Building Envelope Systems FAQ
Whether you are a building professional or building owner, we hope you’ll find the information you need here. If you don’t see what you’re looking for, please contact us, using the link above.
What is a building envelope system?
A building envelope system is the physical separation between the interior and exterior of a building. Tyvek® weather barriers and related products, like sealants and flashing tape, are used to help create a building envelope system for homes and commercial buildings. Tyvek® can reduce air and water infiltration to help prevent drafts and water damage. But it is also vapor permeable, to allow water vapor to escape when it does get into walls. Advantages a building envelope can provide include protection against water damage, improved energy efficiency, increased comfort, and reduced building maintenance.
Is a weather barrier like Tyvek® WB still useful if I install insulation?
Yes. The installed R-value of insulation is only realized if the air within the wall cavity stays still and dry. An average 8-mph wind can easily penetrate cracks and crevices, even in new homes. You could be losing up to 30% of the performance of your insulation. DuPont™ Tyvek® weather barriers are designed to help block air from getting inside walls. Properly installed, they help keep drafts out and protect your insulation’s rated R-value.
In addition, Tyvek® weather barriers help keep bulk water out, to help protect insulation in walls of both residential and commercial buildings. At the same time, DuPont™ Tyvek® WB is made with unique material science, to allow moisture that does get into walls to escape as vapor. This combination can help prevent moisture-related problems, such as rot, corrosion, mold, and mildew.
Is DuPont™ Tyvek® a vapor barrier?
No, DuPont™ Tyvek® is not a vapor barrier. It is made with unique material science to keep air and bulk water out while allowing moisture vapor inside walls to escape.
Can I use a Tyvek® weather barrier in combination with a vapor barrier?
Using a Tyvek® weather barrier in combination with a vapor barrier depends on how the rest of the wall system is constructed, and the climate the building is in. If the majority of the year is spent heating the home, where the inside temperature is greater than the outside, it is generally good to use a vapor retarder behind the interior drywall. In hot, humid climates, vapor barriers should not be used.
Do Tyvek® weather barriers have an R-value?
No; however, properly installed Tyvek® weather barriers help protect against loss of R-value in insulation due to wind washing. Even at wind speeds of 5 mph, a wall without an air barrier retains less than 40% of its original installed R-values.
In addition, Tyvek® ThermaWrap™ and Tyvek® ThermaWrap™ R5.0 can actually help increase the R-value of insulation. ThermaWrapTM is a metallized, weather resistive, insulating, breathable membrane designed to reflect radiant heat back into the wall in winter, and back out in summer.
Can housewrap make a house too tight?
With more energy efficient construction, "build tight, ventilate right" is the best practice. Mechanical ventilation is more important with today’s sophisticated energy saving home features. However, blower door testing on homes wrapped with DuPont™ Tyvek® weather barrier show natural air exchange rates per hour that are well within acceptable guidelines per ASHRAE Standard 62.
How to Specify and Install Tyvek® Materials
Can DuPont™ Tyvek® WB be installed with foam insulation products?
Yes. DuPont™ Tyvek® is compatible, and can be installed with foam insulation products. For specific inquiries, please contact us.
Can you install Tyvek® WB with the lettering facing inwards or upside down?
Tyvek® HomeWrap®, Tyvek® StuccoWrap®, Tyvek® DrainWrap™ and Tyvek® CommercialWrap® are equally effective in both directions and the logo may be on the inside or outside. However, Tyvek® StuccoWrap® and Tyvek® DrainWrap™ have a specially engineered surface that should be placed with the grooves facing outwards in a vertical direction.
Can Tyvek® weather barrier be installed vertically, instead of horizontally (drop it down from the top)?
DuPont™ Tyvek® StuccoWrap®, DrainWrap™ and CommercialWrap® D cannot be installed vertically. Although the vertical (drop it down from the top) installation method is not recommended for DuPont HomeWrap®, ThermaWrap™ LE and CommercialWrap®, it is important to ensure that, if this method is used, the vertical seams overlap by at least 6 inches and are taped with DuPont™ Tyvek® Tape. This will provide the greatest level of air infiltration and bulk water holdout protection. Recommended installation instructions can be found on this website, or on the roll label affixed to the product.
Is there really an advantage to using DuPont™ Tyvek® Tape?
Yes. Taping the seams with Tyvek® Tape provides the best Tyvek®-to-Tyvek® adhesion, helping to provide optimal protection against air and bulk water penetration, and extra durability protection during the building’s construction phase.
How long should Tyvek® WB be exposed before it is covered with siding?
Tyvek® HomeWrap® and Tyvek® StuccoWrap®, Tyvek® DrainWrap™ and Tyvek® ThermaWrap™ should be covered within 120 days (4 months). Tyvek® CommercialWrap® should be covered within 270 days (9 months).
Is it necessary to remove old building paper, or even old Tyvek®, before applying a new layer of Tyvek®?
No, it is not critical to remove building paper and/or Tyvek® prior to installing a Tyvek® weather barrier However, it is necessary to carefully inspect for damaged areas that may not be clearly visible under building paper. Since building paper does not have the same breathability characteristics of Tyvek®, the wall may lose some of its ability to dissipate moisture to the outside if the paper is left on the wall.
If you suspect previously installed Tyvek® has been compromised – and for all other specific inquiries – please contact us.
Should Tyvek® weather barrier be placed over or under building sheathing?
DuPont™ Tyvek® weather barriers can be used either over or under sheathing. When Tyvek® is used under sheathing, it functions only as an air barrier, and does not protect the sheathing as a secondary weather barrier. Tyvek® has been used directly over studs where there is no sheathing, although use of sheathing is a highly recommended building practice.
Is Tyvek® WB necessary over foam board?
DuPont™ Tyvek® weather barriers add considerable protection against leaky seams in foam board, similar to the protection provided over wood sheathing. Foam boards alone, even interlocking foam boards, do not adequately stop air leakage due to wall movement from settling and thermal expansion and contraction.
Can a Tyvek® weather barrier be used under any primary façade?
Yes, DuPont™ Tyvek® WB can be used under any façade, including brick, stucco, vinyl, cedar siding, metal, and stone. Proper installation under each façade is essential to ensure Tyvek® provides the maximum level of air infiltration resistance and bulk water holdout.
Can Tyvek® be used on roofs? Under floors? On the interior?
No, these uses are not recommended. All Tyvek® products in Canada and the U.S. have been tested and approved as products to be installed behind exterior walls. However DuPont™ RoofLiner provides a high-quality roof underlayment choice.
Can I use Tyvek® HomeWrap® under stucco?
Tyvek® StuccoWrap® is recommended under stucco because it has been specially designed to work with both traditional and synthetic stucco applications. The engineered surface, with special grooves, is designed to assist in drainage of incidental moisture that may penetrate the primary cladding in synthetic stucco systems.
Tyvek® HomeWrap® will also provide weather barrier characteristics in an EIFS wall system, but its drainage properties will differ. Therefore, in synthetic EIFS stucco systems, Tyvek® HomeWrap® can be used as the secondary weather barrier, but in conjunction with an additional drainage medium (either matte or grooved foam) to achieve the desired drainage characteristics.
Can Tyvek® StuccoWrap®, Tyvek® DrainWrap® or Tyvek CommercialWrap® D be used under brick?
Yes. It is perfectly acceptable to use Tyvek® StuccoWrap®, Tyvek® DrainWrap® or Tyvek® CommercialWrap® D under brick. Whether using Tyvek® HomeWrap®, Tyvek® CommercialWrap®, Tyvek® StuccoWrap®, or Tyvek® CommercialWrap® D under brick, it is important to follow the brick manufacturer’s guidelines regarding the use of an air space between the brick veneer and sheathing. Typically, this space is 1-2 inches, and will act as a drainage plane if incidental moisture penetrates the brick, in addition to ventilating behind the cladding, which aids in drying of the wall assembly.
Can a Tyvek® weather barrier be used as flashing?
Tyvek® weather resistive barriers have not been tested or approved as a flashing material. However, DuPont has introduced the DuPont™ Flashing System, which provides comprehensive protection from water leaks. It is designed to help direct water to the building exterior, instead of trapping it inside the wall system and causing water damage.
Can sheathing board seams be taped?
Taping sheathing board or fan-fold seams creates a continuous vapor barrier, so moisture vapor would have nowhere to escape. Adhesion of tape to foam and wood would also be temporary, due to thermal expansion and contraction of the wall assembly. A more effective and efficient means of providing air infiltration resistance and bulk water holdout is to properly install Tyvek® weather barrier, using our best practice guidelines. Since Tyvek® tape is flexible, it will continue to provide protection to the sheathing when undergoing thermal expansion and contraction.
What type of fasteners are recommended when installing Tyvek® weather barrier?
Tyvek® WB can be installed using a variety of fasteners, depending on the application. To attach Tyvek® to wood, insulated sheathing board or exterior gypsum board, use nails with plastic washer heads, such as Tyvek® Wrap Caps. Or you may choose to use wide staples with a minimum 1-inch crown. For steel frame construction, use Tyvek® Wrap Cap Screws.
What are the recommended sealants for use with Tyvek® weather barriers?
DuPont recommends DuPont™ Residential Sealant for residential installations. For specific inquiries, please contact us.
Can Tyvek® WB be used under cedar siding?
Yes, Tyvek® DrainWrap™ can be used under cedar siding. It is recommended that the cedar siding be installed per manufacturer’s guidelines and recommendations by wood siding associations, such as the Western Red Cedar Lumber Association. This requires priming all surfaces, including the back and ends, before installing. Additionally, the use of furring strips will help promote drainage of any incidental water that may penetrate the cedar cladding.
How many rolls of Tyvek® WB are required for a typical two-story house?
For a typical two-story, 2500-square-foot house, the general rule of thumb is that two rolls of Tyvek® size 9’ x 150’ should be adequate to wrap the house. However, this estimate may vary slightly, depending on the house elevation.
Why Choose DuPont™ Tyvek® Weatherization Products?
What is the difference between a DuPont™ Tyvek® weather barrier and black paper?
Black paper, or building paper, cannot match the unique material science of DuPont™ Tyvek® WB. Unlike Tyvek®, building paper is not designed to block air flow, and can absorb water. Building paper tears more easily than Tyvek®, and can degrade over time when under continual exposure to water. Building papers are less permeable to moisture vapor transfer than Tyvek®, increasing the potential that moisture vapor trapped inside the wall could cause mold, mildew and rot.
What is the difference between DuPont™ Tyvek® weather barriers and other weather barriers?
Many other wraps are perforated, which means that in order for them to breathe, the manufacturer has punched holes in them, resulting in a reduction of air and water holdout effectiveness. DuPont™ Tyvek® WB is a non-perforated, nonwoven product with microscopic pores that are so small, air and bulk water have a difficult time passing through. But since Tyvek® is breathable, moisture vapor can easily escape from the wall.
Will duct tape work as well as Tyvek® Tape?
No. Duct tape is not designed to be used with Tyvek® sheet. Tyvek® Tape has been specifically designed to work with Tyvek® products, and should be used in all situations when sealing of the Tyvek® seams is necessary.
Does using a DuPont™ Tyvek® weather barrier help make buildings more energy efficient?
Tyvek® weather barriers can have a positive impact on energy efficiency by helping to control air and water intrusion in walls. Properly installed Tyvek® weather barriers help protect against loss of R-value in insulation due to wind washing. Even at wind speeds of 5 mph, a wall without an air barrier retains less than 40% of its original installed R-values.
In addition, Tyvek® weather barriers help keep bulk water out, to help protect insulation in walls of both residential and commercial buildings.
Can using a DuPont™ Tyvek® weather barrier help improve indoor air quality?
Tyvek® WB can improve indoor air quality by helping to reduce uncontrolled air leakage, which helps the HVAC system maintain comfortable temperatures; helping reduce the formation of mold by preventing bulk water intrusion into the wall system and allowing water vapor from inside the wall system to evaporate ; helping prevent external contaminants from entering the building.
What is the impact of the building envelope system on energy efficiency?
A 2005 National Institute of Standards and Technology study* indicates that a weather barrier, such as Tyvek® CommercialWrap®, can reduce building air leakage by as much as 85%, realizing up to a 40% savings in natural gas and up to a 25% savings in electricity, annually.
Overall, what makes DuPont™ Tyvek® weather barriers different from other products?
Four properties are critical to optimal weather barrier performance for increased energy efficiency: durability, air resistance, water resistance, and vapor permeability. Most products rate high in just one or two properties. Only Tyvek® products deliver performance across all four properties, to help create sustainable buildings that cost less to operate, are easier to maintain, and provide better comfort, year-round.
*NISTIR 7238 U.S. Department of Energy, June 2005, by S.J. Emmerich, T. McDowell, and W. Ains.