How do you stop water from getting into your house and, at the same time, get rid of any moisture that got in? Use a drainwrap or a housewrap. But the challenge is to determine which product is appropriate for your home.
Housewraps are great for overall home weatherization, as they keep air and water out while allowing vapor to escape. At the same time, drainwraps are better suited to venues with a rainy climate and communities where fiber cement siding is common, as it tends to retain water.
Read on for the details of each product’s merits and to find out which one suits your particular situation.
Benefits of Drainwraps
Protect From Water Damage
They protect houses against water seepage by providing enhanced drainage behind claddings. They were created to safely siphon bulk water away from wall systems. They are excellent moisture deterrents.
They are better at draining than standard non-perforated housewraps. The best drainwraps are durable and sustain a steady drainage rate even after multiple wetting and drying cycles.
A leading brand is the DuPont™ Tyvek® DrainWrap™. It is available from the DuPont website or from Spring Lake Park Lumber Company, which stocks 9’x125’ rolls. Drainwraps are also available in 10-foot rolls.
Provide Air Resistance
Apart from providing water defense, they combine the superior air resistance, vapor permeability, and strength of housewraps with vertically grooved surfaces to drive water safely away from wall cavities.
They assist insulation in performing closer to its total R-value, making homes more energy-efficient.
Protect Against Mold and Mildew
Their moderate to high-vapor permeability encourages drying in wall systems to prevent mildew and mold formation.
They are pliable and easily wrap around corners and interfaces at joints. They complement architectural elements.
Easy to Install
Being lightweight, they are fast and easy to handle and install.
Drain Better Than Wrinkled Housewraps
Green Building Advisor’s Martin Holladay claims that wrap combinations of conventional weather-resistive barriers (WRBs) and three-dimensional plastic drainage mats, such as the Home Slicker Plus Typar, provide better drainage than wrinkled housewraps.
You may choose to install individual Obdyke Slicker rain screens over your chosen housewrap or buy the two-in-one mentioned above, which is a combination of non-woven, spun-bonded Typar Building Wrap attached to a mesh.
Better for Fiber Cement Siding
They are appropriate for use with fiber cement siding because they have vertical ribs. These are better at draining, as opposed to the flat surfaces of housewraps.
Benefits of Housewraps
Excellent Water Deterrents
A housewrap is a WRB installed between the cladding layer and the sheathing as a form of defense against the elements. It is an important tool builders use to prevent water from entering a house.
In the old days, builders depended on wall claddings as barriers against water. But they leak, regardless of the material covering exterior walls. This is why dwellings that weren’t as properly insulated or securely built were at the mercy of water infiltrating the back portion of the siding and staining items stuck on walls, like wallpaper. Claddings, however, were at least useful for rot prevention.
Act As Wall Defense
Regardless of composition, all housewraps contribute to wall protection. Some housewraps are made from a weave of synthetic polypropylene. Others include tiny perforations that release moisture. Others consist of spun fibers bonded together. The last fabric type is water-resistant but also allows water vapor to escape. The DuPont™ Tyvek® HomeWrap™ is an example.
Prevent Air Infiltration
A housewrap’s main purpose is barring water infiltration. But it is also an efficient air deterrent. This function has become more significant as building codes get stricter. The 2012 IECC, for instance, has elevated air leakage standards for home construction by requiring both visual inspection and blower door trials.
Housewrap air permeability differs per brand. Perforated wraps have holes punched in them, which help in air reduction and water holdout effectiveness. Non-perforated versions are usually better barriers against air penetration than perforated types.
Some housewraps are vapor-permeable, like Tyvek. This means they are breathable, allowing vapor to pass through them. Tyvek is a non-perforated, non-woven product with microscopic pores that prevent air and bulk water from passing through but allow moisture to escape.
Others are vapor-impermeable, like foil-faced polyisocyanurate. Both work well, provided the wall assembly is engineered to dry out when it gets damp.
Improve Domestic Energy Efficiency
Housewraps reduce energy bills by controlling airflow and water intrusion, contributing to better insulation and making HVAC systems work more efficiently.
Franklin and Associates did a study in 2000 that claimed that correctly installed housewraps reduce the energy needed to heat and cool infiltrated air by 10 to 50%. This means yearly energy savings of 12 to 60.2 million Btu for a regular household.
Synthetic housewraps are lightweight, durable, and come in large-width, nine-foot rolls, making them quick and easy to install.
Housewraps are equally effective in both directions—with the lettering facing in or out.
They can also be used under or over sheathing. When used under sheathing, however, housewraps function only as air barriers and do not protect the sheathing as secondary water barriers.
The VP 100 can be applied to concrete block, steel, galvanized metal, aluminum, plywood, and wood. As it doesn’t need fasteners, it significantly minimizes the entryways through which air and water can flow.
Minimize Building Maintenance
As they create a physical separation between the interior and exterior of buildings, they reduce air and water infiltration, preventing drafts and water damage. This improves building durability, eliminating the need for constant monitoring and building repairs.
Provide All-Season Protection
They are designed to keep homes cool in the summer, warm in the winter, and dry throughout the year.
Housewraps Have Evolved to Include Creative Innovations
The modern housewrap combines moisture resistance and breathability with air-sealing benefits. Innovations to the original design include liquid-applied versions, drainable models, insulated kinds, and peel-and-stick types. The last one doesn’t need taping or fastening. Insulated housewraps came about because of the use of rigid foam exterior insulation with regular housewraps.
The housewrap isn’t perfect, however. For a proper air seal, it still requires sealing the laps and places where the wrap ends. This is why insulated housewraps are valued.
An example of a multipurpose wrap is the HydroGap® Drainable Housewrap. It combines the benefits of housewraps and drainwraps. Its manufacturer claims that it is the best performing drainable housewrap on the market due to its patent-pending one-millimeter spacers that allow at least 100 times more bulk water to drain from a wall compared to standard housewraps.
Trials by the independent CTL Group show that HydroGap removes over 93% of bulk water. This is significant because major siding manufacturers like Boral and James Hardie have issued new drainage requirements for their products. They now require or recommend only housewraps with a drainage efficiency of at least 90% to be installed behind their exterior sidings.
Apart from drainage efficiency, another important factor to consider when choosing a wrap is how fast it removes moisture. The longer moisture remains trapped, the more chances it has to cause mold, rot, and premature structure failure. The HydroGap eliminates excess moisture in a matter of minutes. Its unique design provides up to two times the performance over other drainable housewraps.
The HydroGap and the TamlynWrap® are rare housewraps that have true drainage capabilities. With other wraps, you have to add another product to create a drainage gap, like meshes or furring strips. Both these wraps have rain screens attached to their membranes, yet they install like regular housewraps. You don’t have to change the structure, unlike when you install furring strips.
Limitations of Both Wraps
- Both the Tyvek HomeWrap and DrainWrap can be exposed for less than 120 days before siding. They should be covered before this period is over. The commercial version should be covered within 270 days. Coverage is essential to guard against excessive UV exposure.
In comparison, the VP 100 is not designed for permanent exposure beyond 150 days. Also, after application, the membrane must be rolled to make sure the product adheres to the substrate and laps. The VP 100 may not bond well in colder temperatures below 40 degrees.
- The warranty for the Tyvek DrainWrap is only valid if you use three-inch tape and the grooves are installed vertically.
- The HydroGap may be a great moisture eliminator, but with a drainage gap of about 1/32”, it is not a rain screen.
Criteria of Choice
To stop air and moisture infiltration into wall systems while protecting the sheathing, housewraps and drainwraps need to provide the right balance of elements. They also have to withstand the rigors of construction and resist damage.
Consider these parameters when choosing housewraps and drainwraps:
- water resistance
- air resistance
- vapor permeability
- drainage efficiency
- fire rating
Choosing the best housewrap or drainwrap that can withstand the elements all-season will protect your home for many years to come. That’s why it’s vital to make the right selection. If you can’t decide between the two, try combining either of them with other barrier products, such as rain screens.
If still on the fence, you can opt for a hybrid, which combines the advantages of both weather-protective products.
- Wikipedia: Housewrap
- Wiki How: How to Install Tyvek
- Shanco: What Is Housewrap?
- DuPont: DuPont Tyvek HomeWrap—the Superior Housewrap
- DuPont: A moisture barrier proven to hold out bulk water
- DuPont: Building Envelope FAQ
- Fine Line Homes: Tyvek HomeWrap vs Other House Products
- Tyvek Construction: HomeWrap vs Perforated Wrap
- Real Cedar: Tyvek Drainwrap and Flexwrap Installation
- Spring Lake Park Lumber Company: DuPont Tyvek DrainWrap
- DIY Home Center: Common Questions
- Barricade Building Products: Housewrap vs Felt Paper—Which Is the Better WRB?
- Barricade Building Products: Comparing Home Construction House Wraps—Typar vs Tyvek
- Houzz: Housewrap vs Drainage Wrap?
- Canal Front Builders: Housewraps—What’s the difference and why does it matter?
- SBC Magazine: Reviewing the Good, Better, and Best Water Resistant Barriers
- Houzz: Tyvek DrainWrap vs Tyvek HomeWrap with James Hardie Lap Siding
- Hydrogap: Hydrogap Drainable Housewrap
- Benjamin Obdyke: Hydrogap Drainable Housewrap
- Green Builder Media: Housewrap—What’s the Difference?
- Green Building Advisor: All About Water-Resistive Barriers
- The Journal of Light Construction: Weather Barrier Update—Good, Better, and Best
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