As code requirements become more demanding and energy costs rise, airtight building envelopes become increasingly important. Truly green construction demands an effective, airtight, moisture-resistant barrier that maximizes energy savings.
Sheathing systems that include an WRB must be:
- Able to reduce air infiltration
- Resistant to wind-driven rain
- Capable of bracing a wall
- Easy to install
In the quest for a good airtight, moisture-resistant building envelope, ZIP System sheathing is one option. ZIP panels feature a ½”, ⅝”, or 7/16” layer of oriented strand board (OSB) sandwiched between two layers of treated kraft paper which serve as an air/moisture barrier. OSB is fabricated from relatively large wood chips and adhesive. At first glance, ZIP sheathing is appealing in that it combines two products into one — an air/moisture barrier and sheathing.
Now, Thermo-Brace replaces the need for ZIP System sheathing. It is an environmentally friendly structural panel that does not use OSB. Thermo-Brace’s alternative design resists swelling thanks to high quality, long-fiber plies that are pressure laminated using a water-resistant adhesive.
Let’s look at some of the issues with ZIP System sheathing:
Swelling – Whereas ZIP sheathing can swell along the edges and corners when exposed to water prior to taping, swelling of ZIP sheathing is also a possibility when panels are damaged during construction. Damage, followed by swelling, may compromise the performance of the system as an air/moisture barrier. At a construction site, care must be taken to protect the edges of ZIP system panels to avoid swelling, particularly when inclement weather strikes.
Swelling may lead to taping problems. Unwanted air migration may increase heating and cooling costs which multiply over time. Condensation may occur when taped seams are compromised. If moisture cannot properly escape, mold, mildew, and rotting are all possibilities.
Wet-dry Cycles – In climates with distinct wet-dry cycles, OSB may alternately get moist and then dry out. There are questions as to what these repetitive wet-dry cycles will do to the structural integrity of sheathing containing OSB over time. When OSB takes on moisture and stays wet, rotting may occur.
UV Light Effects – If you anticipate that the WRB may remain exposed for a longer period, you’ll want sheathing that will withstand UV light without deteriorating. ZIP sheathing is rated for three months of UV exposure, while Thermo-Brace is rated 3x longer at nine months.
Installation – However, the system is dependent upon proper installation, including careful taping. Dimensional instability can compromise the integrity of the panels. That is, expansion and contraction may undo tape adhesion enough to allow for unwanted air movement and moisture intrusion.
The Thermo-Brace® Alternative
The manufacturer of ZIP sheathing suggests that ZIP installations are 40 percent faster than house wrap installations. Thermo-Brace also offers the advantages of rigid panel installation, although the light weight of the product further speeds installation. The various ZIP 4×8 panels weigh between 45 and 70lbs. By comparison, Green Thermo-Brace weighs 15lbs per panel, while Red structural-grade panels weigh 20lbs and Blue structural-grade panels weigh 25lbs.
Thermo-Brace exterior wall sheathing excels at preserving the integrity of studs, drywall, and cavity insulation. It is possible to select the perfect sheathing for your particular application. Standard-grade Green Thermo-Brace is .075” thick, while structural-grade Red Thermo-Brace is .101” thick. Finally, the structural-grade Blue Thermo-Brace is .126” thick.
Thanks to the corner bracing included with the Red and Blue structural grades, Thermo-Brace offers structural strength competitive with that of ZIP sheathing.
Contact Us Today
Green, Red, and Blue Thermo-Brace panels meet the standards set forth for water-resistant barriers as set forth in IBC Section 1404.2 and IRC Section R703.2. We’d welcome the opportunity to tell you more about the advantages of our Thermo-Brace product line. For personalized assistance, please contact us today.