Pro Clima’s exterior weather resistant membrane (WRB) and roof underlayment (the SOLITEX system) incorporates a monolithic TEEE* film. This membrane, unlike conventional WRBs, has no pores and is completely waterproof and wind/airtight. This material actively transports the vapor outward by passing it along its molecular chain of monolithic membrane (see image above) – a property of the TEEE material. Therefore, if vapor/water is present on the interior of the membrane, even the slightest vapor pressure differential (inside to outside) will engage the chain reaction and dry out the water/humidity. Consequently, the membrane, unlike conventional housewraps, is very vapor open (38 perms, Sd-value 0,05m) in every condition. Conventional housewraps and WRBs depend on creating a micro-porosity in a normally vapor closed material (PE or PP). In the production process these materials are made vapor open by either spunbonding them into a PE mesh, puncturing the PP or stretching the PP with NaCi additives in production. These micro-pores then allow water vapor molecules to be moved through the water-resistant layer by convection (leaking through the micro-pores).
By being porous, perforated or stretched, these materials are not 100% airtight. They are therefore vapor open because air and water-vapor molecules, driven by convection, leak through the micro-pores. Since the pores are quite small – nanometer scale – a relatively high vapor pressure differential is required for vapor to actually dry outwards through the pores. This is true even if the actual perm rating (per ASTM E96B) is high, which could be the case because the pores are big/perforated. If you can easily blow through the membrane when placing it over your mouth, the pores are probably large – very vapor open, and not very airtight.
The example above shows that actively vapor open SOLITEX MENTO membranes remain dry even when large amounts of humidity enter a roof enclosure with compromised interior airtightness. However, the conventional passively vapor open membrane in the same building is showing condensation – because water vapor wasn’t transported fast enough, casuing a layer of condensate to build up. It looks like the membrane leaks, but the moisture is actually just interior humidity.
How is a vapor open membrane waterproof?
A micro-porous or perforated membrane is “waterproof” because the surface tension in liquid water holds the drops together and prevents water beads from passing through the membrane. But if that tension is broken by oils (found in wood preservatives), wood tannins, soap and dirt, the waterproofing becomes compromised.
In contrast, the monolithic film in SOLITEX MENTO is completely waterproof. In the lab tests shown above and below you can see the effect of applying oil to membranes before testing the water column (EN 20811/AATCC TM 127) of each membrane. The conventional membrane leaks at low water pressures, while the SOLITEX MENTO membrane stays dry at a much higher column (notice the difference in bulge). This demonstrates that the waterproof qualities of the TEEE work even when exposed to oil.
SOLITEX MENTO’s monolithic membrane is also absolutely wind & airtight . ASTM E2173 test results show that the material is so airtight that it exceeds the capabilities of the lab calibration – and goes above and beyond the AABA requirements and ICC-Accepted Criteria 38 for WRBs. The Pro Clima WRB/roof underlayment system offers the ultimate protection against wind-washing of insulation when taped with TESCON tapes and following the other instruction in the SOLITEX MENTO wall installation guide and SOLITEX MENTO roof underlayment system brochures. The importance of protecting insulation against windwashing and the optimization of the insulation value is explained in Mark Siddal’s Passivhaus UK trust conference paper on thermal bypass.
A number of projects using Pro Clima exterior membranes have demonstrated airtightness numbers below 0.6ACH50 – prior to interior airsealing.
Three layers – each with it’s own function
All Pro Clima WRB membranes are multi-layered products, with each layer having specific properties to assure the product offers first class performance during installation and the life of the building. The top layer serves as a protective cover made with a PP microfiber fleece. This offers the weather/UV resistance needed for both roofs and walls:
- SOLITEX MENTO, DA, INTESANA, HUMIDA: 3 months exposure
- SOLITEX MENTO Plus: 4 months exposure
- SOLITEX FRONTA QUATTRO: 6 months exposure. Exposure of 3/4″ gaps in siding indefinitely.
When SOLITEX MENTO, DA or INTESANA is used as roof underlayment, the top layer offers slip resistance, while also protecting the TEEE layer below.
The TEEE functional layer is located in the middle of each product, providing the actively vapor open AND waterproofing properties of the material. It was specifically developed for this purpose in SOLITEX MENTO and FRONTA QUATTRO. The other membranes employ other monolithic materials, for their specific uses/vapor profiles.
The bottom microfiber fleece protects the TEEE layer above against damages from installation over rough cut lumber and allows it to be pulled over structural members.
*TEEE: Thermoplastic Elastomer Ether Ester – is a material that combines the flexibility of rubber with the strength of a membrane, resisting tears, abrasion and corrosion. It also has good resistance to oils, fuels and chemicals.