Attic Ambush

A new Fort Collins home, built by a large production builder, was completed in mid-summer 1999. It was a simple design: a compact ranch with a finished basement, totaling 1900 square feet. The home was purchased by the parents of a Colorado State University student as an investment and place for their daughter and her college roommates to live.

The occupants moved into their new home in August and immediately noticed major comfort problems. All main floor rooms consistently ran too warm—78 degrees Fahrenheit with the air conditioner running virtually full time. Meanwhile, the basement bedroom was consistently too cold—63 degrees even with some supply registers closed. In response to complaints, the builder sent their heating contractor back twice to solve the problem. Some limited duct sealing and minor adjustments to the air conditioning system improved comfort only marginally. The occupants concluded, “Oh well, that must be the way new homes are” and decided to live with the problems. But in October they were puzzled that the air conditioner would run during the day, then the furnace would run at night. By December, they had the builder back to check on their furnace, because the main level was never really comfortable (even when the air temperature registered 68 degrees), while the basement was too hot (75 degrees).

The problem, quickly discovered in a January 2000 site visit by City staff: no attic insulation. Yet the code-required Insulation Disclosure form, on file at B&Z, signed by the insulation contractor, documented 12 inches of an unidentified insulation material, rated R-38, in the attic. Once the builder was notified of the problem, insulation was installed within 48 hours. The comfort of the home improved dramatically with this change.

The missing insulation was clearly an oversight, never caught by quality control. Apparently neither the insulation contractor, the builder, nor the City’s inspectors ever looked in the attic. There was also clearly a major failure in the builder’s callback response; the problem was not identified in at least three return trips to the house. As a result, the owners paid an estimated $150 more than necessary to heat and cool the home. The occupants put up with miserable comfort for six months and were generally jaded about new homes. The builder’s site superintendent wasted time on the phone dealing with callbacks, and the heating contractor spent unproductive time visiting and trying to fix problems. The builder had already paid the insulator for a job never performed.

The missing attic insulation was the biggest single problem in this home – one that fortunately was easy to remedy. Yet City staff (using a blower door, infrared camera, pressure gauge and smoke source) compiled a list of other problems:

• Whole house air leakage. A blower-door test showed that the house was about one-third leakier than the average Fort Collins new home. Numerous leaks to the attic were observed, including connections between the attic and return air duct system.

• Thermal bypasses. One wall, framed 12” thick to avoid building a ledge at the top of the foundation, provided air space for thermal convection and leakage connections to the attic; this reduced the effective R-value of the wall insulation. A decorative archway in an interior partition wall created a framing cavity totally open to the attic; cold attic air drops into this space during the winter, bypassing the attic insulation.

• Exposed fiberglass. The basement walls were finished by framing out a 2x4 wall and insulating with unfaced fiberglass batts. Most of the space was finished with drywall, however the mechanical room had no wallboard or other protective cover to contain the insulation’s glass fibers. This was a health and safety concern and violation of the code’s Insulation Guidelines.

• Duct design.  The home’s supply ductwork system was not effectively designed; by placing a supply takeoff immediately above the supply riser, the basement bedroom received far more supply air than it needed to be comfortable; as a result, it ran too warm when the furnace operated and too cold when the air conditioning was on.

• Combustion safety.  The furnace and water heater were isolated in a mechanical room. Within the room were two major sources of depressurization that could potentially backdraft the combustion equipment: a missing section of panning on a floor joist cavity that served as part of the return air system; and a combustion air duct that ran vertically from the basement to a termination above the roof (and acted like a chimney).

• Bath fan. The typical low-end bath fan was rendered even less effective by the ductwork that was used to vent it. The duct had a 180-degree bend at the fan outlet (reducing flow significantly) and was very tenuously attached to the fan outlet with tape alone.

Last Updated: 08/22/2003