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The INTELLO Primer

June 18, 2013

Intello diagramThe INTELLO membrane, manufactured by Pro Clima of Schwetzingen Germany, is the state-of-the-art for interior vapor control and air-tightness for cold and mixed climates.  It is an intelligent membrane that changes permeability in a range from 0.17 perms in winter to over 13 perms in summer depending on the relative humidity around it.   This intelligent range of permeability can give assemblies maximum protection against moisture damage.

Drying Capacity > Moisture Stress = Freedom from Damage

As insulation levels and air-tightness rise to meet greater demands for energy efficiency and comfort, optimizing the drying capacity becomes ever more important.


INTELLO Plus Membrane

INTELLO Plus Membrane

  1. When Code requires a Class II vapor retarder:  INTELLO provides an interior Class II vapor retarder and interior airtight layer.
  2. Where assemblies have significant vapor retarding or vapor closed outboard layers:  In assemblies that have limited outward drying potential. For instance vapor closed roofs (flat or asphalt shingles), foam insulation boards or exterior sheathing (OSB, plywood).
  3. Historic masonry retrofits with interior insulation:  To help address concerns about moisture levels of brickwork and freeze-thaw, while providing a verifiable and repairable airtight layer.
  4. Batt insulation installations:  INTELLO provides double-duty of providing airtightness (eliminating worries of convective currents) and manages moisture in all seasons, which avoids vapor condensation problems.
  5. When interior air tightness is desired:  INTELLO provides a continuous, visibly verifiable and repairable interior airtight membrane in addition to vapor control.


Similar to natural materials like wood, INTELLO becomes more vapor open when exposed to higher relative humidities and vapor closed in drier – winter – conditions.   However the engineered membrane achieves a range of permeability and safety not possible with other vapor-retarders, -barriers or other materials. And crucially as the moisture content rises around it above dangerous thresholds of approximately 70-80% the membrane dramatically opens up to allow drying and preventing condensation and moisture related damages.

This chart below illustrates the average humidity ranges in winter and summer around the membrane.

Chart of Average Humidities

Chart of Average Humidities

Turning then from the above chart on average humidities to the the chart below showing the vapor permeability curve, we can see how INTELLO reacts as humidity levels reach dangerous levels – opening up radically to allow drying inward.

INTELLO vapor curve

INTELLO vapor curve

(Note: the membrane is not directional, so as it becomes more vapor permeable due to rising relative humidity around it the vapor will move through it in the direction of lower vapor pressure.   Consequently INTELLO is not suitable as an interior membrane in consistently high-humidity occupancies like indoor swimming pools.)

Taut INTELLO and smooth TESCON Vana tape assures that these materials were installed air-tightly and are ready for cellulose after battens are installed

With this ability to promote drying, INTELLO can provide safety in even the most demanding circumstances.   Below is one slide from an extensive Pro Clima study showing the relative drying ability of various vapor retarders.   Here is one of the worst case scenarios, where you have a north facing pitched roof at high altitude with a construction loaded with moisture at the outset – as construction often can be.   You can see where the inboard OSB and plastic sheets are causing moisture problems, the intelligent vapor membrane, INTELLO, is driving down the moisture content to very safe levels.




INTELLO is the flagship material in a complete system of airsealing and vapor control that includes tapes, adhesive caulking and gaskets – giving you robust and long lasting airtightness.



INTELLO Plus, with blown cellulose behind, 2x's as counter battens support membrane, allow sheetrock to be mounted and services (electric etc). to be run on interior of airtight layer

INTELLO Plus, with blown cellulose behind, 2x’s as counter battens support membrane, allow sheetrock to be mounted and services (electric etc). to be run on interior of airtight layer

If you are using dense-pack insulation, cross battens are required to ensure even distribution of pressures.  Ideally the cross-battens provide a service cavity for running wiring and plumbing and thereby limit the number of penetrations in the air- and vapor-control layer.


In addition to the spec outline list below, we have a sample 3-part architectural construction specification for use and editing.

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