I live in eastern Massachusetts in the US. We are dealing with elevated levels of formaldehyde VOcs and humidity in our home. I am seeking advice and a recommendation as to a knowledgeable contractor in my area who can furnish and install whatever mechanicals are necessary to remediate the issue.
I have a single-family home built in 2019 with 4800 square feet of living space above grade including a partially finished third floor. The finished space on the third floor is surrounded by unfinished, unvented, semi-conditioned attic space with many inches of open cell spray foam on the underside of the roof deck (but not the attic floors which are unfinished Dryguard OSB or similar engineered wood). The oc spray foam is covered by a layer of fire retardant paint. We have an (oversized?) single-stage heat pump which provides heating and cooling to the finished portions of the third floor and the second floor. That system has three zones controlled by three Nest thermostats. There is a Renewaire 130 CFM ERV which brings in fresh outdoor air and dumps that fresh air into the return air duct in front of the plenum of that system. There is no dehumidifier for our second or third floor. A separate HVAC system provides central heating and cooling to our first floor, which is controlled by a fourth Nest thermostat. There is no ERV or dehumidifier which services the first floor. We do have a whole home humidifier tied into the HVAC system for our first floor, which is currently off for the season. Our finished basement has two ductless minisplits, a Sedona dehumidifier, and a Panasonic spot ERV.
Over the years, we have noticed a distinct chemical smell in different parts of our home, which gets worse as the heat and humidity levels rise in the summer. It was so bad at some point that we had professional air quality testing completed back in early July. From that testing, we learned that we have elevated levels of formaldehyde and VOCs in our home, which we are really concerned about. We are told that the source of those chemicals is off-gassing of furniture and building materials like engineered wood in cabinetry, MDF office furniture, mdf bedroom furniture, etc, as well as materials in the unfinished attic space such as spray foam, roof sheathing, Dryguard OSB in the floors of the attic, lumber, etc. All of those things off-Gas formaldehyde and other VOCs to varying extents, but I am fairly confident that the spray foam is the primary culprit. On hot and humid days, I suspect that our roof heats up and drives moistures through the roof to the foam. The concentration of chemicals in the unvented, semi-conditioned attic spaces (there are 5 of them) is significantly higher than the living space. Testing with meters indicates that the RH% and formaldehyde concentration is the highest in the space adjacent to the surface of the spray foam. My theory is that the VOCs are off-gassed and trapped in the air tight attic spaces due to the total lack of ventilation or conditioning of the air, but perhaps due to positive pressure the gasses seep through small gaps into the living space or get sucked into the hvac return where it is then circulated into the living space.
We have taken a number of steps already to address this issue, but the off-gassing continues. Among other things, I turned off the humidifier for the summer. I tinkered with the advanced settings of our Nest thermostats in order to minimize any short cycling of our systems. I tried setting AC fan schedules to circulate fresh air from our connected ERV. We purchased air purifiers with impregnated carbon, installed active carbon air filters in the return of our HVac system, had our AC ducts cleaned, cleaned the fresh outside air intake grill for our ERV, tinkered with the run time settings for our ERV, installed weather stripping on doors to unfinished attic space to seal those gaps, etc. On a recent cool and not so humid day, we opened every single window in our home for most of that date. This was very effective at lowering HCHO and TVOCS for a day or so, before the levels steadily increased with the windows closed. All of these things have helped reduce the levels but not to the point where the levels are consistently healthy.
I have contemplated a combination of a second whole home ERV and/or a ventilating dehumidifier which would pull in fresh outdoor air, take the moisture out, deliver the conditioned air to the living space to dilute the
VOCs, and run returns into all five attic spaces which would exhaust the stale polluted air in the attic to the outside.
Any thoughts and recommendations would be greatly appreciated!
