Straw bale house dilemma - winterize? heat more efficiently?

We have a dilemma. We are living in a straw bale “passive tech” house that has a lot of inefficiencies and is waaaay too big for our little family. The stone/ rammed earth floors are insufficiently insulated and we lose a lot of heat through the roof and drafts around the timber bales. In the winter, we are spending over $700 a month in heating costs to keep the house at 16-18 C, a large portion of which is propane for the “in floor heating” which keeps the floors cold but not icy to the touch. Suffice to say, we inherited some major design flaws.

We have a second, much smaller structure on the property that we are considering moving into for the winters. It would cost us next to nothing to heat using a rocket mass stove and our own willow, and no propane at all because the floors are not icy. It’s also much more appropriately sized for our little family.

The house is magical in warmer/hot times of year (stays 20 C degrees all the time passively)  but so incredibly wasteful in winter. We are thinking it could be rented for three seasons and closed down for winter.

Do folks know of whether it’s possible to overwinter an unheated straw bale house without damage to the bales?  Or is there some way to retroactively “fix” a slab on grade floor to be more efficient?  

Ugh what a nightmare. Propane is the absolute worst, expensive even in a modern stick built house. I just wanted to post that I am 100% certain your in floor heating can be fixed. It might get crazy but if it's necessary I am positive it could be pulled up and new heating installed. Not sure how impactful, environmentally, this will be. Off hand, it seems like you must be heating the ground under and around the home instead of your living area. That's a lot of BTUs to burn and not feel the warmth.

Thanks for replying Dan.  Yes that's what we think is happening, improperly insulated slab so the heat is radiating out instead of up.  When we start the boiler, it takes two days for the floor to raise by even a couple degrees.  If we wanted an actual "warm floor" we would be burning twice the propane.  

Replacing the infloor "heating" would be a massive job.  We would have to rip up more than 1000 sq feet of large stones, and pull out a bunch of interior walls, and then dig a couple inches under that to even get to the heating pipes.  And they've been laid out in such a way that we heat totally unnecessary areas (like the utility closet and a storage room!) to even get heat to the living spaces. I'm very nervous to think what we'll find under there, given the sketchy situation we've encountered under the roof metal, in the electrical panel, etc.  

Sorry for the rambling.  Nightmare is right....  Your post is nudging me toward moving to the outbuilding.  

You may want to check if the liquid in the radiant system can handle freezing temperatures.

Hi again,

Yes I would consider the outbuilding at least in the temporary.

I am thinking that with what you are saying about the rest of the build you are most likely right, that you won't find anything worth fixing under your floor. I hope you can find a heating system that can be made to work with your home though before NEXT winter. I have lived in a home where propane was the only heat source and even running it all day barely kept it livable, forget comfortable. I know how depressing it can be. I wish you the absolute best.

If the floor is flat stones bedded in sand or whatever loose-ish material, I would consider pulling what you can without disturbing the interior walls (some can probably be pulled out from under the edges of walls), excavate evenly down to the tops of the existing tubing, install insulation and sand/cob bedding with new tubing in appropriate configuration, then rebed the finish stones. The closer the tubing is to the top, the quicker response you will get from warm water. If you really would need to dig down a few inches below the stone bedding material, that is too deep. I think trying to raise and reuse the original tubing would be more trouble than it is worth.

All the above is assuming you decide that you want to get the big house to work for winter use, and if it is much bigger than your family needs, that may not be the right decision. Fitting up the small house with an RMH and making it comfortable sounds like a good plan, particularly if you are n a cultural location where seasonally renting out the big house is feasible. If seasonal renting is not likely to work consistently, it might be worthwhile doing the floor retrofit (after you move to the small house) so you can rent the big house annually and get reliable income from it.

I rented a guest house from a nice elderly lady who lived next door in a 50’s home that had in floor heating the failed (copper pipes in concrete slab) ultimately. Rather than tear up her nice wood floors they simply converted over to baseboard heating (cast iron in their case). The cottage had aluminum baseboards that loved to make noise (and hide the occasional black snake who visited). The lady even kept the same 1950’s gas boiler that fed the failed in-floor radiant system. The lady died and eventually the house and cottage got torn down and the land became a park. You pump $700 of propane through well positioned radiators and seal up the place some I would expect better results. Another approach would be to build a floor above the stones and lay a pex system under that. You lose the stone floor, but gain warm feet).

But I’m interested in the existing system and how it is designed? Pex tubing under rocks? How thick are the rocks and how deep are the heating pipes? Can you measure what the temps are where the liquid returns from under the floor? I know people who were spending that much to heat their place, but at least they were comfortable. Love to hear whoever designed the system explain their thinking. If the system is abandoned then pumping antifreeze into it may make sense. Due to the unusual design I would look at the plumbing system to make sure if the underfloor system is turned off will water pipes be in danger of bursting. Another thought is the hot water leaking somewhere under those stones? Is their a mysterious hot spring that had appeared downhill from the house?

As far as the structure, I would go outside at night and photograph the structure with a thermal sensing camera (I have a flir attachment for my phone). The images will show the worst leaks. If air is leaking through walls, heavy curtains on could help (explains all those tapestries in castles). Don’t know enough about straw bale houses what the best way to plug leaks are. My main concern would be critters (after I put in the baseboards and hung the tapestries).

Not a short term solution for your problem, but I wonder if retrofitting some perimeter insulation would be a good solution once the ground is thawed?

You would have a couple of easy-ish options: Frost-Protected Shallow Foundation, or Swedish Skirt. Just Google those terms for images of what I'm referring to. Not the cheapest solution with rigid foam, but it may help in the long run?