passivhaus + composting toilets

[mike eliason]

anyone have experience/thoughts/guidance on PH utilizing a composting
toilet? i have seen two projects that are underway. one is exhausting
the fan from the composting bucket to the HRV (squeeze out those
BTUs!).

this doesn't seem ideal to me, but airsealing the toilet lid doesn't
seem like a feasible solution, either. love to hear thoughts on how to
achieve the required airtightness in a situation like this.

[GnormanTheGnome]

I'm sure the health dept would like to chime in too!  I would bet they wouldn't like the exhaust air from the composting bucket run anywhere near a fresh air input even if they are supposed to be separated.  I would think the potential for contamination in the exhaust air to spread via the HRV would be a concern specifically because it was composting human waste.  

How are plumbing stacks handled in a PH?  Could you make a dedicated fresh air/exhaust air circuit for the composting toilet so that the air pressure would not be affected and then insulate the heck out of the pipes.  No wait, I've got it!  You make an hrv specifically for the composting toilet so the heat from the composting toilet prewarms the incoming air to the composting toilet so that the change in temperature does not affect the composting action.  A Poo Heat Recovery Ventilator or PHRV.  

;-)

Interesting question Mike!

--
You received this message because you are subscribed to the Google Groups "Passive House Northwest" group.
To post to this group, send email to Passive...@googlegroups.com.
To unsubscribe from this group, send email to PassiveHouseN...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/PassiveHouseNW?hl=en.

--
"It's not what you look at that matters, it's what you see." Henry David Thoreau

[Rob Harrison AIA]

I've been thinking about this a bit lately too, since I think composting toilets are the next frontier, so to speak, of energy and water intelligence. David Rousseau runs his whole house exhaust through his composting toilet, down to the chamber, then out through the roof. Fan at the roof end. Negative pressure at the lid means no smells, ever! The warm air passing through the composting chamber (which is down a floor from the 2nd floor toilet) helps dry out the chamber, also a positive. Access to the chamber is from the outside, at ground level. As brilliant as this system is, it doesn't address air-tightness or HR aspects unique to Passivhaus.... I suppose you could set up your HRV to deliver an extra 12 cfm of fresh air that you'd allow to be exhausted through the toilet via separate fan....

I've been thinking though, next time I got a chance, I'd use one of these: http://www.envirolet.com/vf.html Possibly more easy buy-in from folks, since it looks and functions very much like a conventional toilet.

Rob

Rob Harrison AIA

HARRISON architects

1402 Third Avenue  Suite 515

Seattle, WA  98101-2120

206.956.0883

http://twitter.com/#!/robharrisonAIA

http://harrisonarchitects.com/

lyrical sustainable design  ::  passive house plus

[David Posada]

Interesting, indeed! For a dedicated supply and exhaust loop just for the composting toilet, maybe a less-expensive and less efficient unit like the $500 Panasonic ERV makes sense.

 

Or, if doing exhaust only for the toilet chamber, would that have to be constant, or could it be on a timer/ occupancy sensor with a high-quality or motorized damper so that you have a good airseal when not exhausting?

 

David

[GnormanTheGnome]

Could you even do something like the heat recovery from a plumbing drain pipe where the dedicated composting air comes in through a copper pipe and wraps around the exhausting air copper pipe.  Someone with better metal understanding could probably work up a design where x amount of coil will make it x amount efficient.

[GnormanTheGnome]

And call it a Poo Heat Recovery Ventilator©LMW2011

[mike eliason]

@linda,

fresh air exhaust and intake would be on a different sides of the
building. was actually thinking of utilizing a semi-diaphonous
'wintergarden' that would act as a buffer between indoor and out
(would be naturally ventilated via EPDM flaps or sim, worked on a
project that did this in germany) and drawing the fresh air from the
wintergarden, which would be pre-heated when it's warm out. pipe
dream, i know.

poo heat recovery seems like overkill!

@rob,
was looking at the envirolet, i guess the biggest question to me for
that system would be similar exhausting issues as a traditional
composting toilet, and how that works with an HRV.

FYI, i'm not the only one who's been thinking this (just in case
anyone thinks i'm not being factual, here are some links)
http://www.passivehouse.us/bulletinBoard/viewtopic.php?f=6&t=223&sid=d76e8463f6bf6f2b3909818608342e65
http://passivebuild.co.uk/ <-- this one supposedly has dry composting
toilet
http://www.cropthornehouse.co.uk/11-10_30_welcome_to_cropthorne/ <--
here are some photos of this PH pulling compost exhaust through MVHR
(HRV)
http://www.passivhausprojekte.de/projekte.php?detail=139 <-- sweet
little PH w/ komposttoilette
http://www.susana.org/docs_ccbk/susana_download/2-1184-2-56-de-susana-cs-deutschland-hamburg-oeko-siedlung-allermoehe-2011x.pdf
<-- german article on composting toilets, some in a PH, i've yet to
really study this

[GnormanTheGnome]

I was responding to your comment of someone mixing the compost toilet fan exhaust through their HRV.  I think that is where the health dept would have a problem.  I think the idea of composting toilets is a natural for many who would be interested in a Passive House.  I then took the obvious problem of air tightness, gave the system it's own version of an hrv (doesn't have to be any more difficult that a homemade air piping system made with some recycled copper pipe and the existing fan) and gave it a memorable name. The Poo Heat Recovery Ventilator©LMW2011 would tell people exactly what it was for, and since we are the leading edge in air tight and heat recovery, having it be a PHrv would tell you who it was for!  (Bonus points to the crazy lady!!!)  Seriously - I think the health department will be the biggest challenge if you try to incorporate the exhaust into anything other than what they are currently used to seeing because of any potential for spread of disease. 

Linda

--
You received this message because you are subscribed to the Google Groups "Passive House Northwest" group.
To post to this group, send email to Passive...@googlegroups.com.
To unsubscribe from this group, send email to PassiveHouseN...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/PassiveHouseNW?hl=en.

[Graham S. Wright]

I lived with a Phoenix composting toilet for about year and a half.  It's designed to be exhausted with a muffin fan, that can run off a small PV panel if need be.  For Passive House purposes I think it would be fine to just hook up a return to the HRV, or even an ERV, like any other bathroom PROVIDED THAT the system is properly designed and maintained.  In my opinion a properly designed and maintained composting toilet does not stink any more than a regular bathroom, maybe even less.  That is a pretty big caveat: the system I had did start to stink after about a year, even though it was preloaded with a whole yard of sawdust.    In hindsight the problem was too much water - it was hooked up to a low-flow macerating toilet designed for boats.  (It was also in an attached sunspace and probably got too cold for the microbes in the winter.  This was in MN.)  Even without the flush water I suspect that urine alone could have overly wetted it.  If I had it to do over again I would put a urine-diverting stool directly over the bin, no added water or pumping.  

This would be a higher-maintenance system than the sit-and-forget we are used to, but if you keep up with it right, the maintenance would not be gross.

In terms of design the important thing is to leave enough space for it, like six feet high by four feet by four.  That almost mandates the bathroom is on the 2nd floor or in the loft.  You also need to think about how you are going to get the the compost out of the thing.  Ideally there would be some kind of thermally broken hatch to the outside.

-gw

[mike eliason]

graham,

phoenix has been in the mix as well. after talking to a few folks, i
think our approach will be a small fan to vent the compost chamber (w/
a bypass inlet between the toilet and the chamber), that has a
slightly more pull than the bath exhaust to HRV. add a charcoal filter
at the bath exhaust. the chamber would be in a semi-conditioned
'basement' so access wouldn't be an issue - though heat loss may be a
slight problem.

regarding urine diverting - we had toyed with the idea of a urinal or
urine diverter that would go to a catchment basin, store for 30 days
and could then be used for fertilizer. i learned about this from a
swede - too much for some folks, but i kind of am partial to the idea.

[David]

Mike,
You may find a plethora of information on ventilation of composting
toilets with Ecosanres group:
http://groups.yahoo.com/group/ecosanres
They are a group focusing on the sanitary, aesthetic and functional
forms to utilize human "wastes".
Happy Holidays,
David

David Burdick (PE)
Earth Harmony Habitats
4917 SE Aldercrest Rd.
Portland, Oregon 97222-4757
USA
Tel: (+1) 503 654 2070
Cell: (+1) 503 753 5564
Fax: (+1) 503 654 2121
email: Da...@earthharmonyhabitats.org
website: www.earthharmonyhabitats.org