Fiberglass getting into house from crawlspace

The first day, the installer "stuffed batts" (as he put it) in the joist channels for about 3 hours. That evening I got the unmistakable feeling of fiberglass in my eyes, and felt kind of itchy in bed (not in a good way.) The next day, a different installer finished the floors and got much of the pipe and duct wrapping done. That night my wife mentioned that she had dropped her clothes on the bathroom floor when she took a bath, and when she got dressed again her clothes made her itch.

In December I tried to do everything under the house that would ever need to be done and would be more difficult after the insulation was in place. One of the things I couldn't work up the energy to do was to tape the joints of the heating ducts. The ducts are 6" round aluminum, installed when a new gas furnace went in about 15 years ago. They appeared to have been installed very well. The joints were tight, but not airtight. I decided that the benefit to be gained by taping the joints was small in relation to the effort involved; if I had put a dollar figure on my time, I estimated that the value of heated air saved would never pay it back. About half the ducts were in joist channels, anyway, and the insulation under them would hold any escaped heat against the floor.

Now that fiberglass dust is getting into the living space, my wife tends to view my decision not to tape the duct joints as if each joint is a large fiberglass intake port. My argument that the very reason for taping joints is to prevent heated air from getting out, not to prevent contaminated air from getting in, is weakened by my lack of certainty that there is never any time during the heating cycle when a negative pressure condition could exist in the system.

Any information or advice would be very much appreciated. (However, please do not suggest getting a new wife---a variation on that particular event is what I'm trying to avoid.)

Thanks, Stan

When I was doing research about the best materials to use for sealing duct joints, all the information related to stopping heat loss by preventing heated air from blowing out of the system. Measurements were generally somewhat indirect for my purposes because the issue was time to failure of various sealing materials. In all cases, however, the standard of measurement was percentage of airflow relative to the airflow measured at the original, unsealed condition. Were these studies simply failing to mention that a system could be both losing and gaining air to/from the outside in different places at the same time, or at the same place at different times?

I hate it when my wife is right about something that she knows essentially nothing about, and I'm wrong about it because even though I know quite a lot, I either don't know or I misunderstand one or more critical things.

Do you have any suggestions for simple ways to test for the presence of fiberglass fibers at the registers or on horizontal surfaces? It would be reassuring to be able to see that the problem was diminishing. On the other hand, I wouldn't have such a depressing feeling of possibly going to needless extremes if I was sure that the problem wasn't getting better and more drastic action was called for.

Thanks, Stan

If you did that then you would:

)1( raise the system static pressure thus burn out the fan motor.

)2( during heating it would cause the unit to trip out on the high limit safety because of low air supply

)3( during the refrigeration cycle it would cause the evaporator to freeze solid with ice.

)4( more problems but that should give you an idea of trying to after engineer filters on the supply air side.

T_Bone

Yes, a poor joint can leak both ways at the same time. It"s like a water drip, it doesn"t look like a lot of water on each drip but it"s 5gals a day on a typical dripping facuet.

I would use a white T shirt to make a ballon over the register for a 1hr period then take the shirt out in the sun as then you can see all the fibers sticking up. To get a average you would need to preform the test several times.

Once you get all the duct leaks plugged you then could call a professional duct cleaning company, about $270 20yrs ago. You would still have some fibers left over but I would think you"d be able to have 90% removed.

T_Bone

My first thoughts would be that the loose material from the recent installation has gotten into a place where it could be picked up again. Hopefully you do not have any return, fresh air duct picking it up, and with the supply lines, it would seem minimal. Anytime you have done work where there is a duct system, it's very possible for some contamination to occur, but one would think that the filter should catch most of this. I'd be changing those out a few times after a short interval of service right now. I'd have to wonder if there was a way to detect those fibers, try to figure out the origin.

When I have to deal with insulation I use a spray bottle and slightly mist each batt, just to keep some of the loose fibers down, sounds strange, works for me though.

One would also think that the loose fibers would have to be airborne, and that a supply or return duct would need to have a certain air velocity, (smaller duct, with a large or oversized air handler /fan to create a vacuum from higher velocity air flow) as opposed to volume (cfm's) to suck in those fibers that you would think should be settled out by now. A residential system probably would not be capable of creating a strong enough vacuum, especially with leaks in the main and branch ducts. What could make the fibers airborn again ?

If an area where the insulation has been installed has positive pressure, then it's possible that some kind of air flow could pick up loose fibers and distribute them elsewhere, where there is negative pressure. Sounds like it could be likely from all the disturbance during the recent installation, would be nice to lightly mist the areas to settle those fibers out, after it drys, it could reduce the airborne contaminants as they would have a slight bond from the misting with water and drying in place, until physically disturbed again. Maybe another substance besides water could be used to lightly cover and hold down the dust and fibers.

Makes me itch thinking about this, I remember how much I hated unloading owens corning trucks that delivered our insulation to the lumber yard, really nasty work, even with a forklift.

If you have any return ducts in the crawl space THOSE would be at a (slight) negative net pressure when the system operates, and could suck in some fiberglass. Check the returns out carefully, if any are down there.

Supply duct leakage into your crawlspace can have the side effect of de-pressurizing the house (your furnace blower pumps air outside the building envelope, where some is lost). Make up air will have to come from infiltration, possibly up through the floorboards. This air leakage will tend to bring fiberglass dust with it.

Something else to consider is "the stack effect". If you have air leaks in the upstairs ceiling (such as from those wretched can lights), then heated air will tend to rise into the attic, again pulling makeup air through the floorboards and pulling in fiberglass dust.

I suspect most of the problem comes with glass fibers knocked loose during the installation, and this problem (whatever its source) will abate itself fairly quickly.

It seems idiotic to me that we work so hard to seal and insulate our houses, then pump our indoor air "outside" into an unconditioned attic or crawlspace in order to distribute heating and cooling.

If we were more willing to sacrifice a bit of floor space and a dropped ceiling or soffit here and there, we could keep the ductwork inside the house where it belongs.