Radiant heat cob floor?

Hi guys! I desperately need help!

I'm building a greenhouse just outside of Boston. I want to run it year-round. I was planning to heat it using a thermal siphon from a rocket stove connected to a water tank connected to copper pipes in the floor.
I planned on encasing the pipes in cob so that the floor would heat up but I'm not sure it will work.
The greenhouse is 12x32. My current design is to have 5 stoves, each running copper pipes up the length of the greenhouse and back into the water tank, and eventually the stove.
My questions:

1) does cob give off heat well or does it retain heat I'd want in the greenhouse?
2) how hot will cob get and how warm is the air above the floor
3) would another material be better to lay on top of the pipes to radiate heat?
4) would 5 stoves heat 384 square feet (up to 75 degrees) through this method?

Thanks for the responses!

Hey Joe,

I am by no means an expert, there are tons of people who have been playing in the mud longer than I've been alive in some cases, but what I lack in years of experience I try and make up for in research.

The thermal mass of cob depends on a lot of factors, such as clay type, ratios of sand clay and straw, as well as what it is coated in. As I'm sure you are aware, thermal mass is basically the objects ability to retain heat energy. So since there really isn't one exact science to cob building, there are a lot of factors in your design that kind of depend on the environment you are building in.

That said, here is a video I found last year in researching earthen floors with radiant heating . I wish it wasn't so cheesey, but if you can sift through that, you might be able to find a little inspiration worth the effort, this guy really did a decent job from what I can tell.

https://www.youtube.com/watch?v=15oN2MFjdVU


Can't wait to see pictures of your finished project!

Awesome Philly!

Thanks for the link!

Joe

Hi Joe!

Welcome to Permies....

You aren't that far from me up here in Vermont...

1) does cob give off heat well or does it retain heat I'd want in the greenhouse?

Anything that forms mass (i.e. earth, stone, heavy timber, etc.) stores heat or cold dependently. The ratio of retention is dependent on medium. Metal will be your fastest conductor/radiator

2) how hot will cob get and how warm is the air above the floor

All depends on the design, the ambient temperature goals, climate, and several other factors that can get pretty complicated very quickly (and hard to really measure with out modeling the system for a given placement.)

3) would another material be better to lay on top of the pipes to radiate heat?

Hmmmm???....Better?....That, is a subjective question...Easier?...yes...more enduring? Absolutely...Traditional for greenhouses?...again without a doubt.

I like (if possible) traditional "Bikooh Garden" or Wallipini with a glass cover over them, but you can do this above ground as well. I am currently designing one attached to a timber frame home for a client here in Vermont. You must employ a well designed drainage systems first for any "radiant system" you would use. I like placing hydronic tubing in a stone dust or sand substrate, then placing stone tile/flagging, brick, or some other masonry unit over this. The system stores heat, is easily survivable, and way more durable for working on, like found in a green house. Cobb just is not going to stand up to toil subjected to most greenhouses.

4) would 5 stoves heat 384 square feet (up to 75 degrees) through this method?

FIVE STOVE !!!

Even if this was required (like for growing orchidaceae) it would be hugely labor intensive and/or consume a large amount of wood. Again, your thermal demands for any give greenhouse system is going to be dependent of design format and location-placement (as well as other factors.) This one might require a phone call if you really want to "dig into" the subtleties of it...as I could keep writing for pages and not even scratch the surface of this topic.


Regards,

j

Thanks for your advice

I'd love to chat sometime.

Shoot me an email at joedivincenzo@comcast.net when you're free.

Thanks so much