The combination of rubberized asphalt and polyethylene in Ice & Water Shield makes it waterproof and also helps to seal around nails/screws of roofing applied to it. The large downside of this material combination is that it is a Class I vapor retarder, trapping moisture/humidity under it when it gets in. This can be caused by leaks from outside or airleaks/diffusion from the interior humidity. As Martin Holladay points out in this q&a on GBA– this is not a good idea unless you throw a lot of foam on top of it – and who doesn’t like the idea of living in a foam box, wrapped with asphalt?
There is a better way. The best protection against moisture issues in most climates is to vent your roof and walls on the exterior of a next generation membrane/WRB (SOLITEX MENTO 1000, Plus or DA). Being truly waterproof membranes (see this blog post and Joe’s explanation why conventional housewraps leak water and air, FHB feb/mar 2001) that are also absolutely airtight is of course crucial for the walls to be protected against water intrusion. You only staple at areas that will be overlapped or taped – but what is the solution for leak-prone situations where you have to mount battens with screws/nails that penetrate this waterproof membrane?
TESCON NAIDECK allows you to keep the roof and the wall absolutely waterproof, preventing humidity-related damages from rot and mold. The double-sided tape seals both the membrane to the tape and the tape to the battens, assuring that no water will reach the punctures caused by the nails/screws. NAIDECK also self-seals these nail/screw penetrations. In sum, it provides additional waterproofing for your roofs and walls while allowing the membrane’s permeability and active vapor properties to move moisture unimpeded.
It is even more important to add TESCON NAIDECK when using SOLITEX MENTO Plus as subroof/sarking membrane and blowing dense packed insulation under it. The slight bulge caused by the dense packing will direct water draining down the membrane towards the batten (see photo below). In this situation, TESCON NAIDECK will prevent this water from leaking along the nails/screws that hold these battens in place.
- A high performance roof should be vented – how to do this properly
- Vapor open exterior – without sheathing – maximizes outward drying potential
- Vented rainscreen: what a high performance building wants