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RMH as a secondary heat source in a passive house questions  RSS feed

 
Posts: 136
Location: Winnipeg, Manitoba
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My wife and I are planning to build a new home next year and we have a lot of questions.

Let me outline our situations as best I can:
-We live in Manitoba Canada and plan to build just outside of Winnipeg so our winters are -35C and our summers can be +35C. Heating and cooling are the major issues I'm currently trying to work out.
-I'm working with a model right now that has 2000 square feet of living space spread out over two floors and no basement with about 800 being a separate suite that I can turn into our offices or develop as needed later (maybe a duplex)
-We're planning the basic south facing windows with thermal mass inside to collect as much winter sun as possible.

-I have no idea how to address cooling in the summer other then to introduce an air conditioner somehow into the system so any ideas on this would be greatly appreciated.
-For heating I'm thinking of using solar thermal hot water heating panels on the roof with a solar electric system to pump the water. I think we will have to use a large stratified water tank to store the heat energy and rely on a high efficiency HRV system to control heat loss with our air changes.
-The house wont be off grid but I don't want to rely on the grid for any of the climate control demands of the house.

Here is one of my key questions, I'm really liking the rocket mass heaters as a secondary heat source for the cold winter months however because its going to be a passive house how do I manage the air changes necessary to feed the mass heater with air? Can I plumb the exhaust into the HRV system so that we aren't just pulling raw cold air into the system? How would I deal with the steam and keep it from frost damning and plugging the HRV?

OR should I be drawing air directly from outside into the heater and then exhausting outside as well? Same issue though how do I deal with the low temp steam? When its really cold out I'm positive I'll get frost damning in the chimney.

Should I look at another secondary heat option?
 
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Sean Rauch : I am only going to try to answer and/ or pontificate, on what I have direct knowledge of, Large overhangs and reflective barriers with Air gaps on both
sides will take care of most of your summer heat loads, but the sun will be able to shine into your house in the late fall thru early spring! With proper positioning of
your rocket mass heater RMH, it too can add to the whole house cooling if the summer sun does not strike it, and with proper positioning much of the center of your
home can be Kept at summer clothing levels !

A RMH will produce large amounts of water rather magically out of your wood fuel, well seasoned hard woods still can contain close to 20% water by weight, plus
there is all that water vapor produced as a product of combustion, we always tell our new Rocket builders to consider the stove pipe that they use in their thermal
mass to be a sacrificial form, and a good place to save money by going with the cheapest cold air return ducting possible, the older your Thermal mass itself becomes
the more of this insensible water vapor gets locked up in your thermal mass, being absorbed both from its internal ducting but also out of the house's air when water
vapor pressur i.e. humidity is high, and releasing it when your house is driest. Due to this fact your H.R.V. will work harder to handle frost From your primary heater
and cooking and showers than your RMH. for this reason you can seal the top of your Thermal mass against spills but don't seal your sides !

Perhaps when we talk about measuring exhaust gas temps at the end of your horizontal chimney at 150dF you thought we were actually saying 150dC, No that is not
the case, your discharge will be 150dF -ish!

We have a policy here at permies.com that if you ask a question and you don't get an answer that seems right to you within 48 hrs after you post your question, YOU
as a fellow member have the right to go all the way to the top to ask for an answer/2nd opinion, I expect that you should have a long talk with the person responsible
for the plumbing of your air system, when you attempt to explain your rocket system to him, you will undoubtedly get more questions than answers, then you can come
back here. For more information try The Cold climate housing research center, (cchrc.org) an arm of the University of Alaska,Fairbanks. You and I know cold,
they know COLD, and have experience with your H.R.V. systems

A couple more sites to visit, with no basement you will be able to build Your RMH directly on a slab isolated from the ground, just the same I want you to look at a part
of what is possible goto> villagevideo.org/products/rmh/scenes/, this is a teaser video ~3/8ths~ of the post production video and a must have for anyone building
on wood floors, enjoy! At Possibles.org you can find some more information on RMHs running in cold climates searchfor> 2 more rmh builds ----

After you have seen this video you will want to check out >ernieanderica.info... And My final word on placement of your rocket mass heater, it can only serve you
best when it is within a hands reach of where you will spend all your time,and if your lifestyle finds you in an inhume office at one end of your house then perhaps you
should rethink your commitment to a RMH! For My final, final words please goto> my 2nd comment to Von Sommerfeldt >Thermal exchange piping- (rocket stoves forum

For the good of the craft ! BiG AL!
 
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