Monthly Archives: June 2022

Air-sealing your ducts for better air quality and energy savings 

In our post “How does indoor air pressure affect ventilation and air quality?” we show a photo of a room being aerosol sealed from the inside out.  This is a great way of closing up the small leaks (up to ½” diameter) that are overlooked by design flaws or construction crews, in order to seal the home’s thermal barrier before finish work on the home is completed.  Here’s how this innovation started: duct sealing.

Before rooms were sealed from the inside out by aerosol sealant, the process was developed for air ducts in 1993.  In one case study by AeroSeal, the innovator and major supplier for this technology, a homeowner had her ductwork expanded to cover previously unserved areas of her home.  After the new ductwork was installed, the system was pressure-tested and it was discovered that air of about 919 CFM (cubic feet per minute) was leaking through the ducts, which is the equivalent volume of about 551 refrigerators per hour(!).  According to energystar.gov, “about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts.”  (To put this in perspective, the average system is 3.5 tons.  A system is required to have 400 cfm per ton of air across the evaporator coil for cooling, thereby 1400 cfm is the normal flow of the average system.  Twenty percent (280 cfm) to thirty percent (420 cfm) would normally leak from the ducts, so this homeowner either had a much larger home, or exceptionally leaky ducts.  In any case, after sealing the ductwork, a 91% reduction in leakage was realized.  Consequently her sinus issues were relieved and she felt more comfort in the home.  The system was previously drawing in dust and contaminants from outside the home and recirculating them in the HVAC system; apparently this problem was relieved by sealing the ducts.

The following diagram shows how air leaks into and out of ductwork (aeroseal.com):

The home is in heating mode shown by the orange ductwork coming out of the furnace in the bottom right.  Ductwork farther from the furnace turns blue (cooler) because pressurized, heated air is leaking from the ducts into the crawlspace and void spaces, before it even gets to to the farthest room.  For air quality purposes, the most important part of the system is the return areas, in the ductwork in the attic of this house.  Because the air pressure inside return ducts is negative (it is being “sucked” or drawn back to the furnace by the fan), any leaks in this area will cause dusty, unconditioned air from the attic or voids into the ductwork (see green arrows entering the ductwork in the top of the picture).  This is one major cause of excessive dust and poor air quality in many homes.  Even more leaky are the ducts in many multi family homes and apartment buildings.  AeroSeal has been successfully used in these buildings since 2007-8.  

The sealant used by AeroSeal is a “water-soluble organic compound” (AeroSeal FAQs) with an extremely low concentration of VOCs.  The sealant smells like Elmer’s glue when wet, but dries to be odorless. The safety data sheet reveals it to be a “vinyl acetate copolymer” (35% max weight) and “vinyl acetate monomer” (<0.01% when dried).  In accordance with California Prop 65, the product “does not contain any chemicals known to the State of California to cause cancer, birth, defects, or other reproductive harm.”  According to the EPA, vinyl acetate definitely has exposure limits due to irritation of upper respiratory tract as a result of acute or chronic exposure.  Due to this information, it’s possible that very sensitive individuals could have a reaction with the dried substance in their ducts, so it may be wise to ask for samples before it’s applied in the home of sensitive individuals. 

Aeroseal is not the only duct-sealing product on the market.  Here are some other options:

• Aluminum duct tape is available online and at most home improvement stores and can be used by anyone.  

• Ductwork mastic should be applied over the aluminum duct tape. It gives extra strength to the seal and encloses any seams of the tape.  It’s applied by paint brush and is usually water soluble (soap and water cleanup).

• Spray Mastic products: These are typically products for professionals because of the spray equipment needed to apply them. 

• Spray-Seal by Carlisle is a sealant applied to the exterior of ducts (especially hard ductwork) manually either after fabrication or as an upgrade to existing ductwork. 

• PROseal Spray by Ductmate Industries Inc. is a sprayable mastic sealer which is also applied by professional spray equipment.  

• Duct-EZ is a water-based zero-VOC mastic that is not only used to seal ductwork; it is also used to seal cracks in your foundation or basement to reduce seepage of radon into your home.  

Since dust is a major contributor to indoor air pollution, the dust may indeed be coming from the attics and crawlspace, and/or directly from the outside through building envelope cracks and crevices.  Before contracting for a duct-sealing service, it would be wise to have an energy audit on your home performed in order to discover the most economical ways to seal the largest leaks.  

What are ultrafine particles and where do they come from? 

In our post “Which particles can get captured by a filter or by my lungs?”, we mentioned ultrafine particles, which are classified to be 0.1 micron or less in diameter.  They are called UFPs (ultrafine particles) or PM0.1 (Particulate matter 0.1 microns), and are dangerous to our bodies in a different way than PM2.5 (Particulate matter 2.5 microns) , because they can migrate from the lungs or respiratory pathways to the rest of our bodies.  Their movements and concentrations are also different.  Learning about them is a good defense for avoiding them, though, so here’s some of what we know.

• PM2.5 consists of a mixture of particles of varying sizes from a variety of sources, with the most numerous particles by count usually falling within the ultrafine size range (<100 nm).  
• UFPs are mainly composed of organic compounds, elemental carbon, trace metal oxides, sulfates, and nitrate ions (2012 and 2016 studies). 
• Among the sources of emission, heavy industries are considered one of the largest anthropogenic sources of trace metals (2012, 2014 and 2017 studies)
• UFPs are unstable.  They have positive, negative and neutral charges,  and become larger particles through coagulation (when two or more particles combine) and condensation (when additional vapors can condense on the particles) (Jan 2022 overview). 

UFPs can be emitted by a number of sources.  

Source: overview study of UFPs

Since Natural Sources are largely not controllable, let’s focus on the anthropogenic sources (originating from human activity). 

Vehicular, aerial and sea traffic:

Airports: it’s estimated that in the United States ∼40 million people live near 89 major airports (i.e., within areas with ≥45 dB noise levels near airports) (study).

Aircraft exhaust is the #1 pollutant at major airports, and neighborhoods surrounding the airports even 10 miles away have higher ultrafine pollution levels.  According to a 2014 study, the “level of pollution at LAX (Los Angeles International Airport) was equivalent to the emissions generated by nearly 500 vehicles stalled in freeway traffic every day.”  Another study in 2018 in the Boston area measured particle numbers (PN) indoors and outdoors.  PN overall indoors was compared during times of impact-sector winds (during prevailing NW or SW winds) to calmer conditions; during impact-sector winds, the indoor measurements were about 1.7 times that of calm conditions.  We know that particles infiltrate homes via cracks in the building envelope, open windows, or forced-air ventilation, and this was shown through the study because outdoors and indoor PN levels usually increased and decreased in tandem, except for indoor events like cooking or cleaning.  Unlike road emissions, aviation emissions do not dissipate with higher windspeeds because of the buoyant nature of the aviation emissions.  This is the reason that some ultrafine particles, like wildfire smoke, can be transported in upper-atmosphere winds for thousands of miles.  Interestingly, significantly higher UFP emission per kg fuel burned resulted under landing conditions as compared to takeoff conditions. (2021 study)

HEPA filtration inside the homes helped somewhat; it lowered indoor PN by approximately 33%.  This is good, however, it didn’t have the same effect as lower number of flights or no impact-sector winds.  This causes us at HypoAir to continue recommending sealing homes to the best of our ability, and using controlled fresh-air ventilation for homes (via filters).  Ultrafine particles from airports are not currently regulated by the EPA, so we need to protect against them!

Vehicle exhaust: In many urban areas, vehicle exhaust is a major health concern. The following pictorial representation is found in the study “Chemical Composition of Quasi-ultrafine Particles and their Sources in Elderly Residences of São Paulo Megacity”

In urban areas with both aircraft and ground vehicle pollution, vehicle exhaust can be identified by larger particle size and higher BC concentration. (2021 study). 

Likewise, roadway emissions can be characterized by the fuel type, lubricants used, thermodynamic conditions, ignition technology, and the number of vehicles running.  This is why large cities have performed emission inventories in order to reduce particulates in certain ranges by certain types of vehicles.  National and local governments have devised three categories of strategies to control PM emissions: (1) fuel-based strategies, which include reducing sulfur levels; (2) engine-based strategies, which could alter combustion to reduce emissions; and (3) exhaust emission control strategies, which include the use of modern technologies, such as DOCs, diesel particulate filters (DPFs), and SCR catalysts, focusing on reducing emissions after combustion has taken place but before they leave the tailpipe. (2020 article).  New engines, paradoxically, emit more UFPs than older engines (1996 Health Effects Institute), but with these exhaust emission control strategies, UFPs can be captured before they are released.

Marine traffic: According to noaa.gov, 76% of all trade in the US involves some sort of marine transportation, and marine transportation touches 90% of all trade internationally.  Barges are extremely efficient transporters; what other mode can transport a ton of cargo 647 miles on 1 gallon of fuel?  In comparison, trains move 1 ton at 477 miles per gallon, and trucks at 145 miles per gallon. (2017 article).  However, the sheer number of tons of cargo moved on ships and barges necessitates huge quantities of fuel and emissions.  The International Maritime Organization (IMO) mandated lower sulfur contents in marine fuels beginning in 2020, at max 0.5% sulfur down from 3.5% previously for heavy fuel oil (HFO).  This cap caused many ships to start using intermediate fuel oil (IFO) or other lighter fuels instead of HFO.  The sulfur cap is a step in the right direction for less sulfur in the environment, but it was not expected to reduce UFPs (in terms of Particle Number or PN) from shipping sources.  The total output of PN from marine shipping in 2016 was similar to the total anthropogenic emissions in continental areas.   Thus, marine traffic is a significant source of UFPs (2021 Environmental Science & Technology article).

A third major source of outdoor anthropogenic UFPs is from coal-fired power plants, which produce emissions that are particularly rich in metals. You can access a map of US power plants here (gas, oil and coal), that gives type of fuels, emissions, and demographic information of the surrounding area.   Many plants may filter their emissions to meet standards, however UFPs can form outside of the stack when SVOCs condense (gasses turn into solids and thus bypass the filter). (2020 article) This process is called nucleation.  The most persistent UFP sources in the low atmosphere near the surface are modern technology fossil fuel-burning power stations, refineries, and smelters, according to a 2018 study. 

A fourth major source of outdoor UFPs is from wildfire smoke and controlled burns, which can vary significantly depending on the type of wood burned and its moisture content.  Wildfires can also smolder for a long time after being “extinguished”, and this smoke contributes significantly to the total wildfire emissions. 

Indoor UFPs are a combination of what has leaked into the house from the outdoors, and what is generated indoors.  Cooking and cleaning are large contributors, as well as candles, incense, smoking and e-cigarettes, and (in unconditioned climates) mosquito coils.  The use of e-cigarettes by children and young adults is unfortunate because their lungs are more susceptible to damage from UFPs.  Also, if you have a laser printer, it is surprisingly one of the major contributors to UFPs in offices (and homes!).  

Toxicological effects from exposure to UFPs; Jan 2022 overview

Here is what happens when our bodies encounter UFPs.  They are normally inhaled (effects via mucous membranes, skin and eyes are much smaller). The larger particles (10 microns and larger) can be trapped and removed via the mucous system, but smaller particles (2.5 microns and smaller) may be trapped in the alveoli and terminal bronchioles.   UFPs go into the deepest parts of the lung, and the body’s cellular defense system is activated.  This includes macrophages, various cytokines, chemotoxins and leukocytes, including neutrophils. Some of these are involved in the body’s inflammatory response, which not only damages the invading substance, but is also detrimental to the body in chronic doses.  

The UFPs can translocate to other organs such as the brain, liver, kidneys, and because they are fat-soluable, also deposit in adipose tissue. The body’s production of oxidizing species places oxidative stress on the body, which can cause damages to the DNA and mRNA, and lead to cancer.  Even transgenerational changes to DNA can (occur through inheritance!  

The toxicity of UFPs depends on a number of factors, including:  

• The age and health of the person affected (children are most affected, followed by the elderly and pregnant women). 
• The emission source, which determines the makeup, characteristics, size and concentration of the pollutants.  For example, black carbon (BC) is one combustion pollutant made up of PM2.5 and UFPs, but it is more harmful than other PM2.5 because of the body’s inflammatory response to it.  Black carbon can also adsorb other toxins before it is inhaled, like VOCs and PAHs (polycyclic aromatic hydrocarbons).  One study found that the smaller the particle size, the greater the inflammatory effects in the lungs, and the greater the DNA damage.  Another study found a positive correlation between the concentration of UFPs from motorcycle exhaust and the physical of damage to mice kidneys (neurological effects, memory loss,  behavioral problems and changes in brain tissues are other effects). 

With all the sources inside and outside, it seems that UFPs are unavoidable in daily life!  They are everywhere, but here are our top tips for keeping them out of your home and your body:

1. Seal up your home as tightly as possible, and use controlled fresh air ventilation through a MERV 13 filter* (see chart below) and your home’s HVAC system.  Balanced ventilation (as opposed to negative pressure ventilation) has less chance of suctioning combustion exhaust from gas appliances such as gas dryers, water heaters and furnaces.  
2. In addition, use a HEPA filter in your home to capture UFPs that are generated in the home or slip past the ventilation filter. 
3. Bipolar Ionizers like those in HypoAir’s Germ Defender, Air Angel or Whole-Home Polar Ionizer help to cluster ultrafine particles into larger particles that can fall out of the air or be captured in a HEPA filter.
4. Use stovetop ventilation during and after cooking and bathroom ventilation during and after showering.
5. Don’t smoke or vape (use e-cigarettes).
6. Use a HEPA mask (outdoors or in a separate ventilated building if possible) during high-risk activities like welding, spray painting, sanding or woodburning and 3D printers. 
7. Don’t allow vehicles or gas engines like generators or lawn mowers to idle in the garage.  
8. If you move, reconsider locations with high UFPs such as downwind of airports, refineries, power plants, bus stations, major highways, etc. 

*Here is the reason we recommend MERV 13 for ventilation filters:  it increases capture of small particles to include that of smog, tobacco smoke, and cooking fumes. 

Above diagram from pureairfiltersdirect.com

Which particles can get captured by a filter or by my lungs?

This is an incredibly important and somewhat complicated question.  I want to present the following graphic, which shows relative particle size.  I’d say it’s pretty surprising how large our hair is and how small those bacteria, smoke particles and viruses are, right?  The “µm” stands for micrometers, which is one-millionth of a meter.  Micrometers are also called “microns”, so the human hair is 50-180 microns.

In our FAQ on “What is HEPA?”, we explored how filters actually trap contaminants like these.  In order to start answering our original question, let’s review that!

“Sieving” is the most simple way a filter “strains” out the particles that are larger than the openings between the fibers of the filter.  

                  (image from classicfilters.com)

Then, there are three types of motion that particles experience in a stream of air, such as the airstream being drawn through a filter.  Filter design actually takes advantage of the size of particles and the way they move through the air, in order to capture them.  

• Obviously, some particles are larger than others.  Inertia acts on larger particles by causing them to continue in their original path of motion when entering the filter, thus colliding directly into fibers instead of sweeping around them with the accompanying airflow.  Particles 0.3 micron and larger (coronavirus size and larger) are affected by inertia. 

                (image from classicfilters.com)

• Air is made up of all kinds of molecules and particles, which are getting thrown about in erratic ways by collision with one another.  This is called Brownian motion.  Taking Brownian motion into consideration is filtering by diffusion, which occurs when smaller particles travel in an erratic fashion through the airflow and are impeded by fibers.  The particles trapped by diffusion are typically smaller than 0.1 micron.

                         (image from classicfilters.com)

• In direct interception, a particle follows the airstream but travels closer than its radius to the fiber, “brushing” it and becoming stuck.  This can happen for many different sizes of particles and just depends on where they are in the airstream relative to the fibers.  

                    (image from classicfilters.com)

So there you have it– four ways a filter uses to capture particles.  Interestingly, because of the gap between inertia and diffusion, particles around 0.3 microns in diameter are the most difficult to filter out of the air, because they are least affected by these methods.   This is called the most penetrating particle size (MPPS)--the size that is most likely to slip through the filter.  

HEPA filters are rated on their ability to remove this size particle—0.3 microns.   They do so with greater than 99.95% efficiency.   There are 2 ratings of HEPA: H13, which removes at least 99.95% of 0.3 micron particles, and H14, which removes at least 99.995% of 0.3 micron particles.  

Without a HEPA filter in your home, you are probably relying on furnace filters of various lower filtration ratings.  That means that more particles are getting through the filter, and remaining in the air for you to breathe.  Yikes!  Particles of 10 microns or less can be inhaled, and particles of 2.5 microns or less are more likely to deposit deep in the lungs.  (California Air Resource Board).  This size of particle is extremely lightweight, and once it’s in your lungs, it can move all the into the deepest part of your lungs and lodge there.  Without filters to capture particles from the air, unfortunately your airway and lungs will act as filters.  Here is how (Canadian Center for Health and Occupational Safety):

• The respiratory system can be divided into upper and lower regions.  The upper region starts at the nose and mouth, and goes down to the vocal cords in the larynx. The lower region starts at the larynx and extends through the trachea all the way to the bronchioles and aveoli (smallest air sacs).

• Particles 10 microns and larger are most likely to lodge in the upper respiratory region by inertia (also called impaction), because in this region, air is flowing at a higher velocities and during the twists and turns particles tend to continue in their original direction and “impact” a wall of the airway and stick there.

• Interception is likely to occur with fibers, like asbestos fibers.  In the range of 1 micron in diameter and 200 microns in length, if one end brushes an airway wall, it will lodge there.  These can make it into the bronchial tree.

• Sedimentation occurs when particles larger than 0.5 microns loose their momentum and gravity takes over, causing the particles to settle in the bronchi and bronchioles.  

• For particles smaller than 0.5 microns, diffusion is in effect (Brownian motion).  This can happen in the small airways and alveoli, when air has virtually slowed to stillness.  

• Although the mucous lining of our respiratory tracts was designed to clear airways by moving it up and out of the respiratory system, it does not always function well in older and diseased people, and the sheer number of ultrafine particles can clog airways. 

Fine particles (2.5 microns down to 0.1 micron) and ultrafine particles (0.1 micron and smaller) are shown to cause inflammation and inflammatory diseases.  Ultrafine particles can migrate from the alveoli to the bloodstream and to other organs, resulting in delayed sicknesses such as reactions to vehicular pollution, welding fumes and burning trash.  The danger of ultrafine particles is not just their size and number (much greater numbers PM2.5), it is also their charge, which can adsorb toxic chemicals onto their surface.    Fine particles have been shown to cause cardiovascular disease; they travel up the olfactory nerves to the brain; they are inhaled by electronic cigarettes, and have been shown to increase risk for hypertension and diabetes and cause cancer (animal studies) . (study)

For all these reasons, a HEPA filter is a great addition to your home, vacuum, and even a mask when you are performing high-risk activities like welding, spraying paint, or caring for a sick relative, so that the filter will do the work instead of your lungs and body!

How is my Crawl Space affecting my Indoor Air Quality?

According to the National Association of Home Builders, 65% of new homes in 2020 were built on slab foundations, 22% had a full or partial basement, and 12% had a crawl space.  From their statistics since 2000, it’s clear that slab foundations are increasing, while basements and crawl spaces are decreasing.  From an indoor air quality perspective, we have to admit that’s a good thing!  We found a lot of other pros and cons about slab foundations, and if you are building or buying a home and have a choice, you should investigate the differences.

Slab foundations became popular in the 1950’s; before that, most homes were “raised” with a crawlspace or set over a basement.  Crawl spaces did their job to keep the main living area “off the ground”, ie. not in direct contact with the earth, and they accommodate floor plan renovations more easily than slabs because of easier access to plumbing.  However, crawl spaces typically are partially sealed off, and very contaminated with dust, mold, bacteria and stale air.  What you did not know about crawl spaces may be the most harmful of all: “Approximately 50% of air on the first floor of your home comes from your crawl space.” (goTerraFirma.com)  How can this happen?  Due to the stack effect which affects virtually every building on the planet, warm air rises through the house and is replaced by cooler air from outside, through leaks in the lowest parts of the home.  If you have a crawl space that is partially open to the outside, you may even place a pinwheel or light tissue in the crawlspace opening on a still (non-windy) day, and see if the air currents are blowing into the crawlspace of your raised home.  Fresh air from outside will be drawn into the crawlspace, pick up dust, mold and bacteria (not to mention musty or animal smells), and infiltrate your home through leaks in the flooring.  Gross!

If you can’t or won’t investigate the condition of your crawl space first hand, find a foundation expert and ask them to conduct a thorough inspection (with photos).  Knowledge is the first step to preventing or remediating the problem!  Here’s what they may find:

• Flooding.  Just like any other ground that floods, if water enters your crawlspace, it can pool and remain for weeks or months, depending on the environment and soil composition.  How about living over a stagnant puddle?
• Moisture damage.  Moldy and rotten timbers are a consequence of constant water contact and high humidity.
• Insect damage.  Termites can thrive in even lower moisture zones, and without proper termite prevention like physical barriers, they can do a lot of damage.  The shredded wood creates even more dust under the house.
• Animals and animal damage.  There are several harmful aspects of animals living in the crawl space under the house.  For one, their feces can carry virulent diseases like hantavirus (from rodents).  Then, unfortunately they may die under the house, with accompanying death smells and a bacteria-laden carcass… Third, they may actually undermine the foundation with burrows.  Did you know that groundhogs can seriously impact your home’s foundation, causing sagging floors and major structural problems?
• Damaged and missing insulation.  Exposure to water, insects and animals all results in deterioration of insulation on pipes, ducts and subfloor, so that the essential systems and floor itself are exposed.  

If you have a crawl space and want to improve indoor air quality, don’t miss this opportunity to take a step in the right direction by hiring a trusted professional to do an inspection, and then get several bids for remediation.  Most foundation companies will recommend a combination of the following to resolve these issues (from GroundWorks.com):

• Encapsulation is a method of sealing off the crawl space from the surrounding elements.  It involves closing crawl space vents, installing a vapor barrier so that moisture from the ground does not intrude, and installing a dehumidifier.
• Insulation is important to prevent condensation and resulting mold issues.  Damaged insulation should be replaced and missing insulation should be installed.
• Sump pumps are necessary if standing water has been a problem in the past, and to remove condensate from the dehumidifier.  
• Repair of sagging and damaged joists and supports.

It may seem like a daunting task, and these tend to get postponed until things get really bad.  If you don’t know the condition of your crawl space, we want to encourage you to take a first step of inspection, which many companies do for free.  If remediation is required, call several more companies for inspections and quotes, and research their work.  When the work is completed, you will have the comfort of protecting your largest investment (your home) and increasing your air quality at the same time.  It’s hard to overestimate the cost of a less humid, healthier, fresher home! 

How can I make sure my basement has good air quality?

If you glanced at our post on crawl spaces, you would know that more new homes have basements than crawl spaces, but they are both declining in popularity.  Here’s what the National Association of Home Builders found:

Still, many existing homes have basements, finished and unfinished.  They can add value to your home value by boosting its square footage and livable space, or they can be a detriment to your home value as a source of mold and poor air quality!   Let’s hope that your basement falls into the former category…but read on to make sure!

The basement shares several characteristics with the attic: many times they are not planned to be living space, and thus often lack the proper ventilation and fresh air flow.(ecolivingexpert.com)  Also, they are often made to be storage spaces containing boxes (cardboard is food for mold and many types of insects and pests), and then home heating systems are often installed there, which if they are gas- or oil-powered, have the potential to leak fumes.  

Whether you use your basement as living space or not, the basement has to be maintained with proper ventilation and dehumidification so that it doesn’t contaminate the rest of the house with poor, even dangerous air quality.  Let’s take a look at these problem areas and sort them out one by one!

Radon is a concern in many areas of the country.  It’s a colorless, odorless gas that that seeps naturally from certain underground rocks and can permeate basement walls and foundations, as well as contaminate ground or well water.  Because radon is radioactive, it can cause cancer (it’s estimated by the EPA to be the #1 cause of lung cancer among non-smokers).  Radon tends to accumulate in basements because it’s heavier than air, so it’s best to have the basement checked for radon levels, and if present, investigate mitigation systems (you can find local qualified contractors through the link on this page, and information on water testing labs here). 

Moisture and mold: If you smell an earthy, musty smell in the basement, it’s most likely mold that is starting to form or has already formed.  The smell is characteristic of the Microbial Volatile Organic Compounds (mVOCs) that the mold releases.  Some MVOCs have been identified as irritants and can contribute to sick building syndrome (easlab.com).  The key is to identify the area (possibly many areas and the whole basement) and remediate in order to stop the growth and get rid of the mold, as soon as possible.  Here are ways to do it:

• Ventilate: Although opening the windows of the basement, if you have them, will help dilute the smell, it will not stop the mold from growing and continuing to produce mVOCs.  Ventilation has to be done with dehumidification (next point), eliminating excess moisture, in order to stop the growth of mold.  Ventilation can be accomplished by a dedicated basement ventilation system (check out EZBreathe), or by installing air vents from your existing HVAC system to ventilate the basement, creating a positive pressure in the basement.  Although installing a return air vent in the basement could utilize the coolness of the basement to lower AC energy costs, if you have a mold problem in the basement, this is not a good idea as it can distribute the mold spores through the rest of the home. 

• Dry it out: Check that any water pipes running through the basement area or behind its walls or ceiling are not leaking or even causing condensation.  Cold water pipes from a well or underground can easily cause condensation to form, leading to…you guessed it– mold!  Drying them off and adding insulation can solve this problem.  If there are no leaking pipes, condensation, or flooding issues, then moisture from the surrounding earth can be permeating the block walls of a basement, because concrete is porous.  (For all of my childhood, I lived in a neighborhood called “Spring Hill Estates” because it had springs, one of which was a constant source of moisture for our basement.)  It’s possible that the humidity can be lowered by running a portable dehumidifier, which should be run to a permanent drain (sink, shower or other drain) in order to avoid shut-off or accidental flooding issues.  Alternatively, there are numerous foundation and basement repair companies which can inspect and suggest drying solutions to keep the basement at a proper humidity (30-60%)--the drier the better!  Don’t wait on calling several firms for inspections and quotes, as these are normally free of charge.  

• Add some active air purification like Air Angel, a purifier that zaps mold spores using 3 technologies for more breathable air.  A standalone HEPA filter is also recommended to filter out mold spores (alive or dead) with an activated carbon element to remove mVOCs and smells.

• Get rid of “consumables” like cardboard: Side story: I was sorely disappointed to walk into my storage building at the beginning of summer and find an antique portable sewing machine case (which was covered in a clothlike material) streaked with mildew.  Similarly, if you have to use the basement for storage, plastic tote containers or vacuum bags are way better at resisting mold and protecting the items inside from moisture and insect damage than cardboard. Try to store containers on shelving with plenty of ventilation under and between them (like wire shelving) instead of stacking them on the floor or against each other or a wall.  If antiques are valuable to you, try to make room for them in your normal living area, where the humidity is more controllable.  Also, furniture that is made of “pressboard” can absorb more moisture than real wood, with less options for cleaning and disinfecting it.  The use of scatter rugs rather than wall-to-wall carpeting allows for easier washing and cleaning of the floor if it has moisture issues, too.  Consider using hardwood or plastic blinds or shutters for windows instead of draperies, which can absorb moisture. 

Combustion fumes: If you are intentionally or unknowingly using a “negative pressure” ventilation system in your home, exhaust from a gas, oil, coal or biofuel (like wood) furnace can be extracted out of the appliance’s exhaust system if it’s not well-designed or sealed.  As we reviewed in the post “How is my crawl space affecting my indoor air quality?”, the stack effect causes warm air to rise through a home and exit through the roof or attic, drawing cool air into lower levels of the house.  The rise of the hot air creates a slight negative pressure on the lowest levels, like a crawl space or basement, drawing in outside air and even extracting combustion fumes from a furnace into the air.  This can create an extremely dangerous mixture of VOCs that spreads through the rest of the home with the air flow. 

Chemicals, paints, batteries and cleaning products: We get it, these are the substances you don’t want anywhere near your pets or children, so the basement seems like the perfect space to seal them up and store them away!  It is okay to store them there, but only if they are truly sealed (hammer to the lid of the paint can or transferred to a more sealable container with a screw top) AND humidity/moisture is under control AND they are not overly old, so that metal containers do not rust.  Due to external or internal moisture, I’ve seen metal paint cans rust completely through the bottom, and then I’m left with a gooey, toxic mess!   The best scenario is to dispose of old paints and chemicals safely; most communities have a toxic material disposal site or a designated day to bring them to the regular garbage site.  It’s just safer to have these things out of the house!  If you use the basement as a hobby space, make sure to have the proper exhaust ventilation.  The stack effect can drive fumes from glue and paint and dust like sawdust particles, right up into the house.  

Install an air monitor to help take the guesswork–or legwork–out of knowing if the dehumidification and purification is working.  Thanks to wireless technology, you don’t even have to open the basement door to know if pollutants are elevated.  AirThings’ View Plus monitors all the important conditions of a basement: radon, PM2.5, CO2, humidity, temperature, VOCs and pressure (if they had to add anything, CO would be helpful for spaces with combustion appliances like gas furnaces or dryers).  Their connectivity to the app on your phone makes it easy to check!  Kaiterra’s Laser Egg + Chemical is a close runner-up that monitors Total VOCs, PM2.5, temperature and humidity (it doesn’t do radon or CO).  Either of these monitors will help you “see the unseen” air quality of your basement.

Your basement doesn’t have to be scary because of mold and poor air quality.  Shed some light on the subject by doing your own inspection, and if it seems overwhelming or the solutions you try are not working, get professional help.   The health of your family and home depend on it!

How to lower humidity in your home by choosing the right dehumidifier

If you have incorporated a humidity sensor or two into your home and monitoring routine, bravo for you!  We at HypoAir believe that these are among the most important tools you can have in your air quality toolbelt.  Now, what you do with that information–home or room humidity–-is equally important!  If the monitor tells you that a space is consistently above 60% relative humidity, after you’ve checked and mitigated the sources of moisture (see our post “Humidity and an Indoor Moisture Inventory”), then a dehumidifier can bring it down into the 40-60% range.

The great thing about dehumidification is that by reducing the humidity, you are also increasing comfort.  In hot climates, excess humidity in the air prevents our bodies from cooling effectively by evaporation, because the air is already loaded with moisture.  In cold climates, excess humidity in the air (such as in coastal regions) causes us to feel colder than in dry air at the same temperature.

You are also saving on energy usage for 3 reasons:

• Air conditioners use less energy to cool dry air than more humid air at the same temperature, and heaters use less energy to heat dry air than more humid air at the same temperature.
• In the summer you will feel cooler at any given temperature, when the air is drier versus more humid.  Therefore, you may be able to set your thermostat higher during the summer!
• In the winter you will feel warmer at  any given temperature, when the air is drier versus more humid.  Therefore, you may be able to set your thermostat lower during the winter!

Dehumidifiers come in all sizes for all applications.  When choosing a portable one for a room, it’s important to know the following things:

• Square footage determines capacity:  Just like air purifiers, dehumidifiers are limited by air flow, so standalone units can’t effectively dehumidify through walls and doors.  If you are choosing a standalone unit, measure the floor space.  The square footage measurement incorporates standard 8-foot ceilings, because it really translates to air space, which is ft3.  For 500 ft2, start with a small dehumidifier (10 pints for a moderately humid space and 12 pints for a more humid space) and add 4 pints capacity for every additional 500 ft2 (bobvila.com).  The capacity is usually measured in pints or liters per day, which is the amount of moisture the unit can draw from the space in 24 hours.  The Department of Energy changed capacity testing and ratings for models released in 2020, so newer models are not comparable to older ones.  This page shows a table comparing older and newer capacity ratings.
• Additional/ongoing moisture sources:   Human occupancy = moisture!  We sweat, breathe, and generally exude H20, and rooms with higher activity or temperature levels (like a home gym or sauna) will need more dehumidification capacity.  Also, leaks in the building envelope like doors and windows can allow moisture from outdoor air to come in.  Then, there are those inherently humid spaces that incorporate running water like bathrooms and laundry rooms.  
• Energy Efficiency:  Dehumidifiers are very much like air conditioners, with similar parts and operation.  A coolant is pumped in a closed loop system from the hot side (condenser) to the cool side (evaporator) to draw moisture from the air, collecting it in a reservoir or allowing it to drain to a permanent drain.  The compressors in these dehumidifiers used to draw significant energy (amps) to do their work of changing the fluid from gas to liquid, but newer models are much more energy-efficient.  Inverter technology decreases the energy draw most of all, because the compressor will have a variable speed motor, allowing it to run continuously at a lower speed to keep a constant humidity, or ramp up when the humidity increases.  
• Method of dehumidification:  There are two main types of dehumidifier: refrigerant and desiccant.  Refrigerant is by far the most applicable to residential needs because it can remove large amounts of water from rooms above 50 degrees F.  These work when humid air is drawn across the cold evaporator coil containing refrigerant; the refrigerant removes moisture from the air and produces condensate, and the dry air is blown into the room.  Desiccant dehumidifiers work in lower, less humid spaces by absorbing water directly into a material (desiccant), which is dried out to be used again.  There are some desiccant humidifiers on the market for small spaces like closets or cars; these require that the desiccant be regenerated in an oven or replaced with new desiccant. 

Installing a portable refrigerant dehumidifier is pretty simple; you will need to: 

• Place the unit in the room you want to dehumidify (not inside of a closet), at least 1 foot away from walls or other obstacles so that air is free to circulate around it
• Make sure it’s placed on a flat and stable surface. Sometimes carpet can be too plush for this purpose, so try to find a board or other flat surface
• Choose your drainage method (ideally you should have this in mind before selecting the unit).  If using the bucket, make sure it’s properly installed (most new units will not start working if it’s not).  If using continuous drainage, make sure that the hose is attached securely, the drain end is placed into a sink or drain, and check for leaks once it starts to operate.  Unless the dehumidifier has a condensate pump included, the drain hose end will need to be lower than the unit so that water doesn’t back up in the unit.
• Plug in and set the desired humidity level.

If you have a humidity problem in several rooms or the whole house (this is common situation in hot, humid regions), it’s wise to choose a whole-home dehumidifier. This is a permanent installation that uses your home’s HVAC ducts to distribute dry air throughout the home.  Whole house dehumidifiers are a bit complicated (not generally a DIY installation) essentially involving hanging the unit, running the ductwork, running the condensate line, connecting the unit to an electrical supply and installing the controller.   In addition, you need to make sure that the ductwork is connected to the right places: having a dedicated “return” vent for the dehumidifier, and sending the dry air to the distribution plenum for your AC, are critical for getting the most out of this unit. (pvhvac.com, bobvila.com)

One slight drawback of dehumidifiers is the heat that they produce.  Unlike air conditioners, the hot and cold sides of the heat transfer system are not separated by a wall, so the heat generated by the unit goes into the air surrounding it.  Unless the unit is placed in a small room, this usually doesn’t make a noticable difference in the temperature of the space, but it’s something to take into consideration.

Dehumidifiers need maintenance, just like HVAC units.  With standing water inside, mold can grow fast.  Some manufacturers require that the maintenance on whole house units is performed by a qualified HVAC technician, for warranty purposes.  Here is in essence what they do:

• Turn off the power
• Clean or change the air intake filter
• Clean the condensate drain line and/or add anti-microbial agents to the line
• If there is a condensate pump (typical in crawl space units), make sure it is clean and operating properly
• Make sure that the house humidity is staying in range of its setpoint

For portable dehumidifiers, you can do the following (cnet.com):

• Unplug the unit
• Wipe down the outside
• Empty and clean the bucket thoroughly with dish detergent.  If your unit is plumbed to empty the condensate into a garden hose or other hose line instead of the bucket, then unscrew the connection at the unit and use a towel to wipe any slime from inside the fitting.  Also at this time, you can dump a cup of vinegar or hydrogen peroxide (not both!) into the hose so that any algae forming in the line will die and be flushed out.
• Remove and check the bucket filter (if your unit has one) and clean it out.
• Rinse off the air filter
• Replace the bucket and air filter, and you’re good to go!

Dehumidifiers work best with air circulation!  With portable units, that means that using a ceiling or portable fan to move the air around the room, so pockets of drier or more humid air don’t form.  With a whole house dehumidifier, the fan inside the unit (if operating independently) or the HVAC fan will provide the circulation.

If you decide to invest in a dehumidifier, be sure to check the Department of Energy’s Buying Guide for additional tips, and to find Energy Star Products and rebates ($!)

To Vent or not to Vent the Attic?  It’s all about air-sealing and insulation

In the early 2000’s, this was not a relevant question for most homebuilders.  Attics were virtually always vented, in line with the thinking that ventilation was the best way to mitigate condensation and moisture issues, ice dams and other damage.  Like many elements of home design, however, practices have evolved to seal homes more tightly against energy loss and pollution.  Sealing the attic is one such evolution. 

In our article “On a home hunt?  Make sure Air Quality is on your home inspection list!”, sealing the attic was mentioned.   If you are building a new home, you will basically need to decide where the thermal boundary will fall–will it exclude the attic, or include it?  Here is a diagram to show what we mean (source: basc.pnnl.gov)

The pink lines indicate where insulation and air barriers will be.  In diagram a), the upper thermal boundary is located at the attic floor.  Notice that the roofline is broken at the eaves (small hooked part on lower ends) and there is also a “vent” in the ridge of the roof.  In diagram b), the upper thermal boundary is located at the attic ceiling (underside of roof), and there are no breaks in the roof line for vents.  Diagram a) will require that the attic is vented, but diagram b) will require that it is unvented.  Why?

Sealing up uninsulated spaces (like diagram a) will cause the air in the space to become the same temperature as the outside, but without ventilation, moisture cannot escape and mold and rot can form.  The alternative is to make sure the uninsulated attic receives plenty of outdoor air ventilation, OR include the attic within the thermal boundary, making it part of the “conditioned space” of the rest of the home (diagram B).  

Factors to consider when determining where to locate the thermal barrier in new construction include climate, desire for additional living and storage space, building design and configuration, and location of HVAC. 

Let’s explore the types of ventilation that are common in attics today (source: roofingcalc.com): 

Passive roof ventilation using:

• Ridge vents

• Soffit vents

• Roof vents including box vents and turtle vents

• Gable vents

Active roof ventilation using:

• Turbine-style (whirlybird) vents

• Motorized roof vents

• Gable fans

Many people are convinced that “if it’s not broke, don’t fix it”, and this applies to the traditional design of vented attics.  In truth, many attics have been able to ward off condensation, rot and mold for decades because they are well-ventilated and properly roofed.  If you decide to stay with a vented attic design and still keep the HVAC ducts in the attic, there are two developments that can help save money on heating and cooling.  

• Laying the ducts on the attic floor and burying them in fibrous insulation can achieve energy savings and can be done at any point, before or after building (although it’s easier whenever new ducts are installed) (basc.pnnl.gov) The key to success with buried ducts is making sure that the ducts are airtight, encapsulating them with foam (ccSPF=closed cell spray foam) if necessary, and deeply burying them in loose insulation.  Here is a diagram:

• If the ducts are hanging in your attic and you decide to keep the attic vented and ducts where they are, you can have them encapsulated in closed-cell spray foam in order to minimize heat transfer. 

Source: basc.pnnl.gov

Vented attics are not a good place for storage because of extreme heat, cold, and sometimes insect and pest issues.  Without the above measures, vented attics are also not the best place for HVAC systems, for the same reasons.  HVAC equipment will last longer and perform more efficiently when it’s operating in a temperate, dry climate.  Ducts passing through a vented attic must be sealed tightly in order to avoid pulling unconditioned air and dust into your home.  

The key to creating an unvented roof assembly is to keep the roof deck – the principle condensing surface in roof assemblies – sufficiently warm throughout the year such that condensation will not occur, or to prevent moisture-laden air from the interior of the home from accessing the underside of the roof deck. (basc.pnnl.gov)  This can be accomplished by installing rigid foam insulation over the sheathing, or (more commonly) using spray foam insulation under the sheathing.  Both require a high degree of air-tightness to avoid condensation.  In an existing home, changing the thermal boundary from the floor to roof or vice-versa can be quite a bit of work, and often it’s best to do/combine this task when reroofing or other modifications, like HVAC system replacement. 

For many people, it’s hard to imagine an attic that is not unbearably hot in the summer and frigid in the winter.  However, when the roofline is properly insulated and sealed to the walls, you have a space that is less dusty, easier to work in when renovations are made, and a better space for HVAC equipment.  It also provides a “buffer space” for all that conditioned air in your home, which tends to rise and escape through the ceiling area.  Without excess temperatures bearing down on your ceiling in the summer or trying to vent warm air in the winter, energy costs can be moderated.  If you do choose to convert to an unvented attic, be sure that the company you choose to seal and insulate it will do a thorough job of sealing, then apply sufficient spray foam insulation according to local code for your climate. 

Whether you decide to go with a vented or unvented attic space, the best choice for air quality and energy efficiency will depend on how well you can seal and insulate.  For vented attics, the living space below and any ductwork within need to be sealed and insulated from the attic space, which is an extension of the outside via ventilation.  For an unvented attic, the whole attic is an extension of your home and therefore must be sealed and insulated from the outside at the roofline.

On a home hunt?  Make sure Air Quality is on your home inspection list!

At HypoAir, we want to give you information that will help you make healthy choices about your existing home or any home you intend to live in (purchase or rent).  Real estate sites have a lot of pretty pictures, but until you step inside a home with critical eyes (and nose), you will not know the impact it could have on your life, because indoor air quality is even more crucial than the school district or neighborhood.  We hope that this checklist helps you make sure that all areas impacting air quality are assessed and addressed.

• Button it up.  It’s 2022, nearly 50 years after the energy crisis that stimulated a myriad of home insulation and building design changes.  If we’ve learned anything, it’s that insulation and sealant against air leakages is good.  The tighter the building envelope, the better air filtering and climate condition systems can do their jobs.  We list some of the points you can check, but for top energy savings, it’s best to hire a professional home energy consultant.  Certification varies by state, and here are two national pages that may help find a consultant: hersindex.com and US Department of Energy.  However, the best place to start looking for a Home Energy Auditer is with your local power company–some even conduct energy audits for free and install energy-saving equipment like lightbulbs for free.  If you need to hire an energy consultant, here are some helpful questions to ask: how do you discover the main air flow patterns in my home?  where will you target your time?  Can you address the discomfort during (winter/summer) in (name room).  What are the average savings homeowners realize with your services?  Energy consultants can perform a blower door test, and use infrared scanners and smoke tools to see the larger leaks that most inexperienced homeowners will miss.  According to energy expert Ken Gadsby, “doors and windows only account for 20-30% of air leakage in most cases”, while it is more cost and time effective to go after the other 70-80% that is coming from elsewhere. (from Solar Age article referenced here).   If you decide to do your own checks with equipment, you may want to buy a smoke pencil to find hidden leaks, you’ll want to find one that is not toxic. This brand uses glycerine, propylene glycol and distilled water to generate a non-toxic white smoke.  There are two main types of air leaks in buildings - direct leaks through the exterior walls or ceiling to the outdoors, and indirect air leaks through interior partition walls, ceilings, or stairwells and plumbing chases. (inspectapedia.com)  
  • Indirect leaks may be part of a larger convective air loop, where void spaces in walls and ceilings can pump warm air out of a house during the winter, or into a house during the summer.  You or the energy consultant may need to investigate penetrations such as ceiling lights and bathroom exhaust fans and uninsulated void spaces like ductwork, soffits (commonly above kitchen cabinets) and firewalls.  It may be that simply installing a physical barrier will interrupt the air loop and stop energy loss.  This can be done retroactively by drilling holes and using spray foam to seal cavities at the ceiling/floor level, sealing plates and void wall tops, etc.  
  • Direct leaks may occur around baseboard heaters, wall sockets and light switches (check out these easy gaskets), around window and door frames/molding, and around penetrations through exterior walls such as cable/telephone wires and gas lines.  These can be resolved with some low VOC caulk.  For larger penetrations like plumbing and drain lines, the only spray foam sealant that is UL GreenGuard Gold Certified is made by FOMO Products Inc., called Handifoam Window & Door.  Some penetrations, like electrical wires, may need a fireblock sealant by code, and Handifoam Fireblock is also GreenGuard Gold Certified.
  • Seal the attic: to vent or not to vent?  Attics are typically very hot or very cold, because the builder chose not to include this space in the conditioned space.  If an attic is insulated on the floor and interior wall boundaries, it will need to be vented so that it acclimatizes to exterior conditions and doesn’t hold excess moisture.  In the case of vented attics, according to the US Department of Energy, just a ¼” gap around the hatch (for a pull down ladder) is equivalent to a ceiling register removing heat from a room.  There are manufacturers of attic stair covers that can seal this difficult opening well.  Secondly, any air conditioning ducts in the attic must be sealed at all joints, which is something you may be able to do yourself.  As for the rest of the attic, this guide has details of all the places to check for undesirable ventilation.  On the other hand, if you live in a hot, humid climate, or want to reserve the attic for extra living space, then it’s wise to move the envelope to the roof line, and make the attic part of your entire’s home conditioned space.  Here is a page that will help you decide between venting and sealing the attic.
  • Seal the fireplace.   In general, it is the fireplace damper that opens or closes the chimney space to your firebox.  It needs to be closed when not in use, but if there is no damper, or it doesn’t seal properly, you can check out this page to decide how to seal it.  Just as importantly, the fireplace surround should be sealed to the stone or brickwork, and vents can be sealed off with magnetic covers.
  • Crawlspaces can be a source of home energy loss or increased heating bills, as well as mold and rot issues (inspectipedia.com)  The old recommendation was to thoroughly ventilate crawlspaces in order to prevent these issues, but now the recommendation is convert the crawl area to a conditioned space with vapor barriers and insulation.  Recognizing air leaks, humidity and mold issues in crawlspaces (and unconditioned basements) needs to be addressed!
• Not location, location, location: Ventilation, ventilation, ventilation!   Tight building envelopes without fresh air ventilation are unhealthy, and leaky building envelopes with the wrong types of ventilation also create problems.  Unfortunately, the average American home has no dedicated fresh air ventilation system. (buildinggreen.com) According to ASHRAE standards (formerly called the American Society of Heating, Refrigerating and Air-Conditioning Engineers), homes should receive 0.35 air changes per hour, but not less than 15 cfm (cubic feet per minute) fresh air per person (EPA.gov).  There are 4 types of dedicated mechanical ventilation; we discuss these in our post “How does indoor air pressure affect ventilation and air quality?”  Most home energy consultants recommend a balanced ventilation system that includes an HRV or ERV, however in hot and humid climates additional dehumidification will be necessary, because ERV’s actually raise the humidity level in your home.  
• Humidity.  If the interior stays above 60% relative humidity for long periods of time, it’s not a question of if, but a question of when, mold will become a problem.  Arming yourself with a simple humidity sensor on a home tour can confirm what your senses may already be telling you–does it seem too humid?  Or too dry?  Dry air can cause germs to live longer in the air, posing increased risk of respiratory infection.  You can do an inventory in your own home with our post “Humidity and an Indoor Moisture Inventory”, and HVAC experts in your area can help rectify under or over humidification with the right equipment.  The following graph shows the benefits of keeping it between 30-60%:

• Radon.  According to the EPA, radon is the #1 cause of lung cancer among non-smokers.  A colorless, odorless gas that seeps naturally from certain underground rocks, radon can permeate basement walls and foundations, as well as contaminate ground or well water.  It’s best to have the home’s air and water checked for radon levels, and if present, investigate mitigation systems (you can find local qualified contractors through the link on this page, and information on water testing labs here).  
• Mold.  As mentioned in our post “Taking our homes back from mold”, using a home inspector who is equipped with forward-looking infrared radar (FLIR) gives you “x-ray views” of hidden sources of mold.  FLIR is a type of thermographic camera that detects infrared radiation, and while it is used in military and spy applications(!), it is also extremely useful in locating areas behind walls where water intrusion may be present, making a hospitable area for mold.  Such a home inspector will also be intimately familiar with construction methods that can be causing moisture issues now or may cause them in the future. 
• Active Air Filtration and Purification.   Buttoning up the envelope and ventilating properly are non-negotiable basics; filtration and purification step up the breathability and comfort of your air.   Is the only air filtration in your existing or potential home done through the furnace filter?  If so, additional filtration and/or purification in the HVAC or standalone will help with dust, seasonal allergies, viruses, mold spores and mycotoxins, and pet dander. 
• Old House Materials.  Asbestos and lead paint are still out there in older buildings (pre-1978 for lead paint and pre-1989 for asbestos), and disturbing them will bring these hazardous materials into the air.  It’s best to make sure that your home inspector identifies any sources of these materials in case you get the (common) urge to renovate!
• Gas appliances.  Heartbreaking but vital information for foodies: gas stoves can throw quite a bit of VOCs and fine particulates (PM2.5) into the air, in addition to whatever you are cooking and what you are cooking it in.  If you plan on keeping or installing a gas stove, make sure that the ventilator hood is powerful enough for the space (check out our post ‘Humidity and an Indoor Moisture Inventory’) and it works quietly, so that you will be inclined to use it to whisk away harmful chemicals and particles.  In addition, inquire about any other gas appliances such as water heaters, clothes dryers and space heaters.  The inspector should note their age and condition (gas orifices can wear or rust over time, causing poor combustion) and if they are vented properly.  Here’s a good article for those who like to see what I’m talking about! 
• Outdoor sources of pollution.  Does it make sense to include the outdoors in an indoor air quality survey?  Yes–and here’s why.  No matter how tight your home’s envelope, we hope that there will be ample times of the year when the weather outside is just so gorgeous that it’s impossible to keep the windows closed.  At that moment, do you want to be worrying about what kind of air pollution could enter your home?  Although there’s little you can do about these sources, it’s good to know what they are and how often they may affect your ability to open windows, depending on the wind and weather conditions.  Here are just some of examples of outdoor air pollution: living near 
  • a busy thoroughfare or bus station
  • oil wells or refineries
  • trash dump
  • Stagnant farm pond or standing water (like used tire recycling center)
  • neighbors who burn trash or wood consistently
  • farms that crop dust or use aerosolized fertilizers
  • Areas that employ insecticide spray trucks
  • Golf courses and other public areas that use copious lawn treatments
  • Businesses that perform outdoor renovation work like sanding or spray painting
  • Seasonal issues like wildfires, tree pollen, ragweed, etc.
• New house smell.  New homes, just like new cars, can have many sources of VOCs, most dangerous and common among them being formaldehyde.  If you consider a newly finished or furnished home, find out if it has the following:
  • Press-board cabinets (most commonly found in kitchen, bathroom and garage)
  • Paneling 
  • An attached garage (see next point)
  • Whole-home air fresheners: terpenes in air fresheners can react with ozone to create formaldehyde (bustmold.com)
  • New drapery (International Association of Certified Home Inpectors)

Those were the biggest offenders, but new vinyl windows, insulation, drywall, caulks and adhesives can also off-gas VOCs.  This site gives detailed reviews on building products that “cure” quickly or are more tolerable for chemically-sensitive people.

• Attached Garage.  What?  Why is my attached garage a liability?  Attached garages are used for activities that people normally wouldn’t do in the home, AND they usually have air leaks that can infiltrate the home, since they are attached.  That’s why generators, motor vehicles and combustion-driven lawn equipment should never be allowed to “idle” or run continuously in the garage, even with the door open!  Also, although it may be the only sheltered place available to do home projects and hobbies, do realize that the fumes from paints and glues may work their way into the home through a leaky door, vents, and other unseen air passageways.  
• EMFs.  Although their effects are very controversial, electromagnetic fields (such as wi-fi, high-voltage power lines and stations outside and communications towers) can actually contribute to lower air quality in a home that is predisposed to mold issues.  If you have researched this topic and are concerned, you will want to know EMF sources in the neighborhood, as well the types of the wi-fi router and smart appliances, and where they are located.  Studies have found that mold growing in homes or buildings can actually be amplified by EMFs – causing mold to grow more rapidly and spread further. EMFs may also trigger the mold spores floating around in your house or body to release more mycotoxins. (jillcarnahan.com).  See our post ‘Taking our homes back from mold’ for more information.
• Wildlife.  Crazy as it sounds, if you live in an area with certain protected species, you may not be able to evict them without a special permit, or during certain times of the year.  For example, the Florida bonneted bat is a Federally endangered species that cannot be evicted from a home or building without a permit (floridabonnetedbat.org). Bat guano is extremely fragile and can become airborne if it is disturbed. Inhaling bat guano can spread Histoplasmosis, a major respiratory illness, and rabies to you and your family. (skedaddlewildlife.com ; this page also shows a short video of how bats can enter the home through the smallest of spaces!)  We at HypoAir were contacted by a homeowner who was not allowed to evict a family of bats during breeding season, and so sought air purification methods.  

Research on home air quality can help you avoid or mitigate unhealthy living spaces, make your home more comfortable, and even save money in many cases!  Make sure to check the date of any published materials on- or offline, because building codes and theories about air quality change (for example, some of the Building America recommendations made in 2005 have been superceded by newer technology).  Thoroughly inspecting and researching where you and your family will spend most of their time is worth it!