SIP Builder's Blog | Foard Panel - Part 2 Blog – Page 2 – Foard Panel

Structural Panel House Sandwich MA

This is a fully structural panel house built in 3 weeks from foundation up including 3 floor decks. Designed by architect Greg Delory and engineered by Fire Tower Engineered Timber.

Bethlehem Balance Yoga Center

Balance Bethlehem Yoga Center in Bethlehem NH is a small commercial building built to high performance standards. Foard Panel was deeply involved in the engineering and built the entire structural shell including the 24″ deep roof trusses and the interior bearing wall. The walls are 12.25″ thick EPS core with an R-value of 45. These SIP walls provide the lovely deep window sills, nearly thermal bridge free construction, and very low air infiltration.

SIPs and the IECC-12 Energy Code

INTRODUCTION

The 2012 IECC requires higher levels of insulation than previous energy codes. As with most ICC residential model codes, there are 2 main paths to compliance, 1) prescriptive and 2) performance. Most conventional (stick-frame-and-infill) homes use the prescriptive method. Because SIPs are not conventional in many respects, the performance method is more technically accurate. However, new in the IECC-’12, the prescriptive path includes some notations for continuous insulation. SIPs qualify for the continuous insulation parts of the prescriptive path. Therefore, included in this note is an explanation of applying the prescriptive code for continuous insulation to SIPs. The method to ensure compliance with the IECC-’12 for SIP buildings via the performance path is the same as for the IECC-09 which is covered in a separate blog and will not be repeated in this post.

SIPs AS CONTINUOUS INSULATION, SUPPORTING DOCUMENTATION

The first listed R-value for the prescriptive method is a “center-of-cavity number”. It’s named this way because that is what it is. Conventional construction assumes that there will be studs, rafters, jacks, headers, etc. penetrating all the way through the cavity insulation. A batt of insulation labeled R-19 is just that, the batt itself is R-19. The 2×6 next to it is closer to R-6, and an equivalent metal stud is close to R-1. Clearly, the performance of the whole wall somewhat less than the cavity alone. According to research done by the DOE at Oak Ridge National Labs, the “whole wall” R-value of this prescriptive “R-19” wall was actually measured to be R-14 .
SIPs have very few wood elements penetrating all the way through the insulation this is the reason they are considered continuous insulation. In the same DOE research program, using the same test, a nominal R-23 SIP returned results of R-22 and an R-15 SIP was measured to be R-14 . This is the fundamental reason that SIPs with R-values below IECC table requirements are still compliant.

U.S. Climate Zones based on 2009 International Energy Conservation Code Source: Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy.

U.S. Climate Zones based on 2012 International Energy Conservation Code
Source: Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy.

DETERMINE THE REQUIRED PRESCRIPTIVE R-VALUE

Using Table R402.1.1 of IECC-’12, select the required infill insulation R-value for the building component in question for the correct climate zone. SIPs are most commonly used as roofs, walls, and floor. The “Ceiling R-Value”, “Wood Frame R-Value”, and “Floor R-Value” are the columns that usually apply. In the “Wood Frame R-Value” column there are two options one is a single R-value for the cavity and the other is a cavity R-value + a continuous insulation number. The second combination is intended as if you are going to put a couple of inches of insulation on the wall on continuous over the studs in addition to traditional insulation. Our nailbase and SIPs are often used in this application. For steel buildings there is an additional table 402.2.6 which gives multiple R-value combinations between infill and continuous insulation.

2012 IECC Prescriptive Requirements For Wood Framing
Climate Zone Ceiling Wood Frame Floor
1 R-30 R-13 R-13
2 R-38 R-13 R-13
3 R-38 R-20 or R-13+5 R-19
4 except Marine R-49 R-20 or R-13+5 R-19
5 and Marine R-49 R-20 or R-13+5 R-30
6 R-49 R-20+5 or R-13+10 R-30
7 and 8 R-49 R-20+5 or R13+10 R-38
2012 IECC Prescriptive Requirements For Steel Framed Wall 16 Inches o.c.
Climate Zones Wood Frame Wall Requirement Steel Frame Wall 16"o.c. Continuous Insulation Option
1&2&3 R-13 R-13+4.2 R-0+9.3
4&5 R-20 R-13+8.9 R-0+14
6&7 R-20+5 or R-13+10 R-13+9.5 R-0+14.6

PRESCRIPTIVE CODE WITH SIPS AS CONTINUOUS INSULATION

In the IECC ‘12 Table R402.2.6 Steel Frame Ceiling, Wall, and Floor Insulation (R-value), there is an explicit listing showing the equivalence of the cavity insulation to various combinations of continuous and cavity insulation. One of the options is R-0 in the cavity. In the table an R-13 cavity is equal to R-9.3 continuous, R-20 cavity is equal to R-14 continuous, and R-21 cavity is equal to R-14.6.
Using those numbers the prescriptive center of cavity number times 0.7 is equivalent to the continuous insulation requirement. Using this information we can find approximate equivalents for the typical prescriptive codes.
Rcavity x 0.7 = Rcontinuous
Example: 49 x 0.7 = 34.3 and 38 x 0.7 = 26.6
Therefore an R-35 or better SIP will meet the R-49 center of cavity code for the IECC ’12, and an R-27 or better SIP will meet the R-38 center of cavity code.

For the R-49 roof code the following Foard Panel standard size panels are the minimum to meet code.
• 10.25” EPS (R-38)
• 8.25” NEO (R-34)
• 8.25” XPS (R-38)
• 6.50” PIR (R-36)
For the R-38 roof code the following Foard Panel standard size panels are the minimum to meet code.
• 8.25” EPS (R-30)
• 8.25” NEO (R-34)
• 6.50” XPS (R-30)
• 6.50” PIR (R-36)

AIR INFILTRATION

There is another effect at work that isn’t accounted for in IECC-’09: air infiltration. Another DOE test program that built several houses of the same design and location but built with different building systems illustrates this point well. The SIP house had about 1/4 of the air leakage of a conventional house of the same design. Air leakage is widely accepted as a major contributor to energy loss. The IECC ’12 has new performance requirements for air leakage. SIPs with Foard Panel’s typical joinery details will meet all the air leakage requirements. Several of our buildings have been blower door tested and reported very low air infiltration (<1 ACH50 meeting Passive House Standards and well bellow the 2012 Code). While, there are far to many details involved in air sealing for SIPs to claim all the credit for the low air infiltration, SIPs are a major contributor to the performance of the buildings tested. In addition, the foam insulation is both thermal and air barrier so that the thermal envelope and air barrier are aligned as required. With Foard Panel Inc.’s recommended joinery, all our joints are air sealed either with spray foam or mastic and we typically recommend that solid wood joints be covered with SIP tape. We manufacture insulated headers that further contribute to a consistent air control layer. All of which can make achieving air sealing goals very simple.

Open Vs. Closed Cell Foams

Introduction

We’re often asked if our foam cores are closed-cell vs. open-cell. Technically, plastic foams commonly used for insulation are all open-cell to a certain degree. There are some materials advertised as “closed-cell”, but it’s a question of degree, rather than simply open vs. closed. The feature that defines an insulation foam is gas trapped within solid plastic. The actual geometry of how the gas is trapped is the focus of this bulletin.
A closed-cell foam is one where distinct bubbles of gas are trapped individually in the plastic. See Picture 1. An open-cell foam is one where there are windows between adjacent bubbles which often create serpentine passages through the foam. See Picture 2. In the case of common insulating foams, none are perfectly closed cell, some just have many fewer windows and passages. In most cases, foam made from the same plastic can be either open-cell or nominally closed-cell, depending on the foam’s density. The higher the density, the fewer windows and passages within the foam.

Open Cell Foam

Picture 2: Open Cell Foam

Closed Cell Foam

Picture 1: Closed Cell Foam

Naming Convention

Best we can tell, the naming convention of open-cell vs. closed-cell originated in the spray-in-place polyurethane foam industry. For polyurethane, foam densities >= 2.0 lb/cuft are called “closed-cell” and densities < 1.5 lb/cuft are described as open-cell.
Typically, the open-cell or closed-cell foam specification is used as a proxy for other properties such as permeance, water absorption, stiffness, and compressive strength. Unfortunately, the “open-” vs. “closed-” convention becomes strained when it’s applied across different plastics and manufacturing methods. In essence, a closed-cell version of one plastic foam may be more permeable than the open-celled version of another because the number of windows in the cell walls isn’t the only factor in a foam’s properties. The size of the bubbles in the foam, size distribution, size of the windows, and the shape of the passages from cell to cell also matter.
Because of all of this, Foard doesn’t use the terms “open-cell” and “closed-cell” because it’s too incomplete. In an effort to get to the root performance issues, we prefer to use the measurable property values, because they work across all foam types, densities, and manufacturing methods.

Material Properties

Typically, the property people are most concerned about is permeance (the rate at which water vapor diffuses through the foam). The most common target value for the allowable permeance of a wall or roof assembly is 1.0 perm or less. Permeance below 1.0 perm is generally considered to be a “vapor barrier”, or, more correctly, an adequate water vapor control layer, by the building codes.
The combination of the foam’s properties and the thickness of foam used determine the permeance of the wall/roof assembly. Focusing on the general permeance of the foam (measured in perm-inches) alone is an incomplete representation. Table 1 lists the fundamental properties of the foams Foard Panel uses. Table 2 lists the properties of whole panels for some of our panel choices, including the contribution of the OSB skins.
As you can see, all of our panels can easily function as the “vapor barrier” in any wall/roof assembly. This is why we often point out that additional vapor retarding materials aren’t necessary. Also, it’s clear that even the most permeable, most “open-cell”, of our foams easily meets code requirements and most all building science recommendations.

Table 1: Foam Properties

Foam Type Typical Density in SIPs (lb/cuft) 1” Thick Permeance (perm) 3.63” Thick Permeance(perm)
EPS 1.0 5.0 1.4
Neopor 1.2 3.5 0.97
XPS 1.6 2.0 0.55
Polyisocyanurate 2.0 1.0 0.28

Table 2: Panel Permeance (perm)

Panel Type / Thickness 4.5” 6.5” 8.25” 10.25” 12.25”
EPS SIP 0.58 0.47 0.40 0.35 0.31
Neopor SIP 0.49 0.38 0.32 0.27 0.24
XPS SIP 0.36 0.26 0.21 0.18 0.15
Polyisocyanurate SIP 0.22 0.15 0.12 0.10 0.08

Practical Considerations

Our long-term durability investigations have shown that exterior finishing details have a vastly larger influence on long term building durability than any difference in core choice or difference in panel permeance. For example, so long as the panel’s permeance is less than 1.0, we have not found an example of long term building damage where a lower permeance panel would have helped. Over the same number of investigations, we’ve seen dozens of cases where long term building damage was caused by using synthetic building wrap or by poorly flashed windows.

Recommendation

Our recommendation is to base the choice of the core type and panel thickness on the building’s desired thermal performance, budget, and allowable wall/roof thickness. The differences in any of the foam’s structure has a very minor impact on the performance and durability of our SIPs.

Cohassett Nearing Completion

The Cohassett Sailing Club is a beautiful timber frame with Foard Panel EPS Structural Insulate Panels. As usual we completed our 3D model and Used it to Pre-cut all the panels so they could be assembled quickly on Site.

Structural Insulated Panel  3D layouts

Structural Insulated Panel 3D layouts

Now that our part is done the exterior details are being completed, to turn our Structural Shell into a luxurious building.

Helzburg Observatory

One of the most unique projects we have ever worked on, this is a personal observatory. None of the walls are or windows are plumb, and the we had to work with custom steel intended to support the big telescopes that will be brought in later. This project is about 2/3rds done and we are excited to go back and finish once the steel crew does the last of its work. We created a 3D model and pre-cut all the walls and even pre-built some sections to minimize the time on the very small site.  We have created custom details for every aspect of this project and are quite satisfied with our ability to meet even the most demanding design challenges.

Huber ZIP System & SIPs

150x0_ZIPSystem-Structural1-SiennaHuber Engineered Woods has released a housewrap-less sheathing system called ZIP System. This is basically OSB sheathing (7/16” thick for walls and 1/2” & 5/8” thick for roofs) with a liquid water resistive/water vapor permeable coating on the outside. Their goal is to eliminate the material and labor cost of applying a house wrap.

We’ve been asked a few times if we could make SIPs with ZIP System sheathing and/or use ZIP System tape on SIP joints.

The simple answer is no. While the ZIP System may work fine on conventional stick framed structures, we’ve learned that having a liquid water resistant material on the cold side of a high performance building system greatly increases the risks of sheathing rot. This includes, not only SIPs, but other building systems that use wood sheathing but have very little in-cavity air movement such as spray foam insulation in stud cavities.

Hilltop 140402_6There are other issues as well like size availability (4’x8′ is one of our least common SIP sizes) and cost.  We could produce 4’x 8′ panels, and we might be willing to do so if the project is built in a warm climate.  However, the durability of a ZIP SIP in the Northeast is highly limited and we choose not to put our name on a product we do not think will last.

Foard Panel recommends using old school tar paper as a housewrap on SIP envelops. It allows water vapor to pass through and allows liquid water to diffuse through. These two functions allow sheathing to dry to the outside most easily. Combine tar paper with a capillary break (1/4” min) behind the siding or other finish and you have the most durable water drainage system we’ve seen since Bo started installing SIPs in 1983.

Paul Malko
Mechanical Engineer

SIPs and the IECC-09 Energy Code

The 2009 IECC requires higher levels of insulation than previous energy codes. As with most ICC residential model codes, there are 2 main paths to compliance, 1) prescriptive and 2) performance. Most conventional (stick-frame-and-infill) homes use the prescriptive method. Because SIPs are not conventional in many respects, the performance method is more technically accurate. A method to ensure compliance with the IECC-’09 for SIP buildings via the performance path follows.

U.S. Climate Zones based on 2009 International Energy Conservation Code Source: Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy.

U.S. Climate Zones based on 2009 International Energy Conservation Code
Source: Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy.

DETERMINE THE REQUIRED PRESCRIPTIVE R-VALUE

2009 IECC Prescriptive Requirements
Climate Zone Ceiling Wood Frame Floor
1 R-30 R-13 R-13
2 R-30 R-13 R-13
3 R-30 R-13 R-19
4 except Marine R-38 R-13 R-19
5 and Marine R-38 R-19 or R-13+5 R-30
6 R-49 R-19 or R-13+5 R-30
7 and 8 R-49 R-21 R-30

ACTUAL SIP PERFORMANCE, SUPPORTING DOCUMENTATION

The listed R-value for the prescriptive method is a “center-of-cavity number”. It’s named this way because that is what it is. Conventional construction assumes that there will be studs, rafters, jacks, headers, etc penetrating all the way through the cavity insulation. A batt of insulation labeled R-19 is just that, the batt itself is R-19. The 2×6 next to it is closer to R-6. Clearly, the performance of the whole wall somewhat less than the cavity alone. According to research done by the Department Of Energy (DOE) at Oak Ridge National Labs, the “whole wall” R-value of this prescriptive “R-19” wall was actually measured to be R-14.

Typical Stud wall on Left and SIP wall on Right, the lighter colors indicate heat escaping.

Typical Stud wall on Left and SIP wall on Right, the lighter colors indicate heat escaping.

DETERMINE REQUIRED SIP R-VALUE

Section 405 of IECC-’09 outlines the documentation when using the performance method. While a sub-section describes the requirements of any software used for energy modeling, it is assumed that sound mechanical engineering calculations that meet the same requirements are also acceptable.
The following assumptions are made in this engineering proof:
• The proposed (SIP) design is of a house with the same design, surface area, orientation, and construction methods & materials as the standard reference (conventional) design.
• The climate, location, shading, & other outdoor features of the SIP design and conventional design are identical.
• Interpolation and minor extrapolation of the DOE/ORNL Hot Box Surface-To-Surface R-value data is accurate within 2 digits of precision.

For simplicity, this bulletin will use a more convenient form of Eq. 1 with units common in the HVAC industry.
Qws=(A×∆T)/Rws
Equation 2
Where:
Qws = whole surface (ws) heat transfer rate in BTU/hr
Rws = whole surface R-value, 1 R-value = 1 (hr sq-ft deg F)/BTU
Setting the heat loss of the proposed (SIP) design and the standard reference (Conv.) design equal to find the SIP requirement and simplifying results:
Qws.Conv=(A×∆T)/Rws.Conv = Qws.SIP=(A×∆T)/Rws.SIP → Rws.Con=Rws.SIP
Equation 3
Where:
Xws.Conv refers to the whole surface value of conventional construction
Xws.SIP refers to the whole surface value of SIP construction

Using the DOE/ORNL Hot Box data we can establish the relative reduction in performance over a whole surface.
Rws.Conv/Rnom.Conv = (14/19)= 0.73
and
Rws.SIP/Rnom.SIP = (22/23)= 0.96
Equations 4 & 5
Therefore, for a SIP wall, roof, or floor surface to equal it’s conventional equivalent this relationship must be held:
Rnom.Conv × (0.73/0.96)= Rnom.SIP
Equation 6

EXAMPLE

If a roof requires R-30 conventional insulation, the required nominal SIP R-value would be:
30×(0.73/0.96)=23
Equation 7
Using reasonable significant digit precision through the calculations, the following range of Foard Panel over all thicknesses meet or surpass the IECC-’09 for an R-30 roof:
• Polyiso SIPs: 4.50” or greater
• XPS SIP: 5.38” or greater
• EPS SIP: 6.50” or greater

Haystack Base Lodge Update

We are done with our part of the Haystack Mountain Base Lodge!
Just in time for the nice Spring weather to come in, though a last minute April snowstorm has left some remnants in the valleys and the mud is a foot deep around the perimeter of the building. The rest of the construction crew is beginning the finishing details, trim is going on and tar paper and strapping is ready for the vented roof.

Tiny House by Foard Panel

Foard Panel has helped a number of people make effective use of small spaces One of our more unique projects is Doug Immel’s Tiny mobile home. Here it is before the finishes are applied.

Doug Immel gives a tour of the the completely functional, energy efficient mobile home.

Same design for Different Use!

We used the same design to make a kitchen for a local catering service. During the Week it is parked for locals to grab a great breakfast or lunch. And on evenings or Weekends it travels to serve as a kitchen for outdoor catered events.

Walls of yet another Tiny house built with Foard Panel’s SIPs

tiny house

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