The Air We Breathe Can Be Dangerous
The Air We Breathe Can Be Dangerous
Everybody is aware of the warning on cigarette packs: “Smoking can be hazardous to your health.” The same can be said for the hazards we face in our homes and offices. It could be worse in some cases.
There is a growing body of evidence that indoor air quality is linked to a host of health problems, such as asthma, emphysema, and COPD. We’re stinking the joint up, both literally and figuratively. Some reports show indoor air quality can be worse than an outdoor industrial smokestack. That’s a sobering thought. That’s why we help builders and contractors mitigate anything that can affect indoor air quality.
The danger is exacerbated by the amount of time we spend inside our offices and homes. Children, seniors, and those with serious illnesses are often cooped up for extended periods of time. Obviously, the COVID “work from home” trend factors into the mix, and some employers and workers are seriously considering this as a “new normal.” Many enjoy the daily commute measured in feet, with a stop in the kitchen for a fresh, hot cuppa Joe.
So what is Performance Point doing about this? Plenty. We again tap into Rick Blair’s expertise. He started with this: “Build it tight. Ventilate right.”
It’s all about infiltration, keeping the bad air and allergens out of the house, and then introducing appropriate levels of mechanical ventilation that’s filtered and not coming from unhealthy places like the crawlspace.
He said the popular myth that a house “needs to breathe” doesn’t wash. That’s because there’s a critical difference between good air and harmful air. Air that leaks in from the attic or crawl space likely has an abundance of mold, mildew, dust, including tiny fiberglass bits. Yes, fiberglass. If it makes the skin itch, imagine what it does in the lungs.
“One of the things that we do concretely after educating is to stop the natural infiltration that comes into the house,” Blair says. We offer an air sealing package to builders where we come out and foam all the particular places in the house where it commonly leaks. One of the leakiest places is at the top plate of any wall. It’s a straight line into the attic. It needs to be sealed with foam or a gasket before the sheetrock is hung. That foam then forms a gasket between the sheetrock and the top plate. There are a lot of penetrations in the walls with electrical wall outlets and switches. If the top plates aren’t sealed, then all of these penetrations in the wall form air channels right up into the attic. Yes, a house should breathe, but not through the attic! 5 ACH50 (Air changes per hour @ a 50-pascal pressure difference between indoors and outdoors) is code in North Carolina. Generally, we recommend even tighter standards – 3 ACH50 or lower.” But once we reach around 3 ACH50 we really need to start introducing mechanical ventilation in order to promote healthy indoor air quality. Long story short, we believe incoming air should come from healthy places, not attics or crawl spaces.
Blair says it all boils down to this: “Knowing how to ventilate right means knowing how it’s going to affect the pressure differential between the inside and the outside of the house, as well as knowing how much air to bring in”
Regarding the volume of air needed for the home, we conform to the ASHRAE 62.2 standard which outlines healthy indoor air quality. It is based on the number of bedrooms, square feet of the home, and natural ventilation that’s already occurring. Beth Ainsworth details this in an earlier blog story.
Regarding the method of bringing in the air, here are 3 strategies for builders to consider:
An exhaust strategy
This approach uses a bath fan with a setting for continuous exhaust. Although it is a low-cost option, the primary drawback is that it creates negative pressure inside, therefore it brings in unconditioned outside air from whatever leaky places it can find. which can lead to moisture and mold problems. This is not healthy, especially for asthma sufferers.
A supply strategy
This approach uses a filtered fresh air duct into the return plenum of the HVAC. This is another lower-cost option. This strategy which creates a slight positive pressure indoors pushes possible contaminants and moisture to the exterior. That said, it can also increase demand on central HVAC systems, especially if the central blower is used to distribute that air throughout the house. There is, however, an improved version of this solution that incorporates a small separate inline fan to distribute the air when the central system is not running, therefore not using the large blower of the central system. Electric bills can go into a low earth orbit when the HVAC blower is running, especially on hot, humid Southern days.
A balanced strategy
There are two options: ERV or HRV. These bring in the fresh air, as well as exhausts stale inside air to create a balanced pressure. An ERV is best suited for hot humid climates like ours, because it transfers moisture from one air stream to the other, in addition to heat. HRV only transfers heat from one stream to the other, so it is better in drier climates. ERV systems do add to the power bill but it’s offset by the lessened HVAC load. It adds more upfront cost but saves money in the long term.
Performance Point’s CEO Sam Galphin gets the last word on the shift in indoor air quality attitudes: “Right now Indoor Air Quality is on everyone’s mind for the obvious reasons of COVID. Builders have a captive audience when they start advertising how their new homes can have better indoor air quality. There is a lot to indoor air quality and consumers usually write it off when considering new homes, but now our industry has a platform to talk about these important issues and the best part is that a strong message here can really win more sales.”
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