Why Structural Insulated Panels?

The role of insulation is to minimize or eliminate the occurrence of heat loss in a building or home. This can be more complicated than it appears, especially considering there are six mechanisms of heat loss that can come into play.

Conduction – the transfer of heat within an object or between two objects that are in contact. A pot gets its heat from contact with the stove element.

Convection – the transfer of heat that occurs when a liquid or gas comes into contact with a material of a different temperature and distributes heat accordingly. Hot air rises since it is less dense than cold air, moving heat upward, while cold air falls.

Radiation – the transfer of heat by means of electro-magnetic waves. The Earth gets its heat from the Sun exclusively via radiation, because the void of space in between the two prevents both conduction and convection.

Conduction, convection and radiation are the three primary scientific mechanisms of heat transfer. But there are also three secondary mechanisms at play in building science.

Air Infiltration – the transfer of heat when air pressure differences between the exterior and interior force air to infiltrate a building. A strong wind will often “push” unconditioned exterior air inside a building.

Air Intrusion – when exterior air infiltrates a wall cavity but doesn’t continue into the building, exiting back to the outside instead. While there is no draft felt inside, the thermal patterns inside the wall insulation are affected.

Moisture Accumulation – when moisture permeates an insulation material, it will reduce the insulation’s effectiveness, contributing to heat loss/gain.

While there are a multitude of products on the market, there are two basic types of insulation: open cell and closed cell. Insulations like fiberglass and low-density urethane spray foam are OPEN CELL insulations because the air pockets are not fully enclosed. Air and moisture can enter and escape the system freely. The cells are “broken” and air can fill or escape the space inside the material. This lowers the insulation performance properties and explains why they usually cost less.

In comparison, expanded polystyrene (EPS) used in Thermapan SIPs is a CLOSED CELL insulation where air cannot enter and escape at all and the insulation performance properties are unchanged.

There are numerous advantages of closed-cell insulation compared to open-cell:

• higher R-value
• high density = strength
• greater resistance to air or water vapour penetration
• resists all six mechanisms of heat loss 

The “broken” nature of open cell insulation invites heat loss from all six mechanisms of heat loss. The open cells provide a natural environment for air and moisture to infiltrate, exfiltrate and circulate within the insulation.

Whereas the R-Value of an insulation is measured exclusively by its ability to resist heat transfer via conduction, in reality its true insulative properties are much weaker due to heat loss from the other five mechanisms.

The key to SIPs is that there is no wall cavity. The EPS insulation is rigid and solid, unlike the porous nature of traditional fiberglass and open cell spray foam.

Consequently, SIPs can truly claim to eliminate thermal transfer from the other five mechanisms. There is no convective loop, air infiltration or air intrusion, because SIPs are a true air barrier – the solid insulation prevents air from circulating. Likewise there is no thermal transfer resulting from moisture accumulation, as SIPs are a vapour barrier as well. Finally, radiative heat transfer, which occurs in the void of space, is negligible. While in theory heat can transfer by radiation within a cell in the insulation, its adjoining cell walls are essentially at the same temperature anyway.

The critical role played by the six mechanisms of heat loss can be demonstrated through various real-world studies.

One very revealing study was conducted by Brock University researchers, who had the opportunity to analyze temperature variances within the exterior walls of two nearly identical houses – one using traditional R-19 fiberglass insulation and the other built with SIPs that featured an R-17 foam-based EPS insulation.

If energy loss in a home was simply a matter of heat transfer via conduction, one would expect very little difference in energy usage between the two homes. After all, the rated differences between the insulations of the two homes was a mere R-2.

However, the study found that the R-17 EPS outperformed the R-19 fiberglass hands down, and highlighted a number of interesting findings:

• During the month of January 2001, the average temperature of R-19 fiberglass was -5ºC (23ºF) when the outdoor temperature was -10.5ºC (13.1ºF).
• The SIP wall house with R-17 EPS insulation maintained its true R-value throughout the duration of the 1 year study.
• The R-17 EPS SIP wall house used 33% less energy than the R-19 fiberglass wall house.

The Brock University study clearly demonstrates that other mechanisms besides thermal conduction are at play in a real world setting. Otherwise the two homes would experience similar energy usage.

The proof is in the performance. When it comes to choosing an insulation for a new home or commercial building, it’s imperative to look beyond the stated R-Value of the material under consideration. Of far greater importance is the nature of the insulation, particularly its microscopic cell structure. An insulation with closed cells, like the EPS used in Thermapan SIPs, will invariably resist heat loss stemming from all six mechanisms far more effectively than open cell insulations.

Thermapan’s standard SIP foundation wall, exterior wall, roof and floor building systems provide residential and commercial builders an efficient advantage over conventional on-site construction methods. The Thermapan SIP system permits faster installation, less job site waste, and superior quality and performance.

The Thermapan SIP system reduces construction time because when SIPs are installed the structure, insulation, vapour barrier and air barrier building envelope components are achieved. Alternative on-site conventional construction methods involve building envelope components that must be installed individually, requiring more time.

Thermapan SIPs are accurate, plumb and are inert to dimensional shrinkage unlike wood frame methods. The continuous SIP flat surface is advantageous for interior and exterior cladding applications; reduces construction defects and provides superior building serviceability for the expected service life of the building.

The Thermapan SIP standard panel system is packaged wrapped for weather protection. Each SIP package is individually labeled listing the contents resulting in a more organized construction site. Less time is needed for sorting and assembly starts immediately.

The Thermapan SIP standard panel building system is flexible to address project variables that occur frequently without effecting your bottom line. Such variables include overall building dimensions revisions, window/door opening dimensions and locations.