Structured Insulated Panels – SIPs

What I’m Learning About SIPs That May Help You With Your Project

Here in the Richmond, Virginia area (RVA), I initially found it challenging to find the right team of architects and contractors to build a home addition using SIPs (structured insulated panels). I made a lot of phone calls, interviewed builders, and conducted a lot of research. It took some time to gain the knowledge needed by a Homeowner GC. But in the end I finally found there are more than enough resources available in Virginia to get the job done; and get it done right.

I truly enjoy learning and I must admit, it has been a journey. I have been told all kinds of misleading “half-truths” and out right wrongs concerning the construction of energy saving buildings. First and foremost, educating yourself is key to managing a successful Homeowner GC project.

But make no mistakes about it, understanding the basics is important to both hands on DIY folks and those hiring a General Contractor (GC). It didn’t take me long to realize not all GC’s are created equal when it comes to today’s energy efficient building methods and his or her knowledge of building science. And guess what? I also found several self-promoted “green” builders and architects are NOT as well informed on energy efficiency or experienced with quoting a SIP project as they claim to be. In addition, I found several lacked an understanding of ROI – your return on investment – when it comes to the myriad of potential energy efficiency solutions.

In this post, I am going to share some of the knowledge I’ve gained about SIPs, energy efficiency, and project management. I hope the info is helpful to you.

Don’t be inhibited by what some folks (if not a lot of folks) will tell you about SIP buildings. You’ll likely hear they cost too much;  I heard they cost too much over and over. However, done right they are well worth your consideration and they don’t necessarily increase your total cost of construction. Actually, I have come to the conclusion they are less expensive to build and subsequently maintain than traditional stick-framed homes and remodels. In addition, there are plenty of scientific studies, university research reports, and experienced professionals that confirm my conclusion. But again, you might not hear that from your architect, designer, and/or many local builders.

Cost Savings – SIPs

Independent R.S. Means study shows 55% labor savings over stick frame in residential construction with prefabricated SIPs

  • 11% savings on electrical rough-in
  • Faster dry-in time
  • Easier trim installation
  • Faster sheet-rock installation – less cutting, straight walls (you can nail molding and hang pictures anywhere on the wall)
  • Less waste and lower disposal fees (less labor moving waste around and less time required for cleaning up the construction site)
  • Shortened duct runs
  • Smaller HVAC required for heating and cooling
  • Less skilled labor needed – significantly less time labor required to construct onsite
  • Source includes: Energy Code Compliance With SIPs by Frank Baker, PFB Corporation and Don Ferrier, Ferrier Custom Homes – Presentation on SIPs published at

Given my environmental, science, and business background, my interest and focus is “smart” energy conversation. Don’t be fooled; some “green” contractors and architects will gladly waste your greenbacks. One popular, local green builder told me it would take more than twice the average cost per square foot to build a “green” addition, “his way.” After interviewing the chap, I could only conclude he was overly focused on incredibly expensive (and utterly wasteful IMHO) nuances of green building. He was proud to say his crew would even control, at your expense, practically every particle of dust that could enter your home during construction. Hiring a maid to clean the house might be a little more practical as well as more cost-effective.

He also suggested I consider tearing the existing structure down; this is one of the more wasteful environmental practices on the planet. His credibility nose-dived on the spot after that comment. I had him out of my house in less than 15-minutes. Sad thing is, his company is building and wasting a lot of homeowners’ money so he can win green awards and get print in magazines.

Seriously, it is not hard to educate yourself concerning the basics.

Whole Wall R-Values for SIPs

Whole Wall R-Values compared to SIPs - Structured Insulated PanelsThere’s more to exterior walls than meets the eye. It is important to note that the R-value of a whole wall can be considerably lower than the R-value of the insulation. Whole wall R-value calculation procedures factor in all of the effects of additional structural members at windows, doors, and exterior wall corners.

The following table is from R-Controls, a SIP manufacturing company:


at 75o
at 40o
4-1/2″ 14.9 16.0
6-1/2″ 22.6 24.3
8-1/4″ 29.3 31.6
10-1/4″ 37.0 39.9
12-1/4″ 44.7 48.3

Here are a few resources I found particularly helpful:

Arlington Passive House

Building Science

Green Building Advisor

My search began as usual on the Internet. I found several local “green” architects and designers and subsequently contacted them. Unfortunately, putting the right “team” together was more challenging than expected. We were also referred to a local but small architectural firm with SIP experience which we hired. The architectural firm was involved with a SIP home being built in our area. To make a long story short, we fired the architectural firm  (that’s another story) and we were disappointed with the “experienced SIP builder they recommended. The guy “talked the talk” but just didn’t “walk the walk. We called the builder and requested a quote for a project at one of our rental properties; they did a brief site visit then never quoted the job or called us back after telling me he would twice. When I mentioned his company to other folks in the industry, they said they had similar experiences with the guy; never called them back or came up with references that were requested. Again, the architectural firm we fired “highly recommended” this particular builder; again, do your homework and definitely get multiple references.

How About Spray Foam Insulation?

No doubt, spray foams offer better insulating value than fiberglass. However, the studs in a stick-built structure need to be considered. Studs actually lower the insulating performance of the wall and may allow water vapor, as well as air, to enter the house. Air infiltration is considered the greatest contributor to energy loss. By the time a stick-built house is properly sealed with spray insulation, the “total cost” of the wall generally exceeds the cost of installing SIPS. Of course, you want to add up all of the materials used and the additional labor required to stick-build. And, don’t forget to add in the additional cost of waste disposal for stick-built walls; there is far less waste created during construction with SIPS.

The use of “rain screen management techniques” for wall assemblies is recommended and often required by code in certain jurisdictions. Design requirements for wall cladding systems must consider local environmental conditions and assembly restrictions as defined in applicable building codes. Check with your SIP manufacturer’s installation guide for general reference information; there are also several SIP Installation guides available online (one example: SIP manufacturer, Insulspan SIP Installation Guide).


1. Pre-Plan Electrical & Equipment Needs

During the design phase it’s extremely beneficial to pre-plan for electrical chases. Since SIP panels are manufactured to meet the project’s specifications, it’s important to plan for electrical chases in advance to prevent time consuming and sometimes costly changes to make modifications during installation. For example, SIP facings should never be cut horizontally for the installation of electrical wiring. Cutting the SIPs will result in compromising the structural performance . Also, during the design phase, it’s important to determine if there are any equipment needs for the installation of the panels. If the project specifies roof panels or wall and floor panels larger than 8’ x 8’ in size, equipment such as a forklift or crane may be needed to install the SIPs.

2. Organize the Panels for Installation

After your SIP panels are delivered to the jobsite, proper storage, weather protection and handling will help to make the installation process more efficient. First, set aside a level spot to store panels and try to store panels for the first floor separately from the second floor and so on. Essentially you want to organize the panels by the sequence in which they are installed. Lay the panels flat, no closer than three inches to the ground and give them plenty of support. Panels should be stacked so that identifying marks can be easily read. Third, prior to the start of construction, keep SIP panels dry when stored on site by covering them with a breathable protective covering.

3. Installation & Sealing

During installation it’s important to note that panels need to be fully supported. The panel slips over a wall plate, which needs to be set half an inch from the building edge to ensure that the panels are fully supported. Next, set panels in place in order – start in the corners or valleys and work your way out. Once the panels are installed you should always follow the manufacturer’s joint sealing recommendations. Panel joints and voids must be properly sealed using Do-All-Ply® adhesive or SIP tape to minimize air leakage and most importantly to maintain the structure’s long-term durability.

4. Protect the SIP Panels from Weather Penetration

Once the SIP panels have been installed and sealed, weather protection such as housewrap will prevent moisture deterioration. Windows, openings and penetrations require proper flashing and sealants. Improperly installed flashings can result in trapped moisture. Follow the housewrap manufacturer’s installation guidelines. Flash all penetrations; windows over time will eventually leak some water at the window sill. Installing flashing under and around windows and doors will direct water away from the wall structure.

5. Sizing up Your HVAC

One common mistake is under-estimating the high insulating and air sealing properties of SIPs when selecting an HVAC system. SIPs allow for smaller HVAC equipment. When working with a HVAC contractor, make sure they take into account an estimate for low levels of air infiltration. Proper HVAC sizing is critical because an underused system will fail to reach a steady operating rate, resulting in short cycling which is less energy efficient and requires more maintenance.

Factors Used to Determine HVAC Sizing:

Caution! Many builders are not keeping up with the trends in energy efficiency and building technology. Case in point. We obtained quotes from builders that included a new HVAC system for the first floor of our home. The builder’s HVAC sub-contractor visited our house but neglected to collect the critical data necessary to properly size the HVAC. Although he claimed he would base his recommendation on a Manual J calculation (HVAC load calculation), it appears he did what many HVAC subs do. He likely based his recommendation on his decades of experience on NOT on our specific situation.

Many local codes require Manual J and Manual S calculations for new homes and remodels. The fact is, few contractors take the time to collect the necessary data to properly perform the calculations. The methods used to insulate a home are changing rapidly; air infiltration is the culprit. Significantly reduce air infiltration and you’ll need a smaller HVAC system (costs less to buy and saves energy). The typical HVAC contractor often selects an air conditioning system for a home based on the old rule of thumb, “500 sq. ft. per ton.” Wrong!

The sub-contractor in this case over-sized the HVAC by a ton – literally (12,000 unnecessary BTUs). We had the HVAC load calculations performed based on our specific situation and we know for sure his recommendation was way off. Over-sizing of HVAC systems is a really bad idea – they don’t run efficiently, they cost you more to buy, and they wear out faster.

Here are a few of the things to consider when sizing an HVAC system properly:

  • Size of Building (each floor analyzed individually)
  • Orientation of Building
  • Conditioned attic and crawl space verses unconditioned (proper attic insulating methods makes a big difference in your energy use – if you want to save money in the long-term, make sure your attic is properly insulated).
  • Type of Wall Construction (and associated R-value)
  • Window information (number, location, insulation value, fenestration rating, total square feet of windows, etc.)
  • Door information (number, location, insulation value, fenestration rating)
  • Duct location (in heated space, in unheated space, in attic, in crawl space)
  • Fireplaces (number, type)

SIP Do’s

1. Do provide adequate support for SIPs when storing them. Store SIPs laying flat and covered.
2. Do study installation drawings before setting panels.
3. Do remove debris from plate area prior to panel placement.
4. Do provide level and square foundations or floors that support SIP walls.
5. Do provide adequate bracing of panels during erection.
6. Do hold sill plate back from edge of floor system 1/2” to allow full bearing of SIP OSB facings.
7. Do provide 1-1/2” diameter access holes in plating to align with electrical wire chases in SIPs.
8. Do store R-Control® Do-All-Ply® sealant and SIP Tape in a warm area for best application results in cold weather.
9. Do always follow manufacturer’s recommended joint sealing techniques.
10. Do place R-Control® Do-All-Ply® sealant along the leading edge of wood being inset into panel.
11. Do use R-Control® Do-All-Ply® sealant on wood-to-wood, wood-to-EPS and EPS-to-EPS connections.
12. Do use SIP Tape or equivalent vapor retarder on roof panel joints.
13. Do install proper flashing and sealants around all rough openings and penetrations as required.
14. Do use only continuous 2X’s, I-Beams, and Insulated I-Beams for spline connections.
15. Do use proper underlayments for roofing and siding. SIP walls are airtight without housewrap but they do need a drainage plane material.
16. Do install plumbing in interior walls. Furr out interior sections for pipes if necessary.
17. Do provide adequate ventilation to maintain indoor air quality.
18. Do use termite resistant and mold resistant materials when required such as Perform Guard® Termite resistant EPS SIP core or Frame Guard® mold resistant OSB treatment.

SIP Don’ts

  1. Don’t leave panels exposed to the elements for long periods of time.
  2. Don’t lift SIPs by top OSB facing or drop SIPs on corners.
  3. Don’t install SIPs directly on concrete.
  4. Don’t cut wall panel skins horizontally for installation of electrical wiring or overcut the OSB facings for field-cut openings. Use factory provided chases in SIP core.
  5. Don’t be afraid to field trim panels for an exact fit.
  6. Don’t install recessed lighting inside the panels.
  7. Don’t put plumbing in R-Control® SIPs Panels.
  8. Don’t install or use unvented combustion equipment such as vent-free gas logs, fireplaces or heaters in an airtight SIP house.

Additional Resources:

“SIPs perform at about 97% of their stated R-value overall, losing only 3% to nail holes, seams and splines. Because of the variety of thermal breaks in conventional wall construction, the whole wall performance is 30% less than the stated R-value of the wall. Stud walls lose thermal performance to studs, nails, screws, wiring, switch boxes, and other breaks in the thermal barrier.

Even this relatively poor performance by conventional walls depended on fiberglass batt insulation being carefully installed with no air voids. If there are even small defects in installation, R-value plumets. The ORNL study’s authors, Jeffrey Christian and Jan Kosny, reported:

“[T]the whole-wall R-value of a 2 x 6 wood frame wall with R-19 fiberglass batts installed with rounded shoulders, 2% cavity voids, and the paper faces fastened to the inside surface of each stud was only R-11. This whole-wall R-value represents a 42% reduction from the R-19 value printed on the fiberglass batt’s label. The seemingly insignificant insulation installation errors and thermal shorts resulting from interface details accumulate to significant impacts”. (“Calculating Whole Wall R-Values on the Net” from Home Energy Magazine Online, November-December 1999).
SOURCE: Star Craft Custom Builders

Septic System Information

Central Virginia area – SIP Manufacturers

Acme Panels – Radford, VA

Panel Wrights 

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