The 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.
WHEN TO USE INTELLO
- When Code requires a Class II vapor retarder: INTELLO provides an interior Class II vapor retarder and interior airtight layer.
- 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).
- 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.
- 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.
- When interior air tightness is desired: INTELLO provides a continuous, visibly verifiable and repairable interior airtight membrane in addition to vapor control.
THE SCIENCE OF INTELLO
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.
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.
(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.)
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.
THE APPLICATION OF INTELLO
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.
THE SPECIFICATION OF INTELLO
In addition to the spec outline list below, we have a sample 3-part architectural construction specification for use and editing.
Related Blog Posts:
- DA and INTELLO: the Hot & Humid Climate Solution
- Foam-Free Wall Assembly Guidelines by Climate Zone
- INTELLO Plus: airtight in the lab for ASTM 2178 and onsite
- Intentional “holes” in your air barrier (and sealing them)
- An Interior Air Barrier Does It Better
- When Buildings Move – Airtightness Should Last