 Basement with Deck
#10 Rimpanel Detail
#11 Rimpanel Detail
#12 Cantilevered Deck
#13 Cantilevered Deck
#34 Panel Floor

Building Eaves & Rakes

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.

#25 Plumb-cut Eave with Ladder Frame
#26 Square-cut Eave with deck
#27 Flush-cu Rake with Ladder Frame
#35 pentalam-eave
#36 pentalam-rake

Ridges & Valleys

Notes: A non-structural ridge or valley is generally the better option: easier to air seal, no thermal bridging, and more durable.

#24 Ridge Beam

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.

#28 Dropped Heel Truss
#29 Raised Heel Truss
#30 Truss to Top of Wall