[Greenbuilding] Bubble Wrap 101 (was Hydronic Radiant Underfloor Heating)

Tue Oct 30 13:48:49 EDT 2007

Ahhhh, does the bubble-wrap never go away? Here's the word on this  
product directly from Natural Resources Canada, supported by other  
North American agencies.  Please note the R-values and the specific  
installation/placement of the material, and see note #1 for the  
biggest challenge to the claims of the manufacturers: extrapolating  
from existing standards for materials with different capacities etc.  
does not a qualified test make.

As a result of countless inquiries from the general public, building  
contractors and building professionals concerning claims made by  
manufacturers of foil-faced bubble insulation (FFBI) products,  
Natural Resources Canada (NRCan) has prepared the following  
information dealing with the effective thermal resistance (RSI/R  
value) of FFBI and other non-bubble structure types of products for  
the purpose of modeling under its energy efficiency housing initiatives.

Canada Mortgage and Housing (CMHC), the National Research Center  
(NRC) and other various agencies across North America have performed  
studies on reflective films, such as foil-faced or foil embedded  
bubble insulation, and caution potential buyers about exaggerated  
claims and limitations of these products.

Currently, despite advertisements and comments made by manufacturers  
and salespeople in the Canadian marketplace, and unless otherwise  
proven by a respected third-party testing agency against a recognized  
standard for the testing of such reflective materials, NRCan  
recommends the following effective thermal resistance maximum values  
for FFBI products when modeling them with HOT2000™ software.

RSI 0.26 (R 1.5) where the bubble layer is between two layers of foil  
without air spaces in front of the foil.
RSI 0.53 (R 3) where the bubble layer is between two layers of foil  
with only one air space in front of the interior facing foil.

RSI 0.62 (R 3.5) where the bubble layer is between two layers of foil  
with air spaces in front of the foils.
RSI 0.62 (R 3.5) where the foil layer is between two clear layers of  
bubbles acting as air spaces Refer to #5 below for information on the  
thermal resistance of other foil-faced products that do not  
incorporate an air bubble structure.

Issues Concerning FFBI Products:

1.      There is no specific ASTM standard (American Society for  
Testing and Materials) applicable to FFBI products by which to rely  
upon. Manufacturers refer to various standards and extrapolate  
portions of various tests to indicate how the product will perform  
overall in the house.  Therefore, it is currently extremely difficult  
to obtain proven, unbiased, third-party technical data on FFBI products.

2.      The United State's Federal Trade Commission (FTC) has  
explicitly stated that manufacturers in the U.S.A. must label their  
product with its basic R-value for the materials involved.  This is  
the same method that NRCan uses for its rating of up to RSI 0.26 (R  
1.5), where there is no air space.  If the foil product is installed  
with an adjacent air space or other system, such as a layer of clear  
bubbles, then the FTC states that a "system R value" can be labeled  
to include the benefits of the material’s reflective qualities  
together with its basic R value.  In Canada, no such information has  
yet been found on Canadian labeled products.  It is important to note  
that in order to benefit from the system R values, the air space must  
be present and reflective coatings must be clean.  Even the clear  
plastic bubbles can reduce reflectivity and overall performance.  For  
a report on a system R value by the Canadian Construction Materials  
Centre (CCMC), visit

http://irc.nrc-cnrc.gc.ca/pubs/ci/v4no2/v4no2_7_e.html.  It should be  
noted that due to the very complex nature of evaluating FFBI  
insulating products and their reflective/insulating properties, they  
are best evaluated as part of an assembly (e.g., wall, floor, slab  
and ceiling).  Unfortunately, very little third party assembly  
testing has been undertaken to date.

3.      The majority of heat loss in the average Canadian home is  
from conductive heat loss and air leakage (not including windows).   
However, for houses with in-floor hydronic or electrical radiant  
heating, no substantial figures for radiant heat loss versus  
conductive heat loss are readily available (especially from basement  
floors).  Nonetheless, leading manufacturers and researchers of in- 
floor hydronic heating systems do NOT recommend anything but foam  
based sub-slab insulation.  You will not find reflective type sub- 
slab bubble insulation products or foil faced foam products in their  
manuals at this time.  This includes bubble insulation where the  
reflective foil is between two clear layers of bubbles.  An  
interesting report by CMHC on the Comparison of Under-Floor  
Insulation Systems can be found at: http://www.cmhc.ca/od/? 
pid=63728.  The bubble insulation foil used in this report is the  
type where the reflective foil is between two clear layers of bubbles.

4.      According to the Reflective Insulation Manufacturers  
Association (RIMA), "Reflective vapour/air barrier products and  
reflective sheathing can, if properly installed, provide additional  
thermal resistance to wall and ceiling assemblies.  To do so the  
surfaces must be faced with intervening airspaces and the surface  
characteristics of the reflective material must remain unchanged.   
The NRC has indicated that the thermal resistance of a 20-mm airspace  
with two reflective surfaces would be RSI 0.61 (R 3.46) for wall  
applications.  However, the absence of an airspace on either side of  
the insulation prevents any additional reflective thermal  
resistance.  In such applications these products are expected to  
provide a maximum of RSI 0.26 (R 1.5), assuming the bubbles remain  
intact and unperforated."

5.      If modeling a reflective foil film with or without a  
laminated layer of foam or fibre-based insulation board and there is  
a dead air space of 12 - 22 mm (½ inch to 1 inch), NRCan will accept  
an RSI value of 0.26 (R 1.5) for the foil and dead air space.  If a  
layer of insulation is laminated to the foil with its adjacent air  
space, then also add the insulation's RSI/R value.  For the RSI/R  
value of the laminated insulation itself, use the values in Appendix  
1 of the Energy Advisor Workshop Manual or other reliable sourced  
value).  As noted, if there is no air space, then just calculate the  
value of the insulation (single-layer foil membranes without an  
airspace have an RSI/R value of 0).  If there is the possibility of  
air movement within the air space, the air currents (mass flow or  
convective air current) may negate the value of the reflective foil.

NRCan does not discredit other valuable characteristics of foil-faced  
bubble insulation, such as its flexibility, its air/vapour barrier  
characteristics or its use to reflect solar radiation in cooling  
climates.  The intent of this paper is only to provide information on  
the effective insulation value accepted by NRCan for this type of  
product, for the purpose of modeling houses under its energy  
efficiency housing initiatives.

Shawna Henderson
principal
Abri Sustainable Design & Consulting
Nova Scotia, Canada
www.abridesign.com

On 15-Oct-07, at 10:52 AM, Chris Green wrote:

> Philip Proefrock wrote:
>> Hi John (and others),
>>
>> What about foil insulation with "bubble-wrap facing" that holds  
>> the foil
>> film itself 1/8" - 1/4" away from the surface of the concrete?  Do  
>> those
>> provide better performace as radiant reflectors, or are those no  
>> better than
>> face foil radiant barriers?
>>
> The following page discusses those bubble wrap layers.
> http://www.healthyheating.com/Page%2055/Page_55_o_bldg_sys.htm
>
> Oh, this link from the above page is funny:
> http://www.therightfoot.net/mystuff/whatever/swf/bubblewrap.swf
> "..must have...more..." :-)
>
>
> Cheers,
>
> Chris Green.
>
> _______________________________________________
> Greenbuilding email list
>      Environmentally-preferable design, construction, building  
> elements
> List info: http://listserv.repp.org/mailman/listinfo/ 
> greenbuilding_listserv.repp.org
> List email: Greenbuilding at listserv.repp.org
> Managed by BuildingGreen, Inc. http://www.buildinggreen.com
>       publisher of Environmental Building News and GreenSpec
> Hosted and archived by REPP / CREST http://www.crest.org
> To get on the list:
>   http://listserv.repp.org/mailman/listinfo/ 
> greenbuilding_listserv.repp.org
>   or mailto:greenbuilding-request at listserv.repp.org? 
> subject=unsubscribe
> To get off the list:
>   http://listserv.repp.org/mailman/listinfo/ 
> greenbuilding_listserv.repp.org
>   or mailto:greenbuilding-request at listserv.repp.org? 
> subject=unsubscribe