Reducing Indoor Air Pollution in Residential Construction and Building.

Indoor Air Quality Should Be a Major Goal for all Residential Construction.

If you could pick the most important quality of a home what would it be? You are not alone! “Indoor Air Quality” is not high on most people’s must have list. Its mainly been green builders/designers and the hypersensitive to trumpet its importance but there is a dramatic shift underway with ALL residential construction in regards to this issue. While not everyone is willing to make an effort reducing their home’s environmental impact, most people should be interested in having a home with healthier Indoor Air Quality IAQ.

Diagram showing the many sources of indoor air pollution. Building a new custom home is an excellent opportunity to address these problems

Indoor Air Pollution is everywhere. Many sources are hard to eliminate and should be controlled.

Healthier Indoor Air Quality IAQ is another great reason for building a new home. Much like improving an existing home’s building envelope or energy efficiency, its easier to build IAQ into a new home opposed to fixing existing construction.

 

3* Main steps to improved IAQ in residential construction:

1. Choose construction materials that limit harmful off-gassing and finishes that are easy to clean.

ex. No VOC paint, Floor trusses instead of TJIs to reduce formaldehyde exposure. Reduce or eliminate carpeting.

2. Positive influence on occupant behavior.

Reduce or eliminate smoke from combustion appliances, incense, candles. Bath fans for humidity control, Vent hoods for reducing NO2, cooking particulates and excess humidity.

3. Provide Outdoor Air with mechanical or passive ventilation.

Mechanical ventilation: ASHRAE 62.2 or BSC 01. Passive ventilation: windows, earthtubes, leaky walls.

*Radon and other soil gases are relevant in all of the above strategies. Passive radon mitigation systems are dirt cheap compared to retrofit and/or adding a fan to existing homes that are found to have risk action levels. Good passive radon systems pair well with sub slab drainage details. In new construction, these are cheap and easy ways of building in long-term soil gas and moisture resistance. Check back for the coming blog.

Many residential construction products emit harmful substances like formaldehyde and Volatile Organic Compounds VOCs. There are many options and alternatives available that can reduce exposure. Some details like electrical, plumbing and appliances can increase upfront costs and complication a great deal and makes the most sense for those with hyper sensitivities.

For the most part, its difficult to eliminate ALL of the offending construction materials. Then comes electronics, furnishings, appliances, CO2, humidity, etc?.. and it becomes clear that building material selection is not nearly enough to provide sufficient IAQ.

Pie chart showing that building materials are only a small part of the IAQ pollution sources in new, residential construction

According to NIOSH, building materials account for only 4% of a typical home's Indoor Air Quality problems. Reductions can help improve IAQ but realize the bigger picture and appropriate solutions: outdoor air exchange.

Outdoor Air is MUCH more important than eco-friendly building materials.

 

Most experts (I agree with) agree that mechanical ventilation is the best way of providing better IAQ. A better term could be outdoor air introduction. Outdoor air is almost always cleaner than indoor air. Its a good thing to reduce harmful materials and finishes but I want people walking away from this blog knowing the truth about IAQ: supplying outdoor air and exhausting indoor air should be the main strategy for better IAQ.

Be a control freak

Controlling air is good. Having control over conditioned air and fresh air should be one of a designers, builders and homeowners most important goals. This is the essence of building air-tight. The more leaky and drafty a home, the less control of conditioned air (high energy and environmental costs), delivery of fresh outdoor air and exhaust of polluted indoor air. By building tight, we gain more control of these air concerns and it also helps prevent humid air flowing through building cavities which is a recipe for mold in hidden places.

Be conservative and extremely careful with combustion appliances

The best way to eliminate risks from combustion appliances is to avoid them altogether. This is an increasing trend among high performance home builders and designers. “All-electric” homes have less risk of fire and have healthier indoor air quality.

Picture from Energy Vangaurd blog showing atmoshpheric combustion water heater existing house construction

Energy Vangaurd's picture of an atmospheric combustion water heater in existing construction

Avoid atmospherically vented appliances and especially vent-free fireplaces. Power vented and direct vented combustion appliances need to be meticulously installed and regularly inspected. Even a properly installed, power vented appliance can eventually be a source for indoor air pollution.

 

Induction Cooktop with cross section of pan and half melted chocolate bar.

Induction cooktops have the best indoor air quality. Energy is focused to the metal, reducing smoke and cleaning.

 

Consider an Induction cooktop. Due to the cooler surfaces of the glass cooktop, they have better indoor air quality than conventional electric cooktops. Gas cooktops have the worst IAQ. Down draft vent hoods require special care in layout and installation and rarely perform as well as overhead. Vent hood capture efficiency is one area researchers are finding measurable improvements. The variables are vertical height from stovetop to vent hood and the area of the hood around the cooktop.

Avoid parking the car in your house

Garages are a major source of indoor air pollution and can introduce dangerous situations. Detached garages are the best. The more attached the garage, the greater the risk. There are strategies available for dealing with the dangers of attached garages but its always risky when a garage shares a wall with the home. There have been many cases of death from automobiles left running in a garage but many more undiagnosed cases of Carbon Monoxide poisoning.

Diagram of a home construction showing sources of carbon monoxide

The Attached Garage is an often overlooked source of Indoor Air Pollution in residential construction.

Avoiding attached garages and combustion appliances in new construction is an easy way to eliminate indoor air pollution sources.

Air-tight Building Envelopes and mechanical ventilation gives us control over the where, when and how air moves in our houses and new construction.

Where

Providing fresh air introduction is easier when we know exactly where it is going and coming from. A leaky basement or sub-floor can introduce radon, excess moisture and mold spores. A drafty attic can bring in hot temperatures and outdoor humidity. Humid air leaking through random cracks in the building envelope can cause mold growth inside walls and other hidden building cavities.

WheN

We can also control when the building breathes.  In extreme weather or times of high pollen, turning down the ventilation might be better. During times of kitchen use, cooking odors and smoke, dialing up the ventilation can help clear the air quicker.

How

How we provide the ventilation is where things get more interesting. ASHRAE 62.2 provides the minimum ventilation requirements that International Building Codes recognize. There are many strategies and variables to consider in a well designed ventilation system for new home construction. We will explore much more in our future posts. How exciting!

Providing fresh, outdoor air with mechanical ventilation is probably the best way to reduce indoor air pollution in residential construction and home building projects. Visit understanding ASHRAE 62.2 for more on this important topic.

Springtime Homes is a custom builder in the Asheville NC area specializing in Indoor Air Quality, cost-effective energy efficiency and building science best practices beneath the finished surface.

 

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