Hi everyone, as a first post I would like to expose my design idea and see what you all think.

We bought a 5 acres lot and are currently thinking about design.

My first goal is NO MORE MORTGAGE and I would like to accomplish this goal while going as green as I can and  using an efficient design.

I was looking at underground houses and earth ship recently. I like the idea but they involve quite a fight with the municipality and my wife would never accept the look as reasonable as she is.

We talked about building a 2 story 33X33 + loft (the 2nd story and loft would have an open to below space so not full floors.... The foundation would be ICF, straw bale for the rest, south wall is mostly windows, sun room attached to the south wall.

To be even more efficient, I tough maybe the best design would be to build semi underground. Dig just under the frost line (4 feet here) and build an ICF foundation. This would mean no more 2nd floor, no loft. The whole building would be underground to profit from the earth constant temperature.

To have the same square footing the foundation would have to be more then twice as large then originally planned, but not as high. The floor would be a concrete slab with radiant + maybe an earth floor on top if we find the courage. This would allow us to have radiant everywhere in the house instead of trying to find an alternative for the 1st, 2nd and loft.

I figure all the I joist that would have been used for the floors will go up to the roof..  The amount of wood for framing is probably the same but the roof is the issue. The roof would cost a lot more due to more metal sheets,  insulation, ridge pole and ridge pole support. (I don't want to go with trusses if I can avoid it.

This house would be a lot more energy efficient being semi underground, no need for air conditioning and less heating is needed. It would allow windows on the full south wall like earthships.


So what do you all think? I know its not easy to compare costs between the two design but maybe some of you already did it and have some input.

Thanks
Pierre

Underground houses have been around forever. But you can accomplish the same thing with traditional insulation for less cost and more livability.

> no need for air conditioning

As soon as you add some insulation (against the ground temperatures) and some heat sources (ventilation air, people, electrical devices), you do need AC (depending on climate) and dehumidification.

I think the straw bale can be good depending on your location (AZ, New Mexico, Nevado, etc), but in more humid climates it could be problematic. Plus they can get a bit costly depending on available resources.

Why not take the ICF all the way up?

Yes maybe straw bale is good enough but I wouldn't be surprised to see a good diffenrence in temp between the basement and the 1st floor even in a straw bale house. I wish I could visit one.

As for taking ICF all the way up, I would like to go greener then that and minimize concrete use If I can. ICF probably doesn't breath much compared to straw bale.

Having designed and built several earth sheltered homes in the early 1980's I know you can find really good examples of really bad design...stuff so ugly the Flintstones wouldn't live there. It is also possible to create extreamely livable and attractive spaces that perform well and blend well with the site. Based on your comments you sound like you might be enamored with various building systems and are trying to use them all. ICF's, strawbale, earth shelter, super insulated all have their advantages and drawbacks. Personally I would not combine strawbale and earth shelter unless I had some really creative design that flowed out of the earth into living space around a courtyard or something like that which still requires very good moisture protection from both the roof and the wall/straw interface.

University of MN is a great resource for good earth shelter design considerations and since you are researching options, make sure you have natural lighting to the back/north of the home with clerestory windows or some other source or your glare will require blinds etc reducing the efficiency of your south facing glass. Of course waterproofing and drainage are paramount as is a good energy analysis of the design for proper sizing of mech systems. HRV/ERV system is not optional in my mind and remember there is lots of moisture in the concrete that will have to come out through the living space since it is waterproofed on the earth side. People are living in homes with my mistakes and I have become a lot smarter over the years. If you want to discuss other considerations please contact me directly at [email protected].

Hi, Pierre. I recommend reading Rob Roy's Earth Sheltered Houses (2006 edition), as he discusses how he has built many of the ideas you're looking at. Also read Dan Chiras' The Solar House for the same reasons. Both have been my bibles for a house I'm having built this summer.

Like your plans, it is cut 5' down into the side of a south-facing hill, and I'm berming up another 3' on the two earth-sheltered sides. Think of it as a walk-out basement with a roof on it. The east side is exposed for a pair of windows with a lake view, and the south side is mostly windows. 

The earth-bermed sides are ICF to the roof, but I'm using Durisol ICF blocks to boost my thermal mass and concentrate the insulation on the outside, and to avoid EPS or XPS. Like Faswall ICFs, they're made of recycled wood chips glued with Portland.

I had wanted to have an earth-covered roof (green or living roof) but changed my design to a trussed steel roof due to (a) cost, (b) replacing EPS or XPS with cellulose, (c) structural design issues, and (d) desire to have rainwater collection.

My south wall is mostly windows, so I'm using stick frame instead of, say, straw-bale (which takes up a lot of real estate). The two earth-bermed walls are R30, the two stick-frame walls are R42 (mostly Roxul), and the attic is R80 (blown cellulose, so will settle down to R66-70).

If planning for passive solar with lots of windows, be sure to use load calculations like those in The Solar House to ensure your concrete floors (and walls, if using Durisol/Faswall) can soak up all the heat given them for night-time release. That was the biggest omission of most 70s and 80s designs.

It's true you can get equivalent free heat by focusing above-ground on super-insulation, airtightness, and limited south-emphasis windows. Read up on passivhaus designs for this. In any case, you'll want that HRV GreenGuru recommends.

Good luck!
...Terry in Ontario

Thank you very much for your input, i will continue to work on my design and will post my ideas. You helped a lot thanks a gain

GreenGuru, do you have a link to the U of MN for more info?

I am in the minneapolis area have have a terraced south facing lake lot. The drop is about 18' from level to level and I am trying to figure out the most cost efficient design, whether to build more into the hill for the lower level? or build more along its contour. IE. Is it cheaper and more energy efficient to build foundation/basement walls into the earth or build where the lower level is more exposed. I've had a passive house designer out and he says you'd want to isolate the walls from the earth so there must not be a big advantage to build in the lower level more into the hillside. Trying to reconcile this issue in the design process. I supposed earth homes make more sense in A/C dominant areas in the south US vs. more heating intense areas of the north.

http://www.guarchitecture.com/berm_house.htm

Sounds like you are looking more at a berm house.

Not everywhere needs air con, we certainly do not.