Proper Window Installation

Due to the types of windows as well as the differences in window quality and fenestration materials, proper window installation is an expansive, varied, and detailed topic. For example, ASTM E 2112-01: Standard Practice for Installation of Exterior Windows, Doors and Skylights is an 83 page document. The introduction devotes two paragraphs in specifying rainwater leakage as the most important factor in window performance. To quote the text, “…this practice places greater emphasis on preventing or limiting rainwater leakage than on any other single performance characteristic.” An article appearing in the April 2002 edition of Window & Door cites that eight to nine out of ten windows are improperly installed. Window leakage is the major culprit.

This is clearly a training issue and the industry has begun to take steps in attempting to remediate this problem. Consultant Barry Hardman of Hardman Associates gave a presentation concerning improper window installation at the BETEC 2003 Spring Symposium M4: “Mold, Moisture, Misery and Money” in which he cited improper construction techniques and sequencing as being the main mechanism of water/moisture infiltration. He goes on to underline the importance of training and of viewing window installation as a multifaceted and exact task. A successfully installed unit is based on the quality and correct use of its parts – laxity in any one area causes the entire system to fail. To quote Mr. Hardman, “We need to have serious national training to installers for both fenestration and fixture type products; and membrane, flashing, siding, and cladding trades. More importantly, they need to be taught that their trade, although standing alone, is in fact part of an integral building envelope, and they must be taught integration methods and be conscious about making sure that integration has taken place.”

Though it is difficult to make all-encompassing generalizations, these can be said to hold true:

• A window unit is only as good as its installation. Poor installation equals assured failure.
• The better the unit and the installation components, the better the performance, the protection from leakage and the durability of the unit.
• The U-value of a window is dependant on the insulation of the shim space.

In addressing the importance of insulating the shim space of a window, one can see that Handi-Seal®, an expanding, low pressure build, closed-cell, polyurethane foam has marked advantages to that of chinking fiberglass. The use of these types of foams provide for an air barrier and act to retard moisture infiltration as well as secure the window and reduce vibration by bonding to the window sill, jambs and rough opening. They serve to enhance the quality and performance of the window as well as provide for another layer of protection in preventing rain water from entering the home.

Even within this small part of the total installation, training becomes important. Many installers will use polyurethane foam indiscriminately – viewing them as the same. Only low pressure build foams should be used in window installation, those not generating more than 2 psig as sited by the testing protocol in AAMA 812-04. There is an erroneous conception in the industry that minimum expansion produces minimum pressure. In reality minimum expanding foams tend to generate pressures higher than 2 psig. To illustrate, soap bubbles expand greatly yet produce little pressure while water when freezing and slightly expanding to ice produces pressures great enough to heave sidewalks. Likewise, not all low pressure build foams are of the same quality. Many of the low pressure build foams do so by sacrificing the desirable quality of being closed-cell foams. Handi-Seal® Window and Door foam is both low pressure and closed-cell. In closing, the following generalizations can be made:

• In order to prevent window distortion or jamming, use only low pressure build foams.
• Maximum expanding foams will give better yields and coverage.
• Closed-cell foams are better than open-cell foams.

This information is provided as a service, and is not necessarily meant to reflect any recommendation, guideline or position of Fomo Products, Inc. Each individual user must determine product suitability for any particular purpose.