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mason contractors
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Discussion Starter · #1 ·
seems no matter how many times we think we have it all upstairs there's that old forget factor..... here's a good trouble shooter read.

I was surprised to find that the calculations for makeup air which is based on a room's cubic ft total, were dead on. I came within 6 sq inches of what they say is needed for a 30' by 18' room. ie they suggest 28 sq.inches for a 1000 cu ft and 4 more sq.inches for every extra 1000 c.f.

That would mean I need 28 plus 48 = 76 sq inches for a throat or "chimney access" as they put it. I have 47'' by 1-3/4'' = 82.25.
Interesting is the fact I have never hooked up the make up vent....I guess it gets what little it needs via crevaces via the chimney being long and warm.
Noteworthy is the mention of the need to limit the draft of powerfull chimneys and leave unchoked the weak ones. Yet even more noteworthy is that they mention using a blower on weak chimneys and keeping the throat in check which means choked to a oportune volume/and velocity, basically the same as with the stronger chimney.
If one thinks about it, a fully open throat on a weak or ill built fireplace will only result in eddies passing down through.

Nothing is ever mentioned about facilitating for draft fluctuations in a fireplace no matter where you read. I guess the fume hood people are up on the so called "knowledged" fireplace industry ..heck those people have to work in front of those fume ridden hoods 24 7!
They know there is nothing better than utilizing a vortex friendly cavity to shock absorb flow inconsistancies which can be as as a door opening. that cure smoky fireplaces&f=false
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