Does Reflectix Double Bubble Duct insulation have a stand alone R-6 insulation value when installed with no airspace ?
I have been reading your responses to the various situations where the bubble wrap radiant barrier product was being used by HVAC contractors as a duct insulation. I recently had to replace all the duct system in my crawl space due to Sandy flood damage on the eastern shore of Maryland and the new duct system was installed with the 1/2" Reflectix double bubble product installed as an R-8 duct insulation. The installation neglected to include the 3/4" spacers to create the airspace needed for the radiant barrier assembly to work as a duct system insulation assembly effectively. As a BPI Building Analyst & Envelope Professional and HERS Rater, I informed the contractor that the installation was not done correctly. The contractor contacted Reflectix and they told him that the 1/2" double bubble product used with no air space still has an effective R-6 duct insulation value. They are basing this claim on another Test Report done by R & D on August 2, 2011 measuring Thermal Resistance Measurements according to ASTM C1668/C335 on the Reflectix Double Bubble Duct Insulation. As a building science professional and building contractor I am still somewhat skeptical on that claim being made as a result of that single test. Here is a page from the report that describes the testing that was done. I have the whole report but I am still somewhat skeptical about how accurately the results of this test equate to the claimed stand alone R value of R-6 for the Double Bubble product. I spoke to Reflectix and explained my concerns with my fairly extensive new duct system being wrapped with the product and what my options are to get the duct system insulation up to the R-8 insulation value. My HVAC contractor will do what ever is recomended to achieve the minimum R-8 value. One suggestion is to wrap over top of the Double Bubble wrap with conventional foil faced FG duct insulation. The other is remove the bubble wrap and rewrap using new Bubble wrap with the proper installation with 3/4" air space, which would be a nightmare with the duct system already installed, or rewrap using conventional R-8 foil faced FG duct insulation. I asked Reflectix what their recommendation would be and they seemed to indicate not wrapping the Double Bubble with a layer of conventional foil faced FG insulation. I am hoping to get some feedback on the best possible practical solutions to achieve an effective R-8 duct system insulation.
Page 2 of 5
P.O. Box 2400
Cookeville, Tennessee 38502-2400
Thermal Resistance of External Duct Insulation
R&D Test Number: RD112169DT Date of Test: July 20-29, 2011
Specimen Number: 1071110622-6 Manufacture Date: Unknown
Test Method: ASTM C 335, “Standard Test Method for Steady-State
Heat Transfer Properties of Horizontal Pipe Insulation”
Report Prepared for: Reflectix, Inc.
Contact Person: Monty Millspaugh
Description of Test
The resistance of externally applied air-handling duct insulation is determined using a calibrated
end apparatus operated in accordance with ASTM C 335 with analysis in accordance with Section
10.8 of ASTM C 1668-09. The calibrated end apparatus is discussed in Section 5.4 of the test
method. The test apparatus is a seven-foot long section of 8 by 12 inch rectangular steel duct.
An electrical resistance heater is mounted horizontally along the center–line of the duct. Fans at
each end of the duct provide internal air circulation. Eight Type-E thermocouples are
permanently attached to the interior surface of the duct to provide a hot-side temperature. Four
thermocouples are attached to the outside surface of installed duct insulation to provide a coldside
temperature. Thermocouples are attached to rectangular end caps of known thermal
resistance in order to determine heat loss from the ends of the apparatus. Two thermocouples are
placed four inches from the exterior side of the duct insulation to measure the temperature of the
air adjacent to the insulated duct. The entire apparatus is located in a conditional space that is
maintained at 70 +/- 2 ºF and 50 +/- 5% relative humidity. R-value for the duct insulation is
obtained from Equation (1) where the heat flow through the insulation is determined from
Equation (2). The heat flow through the end caps is calculated from Equation (3) where the Rvalue
for the end caps is obtained as a function of temperature using a heat-flow meter apparatus
operated in accordance with ASTM C 518.
Reflectix_rd11418(1) R&D Test.pdf 93.31 KB
Answered by Bruce Howe
Posted Fri, 03/15/2013 - 08:47
Edited Fri, 03/15/2013 - 08:54.
|Reflectix_rd11418(1) R&D Test.pdf||93.31 KB|
Posted Fri, 03/15/2013 - 09:26
Other Questions in Green products and materials