[Greenbuilding] air tight wood fireplace

[christian corson]

Alan

Heating with biomass in a PH is neither oxymoronic nor moronic. In central
europe and especially Austria it is business as usual actually. In your
southern (Mid Atlantic?) climate it is however more of a luxury than a
necessity. In PH's in general fire on the floor of the cave is a luxury. In
cold rural climates supplementing with biomass makes quite a bit of sense.
I have designed a few boiler systems with radiant barriers that pipe into a
DHW system and provide the bulk of the DHW in the winter. In Austria ( a
heavily forested rural area, much like my home state of Maine except
warmer) there are companies that supply product's especially designed for
this. ( Austria also does not have the FIT's that Germany has for Solar)
Windhager is one such company, and has been making Biomass boilers for 90
years.

It is not necessary in a PH to have some fancy Damper system. It is nice to
keep the air out at the roof assembly, preferably above the thermal
envelope, but it should not be a deal breaker. Yes, there is a thermal
penalty in the form of a cold bridge but the penalty should not be enough
to contraindicate certification; If the rest of the structure is thermal
bridge free preferably with negative PSI values. If the foundation details
are only mediocre , all bets are off. If your PSI install at the windows is
poor .023 btu/hrft2F ish (default setting in version 6 and &7) than all
bets are off as well.

Although I love the RAIS products (the rondo especially) they are expensive.
Morso makes some nice airtight units, I have used the squirrel in two PH's.
Regency makes some PH suitable units as well, There are many others, all
with make up kits.

There is some Dogma about biomass in the US mostly perpetuated by Kat (with
some good reason BTW) at the earlier stages of the training's going back to
2009. It does make the detailing more complicated and it is just plain
easier to not have the chimney penetration. Also it is for the most part
completely unnecessary and therefore more costly.To me a dual system with a
hydronic connection makes more sense, but is also that much more
costly.Even in a climate with 7400+ HHD I can get by with a small 1.5KW
post heater in the supply air and a single ASHP. It's a no brainer.

cheers
c


*Christian Corson *
*Technical Director
EcoCor Design/Build*
ecocor.us
chris at ecocor.us
207 930-5088


On Sat, Oct 19, 2013 at 12:07 PM, Alan Abrams <alan at abramsdesignbuild.com>wrote:

> we need an air-tight wood stove for a passive house project.  from a PH
> perspective, "air-tight" and "wood fireplace" may be oxymoronic.  one could
> even say, "moronic" but that is another issue.
>
> nevertheless, the ideal unit would have a glass door, and a means of
> providing combustion air and a flue--which not only are "air-tight" but
> also allow air-tight damping close to the building envelope.
>
> what would seem optimum to me for combustion air would be a port on the
> side of the firebox that could mate with a standard pipe fitting.  to that,
> standard pipe could run laterally to a side wall, and could be controlled
> by a gate valve just inside the wall surface.
>
> likewise, the flue damper would be located just under the roof deck,
> operated by a chain or cable.
>
> this would preclude having to insulate long runs of flue and supply pipe.
>
> Others have recommended products by Rais.  One essential feature that Rais
> offers is very low heat output.  The heat demand for this house will be
> miniscule.
>
> What about domestic products?  All suggestions are welcome.
>
> AA
>
> --
> Alan Abrams*
> **certified professional building designer, AIBD
> certified passive house consultant, PHIUS*
> *certified passive house builder, PHIUS**
> *Abrams Design Build LLC
> *sustainable design for intentional living*
> cell     202-437-8583
> alan at abramsdesignbuild.com
> www.abramsdesignbuild.com
>
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