Verifying the Electrical Chases in Our SIPs are Clear

We spent the day working on the electrical chases in the gable roofs.  The chases must be ‘open’ throughout their length so the electrical wiring can be completed.  Any chases that are blocked are not acceptable.

This is our last chance to verify these chases are 100% clear and electrical wires can be run unobstructed in the chases because we will be covering the wood fascia on the flat roofs and gable roofs with zinc.

While it didn’t feel like a productive day, it was an important day.

To explain, let’s go back in time …

Taking an Integrated Approach to Design

We took an integrated approach to the design of our home.  Claude Oakland was the architect that designed the house in 1969.  Subsequently, we had an entire team work on the remodel of the main floor, which followed the original design by Claude Oakland and, at the same time, the team also designed the lower level (basement), which is all new construction.

An ‘integrated approach’ required consideration of architectural design, functional design (ergonomics), structural design, energy efficiency, and the durability of materials.  As well, we included the major components of the HVAC, electrical and plumbing components in the initial, integrated design.

Once the overall, integrated design of the house (remodel and new construction) was completed, the detailed structural design was addressed, which anticipated future seismic forces.  The design and structural requirements were then used for the layout design of our SIPs (Structural Insulated Panels).

Electrical Distribution Strategy and Design

Based on the design of the house, we arrived at an electrical distribution strategy, which the original house had as well.  The electrical distribution in the original house was over the 2×8 Redwood roof decking, which comprised the roof structure (you can see how the original electrical distribution was in a photo of the deconstruction on 09/24/08).  The electrical distribution in the remodel is in the SIPs that comprise the lower and upper flat roofs, and all of the gable roofs.

To provide as much flexibility as possible, both today and in subsequent remodels, the electrical distribution must be through chases that are intuitive and logical, and easy to understand and locate.  We decided to include these chases in the perimeter SIP roof overhangs, which are outside the thermal envelope of the structure.

Background – Design, Manufacturing and Installation of SIPs

SIPs are manufactured using shop drawings for each individual SIP.  The shop drawings are developed based on the design of the house, then the overall layout of the SIPs, and the structural requirements for the house.  We provided our SIP manufacturer, Insulspan, with the overall layout of the SIPs and the structural requirements.  Insulspan then revised the overall layout and developed detailed shop drawings for each individual SIP.  The SIPs are connected (joined) with splines.

Within Insulspan, the manufacturing group reviewed the detailed shop drawings to ensure that the SIP layout and design, as required, could be manufacturing efficiently.  Subsequently, our structural engineer of record, Innovative Structural Engineering, signed off on Insulspan’s shop drawings and then we signed off on each individual shop drawing.  This marked the completion of the SIP design, which was then passed on to Insulspan’s manufacturing group.

Manufacturing SIPs

Insulspan’s manufacturing group made the SIPs, and included all splines not requiring dimensional lumber.  Although Insulspan could have provided a complete ‘ready to assemble’ package with every component and spline required, Insulspan could not provide FSC-certified dimensional lumber.  Accordingly, we agreed to obtain FSC-certified dimensional lumber from our own sources through a detailed cut list and FSC-certified lumber order.

The splines that Insulspan provided included both foam splines and I-joist splines.  The foam splines were included but not connected to the SIPs that were to be joined.  The I-joist splines were installed in one of the SIPs; the adjacent SIP would then be attached as part of the on-site assembly.

Importantly, the holes for the chases were drilled in each of the splines, including both the loose foam splines and the I-joist splines that were glued in place to one of the SIPs.

Assembling Our SIPs On Site

Once the SIPs were delivered to our site, each SIP was identified and placed (stacked) near to where it would ultimately be located, in reverse order.  Essentially, the first SIP to be used was at the top of the stack and the last SIP at the bottom.  This required moving the SIPs around our (very crowded) job site.

When the SIPs were assembled on site, the SIPs were connected with the appropriate splines (either foam splines, dimensional lumber or I-joists).  The assembly team had to drill holes for chases in the dimensional lumber that connected each of the SIPs.  The foam splines and I-joists had holes for the chases pre-drilled in those connections by Insulspan’s manufacturing group.

If the SIPs were manufactured as per the design and the assembly was completed as per the design (with components manufactured correctly) then the chases would be clear and open, and located as per the plans.

Verifying the Chases Are Clear

To verify the chases were open and clear, we drilled holes in each location on the ends (rakes) of the gable roofs so we could insert a length of pipe into the 1-1/2 inch chase.  That pipe should go the entire length of the chase unobstructed.

Any obstructions must be cleared prior to installing the zinc fascia.

Simple, right?

We wish.

Where Could Errors Occur?

Reviewing the process, errors could occur in the design, manufacturing and installation of the SIPs.

Our design was documented, with each a shop drawing for each SIP.  Design errors could occur where chases in adjacent SIPs were ‘disconnected’ and those disconnections not identified prior to manufacturing and installation.  Insulspan’s review process helped to ensure that our design was robust.

Errors could occur in manufacturing, where the chases were located in locations not specified in the shop drawings.  As well, the foam pieces, with the chases, could move or be placed upside down in the manufacturing process.  Any errors in the manufacturing process should be prevented through Insulspan’s  Quality Assurance program.  Any errors that do occur in the manufacturing process should be identified through Insulspan’s Quality Control process, prior to shipping to our job site.

Finally, errors could occur in the on-site installation.  First, the dimensional lumber splines that were not provided by Insulspan had to be ‘manufactured’ (i.e., cut to length and holes drilled for chases) on the job site.  Other errors could occur where panels were not connected correctly (using the wrong foam splines, moving or ‘flipping’ the foam splines) or where panels were not assembled plumb and square (offset).  As well, the mastic used to joint the foam splines, I-joists or dimensional lumber splines could leak/drip into the chases causing blockage.

Also, the on-site installation is the last part of the process where quality control is possible.  Any errors in the design, manufacturing and installation should be identified at this time.  Prior to putting the LVL into the gable ends (rakes) and as each panel is assembled, inspection will identify blockages in the chases.

As you can see, there are multiple parties involved in the process and multiple opportunities for errors to occur.  However, there are also areas where any errors could, and should, be identified.

Last Chance

Given this is our last chance to ensure the chases are open, we decided to invest the time and effort to drill 1-1/2 inch holes through the 2x fascia and the 1-3/4 inch LVL on the gable ends (rakes).  Also, we drilled holes through the fascia and LVL in the upper flat roof.

After drilling the holes, we started by using using 20 ft long pieces of ½-inch irrigation pipe to verify that the chases were open and clear.  Subsequently, we used larger diameter pipe.  We found problems.

In several instances, we noted that the pipe was hitting foam, indicating blockages caused by the manufacturing process.  In other instances, we noted the pipe was hitting wood, indicating problems with the installation process.

As well, we found that after removing foam blockages that there were wood blockages.  As well, after drilling through wood blockages, we found foam blockages.

Given the problems we encountered within the sample tested, we are going to verify 100% of the chases in the overhangs where our electric distribution will be.

Using a 20 ft long 1-1/2 inch inside diameter irrigation pipe to identify where the obstructions are in the electrical chases.

Using a 20 ft long 1 inch inside diameter irrigation pipe to identify where the obstructions are in the electrical chases.

Leave a Reply

Your email address will not be published. Required fields are marked *