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EPS Structural Insulated Panels are proven efficient

EPS Structural Insulated Panels are proven efficient

A study implemented by ORNL (Oak Ridge National Labs), has demonstrated that a 4-inch SIP panel outperforms 2"x4" stick and batt construction. Not only that, it even outperforms 2"x6" construction when comparing thermal performance. A SIP panel provides the structural components. There are no braces or studs to cause openings in the insulation. This results in a more comfortable, energy efficient building that performs up to specifications in real world conditions.

Commonly, stick and batt insulated buildings are subject to inadequately installed or even missing insulation. The design of a SIPs panel combines the structural and insulation components joined as one. This means there are no hidden spaces because a solid layer of foam insulation is part of the wall or roof panel.

In additional testing and a comprehensive technical analysis of whole-wall performance indicates that the air losses in stud wall construction are much greater than originally anticipated. Average results showed that the other standard components in stick and batt walls can reduce R-values as much as 30% of the wall area.

The Oak Ridge study discovered that structural insulated panels perform at about 97% of their stated R-value overall, losing only 3% to seams, splines and nail holes. Chases for electrical wiring are preformed into the foam core which provides a continuous layer of insulation. This technology keeps the outdoor elements out and means the interior will be free of drafts and cold spots.

When it comes to maintaining constant interior temperatures, a SIP panel wall also outdoes stick and batt construction which leads to improved occupant comfort. The accompanying chart demonstrates how this works. The interior wall temperature of frame construction drops at every stud location. However, the SIP wall remains consistent across its entire surface. Occupant comfort is improved because there are no changes to the temperature - every part of the building is consistent and comfortable. That is why many people remark that they can immediately "feel the difference" in a SIP panel built home or commercial building.

With a structure built with SIPS panels, thermal efficiency and comfort are built in at the manufacturer. Now the independent lab tests prove it.

Tests prove SIP Panel buildings are superior in thermal performance.

Tests prove SIP Panel buildings are superior in thermal performance.

The Brock University study: Comparing identical buildings
When it comes to quantifying actual heat loss in different wall systems, the Brock University study provided an excellent opportunity for accurate comparison between structural insulated panel and stick construction in the real world.

The two structures involved in the study were rental housing units, located immediately adjacent to one another. Both buildings were identical and had similar east-west orientations, ensuring the same exposure to outdoor temperature and wind conditions. Except for brief periods both houses were occupied throughout the course of the study, which took place over a 12-month period from February 2000 to January 2001. Both units were heated with a natural gas / forced air system.

One unit was constructed with 4.5" structural insulated panels, while the other used 2x6 studs with batt insulation. Both houses were constructed according to the Ontario Building Code (OBC). The units were built by the same crews, with no one being aware that scientific tests would be conducted afterwards.

Wall Type




Whole Wall R-Value





at 75° outside

at 40°




7/16" OSB, 3-5/8" EPS, 7/16" OSB






7/16" OSB, 5-5/8" EPS, 7/16" OSB






7/16" OSB, 7-3/8" EPS, 7/16" OSB






7/16" OSB, 9-1/4" EPS, 7/16" OSB



OSB and plywood increase in thickness depending on lads and spans.

In addition to the thermal performance and thermography components of the Brock study, air leakage tests were conducted to compare the tightness of the two units. This analysis shows the relative convective properties of each, a key determinant of overall energy efficiency.

The results of the air leakage tests showed the structural insulated panel house to be much tighter than the stud house. The structural insulated panel house had 1.55 ACH (air changes per hour) at a pressure differential of 50 Pa, while the framed wall house had 2.60 ACH at 50 Pa, or a 68% more leakage. This means that, all other factors being equal, the structural insulated panel house would use less energy for heating, would be more comfortable, have better heat retention and be less drafty.