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| Strawbale Archive for October 2001 |
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| 236 messages, last added Tue Nov 26 17:42:19 2002 |
[Date Index][Thread Index]
Re: SB: Outside air, was:breathability
At 06:46 AM 2001-10-29 -0600, David Neeley wrote:
>As I understand it, were I to use inside air for combustion, I would also
>have to make sure that each time a flue damper were put in place after the
>fire is out to keep from continuing to draw warm inside air out of the
>house through the chimney effect. With an outside air intake for the
>fireplace, however, and with suitably air-tight glass doors on the
>fireplace, I think I could more readily avoid having to always close the
>damper after waiting until the fire is completely extinguished. Thus, I
>could have a fire late in the evening and safely go to sleep without
>having to set the damper. Otherwise, I would suspect I would have to be up
>until all the coals from the fire have extinguished to avoid the carbon
>monoxide from this source being spread in the dwelling--also a safety
>consideration, is it not?
Hi David:
It depends on whether you can get a door for your fireplace that is truly
airtight. I haven't seen very many.
If you leave the chimney damper open and you have an outside air supply,
you'd need a shutoff on the outside air supply. In that case, there would
be a small amount of air still moving through the system, depending on how
leaky the doors are, and how leaky the shutoff is. Any outside air moving
through the sytem wouldn't be coming through the house, but would still be
cooling the fireplace.
If you didn't have an outside air supply, you'd have the same amount of air
moving through the system with the damper open, minus the leakage at the
outside air damper. In other words, door leakage only.
We did some leakage tests on 18" x 20" masonry heater doors as part of the
CMHC study. At -25 pa, the leakage varied from 2 to 20 litres/second (about
4 to 40 cfm). Fireplace doors are considerably larger, so a reasonable
leakage rate for an airtight fireplace door might be 10 - 20 cfm. Standard
fireplace doors would be considerably higher.
Best ........ Norbert
----------------------------------------
Norbert Senf---------- mheat@mha-net.org-nospam
Masonry Stove Builders (remove -nospam)
RR 5, Shawville------- www.heatkit.com
Quebec J0X 2Y0-------- fax:-----819.647.6082
---------------------- voice:---819.647.5092
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