Heating, Cooling and HVAC

Out with the bad, in with the fresh. Simply put, those are the purposes of the recently introduced standards for creating acceptable indoor air quality. The standards, published as ASHRAE standard 62.2 for Ventilation and Acceptable Indoor Air Quality by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, suggest requirements for new and existing homes to bring in higher-quality air while exhausting stale air.

“Before these were created, standards weren’t specific to residential,” explained Max Sherman, staff senior scientist of the Lawrence Berkeley National Laboratory and chairman of the ASHRAE committee that wrote the original standard. In the past, home ventilation wasn’t a concern; people simply opened their windows to bring in fresh air. Now, as homes are built tighter to save energy, contaminants can be more easily trapped indoors, creating a need for minimum mechanical-ventilation rates.

Max reviewed a few of the ASHRAE 62.2 requirements:
* Whole-house mechanical ventilation. Max noted that the required continuous mechanical ventilation rate is about 50 cubic feet per minute (CFM) for a typical home, but requirements increase with house size. The standard allows for flexibility in ventilation system selection: continuous or intermittent; supply or exhaust; with or without heat recovery. “In colder climates, consider a heat recovery ventilator to recapture the air stream coming in,” Max said. “Humid climates may do well with an energy recovery ventilator [ERV] to reduce the amount of moisture coming in when you ventilate.”

* Kitchen mechanical exhaust. An exhaust from the kitchen to the outside helps control the moisture and cooking-related pollutants generated in the kitchen. “The basic requirement is for a user-operable vented range hood to exhaust at least 100 CFM of air,” Max said.

* Bathroom mechanical exhaust. An exhaust to the outdoors is required in bathrooms, but not in toilet rooms, laundry rooms and utility rooms. “The basic requirement of a user-operable fan is at least 50 CFM, while a continuously operating exhaust fan of 20 CFM is an acceptable alternative,” Max explained.

Max noted that while some state building codes do not require kitchen or bathroom mechanical exhaust fans, it’s a wise choice for all builders to include in their projects. “These fans are much quieter now, of higher quality,” Max said. “The standard range hood is 100 CFMs, but many go up 10 times more than you need. Care should be taken when using them.”

Additionally, Max offered builders this advice:

Humidity control for hot, humid climates. “Your system design must be able to handle the moisture that could be brought in through ventilation,” Max explained. Conventional air conditioning does remove some moisture, but as houses get more efficient, the amount of total cooling needed is reduced—and so is the incidental moisture removal.

To combat the mold that could result, Max recommended humidity-control considerations, such as an ERV, stand-alone dehumidifier or dehumidifier ventilator. “Several air conditioning manufacturers have or will soon have products on the market than can greatly enhance humidity control,” he said. Also consider some of the new options on the market. One manufacturer offers a new control system that incorporates dehumidification and ventilation with the forced-air heating and cooling system.

Know your state’s building codes. Because a standard isn’t a code, the ASHRAE standards don’t necessarily require builders to make immediate changes to their building practices. However, they set a minimum-level expectation. Max advised those who may not be familiar with their state’s building codes to check the requirements. Noting that some states are considering adopting the standards, he pointed out that other states already have adopted similar or higher standards. “It’s in the builder’s best interest to adhere to the ASHRAE standards. If there is an issue with IAQ, you can demonstrate due diligence and good faith because you voluntarily meet or exceed industry standards.”

Source:hgtvpro.com