Housewrap Air Barrier
Air Infiltration Barriers Housewraps
Manufacturers - Installation
Christmas in July. That is what I used to think when we put housewrap on a summertime project. In fact, I would, depending upon the outside temperature (if it was too hot, I would be grumpy), even make a big flat bow(using the seam tape) on the front of the house when the installation was complete. The housewrap, the colored tape for the seams, and the bow made a new home look like a big Christmas gift box.
Plastic Wrap - - That's It!
All of the new housewrap products are simply thin plastic in big rolls. There is poly this and poly that but the bottom line is that the plastics are specially formulated to stop air infiltration and act as a water barrier. Because they are plastic, you need to handle them differently and use special tapes, fasteners and care when installing. Without this care, you are wasting your time as well as future energy dollars.
The housewraps must not be compared to plastic food wrap you use in your refrigerator. These do not usually allow water vapor transmission. Housewraps, however, must be able to breathe. Water vapor created inside your house must not be blocked as it makes its way to the outside atmosphere. Some housewraps actually let water vapor pass between the fibers, while other have very tiny holes poked in them.
Felt Substitute? ... Maybe
Housewraps were introduced in the late 1970's. Prior to that the only way to prevent water from getting to wall sheathing or the inside of your house was to use asphalt saturated felt paper. It has a proven track record and is still used in many applications.
I renovated many a home in my career. Most of these houses had felt paper beneath the wood siding, cement stucco, or other outer covering. Sure, after 50 - 70 years the felt was brittle, but it could still repel water! In fact, in many instances, felt paper does a better job of keeping out water around the actual fasteners. Some of the plastic housewraps can and do leak if concentrated amounts of water are directed at fastener locations. As far as I'm concerned, this isn't a major problem, since the housewrap is not supposed to be the primary water barricade!
Tough To Compare Brands
If you are shopping for a housewrap, good luck! It is almost impossible to compare performance characteristics. Why, you ask? Because the manufacturers do not have to use the same testing procedures, that's why. Each manufacturer can use a test which makes their product look the best in each aspect of testing. Thus, you are comparing apples to oranges to onions.
Not to worry, however. All in all, just about any housewrap, properly installed, will significantly help you with regards to air & moisture infiltration.
Housewraps save you energy by slowing down or stopping the movement of air through insulation. You know those R- values you hear so much about? Well, those R-values are achieved in test cells where there is virtually no air movement! Air moving through insulation lowers its R-value, plain and simple.
Installation Is Critical
If you think a bunch of bottom feeders are going to install your housewrap, you had better take the day off and supervise them! If the installation is sloppy, you are simply not going to achieve the many benefits these wonderful products offer.
The products must be installed so pieces higher on a wall overlap lower pieces. All holes, seams, edges, etc. must be taped. Flashing details at windows and doors are critical. Tight installation at inside corners is a must. Minimal exposure to sunlight is also important depending upon which product you choose. Just about every one of these plastic wraps begins to degrade when exposed to sunlight. Top performance occurs when you cover them rapidly with brick, siding, or stucco.
Whether you decide to build a new home or a room addition, seriously consider the use of these great products. They can save you money and prevent moisture problems. The old master builders who used felt knew what they were doing. We need to continue in their footsteps when building. Fortunately, we now have a product that can do just a little bit better than felt paper!
Air Barrier Installation Tips & Suggestions
Cheap Sunglasses ......
Have you got your air barrier? Is it a white product? If so, you had better get some sun-glasses. These products are brilliant white and will hurt your eyes, trust me! The darker products are definitely easier on the eyes.
Read The Instructions
You might know that I am a big fan of reading instructions. Not all housewraps install in the same fashion. Certain brands have a definite inside and outside face. Install it backwards and you might not get any water protection! Also, specific tapes have to be used for different housewraps. You can not simply use duct tape or masking tape!!! Nails are important. Some housewraps require large headed fasteners.
Start At The Bottom
Housewraps shed water. This means that the lowest level piece must be overlapped by successively higher pieces, much like roofing shingles. Also, the housewrap needs to overlap brick flashing. If you are using vinyl or wood siding, make sure the housewrap overlaps the top of the foundation. A 3/4 inch overlap will prevent water from getting on top of the foundation and into your house.
Proper Timing For Installation
Housewraps go in before the windows and doors! You simply cover over these openings as you install the material. After the house is wrapped, you come back and slice an X at the window/door locations from corner to corner. Wrap the material inside the opening, fasten to the face of the rough jamb, and trim off excess. Do not put nails within 4 inches of the top of the openings over windows and doors. Why? If your windows and doors come with preformed /flashed vinyl or aluminum nailing flanges, I would like to see you carefully slice the housewrap at the top of the window opening. Slide the window nailing flange (TOP ONLY!) under the housewrap. Tape it to the window after this is complete. This prevents water from getting behind the window.
Watch those inside corners!! The house wrap MUST be very tight. If it pulls away because you do not nail it tightly in the corner, your bricklayers, and/or siding people will slice it!
Keep It Level
When you start, put one single nail at the top. Unroll 15 - 20 feet and align with the top of the foundation (1 inch over, remember!). After the housewrap is aligned, then nail. Nail sideways from top to bottom to remove wrinkles.
You will not be able to install housewrap by yourself. Count on using a minimum of one helper. It takes one person just to hold the roll and keep it taut.
Install the top of the housewrap between the top two wall plates if possible. If not, be sure the top is taped to the wall or else soffit downdrafts will keep you cold!!!
Manufacturers & Comparative Data
The following is a listing of manufacturers of air infiltration housewraps. Remember that there is NO uniform standard for comparing performance! Accckkkk!!! So, you need to look for which characteristic (air infiltration, tear resistance, UV degradation, water vapor transmission, etc.) is of most importance to you. All of the products will perform well in my opinion. They KEY to performance is based much more so on installation than the product itself. You can buy the best air barrier and it will be worthless if installed poorly.
- ABTCO, Inc. ... 800-521-4250
They make Prowrap. It is a perforated cross laminated polyethylene. Prowrap is 3 mils thick, white in color, and should not be exposed to sunlight for more than 6 months. ABTCO sells special sealing tape.
- Amoco Foam Products ... 800-241-4402
They make Amowrap. It is a perforated, polyolefin-coated woven polypropylene. Amowrap is 8 mils thick, green in color, and should not be exposed to sunlight for more than 12 months.
- Celotex Corp. ... 813-873-1700
Celotex makes Tuff Wrap. It is a perforated polyethylene-coated woven polyethylene. Tuff Wrap is 5 mils thick and white in color. It is a good idea to cover this stuff within 3 months.
- Du Pont ... 800-44-TYVEK
Du Pont makes Tyvek, the original housewrap. Tyvek is a spun bonded polyethylene. Tyvek is about 4.5 mils thick and brilliant white in color. It should not be exposed to sunlight for more than 4 months. 3M makes a special seam tape for Tyvek. It is fire engine red.
- Parsec, Inc. ... 800-527-3454
They make Airtight Wrap. It is a perforated, cross laminated polyethylene. It is blue in color and 4 mils thick. You can leave this product exposed for about 4 months.
- Raven Industries ... 800-635-3456
Raven makes Rufco-Wrap. It is a perforated, cross laminated polyethylene. Rufco-Wrap is white in color and 3 mils thick. Evidently, it can be exposed to sunlight for up to 6 months.
- Reemay, Inc. ... 800-321-6271
Reemay makes Typar. Typar is a perforated spun bonded polypropylene coated polypropylene. It is silver colored and is about 7 mils thick. Reemay says that you can leave it in the sun for a long (unlimited) time without damage.
Air Leak Alternative Product
By now you figured out that air leakage occurs primarily at joints - where things abut one another. So, you might ask, why not simply tape these joints? Well, good idea! One company makes a product that claims to be able to do just that. Benjamin Obdyke 800-523-5261 makes a tape called Gap Wrap. It sticks to virtually anything and is applied using a handy dispenser just like you see people use to tape shipping boxes. The reasoning behind this product is sound - i.e. tape the gaps where air is entering. However, I feel that the installation of a water barrier is just as important. This tape method does not address this concern. If you tape over plywood joints, the plywood is still exposed behind brick veneer, vinyl siding, and/or wood siding. Water that gets behind these things can and will rot cellulose based products.