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The Importance of Rainscreen Systems

Protecting Your Home From Damaging Moisture

Furring strips are vertical pieces of wood that create a ventilation cavity when placed between the insulation and siding. They are part of an overall rainscreen system preventing moisture from damaging a home.

The Importance of Rainscreen Systems

While we all want a home that is comfortable and beautiful, we also want a solid structure made of durable materials that will last for years to come.  But the durability of our homes is threatened by environmental factors, especially wind, rain, heat, and humidity.  Incorporating a high-performance rainscreen system will help protect your home from the damaging effects of moisture.

What is a rainscreen?

A rainscreen is not actually an individual product, but part of a wall construction system.  Its overall purpose is to protect the wall sheathing from moisture that gets past the siding.   Rainscreen systems typically consist of the following components:

  • Exterior cladding (siding)
  • Ventilation and drainage cavity
  • Insulation
  • House wrap (drainage-plane material)
  • Air barrier
Rainscreen is an wall construction system that prevents moisture from damaging a home's wall sheathing.
Diagram of rainscreen system. Image by Tom Diamond and Garland Industries 

Perhaps the most important component is the ventilation and drainage cavity which provides space between the siding and the house wrap. This space is typically created by applying vertical furring strips (called strapping) over the drainage-plane material. The siding is then nailed to these wood strips.  

Furring strips are vertical pieces of wood that create a ventilation cavity when placed between the insulation and siding.  They are part of an overall rainscreen system preventing moisture from damaging a home.
Furring strips. Image by Ryan McCoon and Habitat for Humanity

Newer rainscreen products, such as Slicker, achieve the same effect by using a three-dimensional matrix with vertical channels.  These products come in a roll and are laid over the entire surface of the wall, providing a continuous space for drainage and drying.  When compared to a product like Slicker, wood strapping is generally less expensive from a material cost but is more expensive to install from a labor standpoint. Other drawbacks of strapping include the creation of hot spots along studs and trapped moisture from wood-to-wood contact, which can lead to reduced air movement and a greater potential for mold.

Slicker rainscreen provides three-dimensional matrix with vertical channels to provide a continuous space for drainage and drying.
The Slicker matrix provides airspace and vertical drainage channels across the entire wall. Image by Benjamin Obdyke/Slicker

Why would you want a rainscreen?

A rainscreen is important because the ventilation cavity promotes residual water drainage and airflow.  Any moisture held in the siding, or that seeps underneath due to wind-driven rain, will diffuse and evaporate.  If there are ventilation openings at the top (as opposed to only a weep holes at the bottom), the rainscreen provides a path for rising air.  According to homebuilder Martin Holladay, research shows that this type of ventilation is a powerful drying mechanism.   Because airflow is promoted, rainscreens have the added benefit of keeping your siding cool which prevents premature failure.

Homebuilder Mark Averill Snyde suggests the airspace provided by a ventilation cavity is especially important to prevent “capillary action.”  He compares this process to a grade-school science experiment during which a stalk of celery is placed into a glass of colored water and the water is observed to move quickly upwards. The same thing can happen to homes without proper ventilation and house wrapping. 

An example of capillary action, where water is drawn quickly upwards. Rainscreens help to prevent this.
An example of capillary action, where water is drawn quickly upwards. Image from Wikipedia.

Isn’t house wrap sufficient?

Some builders and homeowners believe house wrap (such as Tyvek, Typar, and #15 or #30 felt) provides a sufficient barrier.  But for many homes, especially those in wetter climates, it’s not enough.  The primary function of house wrap is to drain water that penetrates the siding through leaky joints or capillary action.  However, house wraps lose their water repellency over time and do very little to reduce air infiltration due to heavy winds.  Once water penetrates the house wrap into a wall, peeling paint and rotten siding often follow.  According to Joseph Lstiburekis from Building Science Corporation, back-priming wood cladding and trim and adding a ventilation cavity reduce the impact of moisture.

In addition to a rainscreen system, other methods to protect your home from water damage include:

While a rainscreen system is important for most homes, it is especially vital in climates that are wet and hot.  Some experts advise rainscreen installations for all houses in areas with an average annual rainfall of 50 inches or more.  Many coastal areas get that much rain each year, so if you’re planning to build a beach home make sure you discuss rainscreens with your contractor.


Blog by Jessica T. Smith for the Coastal Cottage Company

V-zone

Laying Concrete in V-Zones

During a hurricane, Mother Nature is a force to be reckoned with.  The intense precipitation, flooding, and high winds strip materials from buildings, including siding, roof shingles, doors, and windows.  These airborne debris are a major contributor to home damage and human injury.  Therefore, when building on the coast, it’s imperative that your home is compliant with V-zone building codes.  One building material to be very careful with is concrete.  

V-zone
Large pieces of broken concrete can damage buildings and harm people. Image by Mark Wolfe, courtesy of FEMA

Forceful waters and high velocity winds can cause concrete slabs to hydroplane, flip, or break into large chunks that could damage buildings and injure, even kill, people.  As a result, building codes require such slabs be of frangible concrete.  This means they are designed to break into smaller pieces which will sink rather than travel.  So when constructing driveways, pool decks, and patios, it’s important your contractor follows these guidelines:

  • No reinforcement should be used
  • Slabs should not be thicker than four inches
  • Slabs must remain structurally independent of the building
  • Control joints must be spaced at 4-foot squares to encourage even breaking

When laying cement in V-zone areas, proper control joint spacing and depth are essential.  According to the Portland Cement Association, placing control joints in the concrete surface at strategic locations creates weakened planes allowing the concrete to crack evenly.  Spacing the control joints at 4-foot squares ensures the concrete will break into smaller pieces which will cause less damage during hurricanes.

Control joints may be tooled into the concrete surface at the time of placement or they may be sawed into the hardened concrete.  Regardless, control joints should be cut to a depth of ¼ the slab thickness.

V-zone
Control joint. Image courtesy of Portland Cement Association.

Not only is this control joint approach safer, it also produces a more aesthetically pleasing appearance since the crack forms below the finished concrete surface. This method can reduce the amount of hairline cracks on the surface of the cement.

So, when building your vacation home or remodeling to add a backyard oasis, make sure you only work with licensed contractors who are familiar with V-zone construction and the importance of cement control joints.  If you’d like to learn more about concrete, check out our post about reducing surface cracking.


Blog by Jessica T. Smith for the Coastal Cottage Company

hurricane fabric

Boarding Up with Hurricane Fabric

HURRICANE FABRIC: THE FUTURE OF STORM PROTECTION 


hurricane-fabric-astroguard-outerbanksAs a homeowner in a coastal area prone to Hurricanes, you have probably considered hurricane panels at one time or another.  Hurricane panels or shutters protect your home from damaging winds, driving rain and flying debris often associated with hurricanes and severe storms.

In the past, hurricane panels took the form of plywood, metal and corrugated lexan. The materials used for these panels typically produce heavy, cumbersome panels which require a massive storage area when the panels are not in use. A typical rigid panel is mounted on tracks, protruding anchors or brackets which often remain in place even when the panel is not in use. This hardware is unsightly and detracts from the overall aesthetic of your home. In addition, installation of most rigid panels will require the help of two or more people to position and attach the panels to the openings. Rigid panels such as plywood, metal and lexan can be dangerous if you are installing the panels in a high wind situation. Don’t worry, there are less dangerous alternatives. 

Times and technologies have changed and given rise to a new option in the fight against the storms fury. Introducing hurricane fabric panels, yes fabric! Advancements in fabric technology have given rise to the fabric hurricane panel. Fabric panels are typically made from polypropylene mesh or a layer of woven fabric that is coated with a geo-synthetic PVC material, in some cases, Kevlar. So how do they stack up against their competition? 

plywood-hurricane-shutters-outerbanksCOST: At only $3 – $5 sf installed, plywood is the least expensive storm panel on the market.  Rigid steel corrugated panels, average between  $10-$14 sf installed.  Accordion style storm shutters can be installed in the $18-$28 sf range. The fabric panel is the second least expensive panel on the market at $9 – $12 per square foot professionally installed. 

DEPLOYMENT: Fabric hurricane panels are extremely lightweight and easy to handle. After the initial installation, panel deployment can be handled by one person. On the other hand, rigid panels (i.e. plywood, metal and lexan shutters) are awkward, cumbersome and heavy requiring multiple people to install. Fabric has a clear advantage when it comes time to deploy the panels; they are lightweight and easy to handle. 

corrugated-metal-hurricane-storm-panelIMPACT RESISTANCE: Resistance from flying debris impacts is typically the main deciding factor when choosing a shutter system. Independant tests have proven that some fabric hurricane panels can withstand Category 5 impact testing as well or better than rigid panels. Fabric panels are designed to absorb the impact by deflecting and slowing the projectile. Rigid panels are designed to simply resist the impact by shear strength of the material. Fabric panels have proven they can  match and exceed rigid panels in all impact tests and do it at a lesser cost to the owner. 

INTRUSION: During a hurricane, wind and rain are a major cause of damage to a home. High winds drive rain into small cracks and crevices in and around windows and doors. Fabric panels are both water and wind proof. Fabric panels are available in custom cuts and sizes allowing the installation of one seamless panel across the entire opening. On the other hand, the rigid panel is limited to its size and weight restrictions. The use of multiple rigid panels can create cracks and crevices at panel joints which invite both wind and water leaks.  The fabrics ability to span large openings gives it a slight advantage here. 

lexan-storm-panels-obx-hurricaneAESTHETICS: If you have visited a hurricane prone area, you might have noticed unsightly metal panel anchors or tracks mounted around the windows and doors. Even worse massive roll shutters permanently mounted above and around the door. Some people don’t give it a second glance but if you’re like me, you notice how debilitating it is to the overall architecture of your home. Fabric panels require minimal hardware. Often times the mounting hardware is set flush with the window trim surface and even painted to be virtually invisible. 

GLASS BREAKAGE: Ok, this is where the fabric panel takes a backseat to the rigid panel. A typical storm panel, rigid or fabric, will be installed approximately 1″-2″ outward of the window/door it protects. During an impact from flying debris, the panel deflects inward toward the window. If it deflects too far, the impact will break the window behind the panel. In this scenario, the more rigid the panel the lesser the deflection and the lesser the chance of breaking the window. 

outerbanks-storm-protection-panels-astroguard-fabricSTORAGE-MAINTENANCE: Clearly the fabric panel will prevail here. All rigid panels require a massive amount of space for storage. Storage should be indoors so the elements don’t affect them. Plywood rots and warps, Steel rusts and Lexan degrades from UV rays. Fabric panels will not rot, rust, break or degrade. After use, the fabric panels can be hosed off, folded up like curtains, placed in storage bags and stored in an attic, shed or closet. Fabric shutters are near maintenance free,  require minimal storage space and are easy to store. 

In conclusion, fabric hurricane panels are an inexpensive, lightweight, easy to install, impact resistant, attractive, low maintenance solution to cumbersome, unsightly rigid storm panels on the market today. 


-blog provided by Michael York, The Coastal Cottage Company – www.coastalcottageobx.com

  

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