Dust Mitigation Case Study

Article summary

This is an actual case study of a job in which we significantly reduced the level of dust in a home in Gainey Ranch in Scottsdale. We did not eliminate dust in this home. It is impossible to eliminate dust in a residence. What we did accomplish was to reduce the dust to a level the customer found tolerable. The customer had the financial means to aggressively go after this problem and we had the knowledge, tools and experience to accomplish the goal.


Our customer

The customer ran her index finger across her grand piano in her living room and asked me if I could see the dust streak. The dust was very apparent and the question was asked to establish a point. It was clearly implied, “dust is my problem and if you undertake this job to get rid of it, I will bench mark the success of your work by evaluating how much dust settles on my grand piano the day after I clean it.”

The customer proceeded to tell me that the excessive amount of dust in her house was disgusting. Her husband simply wanted the problem solved so the constant complaining would stop. She skeptically asked, “can you solve this problem?” I told her that I would let her know after Advantage Home Performance’s audit team completed their evaluation.


The dust problem: real or imagined

The first thing I had to determine was if the problem was real or imagined. I have been on several jobs where people were upset about dust levels that I considered to be normal. They simply hated any dust. I can’t help people like this because it is impossible to eliminate dust.

I began by inspecting dust levels on tops of cabinets, pot shelves and other places that cleaners never dusted to determine if the problem was legitimate. Our auditor also took measurements with our laser particle counter. Our visual inspection and measurements indicated that there was a significant amount of dust in the air and on surfaces.


The comprehensive audit

The next step was to perform a comprehensive audit. Advantage Home Performance’s audit team performed a variety of tests including blower door and duct blaster tests, as well as testing room pressures and an infrared scan. The high duct leakage and room pressures indicated that there was a great deal of air communication between the house and the attic. I suspected the dust was coming from the attic and getting into the house due to a variety of holes in the building envelope and pressures driving the air flow. For more information on the comprehensive audit see our article titled “The Home Evaluation Process.”


Filthy attic

An inspection of the attic convinced us that the problem was real and that we could really help this homeowner. The blown white fiberglass in the attic directly under the attic vents almost looked like brown cellulose due to the heavy layer of dust on top of this existing insulation. The amount of dust coming through the attic vents was significant. This dust can be seen in the photo below. I removed a handful of the dirty insulation to show the blown white fiberglass insulation beneath the layer of dust. This dust was finding its way into the home every day.


Duct leakage

The dust found its way into the house via duct leakage and pressure imbalances due to door closure. The air handlers were running 24/7 so the state-of-the-art electronic filters could do their job, but running the air handlers only made the problem worse. Dust was being sucked through every recessed electrical can light in the main body of the house when bedroom doors were shut. Return leaks were sucking dusty air into the house.  For more in-depth information on this topic see Duct Leakage & Repair article

If you examine the two photographs below carefully you can actually see the attic air being sucked down an interior wall and into the return. These are two photographs of the same wall in the house. Notice the return grille on the bottom left. The return is actually drawing air from the attic. This phenomenon can be seen in the infrared image on the right hand side and shows a dark streak going down the interior wall and into the return. Since this photo is taken the in winter that dark streak is cool air being sucked into the house via the attic. The dust in the attic completely overwhelmed the state-of-the-art air filters that were supposed to solve this problem.


The dust mitigation package

I proposed a package of improvements that included insulation removal, elimination of the attic vents, cathedralized half pound foam insulation coupled with duct sealing and fresh air ventilation with HEPA filtration. The homeowner accepted our quote because it provided the greatest likelihood for success. I was confident we could make a great improvement in this house given the problems the comprehensive audit revealed.


Insulation removal

According to the “Guidance on best Practices for the Installation of Spray Polyurethane Foam” existing attic insulation needs to be removed. Here at Advantage Home Performance, we always remove the existing attic insulation prior to spraying the foam. It is the only way we can ensure the job is done properly from an air sealing perspective. Insulation removal also helps prevent odors from lingering in the attic. By removing the attic insulation we effectively got rid of all the dusty fibrous insulation in the attic.  For more in-depth information see Insulation Removal article.


Unvented attic with cathedralized foam insulation

Source control is the first step in dealing with dust and indoor air quality problems. By covering up the attic vents with sheet metal prior to spraying the foam we in effect eliminated the entry point of most of the dust that is getting into the home. The half pound foam is classified as an air barrier, as well as insulation, so we completely sealed off the attic from the outdoors.


Duct leakage & pressure balancing

I also knew that by bringing the duct work inside the thermal pressure envelope, not only were we going to dramatically reduce the dust levels in the home, but we were going to see large energy savings. According to Manual J, the duct load can be 25% to 40% of the sensible load. Insulating at the bottom chord of a truss and leaving duct work in an extremely hot attic will eventually be seen as an obsolete way of building and insulating a home. Foam is the future of insulating and retrofitting homes in the desert when there is an air distribution system in the attic.


Fresh air ventilation system

The post-repair blower door testing proved that we reduced the measured air leakage of the structure dramatically; we had the customer install a fresh air ventilation system with energy recovery because the house was below the minimum ventilation requirement. Not only did we bring in fresh air to meet BPI and ASHRAE Standards, but we filtered the outdoor air through a HEPA filter.


Success!!

Advantage Home Performance’s work passed the piano test. Our customer was very satisfied with our dust mitigation work. Although there will always be dust generated by the occupants, their dog, clothes, etc. the dust levels were dramatically reduced. The customer also noted that their utility bill dropped significantly and the humidity level was much more comfortable. Although the ticket price for the retrofit foam was expensive, the foam retrofit approach proved to be very effective at solving this customer’s dust problem.


Ancillary benefits of foam insulation

In the process of reducing dust levels we also improved the house in several other important ways. Our customers told us that the indoor environment improved in several key ways:

  • Lower utility bills
  • Much quieter
  • More comfortable level of humidity
  • Fewer insects

These benefits are realized when you eliminate the attic vents, spray the roof deck with foam and bring the HVAC system, including duct system, into the thermal pressure envelope. These measures have a very positive effect on the home if done in conjunction with other good building science principles.


Dust mitigation evaluation fee

We charge a diagnostic fee to inspect homes for elevated levels of dust accumulation. The way to produce results is to thoroughly understand a problem before repairs start. We charge this fee in order to slow down our inspectors. We need to do a thorough assessment in order to understand your home. If your home’s architecture doesn’t lend itself to a straight forward solution, we’ll tell you. We charge a fee ranging from $200 to $400 for inspections regarding dust reduction. The fee is based on the size of the house and the number of mechanical systems in the home.


Do your research – retrofit spray foam jobs are complicated

Retrofit spray foam jobs are much more complicated than traditional insulation jobs for a variety of reasons. We encourage all home owners to do their research prior to starting a job. Here is an excellent link for homeowners who want independent information: https://spraypolyurethane.org/Main-Menu-Category/Consumers

The next best thing you can do is be selective when choosing a spray foam contractor. Hire a knowledgeable and conscientious spray foam contractor who has a good reputation. He or she should have an in-depth knowledge of heating and air condition systems and building science. It will most likely cost more to have a knowledgeable professional do the job, but it is definitely worth the cost.


Why Advantage Home Performance?

You do not want to have a company that lacks the in-depth knowledge, multiple contracting licenses, building science experience on staff and the core values we possess to perform this type of work in your home – too much can go wrong. Advantage Home Performance has been spraying foam insulation for over fifteen years. All of our spray foam technicians have over ten years of experience spraying foam. We bring the auditing and HVAC experience to help you understand if your house is a good candidate for a retrofit foam insulation job.


Related Articles & Links

  1. We have an article titled “Spray Foam for Existing Homes”
  2. See our suppliers video called Healthy Home: Spray Foam Home https://www.youtube.com/embed/vUI4EMhpxhU
  3. http://swdurethane.com/

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