Re: SB: Outside air, was:breathability

[Norbert Senf <mheat@mha-net.org>]

At 05:46 PM 2001-10-28 -0600, David Neeley wrote:
>(snip)
>To make my own plans a bit more clear, I am looking at building in a small 
>fireplace of some kind as a very occasional supplemental heat source. In 
>fact, it would be used so seldom that I'm not convinced I'll even bother 
>with it at all. However, if I do I am very interested in the airflow 
>requirements for such fireplace, and what quantity of conditioned air is 
>being used compared to the heating benefits.
>
>So--outside of masonry heaters, is there any realistic data?

Hi David:

Yes, there is. As part of a study I did for CMHC on air requirements for 
masonry heaters, we looked at a computer model of a small open fireplace in 
an airtight house. The bottom line was: if the house was the most airtight 
ever built around here (25 sq. in. Equivalent Leakage Area or ELA), and you 
add two more 5" dia. holes for an HRV, then (theoretically) you can run an 
open fireplace with a maximum flue size of 8" dia or an 8x12 "modular" 
(ie., 6.5" x 10.5") flue liner. This will depressurize the house to about 
-5 pa, which is just at the acceptable limit.

In other words, a small fireplace will work for sure in a house that is any 
leakier than that, and 99.99% of them are. This is contrary to all accepted 
building science, however, since everybody "knows" that of course you can't 
put an open fireplace in an airtight house.

If there is any problem, all you have to do is supply makeup air. Cracking 
a window by 1/2" constitutes makeup air.

In other words, if you have a 65 sq. in. flue, you need about 65 sq. in. of 
leaks. The fireplace doesn't particularly care where they are.

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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