ERV and Poor Indoor Air Quality
We recently put an ERV into a house we recently moved into. The house is a 1950s split level that was recently renovated and flipped. The builder who bought the house and flipped it was not thoughtful about building materials, VOCs and formaldehyde. So we knew we’d put in an ERV as soon as we moved in to avoid chemical exposures as I’m sensitive to a lot of chemicals. I interviewed four HVAC companies and went with a great one. As soon as the system was connected, I started to smell an awful chemical smell from every single vent. I immediately called the company and they came out right away. He reassured me everything was connected right. After a week of this awful smell, my throat started burning and I was feeling like a torch was in my chest. Burning pain and cough (100% not covid). Goes away as soon as I leave the house. Anyways, he came out several times more to help us investigate with no resolution. Today I had an industrial hygienist out who specializes in “sick building syndrome”. He tested the air with the ERV off (it had been off for 24 hours prior to him taking the measurements) and then he turned it on. We waited an hour for the ERV to run and he took measurements again and the numbers showed dangerously high levels of VOCs and formaldehyde. It makes NO SENSE! I’m so frustrated and I’d love any input or insight. The industrial hygienist and the HVAC guy spoke today and the hygienist shared his results and said he suspects the ERV is causing some pressure change thats sending all the VOCs and formaldehyde from the lower level utility room all over the house. Clearly we need to have the ERV out. But then what? What can help with ventilation?
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Replies
Consider pressurizing the areas that you spend time in with fresh outside air.
Done right, an ERV is a good thing - I wouldn't take it out.
How is the ERV hooked up to your HVAC? You have some pictures of the setup?
A decent ERV setup should get house VOC down in no time, mine can clear the VOC spike from cooking in about 1.5h.
May be irrelevant...
Sounds like the ERV is a good thing. Sounds like the utility room and pressure changes are not.
What happens if you change the locations in the house where the ERV pulls in fresh air and spits out bad air. Would that change how diff areas of the house pressurize and the direction of air flow?
What happens if the utility room is made air tight from the rest of the house and gets its own vent system to the outside to exhaust the chemicals?
Are the chemicals getting into the return side and then going throughout the supply side?
How tight are the HVAC seam joints and what type of HVAC filter system is being used?
Your industrial hygienist might be able to map the high VOC emitters in the house, at least by room. Those rooms should run at a slight negative pressure if possible, to contain the VOC's in those rooms. If the lower level utility room is really your source, then that should be the location of the exhaust. You should install the ERV exhaust vents in those areas. The ERV supply vents go in the other rooms so that fresh air is introduced into those spaces, and it flows slowly towards the VOC source areas where air and VOC's are removed by the exhaust side. If fresh air is being supplied to the VOC source rooms, it would have the effect of spreading VOC's from those areas to the rest of the house. This setup would be slightly different than the typical ERV installation (with exhaust from bathrooms and kitchen and supplies in other spaces).
There is also a remote possibility that the VOC's are coming from the ERV ductwork or other parts of the system. Did your hygienist test the air coming directly from the ERV vents, or just the room air? S/he should test the vents themselves. If the ERV is drawing contaminated air from somewhere, if they used solvent based sealants or mastic, or if something else odd/dumb is happening, you need to locate the (other) sources of VOC's and address them too.
The industrial hygienist found the highest levels of VOCs and formaldehyde in a wall in the utility room that separates the lower level bathroom from utility room. He thinks the guy who flipped out used some super toxic adhesive, glue, or possible water proofing solvent in that wall and they didn’t insulate the wall or completely seal it. So we will do both and see if that helps. The utility room is the location of the exhaust. The hygienist measured inside the ERV and it’s not coming from within that. It appears as well f all the pressures are messed up. I just want the entire thing out at this point.
Think going with a single room ERV without any of it ducted into the HVAC system is the way to go? That way we’d be ventilating the most toxic room in the house without messing with pressure changes within the entire duct system?
True, unlike central systems, single room ERVs don't cause air movement between rooms.
Generally you can balance the flow using dampers, adjustable diffusers, or in some cases variable speed fans. You may need to get more extreme with your balancing or need to add some adjustability.
As others have said you want to bias the supply towards your living space (bedrooms/living room), and bias your exhaust to the problem areas (generally kitchen, bathrooms, etc) so that the directional airflow is from good to bad towards where you are exhausting.
If the ERV is in the worst room perhaps you can disconnect the exhaust inlet ductwork (and block it off), so that the ERV only draws from that space. (if you have natural draft appliances you don't want to make the space go to negative).
Are your outside inlet and outlet far enough apart to prevent short cycling of air between them?
Do you have other air moving appliances in the house that good be affecting room to room pressure and airflow? (ie. furnace/airhandler/dehumidifiers/filter systems, etc).
Is every combustion appliance properly vented, and supplied with combustion air?
Some pictures would be nice.
Issues with building or room/space depressurization and pressurization seem to be the most likely culprit. But to ensure that we're not missing a possible cause: formaldehyde is a 'small molecule' that folks at LBNL suspect can transfer across an ERV core. More on that issue here:
https://www.greenbuildingadvisor.com/question/ervs-and-formaldehyde
Any chance that your ERV core can be swapped for an HRV core as a test?
Source control. Rip open the wall identified as the source of high VOC's and get that $#!+ out of your house. And don't use other toxic chemical means to remove it. You can't ventilate nasty stuff away without getting rid of the source of nasty stuff first.
You said yourself the ERV is not likely the problem, it's just making it more evident. Source control.
best of luck,
j
Jason,
You advise is probably the way to go, but as a general rule you really can ventilate nasty stuff away. That's the basis for all our ventilation requirements. The quality of interior air is directly related to the provision of fresh air to dilute particulates and VOCs.
Most VOCs tend to dissipate over time, so as long as you can ventillate the area in question.
By the sounds of it, you have an ERV connected to your furance, which is not what you want in this case.
What you do want is seal off the area in question from your HVAC, so close any vents/returns in there and add in a standard bathroom exhaust fan ducted to the outside. You don't need anything large just enough to get around 1 air changes in hour in the space.
For example, if the utility room is 10x10 with 8' ceiling so 800 ft^3 a 15CFM fan is more than enough.
Once the smell dissipates, you can turn off the fan.
As for the house ERV, if the unit is unbalanced, than it is a bad install. The installer needs to adjust it properly, which is pretty easy with a decent differential pressure manometer.
What's on each side of the wall in question?
Is it just exposed drywall? Or is there tile on one side and utility room equipment in the way on the other?
Could it be that:
Pulling the drywall to expose the wall cavity in question results in finding something simple like PVC pipe with bad glue etc. which could lead to a potential outcome of: replace some pipe, balance the existing erv and things improve greatly without having had to remove an erv or install a new single room erv etc.?
If bad stuff is inside the wall cavity, could it escape up through the floor above it and continue to cause problems, even if the current erv is deactivated?
This source shows that ERVs can work, but may need > .4 ACH airflow rates (perhaps 3X what code requires). So check CFM (in addition to reducing source and fixing airflow patterns).
https://eetd.lbl.gov/sites/all/files/publications/lbnl-6022e.pdf
We have a contractor coming tomorrow to open up the wall to try to figure this out. I spend an hour in Home Depot today smelling all different things like shower liner, caulks, etc. Nothing smelled even remotely close to the smell in question. The ERV has been disconnected (but ducting and ERV not removed) and capped off as of this morning. The house smells so bad. Like pure toxic chemicals. Even with the windows open, I smell it wafting out. I’ve been sleeping at my parents. I’m really hoping to have answers tomorrow. Thanks for all of your replies.
One other piece of info.... the wall in question in the utility room has a shower on the other side of it. So I’m wondering if maybe they used a super toxic and smelly adhesive to glue in the tile?
Any updates?
The utility room has been identified as the area with the highest concentration, correct?
Does that mean the physical source giving off the bad voc's is located there?
Or, could it be that the source is located somewhere else in the house, behind the drywall, and is getting pulled into the return ducts, travelling back to the furnace, leaking out of the furnace, and giving a false reality of assuming the utility room is where the physical source is located?
We believe we’ve located the source in the wall between utility room and bathroom. We pulled off drywall and it stinks on the cavity. Appears to be bad glue and cement board. We also found an abandoned open pipe that we capped. HVAC guy thinks we need to leave drywall off for a while to let it off gas and he will put the extractor for exhaust only in utility room and er shall see
Update: the other side of the wall in suspect is the crawl space and to be sure we weren’t missing anything, we did a smoke test and there is a sewer leak in the crawl space. In addition, the abandoned vent pipe in utility room is leaking sewer gas. We will be getting that fixed, removing ERV (it’s pulling too much air from inside wall cavities, attic and crawl space) And it’s getting
Mixed with indoor air space. We will be installing a ventilating dehumidifier instead. Hopefully the ventilating dehumidifier plus fixed sewer leaks will help a ton!
Green654,
Check out this article (https://www.greenbuildingadvisor.com/article/designing-a-good-ventilation-system). You want to make sure the system is appropriately sized for your home and its occupants.
Sounds like the ERV is depressurizing the house, which exacerbates the problem that there were two sewer vent leaks. Capping the leaks solves the immediate problem, but depressurization doesn't sound good.