[Greenbuilding] Fireplace questions

[William Revelle]

At 7:06 PM -0500 11/6/06, Norbert Senf wrote:
>At 10:52 AM 11/6/2006 -0600, Ian Remmler wrote:

A quick follow on to Norbert's very thorough answer:

Some relevant links discussing fireplaces:

http://homeenergy.org/archive/hem.dis.anl.gov/eehem/94/940909.html

Then, for more than you want to know about fireplaces

http://revelle.net/lakeside/fireplaces.html


We have used the RSF onyx for three years now and 
are very impressed.  It uses outside combustion 
air and provides noticeable heat inside. 
http://www.icc-rsf.com/en/fireplaces/foyer_onyx.asp 
The doors are airtight and so takes no makeup air 
from inside but rather produces about 30-40K 
BTU/hour of heating.

Bill


>
>
>>I know most fireplaces just suck out warmth,
>>but I would go with a Rumford fireplace, which is supposed to be
>>pretty efficient.  I'm in the Austin, Texas area, so I don't
>>need to heat the house with it; I just like sitting by a nice
>>fire!  So as long as there is no net energy loss, I'm fine.
>
>Hi Ian:
>
>All open fireplaces are limited in efficiency by the amount of excess
>air that they have to move. They use 10 times or more air than a fireplace
>with a glass door.
>
>The efficiency of a large open fireplace is pretty much a function of
>outside air temperature, which has to get drawn into the house and heated
>to room temperature. With an outside air temp of -40F, pretty much any open
>fireplace will run in the minus efficiency range. With an outside temperature
>above freezing, a small open fireplace with a reasonably sized flue is
>actually not that bad.
>
>
>
>>1. I've read that bringing in outside combustion air is the only
>>way to go, but rumford.com indicates that due to the Rumford's
>>efficiency, it's unnecessary, and that your ventilation system
>>should take care of bringing in makeup air.  Who's right?
>
>There is no such thing as outside combustion air for an open fireplace.
>It is more correctly termed makeup air. Combustion air goes directly into
>the firebox. An open fireplace doesn't actually
>have a separate firebox, strictly
>speaking, until you put a door on it and separate
>it from the house. Even though
>the codes call for bringing the air in near the
>fireplace opening, the fireplace
>doesn't actually care -- the air could be brought in on the other side of the
>room (through a cracked window, for example).
>
>Whether or not you need makeup air doesn't have much to do with energy
>efficiency. It depends on how tight your house is. If your fireplace is large
>enough, and your house is tight enough, the fireplace can draw enough air
>(around 500 cfm for a 4'x4' Rumford) to depressurize your house,
>causing it (and other combustion appliances) to spill into the house. Again,
>cracking a window is a surefire cure. Actually,
>how much you need to crack the window
>is a pretty good measure of how tight your house is.
>
>
>>2. Assuming rumford.com is right on question 1, would it be
>>better to put the fireplace in the interior, or would an
>>exterior wall be OK assuming everything is well sealed,
>
>Exterior wall fireplaces are a really, really bad idea, for numerous reasons.
>
>Best ...... Norbert Senf
>
>
>-------------------------------------------
>Norbert Senf---------- mheat(at)heatkit.com
>Masonry Stove Builders
>25 Brouse Rd.
>RR 5, Shawville------- www.heatkit.com
>Québec J0X 2Y0-------- fax:-----819.647.6082
>---------------------- voice:---819.647.5092
>
>
>
>
>
>
>
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-- 
William Revelle		http://pmc.psych.northwestern.edu/revelle.html   
Professor			http://personality-project.org/personality.html
Department of Psychology       http://www.wcas.northwestern.edu/psych/
Northwestern University	http://www.northwestern.edu/