In the sharpen-your-pencil bidding process, contractors would have two new elements to consider: a low-power fan (about $100) to supply continuous ventilation, and a carbon monoxide detector (about $75). This would add a cost to builders between $150 and $250 per house, according to ASHRAE’s estimate.

In addition, the normal warranty terms on furnaces and air conditioners would have to be extended to these add-ons. However, since many contractors sell service contracts on hvac equipment, these new elements offer a chance to enhance their sales pitch to new homeowners.

Virginia-based hvac contractor Mitchell Cropp, of Cropp-Metcalfe, said he thinks the standard’s focus on mechanical ventilation will solve the national problem of tight houses.

“You have a lifestyle where both adults in a home are working during the day, kids are sent to be cared for by others, and this means that no windows get opened, no fresh air is introduced into the house.”

What about windows, humidity?

But the document in its present form faces a formidable challenge: the opposition of the National Association of Homebuilders (NAHB), which recently cited several significant points of disagreement with the proposed standard.

The NAHB said the ASHRAE committee made “improvements” to the draft during ASHRAE’s Winter Meeting in Dallas, but the standard still falls short of meeting other objections. These include a need to recognize that natural ventilation can satisfy the needs for homes with operable windows, which the standard does not permit. “Nor does it distinguish between the special needs and conditions of severe cold climates,” said the NAHB.

The homebuilders said the requirement for continuous ventilation air is “problematic” in hot, humid climates.

The association said the need to maintain 75°F, 40% rh indoor air while introducing hot, humid air would result in 16 unwanted gallons of moisture per day. The standard writers should therefore investigate the “unintended negative consequences in hot, humid climates.”

Not all homebuilders agree.

Joe Lstiburek, a homebuilder and a member of the standard-writing committee, said these products would reduce the number of callbacks due to condensation and mold problems. He said the standard would level the playing field for all builders by setting a defensible standard of care for IAQ contaminants.

Lstiburek called the standard “good, basic common sense. People need fresh air. Here’s how you provide it and here’s how you avoid common problems.”

The proposed standard also sets a minimum for whole-house ventilation, performance criteria for air-moving equipment, and guidance on selection, installation, and operation of ventilation systems.

Sidebar: Not in perfect harmony

With all the benefits of vfd’s there also come a few problems. The primary problem is harmonic distortion, which is “noise” caused by variations in fundamental voltage. If there are multiple drives in a building, you might see higher harmonics.

Harmonics also occur when there are large numbers of PCs, printers, copiers, fluorescent lighting, and other electric loads in a building. Harmonic distortion can damage equipment and also cause problems for the electric utilities.

Mike Rapp believes that with deregulation, utilities will be cracking down on those buildings that have harmonic distortion problems.

“If you have a distributor of clean power, and they’re getting harmonics back and wave distortions, I think they’re probably going to come back to the customer and say, ‘Hey, you have to clean this mess up or we’re going to charge you for dumping this dirty power back on our system.’ I think it’s going to become more critical.”

Scott Needham says that with more vfd’s being installed, the harmonics problem is being exacerbated. “You can’t just let it ride — you can’t let the electrical system absorb it anymore. I read about that early on, so I always include a harmonic filter on all the jobs we do.”

He adds that the cost of the filter is small compared to the cost of the overall project, and it’s always better to be safe than sorry.