Penny McLoughlin

We have spring water that comes out of limestone and actually found that putting a ring of magnets around the pipe significantly reduced our timescale. Not sure why since the science behind it still doesn't make sense to me but it actually does seem to help. We also flush our on demand water heater periodically with vinegar, a couple times a year.

So I found a fairly local supplier for ceramic fiber board and mineral wool but before I called them I was going to see if all you folks could give me an idea of what I should be asking for?

For the ceramic fiber board, do I want the 1/2 inch or the one inch? And the 2300 deg or 2600 deg F or something else?  

We are also planning to build a rocket mass heater next summer so I'd like to get some ceramic fiber board for that as well. Any recommendations on that? We'd be building an 8" system if that makes a difference and we've got Erica and Ernie's book to use for guiding us as well as the 4 DVD set (although I haven't watched the DVDs yet).

They also sell firebricks there. Is there a standard dimension on those too?

Also for the mineral wool. Does it come in different ratings and thicknesses as well and if so what should I be asking for?

Sorry for all the questions !

And thanks in advance for your help.

Great video for the builing of the rocket oven !

Wonderful use of detail and great directions of how it all goes together on the oven part.

Is there anything that gives the dimensions for the j tube portion of the oven?

While I feel completely confident that I could build the barrels, insulation and exhaust part of the oven, I am also almost completely sure that any attempt that I made to construct the j tube heater for the oven would be a lost cause without dimensions for the firebricks and openings. Or are they the standard 6" j tube system dimensions?  I have Erica and Ernie's Builder's Guide so I could use the 6" dimensions from there if they are the same. Other than you said in the video that you had to shorten the heat riser and therefore the fuel feed.

And how short did they end up?

Sorry, but I know that you are a giant guy so it is hard to judge how tall the unit actually is compared to you when you're standing next to it.

Thanks for all you do !

Wow, 36 inches is quite a lot of weight to support. And then they will have a snow load on top of that in the winter as well. Quite a substantial roof.

S Benji - I like the second design better. It looked to me like the bedrooms in the first design would have little to no natural light. I wonder if you could arrange to have a hallway between the greenhouse and the bedrooms in the second version so that you didn't have to go thru the greenhouse to get to the bedrooms.

I think the idea of having the really thick earth covering over the roof and berming the walls so thickly as well is so that you would not need to heat (or cool) the house. The idea is to heat up the earth trapped under the large water proof umbrella during the summer so that it keeps the house around 70 deg all winter.

That's why they go to all the trouble to make the umbrella so large and put so much earth on the roof.

John Hait also uses insulation between the layers of plastic on the roof. Does anyone know if Paul did something similar on his WOFATIs?  I don't remember hearing anything about that.

S Benji - From reading some more in John Hait's book, it looks like he recommends 24 inches of dirt above the waterproof umbrella but because of the weight that that causes, he has vey little dirt between the house and the umbrella. He did say that the increased soil depth on the plastic kept you from having your roof turn brown from lack of soil moisture and that it also created a sort of transition zone between the outside and the home.

I'm still only in the 3rd chapter though so my understanding may be incomplete yet.

It seems like if I used 24 inches above the waterproof layer, then I would need significant insulation between the house and that since the freezing depth itself would be two feet in the winter in the area I'm planning to build.

You're right though in that I was asking how strong the roofs were designed for on the existing WOFATIs just to get an idea of what kinds of structural strengths might be needed.

I like the longer rectangle design of the Earthship homes though. It seems you would have more natural lighting that way. Where the house is basically only one room deep and all the rooms have one side that opens to the windows to allow light penetration.

S Benji -  yes that is sort of what we are imagining. Although with an actual wall between the living part of the house and the greenhouse part so that we can have better control over how much heat we're letting into the house.

Thanks for the links. I'll check them out.

Thanks for all your help here.

The dirt weight was what I was hoping for.

I have the $50 Underground house book and have read it but from my understanding, Mike Ohler did a much lighter roof since he was only doing 1 layer of plastic and fewer inches of dirt over it.

I'm reading John Hait's book right now about the passive thermal inertia as I think that his roof loads are probably going to be more comparable to the WOFATI style roofs but I'm not very far into it yet and haven't seen any structural calculations yet.

I really appreciate all your inputs.

Hmm, I guess what I was asking is what kind of weight per square foot has been used for some of the WOFATI's up at Wheaton labs?

I can figure out the snow load and understand about different soils weighing different amounts but I guess I was looking to see what others were using in their calculations so far.

Thanks

Yes that is the exact thread I'm trying to post in/reply to.

I'll try a different browser when I get home

Thanks

I've made maybe 6-10 posts this way in the past without problems. Until yesterday.