How to improve indoor air quality

In my last blog post I wrote about how Portland’s air stinks and generally indoor air (including the air in my drafty old home) stinks. Homes, I mentioned, mimic living systems, and my home is like a smoker on life support. How do I reconcile this?

A quick review why indoor air stinks: Buildings often get their so-called “fresh” air by infiltration. Drafty old homes exchange air through their building shells, picking up generations of collected dust such as pollen, dander, lead-paint and asbestos. Fortunately, they tend to leak so much the dust is diluted; however, the air becomes very dry with relative humidity (RH) often below 40 percent. RH between 40 and 60 percent is ideal for human health. Below 40 percent, viruses like influenza and measles thrive and our mucus membranes dry up making us more susceptible to respiratory infections. The flip side is more efficient homes tend to trap dust and chemical off-gassing. Moisture is trapped, too, and RH can climb above 60 percent allowing other viruses, fungi, bacteria, dust mites and molds to infect our air.

Source: ASHRAE Transactions 1985 Vol. 91 Part 1

So how do I mimic a healthy living body and improve my home’s indoor air quality? In a perfect world I would make my vintage home air-tight and continuously provide outdoor air through a filter and exhaust the moist, stale, polluted air. For Portland and Seattle this air control is ideally done with a heat recovery ventilator (HRV). Like a lung, an HRV is a whole house ventilation system that both filters and conditions incoming air. The best practice is to install the system to provide continuous air to the bedrooms and extract air from the bathrooms. Efficient HRVs use less energy than a 20w light bulb and lose less than a degree or two of air temperature even on the coldest days.

Additionally, I will reduce leakage in our home, which currently leaks its entire air volume 25 times per day. The tighter the better, but from experience a reasonable target for an old home would be to tighten to 6 times per day. This will be accomplished by air-sealing accessible areas of the home, primarily the floor system and attic. We also plan to clean out, air-seal and convert our fireplace into a new home for plants. Our leaky old windows are in major disrepair, so we plan to replace them as well. To minimize adding chemicals into the home, I plan to use a combination of wool, cellulose, advanced tapes and low VOC sealants to insulate and air seal.

Finally we get to remove the monster lurking in our basement: a 30-year-old gas furnace with an octopus of asbestos wrapped ducting. The plan is to upgrade to minimal duct work in our conditioned attic that our new Mitsubishi heat pump and HRV will share. The heat pump now replaces the last combustion appliance in our home eliminating any concern of combustion air, or natural gas leaking into our air.

A couple simple tricks will help ensure best results: I plan to balance the HRV to have slightly positive indoor air pressure to help ensure our fresh air comes from our HRVs filter and is not sucked in through the walls. This also helps to keep Radon from seeping in. The smart control for the HRV will respond to interior RH and change ventilation rates to help balance RH in the healthy zone.

OK, that’s how I plan to do it. But every home and situation is unique; at Green Hammer we’ve improved indoor air in countless ways. I always recommend starting with an experienced crew, diagnostic testing and a comprehensive approach.

And, sometimes the simplest solution is best. For those of you looking to improve indoor air without all the hoopla and major expense, or you already upgraded your home, we LOVE this living system idea about air-cleaning plants.

20 thoughts on “How to improve indoor air quality

  1. Healthier indoor air is critical – especially for those who are susceptible to breathing ailments, colds, viruses and bacteria. Studies by the Environmental Protection Agency indicate that billions of dollars are spent every year on medication to help Americans cure respiratory illnesses, including such ailments as asthma, hay fever and other allergies. Many times it’s the imbalance between the negative and positive ions found in all home environments, particularly where homes or buildings are insulated to save energy. An inexpensive permanent solution that improves indoor air and removes odors. Air-ReNu is a natural inorganic mineral that you mix with paint and apply to the walls of a room. Air-ReNu continues working 7/24/365 and only has to be applied one-time.

  2. I would invite you to become assoicated with NADCA: The HVAC Inspection, Maintenance and Restoration Association, otherwise known as the National Air Duct Cleaners Association (NADCA), was formed in 1989 as a non-profit association of companies engaged in the cleaning of HVAC systems. Its mission is to promote source removal as the only acceptable method of cleaning and to establish industry standards for the association.

  3. Thanks for sharing. This is really informative article.Air Pollution has become major issue. And chances of heart diseases are increasing because of air pollution. Necessary steps should be taken to control air pollution.

  4. I googled this most recent post after the 20th time I opened my windows and thought about your last cliff-hanger…

    Informative, as usual. Just wondering– if you employ all of these options, does your house stay between 40 and 60 relative humidity? How do we keep up with that particular stat in our households?

    Also, thanks for the link about the tree-cleaning plants. I love the idea of plants and people living harmoniously for the greater good of all.

  5. Cleaning out the old ventilation shafts could be a good way to freshen up indoor air. A quick check into those old vents is telling about how bad the air quality can be. Mold, rust, and lots of grime means the air you are breathing in at home is potentially deadly. Get a mold removal expert to clear them up if needed.

  6. Thanks for the information Stephen. A lot of folks in my industry don’t even consider humidity when suggesting a product. I’ve been selling room air purifiers (and whole home systems) for about 10 years and the first thing I tell folks is that they need to address the pollution source if possible. Often, a moist basement or crawl space can cause a lot of problems. IQAir air manufacturers a kit for their room air purifiers that can create a positive pressure and their purifiers are high quality. However, I believe Blueair makes the best unit.

  7. That’s right! In fact, airborne particulate (not necessarily a lead, radon or a biohazard like mold and bacteria) is causing lots of health issues around the world. The EPA considers airborne particulate to be one of the biggest threats to our health. @air pollution facts

  8. Good article. I have copied and pasted partial but relevant consumers related information from above into my face book page at k.thiru k.thiru for public reading.For 9 years now, i have visited at least 3,000 houses of all sizes and demonstrated what poor indoor air quality is like with a basin of water and a powerful light. WET DUST CANNOT FLY and within 3 minutes catch enough in that basin of 2 litres water with the aid of good air suction. has details. Thank you Mr. Stephen Alguier for enabling me to teach the public at large.

  9. What about leakage through doors? Is there anything that can be done to improve the air leakage through doors, particularly old ones? I also realize that screen doors tend to trap dust, dirt and other stuff that will affect the respiratory system. How would that negatively affect the air quality in one’s home? I wonder if there are any tips on prevention or on the proper ways of cleaning these screen doors.

  10. I have a lot of potential clients contact us about a smell or odor in their home or business. And most of the time a good cleaning will go along ways to helping the situation. I do however always inform them that we’re potentially masking the problem. And that if it persists to look further and at potential “environmental’ factors.

    You’ve put together a nice writeup here. One thing that I do use from time to time is a pair of industrial ozone generators that I picked up a while back. When a client has a serious odor issue or has had a mold issue due to a wet carpet situation. I always get any plants and pets out of the house and give it an all day run with the generators running on high. The clients love the fresh smell after I shut them down and air out the house. Still though. The environmental approach that you suggest here is a “solution” not a masking or cover up method. A good read !!

  11. As for my, my favorite means is use a humidifier. This ways un harmful for health especially if add there essential oils

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