Cohousing-L Mailing List: re:heating ductwork

[Robert W. Tom (be417]

on Fri, 20 Mar 1998 
Virginia Moreland <vmoreland [at] mindspring.com> wrote:

>    ...differences between fibreboard and metal ductwork in
>    heating systems?  
>    ...wondering whether there is any long-term danger of
>    fibreglass particles getting loose in the air circulation.

Hello Ginny;

Any old fibreglass duct liners that I've seen have always acquired
a nice grey or blackish patina (having started out as a brilliant
yellow when new). 

I assume this black stuff to be at best, merely dirt... and at
worst, some nasty mould... neither of which I'd be too delighted to
have in the ventilation airstream.

All ductwork accumulates crud in its lifetime ...even slippery-
smooth sheet metal ductwork ... and it would seem reasonable to
assume that fibreglass ducts (which are far from being smooth)
would be better at accumulating crud than sheet metal. (Probably
one of the reasons some types of furnace filters are made of
fibreglass eh ?).

I think that it would be pretty safe to assume that it is
impossible to clean fibreglass ductwork without releasing glass
fibres into the ventilation airstream.

With glass fibres, it is the size of the fibre, not the chemistry,
that poses a potential health hazard (they say ratio of 3:1
length:width probably being carcinogenic);  the small ones being
the most likely to be inhaled and become lodged in the lungs. 

>From what I've seen, duct liner material appears to be the short
fibre variety.

Then there is the issue of offgassing of the binder used to hold the glass
fibres together (assuming a binder is used).

Obviously most of the above is merely conjecture from a Chicken Little and
probably not worth the paper it is printed on (note no paper). 

Given the tremendous negative impact that poorly designed
ventilation systems can have on human health, I would suggest that
your question be posted to a List whose memebership is comprised of
IAQ experts (ie the Greenbuilding [at] crest.org  or the ee-
building [at] crest.org Lists).



--
Rob  Tom
---------- * ------------
be417 [at] FreeNet.Carleton.ca
Kanata,  Ontario,  Canada