Housewrap for Building a Tight Home

Housewrap on New Home

One of the biggest reasons people choose to build a new home is to add all the latest technologies and building techniques to create a high performing structure.  Older homes in many cases have insulation and moisture problems that can create mold, increase maintenance, and lead to higher energy costs.  One of the ways we can increase the performance of new homes (and old homes when siding is being replaced) is by adding housewrap.  But what exactly is housewrap, how do you compare the many options on the market, and what are some best practices for installation?

What is Housewrap?

To put it as plainly as possible, housewrap is the paper-like product installed on the exterior walls of a home prior to the installation of siding.  Housewrap helps to weatherize new homes prior to getting the siding installed.  Depending on how the new home schedule is managed, it can take several months to finish up all of the stone, brick and other claddings on the exterior of the building.  By having housewrap installed early on in the process, the home is essentially weather tight so interior work can continue.  Be sure to read the manufacturer’s information prior to choosing a housewrap for this purpose.  Most materials are only good for so long when exposed on the exterior of building.  Why?  The sun degrades the material in many cases and can render it useless if left uncovered for too long.

So that’s a great reason to have housewrap installed during construction but what are the benefits to the occupants once the home is finished?  Here are some of the major reasons for considering housewrap for your new home…

• Secondary Drainage Plane – No matter what kind of exterior wall cladding is used, water will ultimately get behind and through it.  Brick and stone absorb moisture.  Vinyl siding has all kinds of gaps that let water in.  And even if the original siding is completely sealed, the caulk can degrade over time leaving it susceptible to leaks.  So the housewrap behind the siding acts as a secondary barrier to the water intrusion.
• Air Seal – When housewrap is installed correctly, it can help to seal up all the small cracks and crevices left in a framed wall when finished.  By spanning over these openings, the housewrap helps to slow down air movement through the wall.  This improves energy efficiency and cuts down on drafts in the home.
• Allows Moisture to Escape – The interior of every home has moisture that’s created by breathing, taking showers, humidifiers, cooking, exterior siding breaches,…etc.  A very important part of the home design process is creating a structure that will breath so this moisture doesn’t create air quality issues and premature degradation of building materials.  Most housewraps are designed to allow moisture to escape from behind it to allow the home to breathe.

There’s also a new housewrap on the market created by Dupont (Tyvek Brand) that has an R-Value of 5.0.  You can check it out here.

Best Practices for Installation

Just like every other product installed in a new home, it’s important to follow best practices and manufacturer recommendations when installing housewrap.  Why go to the added expense of the material and extra labor for housewrap only to miss the detailed requirements of a proper installation and negate the benefits of having the product?  Here are a few tips for a proper installation (be sure to read the manufacturer’s direction as well and make sure your carpenter knows them prior to installation):

• Cladding – Make sure the housewrap is designed to work behind your particular exterior cladding choice.  For example, not all housewraps should be installed behind brick or stone.
• Lap Joints – For horizontal joints in housewrap, there should be an overlap of at least six inches (or per manufacturer rec’s) and the top piece should always overlap the piece below to properly shed water.
• Taped Seam – For best installation, all seams in the material should be sealed with a compatible, high quality tape.
• Gables – Just because your attic doesn’t have living space, doesn’t mean the exterior walls shouldn’t have housewrap installed.  Remember, the wrap functions as a secondary drainage plane to keep rainwater out so it’s imperative that gable ends be covered.
• Fasteners – Cap nails are the best…these are those nails that come with a big flat area to keep the material from pulling through.  Be sure to use what the manufacturer suggests and be sure the spacing is also per their recommendations.
• Penetrations – Any hole in the wall (examples = windows, vents, doors…etc.) require special attention to allow the drainage plane to keep water out of the wall cavity.  The housewrap above openings should be lapped out over top of the openings when possible.  Flanges should be taped to the adjacent housewrap on the sides and bottom per the manufacturer recommendations.
• Roof to Wall Intersections – When a wall is located above a roof plane, the housewrap should lap over top of the roof flashing.  This will direct any water that gets behind the siding out onto the roof.  See photo below.

Housewrap Ready to be Lapped over Roof Flashing

Comparing Different Housewrap Options

So how does one compare the many options available out there?  First, don’t go by price alone.  Remember, a big portion of the cost will be in the installation so don’t go cheap on the material as it really won’t save you all that much.  When comparing your options, check to make sure any materials you are looking at will work with all the types of cladding on the home.  Also check the stability of the material prior to cladding installation.  Meaning, how long will it last when exposed to the sun prior to siding, brick or stone installation?  And how about that warranty?  What is covered and for how long?  Below is a video showing how the water resistance of housewrap can be tested.

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