August 1, 1998
At our last SIPA meeting, Sam Rashkin, the E.P.A. Energy Star Program Manager, asked us to consider SIPs as similar to Japanese cars in the 1970's. If you'll recall, in the 70's, American cars were characterized by cheap components, poor fit, poor durability, soft performance, inefficient oversized engines, and high fuel bills. They relied upon sale by first cost- the initial cost of acquiring the vehicle.
The Japanese could not compete on a first cost basis. Their land and transportation costs forced them to re-think the process. They decided that consumers would buy a high quality efficient car that cost more initially if the overall value worked- the combination of first cost, maintenance, operating cost and resale. To this end, they paid attention to detail, with tight construction, outstanding durability, improved performance, an efficient, appropriately-sized engine, low fuel bills, and excellent overall value.
Currently, most homes are built using stick frame construction methods developed over the past 100 years, which were created to allow mass construction and to utilize massive first growth forest resources. They are characterized by cheap components, compromised comfort and quiet, inefficient, oversized HVAC, poor durability, high utility bills, and are sold entirely by first cost.
SIPs use the Japanese car method of the 70's. We build using engineered materials which increase comfort, strength and performance, are extremely quiet, which can utilize appropriate HVAC systems, with excellent durability, and very low utility bills. As a result, we make sense from a real cost perspective.
SIPs and Insulated Concrete Forms are the only systems which automatically meet Energy Star specifications.
A new video, designed for homeowners and builders has been produced for the Structural Insulated Panel Association (SIPA) and is available to the public. Contact SIPA at (202) 347-7800, or visit their webpage on the Internet at http://www.sips.org .
President Clinton launched the new Partnership for Advancing Technology in Housing (PATH) program. The aim of this program is to improve the quality and energy efficiency of new housing. The goal is to reduce residential energy consumption by 50% by 2010. SIPs are one of the technologies specifically endorsed by the program. The PATH website address is http://www.path-net.org. Or contact John C. Blair, Director of Communications at (202) 708-0614 ext. 5721 if you have questions about the program and how it can help you build more energy efficiently. The announcement of the initiative was emceed by Bob Vila, a SIP proponent.
The May, 1998 issue of Environmental Building News reviewed SIPs from an environmental perspective and found them to be useful from a renewal resource standpoint. Their checklist for building with SIPs includes a number of useful comments including: avoid SIPs produced with ozone producing HCFCs- specify EPS; specify a company that optimizes panel utilization (CAD system, for example) to reduce scrap; select a company that utilizes scrap rather than discarding it; use panel scraps for kneewalls and headers; use foam sealing channels to seal panels; use construction tape on all joints to further reduce infiltration/exfiltration; don't push spans on roofs; make sure you use an adequate 15 minute fire barrier (1/2" drywall for example); and provide mechanical ventilation in SIP homes (or any tightly constructed home).
One of the major benefits of SIP construction is reduced jobsite labor. Generally, the labor required to erect a home is reduced 40% to 70%. Typically this is factored in as a cost in computing relative savings of SIPs compared to stick frame, but what is the cost for stick frame if workers are not available. In a recent article in Rural Builder (May, 1998) contractors's hiring woes are detailed. The problem is severe, and likely to get worse.
Two problems exist, the skilled worker base is aging, and the replacement worker base is shrinking. Basically, fewer high school graduates are opting for construction as a career, and this is a continually-worsening twenty year trend. A recent analysis done by the National Association of Home Builders indicated that the average age of journeyman trade workers had increased dramatically over the past ten years.
This is showing up on-site as delays and decreased quality (more callbacks). Construction schedules are starting to get extended. Unfortunately, on a case by case basis, this is never anticipated, so schedule delays get amplified. A two week delay in excavation or framing affects everything scheduled behind that step, causing multiple delays in re-scheduling. Generally, a two week delay in the early steps can cause a four to five week delay in the total schedule, so it is critical that the early procedures in the schedule stay on schedule. Contractors bemoan their callback rate increases and the resulting reduction in profits.
Not only are panels delivered to the jobsite pre-cut and ready to install, they are also pre-planned, with panel plans and panel numbers to expedite the process. This means that workers with less experience and skills can handle the labor, and get it done on schedule and right. The erection process is rapid, often in the 1,000/sq ft per day range, allowing close-in in 2 - 10 days on average. The labor outlook for construction is a continuing trend of reduced quantity of entry level workers. This is a favorable trend for panelized construction, especially for SIPs.
For the past ten years, I have been hearing about diminished lumber quality on jobsites. Contractors tell me that every year two-byes get worse. They say that when you pop a bundle of two-byes on the jobsite these days, they're so twisted and warped that the pile virtual explodes when released. One contractor sorts his two-byes by offering rewards for the first straight one, the straightest, etc. to get his crew to go through the piles. He says that about 40% of all the lumber in the bundles in not structurally usable.
Lumber is graded at the mill, A through C, with A being the best. Ten years ago, more A lumber was produced than demanded, so about 20% of all B lumber was actually A, and about 40% of all C lumber was actually B. Then the Japanese discovered stick frame construction, but due to extreme labor supply and skill levels, they could only use the straightest materials. A new grade was created, J-grade. Not only was the demand increased significantly relative to the lumber resources available, but the best was what was demanded. At the same time, supply was reducing, both due to diminished resource actually (fewer trees available due to prior use) but also legislatively (environmental issues, land use issues).
The overall effect is that the lumber used to build stick frame homes in the United States today is not of the same quality as the lumber used ten years ago. The lumber is not as straight and true, the edges are less square, the strength is diminished, and the splintering and checking is much greater. This means that homes built today require more skilled labor to build properly. Since skilled labor is in short supply, it seems likely to assume that "They just don't build them like they used to." SIPs require less lumber, and do not rely on the lumber for strength. This is more good news for SIPs.
Two and a half years ago, I first talked with an engineer in Northeast Tennessee who had seen an advertisement for stress skin panels in a loghome magazine and wondered if the panels could be used in other ways. I told him about timber frame applications and Structural Insulated Panels. He sent in a copy of his house plans and asked if his house could be built using SIPs I assured him that virtually any home could be built with panels and I proceeded to put together a bid for him. As is usually the case, the bid was enlightening, but useless out of context. Without knowing what the house would cost to build using other methods, my bid didn't really tell him what he wanted to know.
He decided to put his home out for bid and see what contractors would charge using conventional construction and using SIPs. He had three contractors bid the package. None of the contractors had any experience using SIPs and each declined to bid using SIPs. All bid based on conventional two by four stick framing, meeting minimum strength and minimum insulation requirements (R-13 walls, R-30 roof- all fiberglas). The low bid was $71.00 and he didn't feel comfortable working with that contractor. The next lowest bid was slightly higher for this 3,750 sq ft house.
He came to one of my panel information seminars at about this time, and sought advice on how to build with SIPs when his contractors were reluctant to do so. I introduced him to my SIP tech rep, Charles Judd and we talked about various ways to go about getting a SIP home built. The options presented were, 1) hire a tech rep to train his contractor or to provide technical assistance to the contractor, 2) have the contractor hire a panel erection sub-contractor, or 3) self-contract- he could become his own contractor.
After some thought, the he decided that he would be more certain of cost and quality if he handled the contracting than he would any other way. He put the house out to bid, including separate framing and SIP installation bids. In the initial bids, SIPs and stick framing came out very close together in cost, with stick frame approximately $900 less (but to a lower strength and insulation specification). After an energy analysis, he decided to upgrade to thicker SIPs, and the differential increased to about $3,000. The projected energy savings due to the increased energy efficiency resulted in a monthly savings of $450.00, so it was an easy decision to make. He ordered the SIPs and started his project (see article in last November's SIP Update http://www.natraweb.com/keeper/update/ ).
He decided to fabricate panels on-site and panels were delivered the last day of May, 1997. After a number of delays due to weather, plan changes, etc. the close in was completed at the end of July (the plans expanded to 200 sq ft and some walls changed). Due to a series of problems with subcontractors and El Nino weather, his move-in was delayed until May 15, 1998. In spite of these problems, he is very happy with the SIP building experience.
When he first put the house out to bid last Spring, the house was 3,750 sq ft and his low bid was $71.00/ sq ft, with specifications at minimum. He decided to take a chance and contract everything himself and upgrade to SIPs. His final construction cost has tallied up to just over $193,000, or $49.00/ sq ft. His close-in cost worked out to just under $19.00/ sq ft.
As an engineer, he is much more comfortable with the quality of his structure using SIPs than he was with the two-by-four stick built option that the contractor had offered. Also, by contracting everything himself, he is comfortable that no material changes happened to down-grade the home and that no shortcuts were taken.
When he started up his HVAC system at the beginning of May, 1998 to test it, he ran the system at 70 degrees for a day (heating), which is the temperature the home they were living in was set to, and when he walked in the next day, everyone found that it was too hot. He measured the temperature throughout the house and determined that 70 degrees was the true reading. He set the temperature back until it was comfortable and found that 64 degrees was where everyone was comfortable. Later, when using the air conditioning, he found that 75 degrees was comfortable.
He called me to find out what was going on and I discussed a temperature gradient test performed in Washington State on two identical Timberframe homes with a 42' ridge beam, one enclosed with SIPs , the other insulated conventionally. The temperature gradient in the two homes was measured by a series of digital thermometers (accurate to .1 degrees F) set every six inches on a string hung from the ridge to the floor. In the panel house, the differential ridge to floor (42') was 2.2 degrees F. In the fiberglas and cellulose insulated home, the differential was 18.7 degrees. My opinion was that the increased comfort range in his home was due to this reduced gradient.
As SIPs continue to gain ground as the 21st Century's building material of choice, it's both gratifying and worthwhile to note the history of SIPs. (compiled by Frank Baker, Great Lakes Insulspan)
Current estimates are that SIPs will account for 1 1/2% to 2% of the total residential market for 1997. Estimates run from 2% to 3% for 1998. Our goal is 10% by 2001.
Timber Frame great rooms are extremely popular these days, but often the building budget does not allow enough for true timber framing. Recently, a number of timber frame companies have introduced timber trusses which are left exposed with a cathedral ceiling. The trusses are placed on top of SIP walls with SIPs or stress skin panels used for the gable ends and stress skins or nailbase panels used for the ceiling/roof. This technique is an excellent way to get a rustic timber frame look for less money than a traditional timber frame structure. It also has the advantage of being a more suitable building technique for carpenters with limited or no experience with timber frame joinery, allowing the normal carpentry crew to assemble and set the trusses rather than requiring an experienced timber frame crew out to set a frame.
A recent project for a 26' x 40' great room (three walls) using osb/osb stress skins for the walls, 4 26' trusses with purlins at 4' o.c., and osb/gypsum R-24 roof panels (12 in 12 pitch), shipped for under $14,000, or $13.46/ sq ft.which was less than the initial bid for just the timber frame. A similar great room with T&G ceiling and nailbase roof panels worked out to $14.87/ sq ft. Please contact me if you would like to get more information on this technique.
Perma "R" is adding 24,000 more square feet of building to it's production facility to increase capacity to meet skyrocketing demand. This brings total production space up to 56,000 square feet and allows them to meet increasing customer needs (over 20% per year increase each of the last 3 years). The expansion should be complete by June 1st.
Stress Skin Panels are SIPs which are not certified for extended spans and crush strength. Typically, they are built to the same specifications, by the same manufacturers, but the engineering, testing, and certification process is skipped. Without these steps, stress skins fall under the Model Building Code under APA Supplement Four with reduced spans and crush loads. These panels are intended for use where the panels augment the strength of the structure or where the panel's requirement is merely to support itself. Common uses of stress skin panels include timber frame enclosure (where the timber frame carries the bulk of the structural load), log home roofs (with spans of 12' or less), conventional cathedral ceilings (with spans of 12' or less), and light structural duties (garages, workshops, and homes with 8' walls, spans not greater than 12', and limited structural requirement).
Often, when building in unregulated or lightly regulated areas, stress skins can be engineered to replace SIPs. In areas where Code compliance is rigorously regulated, although stress skins are certainly stronger than the conventional structure they would replace, the stress skins may not meet Code requirements when used in a purely structural application. Often this can be overcome less expensively with stress skins and more framing lumber than by conventional framing or by SIPs.
The SIP Building Update is published by Perma "R" Products, Inc.. Our address is PO Box 5235, Johnson City, TN 37602. The editor is Butch Johnson. We can be reached at (800) 251-7532. Our homepage is http://www.sipsproducts.com
An engineer in Gate City, Virginia has started construction on his 3,747 sq. ft home with completion projected for November. His decision to build was based upon an energy evaluation he ordered from a Texas firm that specializes in comparative energy usage evaluations. His original plan was to build using standard code construction and insulation, which was projected to cost $297 per month in heating and cooling costs annualized. The analysis showed heating and cooling costs would be reduced to $41 per month annualized if he built with SIPs. Since the upgrade cost to SIPs in this project was approximately $4,000, the payback will be less than 16 months. The projected 20 year savings, assuming 4% increases in energy costs, will be $83,378. The decision was not too difficult to make.
The homeowner, Eric Fugate, is so impressed with the SIPs and their energy saving potential, ease of construction and strength that he has started a development company to build custom energy saving homes in Southwestern Virginia called Energy Home Builders (540) 386-2458. Fugate home in Gate City, VA.
Evidence mounts that venting is not useful in solving common shingle degradation problems. For some time many roof shingle manufacturers have voided their warranties when their shingles were installed over closed roof systems such as SIPs. To prove their point they asked their trade association, ARMA, to perform testing to determine shingle degradation probability in various circumstances. Among the circumstances tested were standard attic vs. closed roof systems and vented roof systems, shingle color (shade), shingle thickness and weight, and various other conditions. The test is scheduled to continue for at least three more years, but the preliminary results indicate that there is little variation in shingle degradation between vented, closed, or attic roof systems.
The best indicators of degradation were shingle weight and color- the heavier the shingle and the lighter the color, the better the wear. SIP manufacturers indicated that this was virtually everyone's experience with roofing products.
A number of architects have determined that using panels for roofs in commercial applications makes sense. Recently, the Rutherford Memorial Methodist Church in Corryton, Tennessee ordered panels as specified by the architect to allow spans of 6' o.c. between trusses. In addition to upgrading the insulation by using panels, the roof deck went on quickly and on schedule to the delight of the contracting firm, who had no experience with panels. A strip mall near Knoxville also used panels to reduce their truss cost by spanning further between trusses, requiring fewer trusses. The contractor there was also pleasantly surprised how easy panels were to put up. In particular they commented on how the panels were straight, rigid, and could be built in large sizes, reducing crane rigging time and crew size.
The Clinton, Tennessee Latter Day Saints Church was recently built using Insulspan panels provided by Perma R Products. The developers, Champion Development of Acworth, Georgia, chose SIPs due to ease and speed of construction, energy savings for the on-going operation of the church facility, and the super-straight walls, which allowed use of elastomeric stucco and an excellent exterior finish.
Ken Bishop and Bill Grubbs, the principals of Champion report that the project took a little over three months, start to finish, and could have been completed in seven weeks, except that weather prevented completion of the parking lot grading and elastomeric stucco application. They are so impressed with SIPs that they plan to build exclusively with them. They are developing a warehouse suites project in the Atlanta area, a residential development in the Knoxville area, and other church projects.
The church is very impressed with SIPs according to Ken Bishop. A number of officials have visited the church and they are all impressed with the operational costs for the building (the heating bill in March was $100.00 for an 8,600 sq. ft building), the neat, square, straight exterior, and the speed of construction. They are also impressed with the firmness and strength of the building.
Recently, two home designs were presented to us which had roofs that were either too complex or too expensive to build using SIPs, but the homeowners wanted to use SIPs for energy-savings. The solution in both cases was to marry SIP walls to standard truss roofs. The walls were pre-cut SIPs that we provided which produced a wall with a top plate for the trusses to be attached to. In one case the homeowner used EPS ceiling insulation and slab insulation to complete the highly energy efficient building envelope. In the other home, the ceiling and floor used conventional fiberglass batts. The homes are still under construction, but both homeowners have agreed to provide utility bills for comparisons in insulation effectiveness. Both homes are in South Carolina.
Jeffrey Christian at Oak Ridge National Labs near Knoxville, Tennessee recently performed tests to calculate insulation effectiveness of SIPs and other wall systems. SIPs rated second best in efficiency, behind cast-in-place EPS blocks, highest in overall ratings, and highest in "bang for your buck", overall efficiency per dollar cost. Mr. Christian presented his most recent findings to the Structural Insulated Panel Association (SIPA) at the May meeting in Arlington, Virginia. He stressed that the efficiency of SIPs were affected greatly by the joining details, especially joint sealing. In one experiment, it was found that whole wall insulation efficiency was reduced over 30% by not sealing the spline joints. Mr. Christian conducts tests for the Department of Energy, the Environmental Protection Agency, ASHRAE, and SIPA, among others.
At the 1997 Timber Framers Guild Western Conference, Tedd Benson, a respected Guild member, presented the concept of Open Building. According to the Conference Proceedings, "Open Building is a way of designing and constructing buildings and homes such that the changing requirements for the building may be well met over time. People's needs change, inhabitant's will change, even the fundamental purpose for the building may change. Open Building is therefore a design and construction theory that addresses this reality by disentangling the shell (structure and skin) from the infill (partitions, mechanical systems, cabinets, etc.). The intention is to allow the infill elements to be changed and modified relatively easily, though the structure itself is relatively permanent."
"Open Building is based on the understanding that a building exists in layers, which live in time based on two factors: durability or life span, and need for alteration to suit the owner's needs and changing circumstances."
Obviously, we can build structures which last hundreds of years, and it is appropriate to use of resources to do so, but services, space plans and "stuff" have a much shorter useful life. Timberframes and other envelope structures (like SIPs) are appropriate for this concept.
A recent article in the Journal of Light Construction, "Building with Foam-Core Panels," by Jim Leroy effectively details the construction of SIP residences. Jim was recently selected by "This Old House" to install the panels for Norm Abrams's new workshop. The installation process is delved into in detail in an article in "This Old House" magazine (Nov., 1997). As Norm says, "For new construction, I don't think there's any reason to use anything but the panels."
A feature article in Builder/Architect Magazine (October, 1997) features Perma "R" Products panels (reprints available upon request).
Recent papers presented at the 1997 Excellence in Building Conference (Energy Efficient Building Association) included "Adding More Value to your Home's Energy Package with Insulation, Installed the Right Way", by Reed Larson, which indicated that insulation currently installed saves the equivalent of 51% of the current annual industrial energy consumption and if all residential buildings in the US were upgraded to the Model Energy Code levels, an additional 9% of the annual industrial energy consumption could be saved. Also presented was a paper entitled "Innovation in Manufactured Housing: Structural Insulated Panels", which deals with the HUD Code industry's planned use of SIPs to meet new energy regulations cost effectively. A paper entitled Testing and Analysis of the Comparative Performance of Cellulose Vs Fiberglas Insulation" shows a 12% to 14% better energy cost projection for cellulose than for Fiberglas, but cautions that for either material installation quality control is the most important predictor of achieving hoped for insulation effectiveness. In "Green Building" Richard Wodehouse says, "with batt insulation, fill all voids carefully. A 4% void can loose 50% of the R-value for that area. Use masks when installing Fiberglas insulation to limit particulate inhalation."
I recently discovered Oak Ridge National Lab's Whole Wall R-Value Calculation on-line program to calculate whole wall insulation values for specific homes. It allows you to calculate energy usage accurately for different wall systems in order to compare them head to head for insulation effectiveness.
To test the system I specified a one story, 2,400 sq ft home, with typical door and window openings (20 total openings) and ran calculations on 5 5/8" structural insulated panels (stress skins), 2" x 6" wood frame, 2" x 4" wood frame, 2" x 4" steel studs, and 12" masonry block.
The whole wall R-Value of the SIPs was 20.36, the 2" x 6" wood frame was 11.8, the 2" x 4" was 8.8, the 2" x 4" steel stud was 4.92, and the 12" masonry block was 3.32. The SIPs were far and away the best at retaining R-Value as a system, maintaining 82.4% of it's center of cavity R-value. The other systems ranged from a low of 64.5% to a high of 70.4% R-Value retention.
The Oak Ridge National Lab home page is at http://www.ornl.gov, the whole wall r-value home page is at http://www.ornl.gov/roofs+ wall/, the calculator is at http://www.ornl .gov/roofs+wall/rvalue.html.
In an issue dedicated to Structural Insulated Panels, Building Systems Magazine (Nov/Dec '97), published an editorial entitled "Dispelling Myths about SIPs" which deals with the gap between perception and reality for builders considering SIPs. Myths included "they're too expensive and a hassle with building inspectors, home buyers couldn't care less about energy efficiency- they're price point shopping, and homes built with them are boxy." The editor debunks these myths using interviews with SIP builders and home owners.
In the cover story, "Arrival time for SIPs", these interview technique continues, but with the emphasis on industry growth. The author indicates that the industry growth is primarily fed by the merits of SIPs. "Drawn by the product's simple construction style that requires fewer skilled laborers- panels combine the structural system, wall and roof sheathing and insulation into a single step- and a diminishing pool of talented craftsmen, many builders are finding it's in their best interest to offer SIPs."
One builder says, "My clients tend to be scientists, surgeons, stock brokers and engineers. People who typically embrace new technology and who are looking at conventional construction and rightfully concluding that there's got to be a better way." Once a stick builder, he says, "now I wouldn't touch it. Once you build this way, you'll never go back."
Bruce Hehn is an engineer in North Carolina who has had the dream of building a Frank Lloyd Wright-inspired design home for some years, but couldn't find materials which would work. The original home which inspired him was built with Wright's composite panel construction, which no longer meets building code requirements, and no other building method allowed him the open volume, energy efficiency, and strength he needed to make his dream a reality. His home has low pitched roofs (2 1/2 in 12) into hips with the third floor walls cantilevered in from the second floor walls and the same for the second floor over the first. By going to SIPs, the engineering problems were greatly simplified- to the point where the home was feasible.
The home is under construction now near Asheville, North Carolina. Mr. Hehn is very satisfied with the SIPs in the project and is an ardent supporter of the use of the material.