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HEALTHY HOME DESIGN: How To Improve Your Home's Indoor Air Quality To Improve Your Health

Updated: Jun 11, 2022


You need to understand what you're breathing in at home whether you live downtown in a major city or in a farm house in a country field because the quality of the air in your home has a huge impact on your physical health in both the short term and the long term. It also affects both your mental health and the quality of your life.

Indoor air quality is largely dictated by indoor air pollution but also by outdoor air quality. Contaminants can be either airborne particulate matter or gaseous compounds. By extension, infiltration of outdoor air brings outdoor air pollution into the home either via air leakage or through air filters.


Indoor air contaminants have more sources of pollution than you might consider. Contaminants can be either biological or chemical, or they may be airborne particulates caused by abrasion (rubbing). In addition, the source may be either indoor or outdoor.

Biological Indoor Air Contaminants

The most visible indoor contaminant is dust. It's a popular concept that dust is made of dead skin and hair - and that's true - but it also contains a wide variety of other biological and non-biological pollutants. Small insects such as dust mites and spider mites multiply, and their empty carcasses accumulate. In a house with pets, tiny bits of animal hair and pet dander spread and are kicked up into the air regularly.

Other organic compounds include mould spores or indoor allergens such as pollen from certain indoor plants and may also be present in the air in your home, but you generally will not see them. When you flush the toilet, a spray is generated by the draining contents. What you notice as bathroom odour is partly gas but also freed chemical from the urine and faeces.

Chemical Indoor Air Contaminants

Indoor air contamination is generated by various means. Simple chemicals such as carbon dioxide or carbon monoxide are produced by natural processes such as people breathing or combustion of a furnace or gas-fired stove or oven. Radon is an elemental compound, and if measures aren't taken to keep it out, the levels of radon could rise to hazardous levels.

Complex harmful chemicals are found in - and released by - household cleaners and hygiene products. Dishwashing detergent, laundry detergent, general purpose or glass cleaning solutions, soap, and toothpaste all function by way of agitation which creates suds that eject greater amounts of the cleaners into the air than are released naturally from the surface by evaporation.

Cooking food also produces complex chemicals; greases, oils, and fats from both animal and vegetable sources and are released into the home either raw or partly combusted. Natural gas or propane used for fireplaces, cooking appliances, or gas water heaters may also escape in trace quantities. Secondhand smoke either from tobacco or marijuana is unfiltered, and its health risks are well studied and documented.

Abraded Indoor Materials

Another category of indoor air pollutant is airborne particulate matter rubbed off of surfaces. The most vulnerable and prolific is bits of synthetic fibre from carpet gradually worn down and kicked up via foot traffic. Furniture and other household items also suffer wear; this means that tiny particles are ground off and ejected into the air. Similarly, the fibres from clothing break off during use and become airborne. During laundering and mostly in the clothes dryer, heavy rubbing increases the amount of partial fibres released; the lint trap only captures particles above a certain size. Wall paint is worn down much less quickly, but every little rub or scuff wipes off some molecules.

High touchpoints such as door handles are designed to resist wear, but they do wear away. The same applies to light switches. Invisible particles of metal or plastic are rubbed off onto your hands, and they will be brushed off of your hands gradually - many of them becoming airborne.


Any building is not a hermetically sealed closed-loop system; the air inside your home is directly or indirectly created by the outdoor air quality. Consequently, some of the indoor air pollutants come from outside.

Chemical Outdoor Air Pollutants

Vehicle exhaust is the most vilified outdoor air pollutant, but there are countless others. In an urban environment, every building - residential, commercial, industrial - exhausts its used air into the outdoor air. After being diluted with "fresh" air, a small amount of contaminants are then introduced into another building's interior through the fresh air intake. Consider the disparate materials such as used printer toner from office buildings, smoke and grease from commercial kitchens, and bathroom exhaust fans from every building.

Abraded Outdoor Materials

Anything that wears down is gradually losing bits of itself - some which will become airborne immediately and others which may fall but then be rubbed or scraped and thrown into the air. The air is therefore teeming with bits of vehicle tires, brake dust, and autobody paint. Other structures which suffer erosion due to weather also become possible contaminants in the atmosphere. The tar component of asphalt roads, the cement component of concrete sidewalks, and degrading caulking joints on buildings all seem to disappear; the vast majority are particles too heavy to become airborne and are washed into the stormwater system, but strong wind can pick up some lighter bits.

Biological Outdoor Air Pollutants

To differing degrees, urban, suburban, and rural environments all present air pollution biological in nature. We're most familiar with allergens such as pollen, but bits of dead insect bodies, decomposed plant matter, animal dander from local animals, and even dirt itself become airborne and find their way into your home. Wildfire smoke is mostly burnt plant matter. A sufficiently large wildfire may generate smoke that travels halfway around the world in easily measurable quantities. The smoke particles usually are small enough to become part of your fresh air supply.

Airborne Microorganisms

Living matter that is small enough can also be airborne and therefore be an indoor air pollutant floating around in your home - invisible. Viruses, bacteria, and most other pathogens are small enough to pass filters easily,. Even microscopic insects can enter through cracks and gaps in your house.

Free Radicals

A category of its own is free radicals - a classification of any molecule that either is missing an electron or has an extra electron compared to its stable configuration. The sources of free radicals are typically electronic equipment - an increasingly common element of the modern home.

Indoor Relative Humidity

Although indoor air quality is predominantly determined by the amount and type of indoor air pollutants, two other important properties are oxygen level and humidity levels. The level of oxygen typically is inversely related to the carbon monoxide and carbon dioxide levels. A healthy range of relative humidity is from 35% to 55%, and 45% relative humidity is generally observed as comfortable by anyone.



Dust accumulation is unsightly, but it can also be a hazard since dust on a chair, sofa, or bed will be blasted up when you sit or lay down and create a cloud of contaminants that you breathe in. Dust piles or even dust particles provide a breeding ground for dangerous microorganisms.

Human Need

We require an adequate level of oxygen to operate. A level too low in the short term results in headaches or tiredness. In the long term, inadequate oxygen can deteriorate your brain function.

Respiratory Health

The most immediate and obvious health risks of poor indoor air quality are acute respiratory reactions to airborne contaminants of any sort. The most egregious pollutants will irritate anyone's lungs, but some people are more susceptible to pet dander, mold spores, and other indoor allergens and experience more severe symptoms. Allergies may elicit an initial reaction such as shortness of breath, sinus congestion, or aggravate longer-term asthma symptoms. These reactions are more noticeable in the winter months since windows are generally kept closed and the dust accumulation in the ducting of a common forced-air heating system is blasted throughout the home.

Other Health Concerns

Poor air quality in your home results in more than just respiratory trouble. Occupants may experience headache, fatigue, and irritation of the ears, nose, and throat. Research continues to learn about the effects of long-term exposure to synthetic outdoor chemicals, but it's already clear that the relationship is not a positive one. Free radicals noted above cause oxidative stress to human biological compounds and tissue. What that means in non-medical babble is that your body ages faster. Foods' antioxidative properties are touted specifically to fight this phenomenon.

Dry air - less than 30% relative humidity - also contributes to the deterioration of your body's tissue - most importantly your skin. Chronically dry skin is not only an aesthetic or comfort issue; dry skin is a less effective barrier and is less able to resist entry by pathogens.

At the other end, excessive indoor moisture - over 60% relative humidity - fosters the growth of black mould. This mould is a fungus which will release spores into the air which could be inhaled. Mould growth also results in damage to your house as it feeds on the building materials.


At this point, you might be disgusted or horrified at everything floating around your home and into your mouth, but there are many ways in which you can improve the indoor air quality.

Air Purification

The first step in understanding your indoor air quality is measuring the airborne pollutants. Monitoring systems and equipment are increasingly accessible and affordable. A carbon monoxide detector is an important tool to help prevent dying in one's sleep. Increasingly popular also are portable air purifiers and air purification systems to remove the airborne contaminants. A portable air cleaner equipped with a carbon filter can also remove gaseous pollutants. Humidifiers are also a means of raising the relative humidity to a safe and comfortable level. Some indoor plants are an inexpensive alternative to an air purifier they do require effort to maintain. Enough indoor plants can also help raise the humidity to an appropriate level.

Natural Indoor Materials

Cleaning your indoor air of indoor pollutants is a fix to a problem that can be minimized to begin with and the indoor sources minimized. Choosing clothing fabricated of natural fibres will reduce the amount of microplastics and plastic nanoparticles floating around. Similarly, choose furniture that is built of natural materials - wood, wool, leather, and cotton. The building materials in your house itself can be natural. Interior plaster such as tadelakt are durable, resistant to abrasion, and comprised of clay and other natural compounds. Interior wood finishes have come a long way since the faux-wood paneling of the 70's and 80's, and numerous attractive, contemporary natural wood finish products are available.

Eliminate Uncontrolled Infiltration

The outdoor pollutants described above enter the home both through the air intake - past the filters - and through gaps and cracks in the building. These openings are sometimes visibly large, but most are miniscule and concealed. Residential construction has always been comparatively leaky to air, and the ventilation strategy has relied on that fact. The bathroom exhaust fan, clothes dryer fan, and kitchen fan pull air out of the building, and local air enters to balance the air pressure differential. As more homes are located in urban areas and local air conditions are deteriorating, the importance of preventing uncontrolled air infiltration increases.

Improve and Control Quality and Quantity of Fresh Air Supply

As the building envelope is tightened, it is crucial that proper ventilation is provided. First, the exhaust systems in place must be functioning effectively; exhaust ducts must be cleaned regularly and kitchen fan filters must be cleaned or replaced routinely.

Similarly, the air intake equipment filters must be replaced regularly. The typical filter on most residential furnaces is rated approximately MERV-7 to MERV-10. MERV is a rating system from 1-20. At the very lowest MERV rating (1-4), your filter will still capture pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers and carpet fibers. Higher-performance allergen-specific furnace filters may be as high as MERV-13, but the extra resistance will cause excessive wear on the furnace blower, and the resulting reduced airflow may be inadequate to flush out the indoor pollution.


A typical residential HRV/ERV is outfitted with - and designed to use - a MERV-13-rated filter. A filter of this type will trap allergens, fine dust, tobacco smoke, and bacteria that most furnace filters do not. A MERV-13 filter removes a majority (60% according to one study) of the diesel exhaust and nearly all (>99.97%) of tire dust and brake dust.

A heat recovery ventilator (HRV) or energy recovery ventilator (ERV) is a mechanical heat exchange device that trades heat between incoming and outgoing air. The HRV or ERV operates all night and all day and therefore ensures a consistent supply of fresh air.


In addition, a HRV/ERV may be outfitted with a HEPA-rated filter (at least MERV-17) which will trap 99.97% of air particles that are 0.3-1.0 micron in size and an even better % of particles below 0.3 microns and above. This is the type of filter used in hospital air handling equipment Coronaviruses (MERS, SARS, COVID-19) are 0.1 microns in size (+/- 40%). One Minnesota study found that HEPA filters trapped 99.9% of silver particles 0.02 microns in size (a third the size of a coronavirus).

One must understand that a filter does not work like a net or even like a sieve. A particle that is smaller than the typical opening size is more likely to pass through, but it is not guaranteed to pass through. Re-read that last sentence, because it's not an obvious truth. In addition, particles smaller than 0.1 microns have such little mass and therefore inertia that some of them are stopped or deflected by electrostatic forces, molecular forces, and collisions with air molecules. In other words, some particles that are smaller than the size of the openings will be trapped. A HEPA-rated filter by definition must trap at least 99.97% of particles 0.3microns in size.


Quality air is useful only if it's being distributed appropriately. Air movement must be sufficient to evacuate contaminants but not too much as to create drafts. A house equipped with only electric baseboard heaters has limited airflow, and respiratory issues are likely to be the result of contaminants. A house equipped with a furnace is better at creating well-ventilated areas, but the excessive airflow resulting from heating f in the cold months

Subjective Notion of 'Fresh' Air

Many aspects of air quality can be measured, but there is an aspect which is more qualitative. "Fresh air" is a somewhat subjective notion beyond adequate oxygen, minimal pollutants, and a comfortable relative humidity. Air fresheners are sold solely on this concept, yet they emit harmful chemicals into the air.

The Intelligent Retrofit

Small measures yield small results, but you don't have to break the bank to improve the indoor air quality of your home drastically. The right strategy to address the issues in your home can be very cost-effective for both existing houses and houses yet to be built. The EnerPHIT system includes techniques that will greatly improve the quality of your home's indoor environment.

If you are interested in techniques to ensure that your new home build avoids the shortcomings and health hazards of existing houses, please book a free call with me using the button below. My Live Strong Age Well process produces a home nearly guaranteed to be more comfortable than any you have experienced before. I look forward to hearing from you.


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