Venting a Rocket Mass Heater into the Attic

I have an old, almost square, but slightly rectangular house. I want to install a rocket mass heater in the center of it to distribute heat evenly. I feel confident putting a hole in the drywall ceiling to put the exhaust pipe through and into the attic, but I do not feel confident cutting a hole in the roof and sealing it correctly. If the exhaust is just co2 and steam, can I just vent the exhaust into the attic and not cut through wood and asphalt shingles to get it outside? My attic has two vents to the outside in the eves. Do you think there would be enough steam to cause a real moisture problem?

Oh my goodness Nathan;  Please don't try that!
Start up does produce smoke, and yes the steam could damage the rest.

If you really can't go proper thru the roof , what about thru a window and then up over the roof ?  That is a poor substitute but it can be done.

EDIT) The attic window is not an option.

No, you cannot do that. If there is a negative draft, that CO2 might find its way down into the main living area of the house and could honestly...no drama here...kill you. And you cannot taste it, smell it, or see it...

I think you lack the confidence, but I also know that you can cut a hole in your roof and seal it properly. You buy a kit to do that that has all the parts, and it is pretty loose on dimensions, so you do not have to worry...'oh no, I am not exactly on the line." It is not like that at all.

You can watch a few videos on yourtube on how to do it too, and will see it is very easy. Again the roof kit really helps make it easy for you.

You could also get a handyman to do just that part of the installation too if you wanted.

Worth repeating..... "Please don't try that! "  ☠☠☠ ☢☢☢

Build a welded box or get one made with the exit portion of the chimney welded on. Cut a hole in the roof. Put the box with the welded pipe on the roof over the hole. Bolt box to the roof and seal.

I was nervous to do it as well, but absolutely no problem and a flue running right out the top of the highest point on our roof gives us an awesome draft in our system. Never any problems so far. Still our first season so can’t say 100%, but I would do it the same again in a heart beat.

You’re burning wood at high temperature. There are lots of gases you don’t want in your house weather you can see them or not. Asking the question here was the right thing to do. Just make sure you listen to the advice of those that really understand what a rocket mass heater system does. You’ll be glad you did in the end.

See attached photos for details of the process we went with.

Concerned citizen...

Peter Martin 🏔🙏🏼🏔

I wonder if you got the roof flashing bonnet, if you could find a Permie near you that could help you?

It really is an easy job, and I think you just need a little confidence in which to go ahead and do it. I know it seems daunting..."I am chopping a hole in my roof", but honestly it is not that bad. The absolutely worst thing that could happen is that you get a leak down the chimney pipe. But you know, they make roof cement that can be applied that would eliminate any mistake you could make. That costs about $20 for a whole gallon.

So what I am saying is, even you did mess up...and I do not think you will...the cost to fix it would be $20. Hiring someone to do this would cost you way more than $20, and there is no guarantee they will do it perfect either.

People have been putting holes in their roofs for thousands of years, it is not a big deal, it just sounds daunting.

don't risk killing yourself with carbon monoxide, cut hole in roof, get big tuber two of goopy roof caulking and seal the vent where it goes through roof put outside vent cap over end of pipe and your done. you can use plumb bob from inside of roof to get centerline if your not sure where to cut

Co2 will settle.... And co2 WILL KILL YOU.... if you want to do what you are saying simply put a 90 degree elbow and run a pipe out one of your vents.  I.e.... No whole in roof. If you do go through the roof get an adjustable angle joint and run the stack as close as you can to the apex of the roof. This will make it way Easter to get and install waterproof flashing. You can buy a roll of copper flashing that is like thick aluminium foil.