[Greenbuilding] Visible Flames (Fireplaces) in Tight Houses

[Alan Abrams]

Norbert-

taking your discussion forward suggests that combustion air could be
provided by a self balancing ERV, but the IRC mandates an exterior air
supply using "*listed* components of the fireplace." [their emphasis]

Have you worked around this before?

-aa



Alan Abrams

*certified professional building designer, AIBDcertified passive house
consultant, PHIUS*
*certified passive house builder, PHIUS*
cell     202-437-8583
alan at abramsdesignbuild.com
HELICON WORKS *Achitecture and Education*
<http://www.heliconworks.com/index2.html>

On Wed, Dec 3, 2014 at 11:47 AM, Norbert Senf <norbert.senf at gmail.com>
wrote:

> On Wed, Dec 3, 2014 at 10:31 AM, Lynelle Hamilton <lynelle at lahamilton.com>
> wrote:
>
>>  My masonry heater did just fine on this count.
>>
>
> Further to Lynelle's point, I did an investigation for CHMC back in 1994
> on air requirments for masonry heaters in airtight houses.
> The only technical issue is whether the appliance consumes sufficient air
> to depressurize the house enough to cause drafting problems for naturally
> vented appliances such as gas water heaters, etc. and thereby cause a
> carbon monoxide danger.
>
> Previous CMHC sponsored research had determined a house depressurization
> limit (HDL) of -5pa as being acceptable. We measured the actual air
> consumption on a number of heaters, and assumed the tightest tested R-2000
> house I could find (ELA of 0.02 m2, or 30 sq. in.). Computer modelling
> showed a maximum depressurization of -2 pa or well under the limit.
> Moreover, when the pressure test is done on a Canadian R-2000 house, you
> have to tape up both of the 5" holes from the HRV, because these are
> actually leaks in the envelope that are not counted as such. Here is the
> study:
> http://heatkit.com/html/papers-n/airreq/Cmhc-rep.PDF
>
> On the other hand, if you install an outside combustion air supply on a
> stove, and the exterior opening is on the leeward side of the house, a
> strong wind can cause the combustion air supply to become a chimney. There
> is a famous video of the flames going into the airwash outlet at the top of
> a zero clearance fireplace door. In addition, to get clean combustion you
> need a hot firebox, and sucking -20F air directly onto the fire is very
> counterproductive in this regard.
>
> Norbert
> --
> Norbert Senf
> Masonry Stove Builders
> 25 Brouse Road, RR 5
> Shawville Québec J0X 2Y0
> 819.647.5092
> www.heatkit.com
>
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