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-John Ruskin 1819-1900

SEISMIC COLORSEAL R-Value matches that of wall system.

 

Are Expansion Joint Selection Decisions Costing Your Client a Fortune?

Thermal rating of structural expansion joint seals is seldom among product selection criteria. Yet the product chosen to seal large structural expansion joint gaps could be setting the R-value for your entire exterior wall system. 

This is because, as was pointed out in “Exterior Wall Systems, R-Value, and Revenue” by Tom Kuckhahn published in the September 2003 Construction Specifier, heat “seeks the path of least resistance, so the R-value of an actual wall is closer to the R-value of the least insulating portion of that wall.”

Kuckhahn continues, “Energy is one of the most significant expenses for commercial facilities, particularly for heating and cooling, which represent about 32 percent of a building’s operating budget.” This means that designers concerned with sustainable, green, or simply efficient design should make energy use their top priority in material selection. 

Among the choices for structural expansion joint sealing in walls are strip seals and precoated, precompressed, impregnated foam sealants.

1)   “Strip Seals” are metal (usually aluminum) rails, mechanically anchored to joint substrates into which are snapped rubber bellows sealing glands.

2)    Silicone-Coated, Precompressed, Impregnated Foam Sealant (COLORSEAL by EMSEAL) is an open-cell polyurethane foam, impregnated with water-based acrylic sealant, and factory coated with low modulus silicone to create a movement bellows.

Strip Seals violate good thermal design in a number of ways.  First, the thin rubber bellows impart little in the way of thermal insulation.  Second, the metal rails create thermal breaks in the wall system in the same way that wall ties and other non-insulated conductive materials do.

COLORSEAL and SEISMIC COLORSEAL are by contrast excellent insulators.  The R-value of COLORSEAL is 3.28 per inch of depth.  This means that on a typical 3-inch joint, the R-value at the structural joint gap of a wall sealed with COLORSEAL is 3.28 x 3.5 (the depth of seal of 3-inch COLORSEAL) or R-11.48.  This compares favorably to a 2 ½-inch thick exterior-insulated façade (R-4 to 5.6 per inch of thickness) as well as to the R-value (around R-12) of a typical insulated precast panel.

Furthermore, because COLORSEAL contains no metal and attaches to substrates without invasive metal anchors, it does not create any conductive thermal breaks in the wall system.

As Kuchahn rightly observes, “decisions made during design and construction stages affect the cost and performance of buildings for decades to come-especially in terms of energy consumption.”

It seems to make sense then, that thermal rating is among the criteria for specification of structural joint sealing materials.

John Ruskin, a nineteenth-century commentator on architecture among other things warned:

“It is unwise to pay too much, but it’s worse to pay too little.  When you pay too much you lose a little money—that is all.  When you pay too little you sometimes lose everything, because the thing you bought was incapable of doing the things it was bought to do.  The common law of business balance prohibits paying a little and getting a lot.  It can’t be done.  If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better."

Expansion joints and precompressed joint sealants by EMSEAL

1-800-526-8365 -- 508-836-0280 --  techinfo@emseal.com -- Fax: 508-836-0281
 

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