Half Underground House?

As fast as our society in the US is decaying, I feel the need to get a house built sooner than later. This is why, instead of building what I really would like, a wofati or earthship, I'm now thinking of a major compromise...a half underground concrete block house with a super insulated roof. The pros are obvious....rot, fire, insect and wind proof; cooler in summer, warmer in winter. The only downsides I can think of are the cost and that its not exactly natural. Any others I'm missing?  Thanks.

Using the concrete walls for the shoring and then insulating the roof to R-40 and likewise for the floor and walls sounds like a wonderful plan.
I would then, add some pex piping for heat exchange. Maybe a mini-split heat pump.

I live in a 1970's house with a concrete block lower level set halfway into a hillside. A second level was added in the 90's of typical 2x4 framing with vinyl siding. I live in the bottom story, and during remodeling with no air conditioning the temperature never rose above 78 degrees in the hottest parts of summer. The bottom story is mostly uninsulated, and is not very air-tight. One thing I would recommend to anyone building a house of concrete/blocks is vapor barriers, vapor barriers, vapor barriers. The temperature is easy to regulate in the botton story, but the humidity is always high, at least 65-95%.

Check if your chosen area has high radon levels.

What you described is an earthship without pounding tires.  I am going to do something similar.  

I agree on vapor barrier, best you can source.  

When you say half buried do you mean that the entire north wall from roof to floor is covered with dirt but the entire south wall is expose to the elements. Or do you mean that 'all four walls' around the house is covered in dirt, up to the window, a good 4ft, with you using casement windows?

You also have to think about both winter and summer. I know that all winter long my un-insulated basement is at 45F, much better than outside, but if I were to heat it, then every single BTU would go straight into the earth with the temp never passing 59F. So I highly recommend that you insulate the not just the roof but also the walls and floor. You can however use PEX piping to move heat from the house to outside in the summer, and to move heat into the house from outside during the fall/etc. And then during the winter you can

Venting the bathroom (hot shower) and kitchen(boiling water vapor), will do a lot to control humidity and temperature too esp in the summer.

Like others have said a Radon Barrier makes a lot of sense to me, ditto for a full vapor barrier too.

You will also need a ventilation system, maybe one with a heat recovery device.

Our house is built on a slab with no insulation. Insulation under it would turn the slab into thermal mass which would help hold the heat from the wood stove. We burn a lot more wood than we would need to if there was insulation on the outside of the mass. So I back having some sort of insulation on the outside of the blocks along with that vapor barrier.

That said, one of the key issues is water run-off. The standard rule of building is that the surface of the soil should be sloped away from the building on all sides. The former owners of our property broke that rule when they built an outbuilding and the sill plates rotted as the place the slope was bad was to the north and wet all winter. So it's also key to consider where the water will come from and where it will go and make sure you budget for re-directing it before it gets to your foundation.

That said, you suggest you're feeling pressured to get something built. I totally agree that with many areas experiencing more major storms, building something that can get through what Nature might throw at you makes a lot of sense. Concrete blocks aren't the most natural, but I've seen what's happened to "stick built" houses in high winds or floods, and what's left is a toxic mess, so building something that will last is a good start. Have you considered building something that can house you safely now, but can be re-purposed as a workshop or other outbuilding later if you get the time to build what you'd really like for living in? Have you considered what are the regular vs extra-ordinary weather you can expect? I've been reading about more serious peak summer heat waves, and those can kill, but what's the flood risk at your building site - is your "half underground" house at risk of becoming a swimming pool if you get some of the incredible rainfall rates that have happened in the last five years? Both of those issues can be helped not just by what you build your house out of, but also by how you build resilience into your soil, plant trees and vines for shade and wind diversion, consider swales and French drains not just near the house, but further out to redirect water well before it gets close. Forest fires are also on the increase, so planting fire resistant plants and planning a simple roof without nooks or valleys to catch embers may be advisable.

Maybe you've thought through all the "big picture" stuff, but I thought it was worth mentioning.

Thanks everyone. Lots of great insights and ideas. I'm referring to all 4 walls being 4' underground mainly so I can get plenty of light in the building and leaving the roof exposed makes the building process really simple compared to a traditional underground house. Agreed on the insulation, vapor/radon barrier. Yes on a very efficient minisplit along with an HRV. 4. I doubt I'll use pex for radiant heat as its so expensive to install.

Paul Ladendorf wrote:As fast as our society in the US is decaying, I feel the need to get a house built sooner than later. This is why, instead of building what I really would like, a wofati or earthship, I'm now thinking of a major compromise...a half underground concrete block house with a super insulated roof. The pros are obvious....rot, fire, insect and wind proof; cooler in summer, warmer in winter. The only downsides I can think of are the cost and that its not exactly natural. Any others I'm missing?  Thanks.

First, I'm jealous. Always wanted to have an earth sheltered home. Sounds cool, though I suspect moisture management can be an issue at times and I'm allergic to mold, so maybe I dodged a bullet?

I don't know where you're located, but up here in New England it gets up into the mid to high 90's Fahrenheit outside. We've got an old house from 1860 that has survived fires, twisters, hail, tree falls, wood boring insects, the whole nine yards. Still standing strong. It's 0% earth sheltered yet doesn't get above low 70's even on the hottest days because it's tree-shaded with deciduous trees and has windows that allow cross breeze through the home.

So what I'm getting at here is proper use of shade and ventilation will make your earth sheltered home a very comfortable place indeed. I think you are in the right track!

I highly recommend adding installing just the PEX piping (total cost is $500) into a slab floor ($3,000). You were probably going to get a slab floor anyway too. You can always get the valves, pump, indirect heat exchangers, controller and heat source later. But for just $500 now you have given your future self a lot of options.

You also don't have to make it too complicated. It can be as simple as an instant hot water heater set to 90F (80F to 110F depending on how cold it is) and a always on recirculating pump. We such a setup you dont even need a thermostat, much less zone control.

If you are going to have a concrete slab floor, I absolutely advise installing pex now even if you don't connect it. There is nothing like a warm floor in cold weather - it allows you to keep the air temperature several degrees lower with more comfort and less heat loss. Solar water collectors can be simple and reliable and further reduce your annual energy expenses.

I would also consider berming most of the north side of the house, interrupting maybe one place for windows. This would hardly affect the construction expense or difficulty, yet reduce constant heat loss with no gain all winter.

Hi

Have you thought about a modified PAHS system? That's what we did and we've been living in it comfortably for the past three years, no heating, no cooling, no mechanical ventilation, no insulation under floor or behind the walls - and with PAHS you can even build the underground walls of rammed earth and a post-and-beam reinforced concrete frame. We have a blog (blepperblog.wordpress.com) unfortunately in French but mostly in pictures describing the whole job and including temperature and humidity readings over the past two years. For ventilation we have implemented Hait's theory of automatic counterflow with entry and exit pipes running next to each other, but not the bends under the umbrella that he proposes, ours run straight down the hill to the end of the garden to avoid any possibility of standing condensation and they are quite shallow for practical reasons, about three feet (1 meter) deep.
Rammed earth has advantages over concrete (natural hydroregulation, no need for plaster finish, it's free, emits no co2, is reusable, and if you choose the site it is right there, no need to transport it) and a similar conduction capacity for heat transfer into the earth. I would add that hand-ramming earth is a great experience, very fulfilling, but don't do what we did, ramming the whole west_north_east sides with the first run about 5 feet high and then going around a second time, meaning we spent half our time trying to protect our work from the rain. Do a third at a time, covering with a third of the roof each time.

Here's a link to a Google Sheets chart of our temperature readings:

GoogleSheets temperature chart

Bruce Lepper wrote: We have a blog (blepperblog.wordpress.com) unfortunately in French

When I went to this blog, google offered to translate it for me. Thanks for sharing the link and showing us your work. It's beautiful. I noticed your earthtubes are grey PVC, and I assume that they have some more flexibility to them than the standard white PVC we get here. That was one thing about John Hait's book that puzzled me. I've installed white, rigid PVC earthtubes around my root cellar and it was a challenge because of their rigidity.

Michael Helmersson wrote:

I've installed white, rigid PVC earthtubes around my root cellar and it was a challenge because of their rigidity.

The white stuff is easier to bend with a little heat. Locally, if they're being used for a high tunnel, they try to bend them after leaving them in the hot sun for a few hours. I've used a heat gun to help, but it's not ideal as it doesn't heat evenly.  Hubby made up a box with some chicken heat lamp bulbs in it and that gives him control for doing serious bending.