[Greenbuilding] Vacuum insulation panels...
johndaglish at free.fr
Fri Nov 4 15:30:50 PDT 2011
And they have to be very carefully handled and protected.
One little tear or pinprick and the insulation value drops back to the inherent
value of insulation material as the vacuum is lost.
With mass production they will come down in cost. In Europe the more
demanding building thermal regulations being enacted and for certain high
rental projects they can make economic sense now.
They are also vapour impermeable with the inherent problems of a
vapour "bridge" and interstitial condensation if the vapour control
layer is not perfect.
and some random thoughts...
The isolation sous-vide is a an isolant that has been encapsulated in an air tight membrane to which a vacume is applied.
Depending on the intensity of the vacume and the porosity of the insulant within thermal values < 0,004W/m.K can be obtained.
The insulant could for example be fibre de bois but mostly synthetic high void material which allready have a very low
thermal value such as aerogel (synthetique amorphous silica dioxide) are used to maximise the performance and thus reduce its thickness.
ame en XPS, PU, MW, aérogels (0,019W/m.K), xérogels granulaires, silices microporeuses pyrogénées ou précipitées
gas filled to improve performance argon, krypton
perméance à la vapeur d'eau du film barrière utilisé
Aging maybe 20 years initial value 0,019 long terme value 0.08W/m.K
Whilst using a high tech synthetic materiaux of little known environemental or health implications and not vapeur
permeable the isolation sous-vide because of its remarkable performance can be considered exceptionally for those
very difficult details/ elements of construction that cannot be more than a mininimal thickness and are of not of a significant area.
This particularly applies in renovation of existing or new
vernacular/classical type buildings where the proportions demand a
certain thickness, for example the sides of a dormer window chiens assis . The vip insulation carefully protected
by covering layers can provide a solution such that chiens assis may be used in a tres bas energie buildings.
Note whilst the VIP maybe very high performance les systems de
fixation and surrounding structure causes thermal bridges/ponts
thermiques which degrade overall thermal performance. Toute rupture de la vide by for example a misplaced nail or
the aging of the membrane joint, renders the coefficient thermique to the initial value of the isolation contained within the membrane.
An alternative is the design of vapour retarding constructions that
with increasing permeable layers towards the exterior. A vapour variable
retardant layer can aid drying of the insulation in summer. Our preference is an
moisture sensitive mechanical action woven fibre that shrinks or swells with humidity
rather than a chemical action layer such as PFTE. The use of natural renewable
or non scarce non-renewable hygroscopic materials for us are the
The above comments are for temperate climates and non air conditioned
spaces. Simulation tools such as WUFI will help in the design.
Regard for example
and of course JS can add a lot more :)
Wednesday, November 2, 2011, 8:29:31 PM, you wrote / vous ecrirez:
JS> I agree with Corwyn. We have looked at a bunch of commercially available and prototype products and really see only modest benefits. Exterior rigid insulation is pretty cheap, effective, and
JS> durable, with the only drawback being it is thicker. A few inches of extra thickness is hardly worth that much money and certainly not the huge premium they charge.
JS> On 11-11-02 1:33 PM, Corwyn wrote:
>> On 11/2/2011 10:40 AM, Gordon Howell -- Howell Mayhew Engineering wrote:
>>> VIPs could be a real game-changer
>>> with respect to net-zero energy homes and buildings.
>> They have a greater insulation value PER INCH of thickness. That is all. Useful in those few applications where volume is at an extreme premium. Otherwise it needs to compete with other insulation
>> on an R-value/$ basis. Or on a R-value/ecological harm basis.
>> Thank You Kindly,
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