Archive for August, 2010

Failed dual paned windows

Monday, August 23rd, 2010
One of the most common findings a property inspector observes, and one of the most taxing to not only the owner of a property, but to the prospective buyer and both agents involved in the sales transaction is "Failed Windows". Failed hermetic seals ( failed glazing) is most commonly found in early generation dual paned windows, those that were manufactured between the early 80's – up to the late 90's and even in some instances, the early 2000's. Since, most window vendors have refined the process of manufacturing these windows, and failed seals are not as common.
The following article was written by Nick Gromicko, Rob London and Kenton Shepard
Why Double-Paned Windows Fail – Solar (Thermal) Pumping
Although double-paned windows appear to be stable, they actually experience a daily cycle of expansion and contraction caused by “thermal pumping.” Sunlight heats the airspace between the panes and causes the gas there to heat up and pressurize. Expanding gas cannot leave the chamber between the panes and causes the glass to bulge outward during the day and contract at night to accommodate the changing pressures. This motion acts like the bellows of a forge, pumping minute amounts of air in and out of the airspace between the panes. Over time, the constant pressure fluctuations caused by thermal pumping will stress the seal and challenge its ability to prevent the flow of gas in and out of the window chamber. Incoming humid air has the potential to condense on the window surface, if it is cold enough.
Can Failed Windows be Repaired?
Inspectors should be aware that there are companies that claim to be able to repair misty windows through a process known as “defogging.”
This repair method proceeds in the following order:
  1. A hole is drilled into the window, usually from the outside, and a cleaning solution is sprayed into the air chamber.
  2. The solution and any other moisture are sucked out through a vacuum.
  3. A defogger device is permanently inserted into the hole that will allow the release of moisture during thermal pumping.
Inspectors should know that there is currently a debate as to whether this process is a suitable repair for windows that have failed or if it merely removes the symptom of this failure. Condensation appears between double-paned windows when the seal is compromised and removal of this water will not fix the seal itself. A window “repaired” in this manner, although absent of condensation, might not provide any additional insulation. This method is still fairly new and opinions about its effectiveness range widely. Regardless, “defogging” certainly allows for cosmetic improvement, which is of some value to homeowners. It also removes any potential damage caused by condensation in the form of mold or rot. Thanks to the authors of this article.
In my opinion, as in all new products, this method has yet to be time tested, and it is more sensible to replace any failed windows

Duct tape should not be used to seal ducting

Tuesday, August 17th, 2010

When conducting an inspection of the components within a crawl space, which includes a general observation of the ducting for the heating and cooling system of a residence, I sometimes come across sections of ducting that are disconnected at the joints, or very poorly sealed. I don't make an attempt to remove any ducting insulation that is perfectly intact in order to view the joints in the ducts. In instances where the insulation (if present) is loose, damaged, or missing, and the joints are clearly viewable, I will have a look at random samples of these joints. I commonly find that duct tape was used to seal the joints, and the tape has become very frail and sometimes so damaged that there are joint separations which allows heat or cooled air to treat the air within the crawl space. This means less treated air into the rooms of the house which in turn is very inefficient and costly.

As the name implies, one would naturally expect to find Duct tape used to seal the joints in the ducting for heating and ventilation in buildings, however, it is not intened to be used for such purpose, and is not what a property inspector wants to find when examining the ducting.   Duct tape   is a polyethylene, reinforced, multi-purpose pressure sensitive tape with a soft and flexible shell and pressure sensitive adhesive. It is generally silver or black in color but many other colors have recently become available, and can be purchased at hardware stores, and some drug stores and super markets. It has many uses, and can be found among the tool collection of most home owners.

Duct tape was never intended to be used to seal ducting, Originally developed in 1942, during World War II as a water resistant sealing tape for ammunition cases. Permacel, then a division of Johnson & Johnson, used a rubber-based adhesive to help the tape resist water and a fabric backing to add strength. It was also used to repair military equipment quickly, including jeeps, firearms, and aircraft because of these properties.

To provide lab data about which sealants and tapes last, and which are likely to fail, research was conducted at Lawrence Berkeley National Laboratory Environmental Energy Technologies Division. Their major conclusion was that one should not use duct tape to seal ducts (specialty tapes are available for this purpose). (They defined duct tape as any fabric-based tape with rubber adhesive.) The testing done shows that under challenging but realistic conditions, duct tapes become brittle and may fail. It is very common for me to find duct tape that has become very frail, and in most instances, is allowing a significant amount of heated or air conditioned air to escape the ducting instead of through them to the registers in the room of the building. This means the system is not very efficient, and is costing the property owner money to condition the air in either the attic or the crawl space under the building, (where ever the systems ducting is located). Commonly duct tape carries no safety certifications such as UL or Proposition 65, which means the tape can violently burn, produce toxic smoke, ingestion and contact toxicity, irregular mechanical strength, and low life expectancy for the adhesive on the tape. Its use in ducts has been prohibited by the state of California, and by building codes in most other places in the U.S. However, metalized and aluminum tapes used by professionals are still often called "duck/duct tapes".