Building on a south-east facing slope

I came across some land that is somewhat difficult to access, with a severe 45 degree slope that faces south east ( in the Southern hemisphere ).  It's about 5000 m2 and is on the local bus route.  The top of the section has drive on access and there's an existing house there.

I wondered if it might be suitable to build social housing using Mike Oehler's integrated earth house construction.  The rear patio on the elevated side of the house would allow for all day sun to enter the house, and small windows on the SE side would allow for views.  My understanding is that Mike Reynold's earthships are highly labour intensive since they need to pack numerous tyres with dirt, and typically they need to face the sun.  So, Mike Oehler's construction method seems a better fit, and perhaps inexpensive to allow it to function as social housing.

Thoughts?

South facing land is not as efficient at passive solar than North facing in New Zealand.
Mike Oehlers work does well in dryland, not wet land and most of NZ seems to be fairly damp so that may be an issue
as well.
45 degree slopes may add enormously to your costs and useless of the land as well.
Good luck anyway

Yeah, 45 deg slope is challenging which is why I thought an earth integrated house was the way to go.  

Earthships need to face the sun, but Mike Oehler's design has the upper patio allowing the sun to come in from the up hill part of the structure.  And the way they are built sheds water as no hard angles are impacted by falling water.  Also you can put in french drains in the upper patio area to take water away from the structure.

Otherwise we are talking about sinking 3-4 m deep piles into the ground and building above it.

This is another structure I found on the net.  https://matthewdevine.wordpress.com/earth-integrated-building/

So, I've mostly read Mike's book and it doesn't seem that solar gain is that much part of the equation for his earth integrated houses.  He talked about hillsides being best for building but didn't specify a gradient.  I've read a bit about the wofati concept which differs in that there's an attempt to create a seasonal heat store around the house with dirt but as far as I've read it has not been demonstrated yet i.e. you can't store the heat in the battery without making the living spaces too hot.

I presume water is mainly a problem if the water table is very close to the surface.  If it's not, then the polyethene or pond liner should divert rain water away from the house.

Anyway, I'd like to brainstorm what it would take to build a number of earth sheltered community houses.  Most existing housing here is crazy expensive and is poorly insulated.

Graham Chiu wrote:So, I've mostly read Mike's book and it doesn't seem that solar gain is that much part of the equation for his earth integrated houses.  He talked about hillsides being best for building but didn't specify a gradient.  I've read a bit about the wofati concept which differs in that there's an attempt to create a seasonal heat store around the house with dirt but as far as I've read it has not been demonstrated yet i.e. you can't store the heat in the battery without making the living spaces too hot.

I presume water is mainly a problem if the water table is very close to the surface.  If it's not, then the polyethene or pond liner should divert rain water away from the house.

Anyway, I'd like to brainstorm what it would take to build a number of earth sheltered community houses.  Most existing housing here is crazy expensive and is poorly insulated.

Just so people understand how steep 45 degrees is, a guard rail on a roadway is required above everything above 10%. 45% is insane. That is nearing the point where excavators and bulldozers have to be WINCHED up the hillside.

But I believe you are right regarding the heat storage, and heat battery charge of a WOFATI. It goes along with physics anyway, and thermal dynamics. It is called "Delta T", and basically is the law of thermal dynamics that to get a given mass to a given temperature, ideally the temperature difference is 15 degrees. In my home that uses geothermal heat, this holds true. In order for me to get my home up to 70 degrees, I actually have to run 85 dgree water through the floor to get my home to 70 degrees. Delta T is the ideal temperature in which heating (or cooling) takes place in regards to mass.

In the case of a WOFATI, in order to get the mass of the earth to temperature (the heat battery), according to the laws of thermal dynamics, the ambient air inside the WOFATI Home would have to be 15 degrees hotter, so it would have to be 85 degrees. It does not matter how that ambient air is heated; by human occupancy, passive solar, a woodstove, or rocket mass heater, the inside needs to be 15 degrees hotter for the walls to start absorbing heat.That is a little warm for human comfort.

But that does not mean the WOFATI is in ineffecient, it just means that it is well adapted to thermal changes. In other words, it will be 57 degrees no matter if it is cold outside, or stifiling hot. But of course there are ways to intrioduce heat. Windows will obviously be added, so there is passive solar, active solar, rocket mass heaters, woodstoves, really anything. The effeciency comes in that the temp does not have to be brought up from 30 degres to 70 degrees like in a conventional home, but rather only up from 57 degrees to 70 degrees.

If a persom really wanted to get thermal heat into their walls, and lived a pretty consistent lifestyle, (having a real job), they could let passive solar heat the WOFATI's inside ambient temperature up pretty high. When it got above 85 degrees, the walls would start taking on heat, and charge the "heat battery bank" while the homeowner was at work. If the inside temp got up to 100 degrees, the walls would really be absorbing heat, but in order to be comfortable, when the homeowner got home, they would have to vent that heat as quickly as they could, with fans or air conditioners. Set on a timer, they could come on 1/2 hour before the homeowner got home, and allow the homeowner to be comfortable.

The more heat tolerant a homeoener was, the more they could recharge the "heat battery ". Again the magic number is that Delta T, or 15 degrees in temperature difference, so if they kept the house at 80 degrees, the heat from the walls would not  be trying to help warm the interior of the house that the homeowner is now living, and sleeping in. So by maximizing the heat inside of the house during the day, and then limiting the walls heat loss duing the evening and at night, the heat battery bank would slowly be charged up.

This may, or may not work for a homeowner. It would not work for me because I am retired and thus need a house that is always comfortable. I do not want to walk into my house for lunch and have it 100 degrees in the summer just heat my walls up. That is okay, because for me, what little bit of heat it would take to keep me at 70 degrees at night would be nothing. Pasive solar (windows) and a small active solar thermal array would do it, with a pot bellied stove as a possible back up for the deep winter.

From what I recall from reading Mike Oehler's book, he also didn't believe in the thermal storage idea.  He just wanted to take advantage of the earth sheltering that provides a base temperature higher than ambient air temperature that reduces the heating cost to raise it to a comfortable level in winter.

The site I'm looking at is in suburbia so there's no woodland to take trees from.  But there are some log house building companies around and I presume that I'd be able to use them to setup the initial frame of the house.

Although the land is about 45 deg, there's a road at the bottom and at the top so I would think one could use a digger and start work at the bottom and infill working up to the top. I just have to convince myself that building this way is cheaper, healthier, and longer lasting than driving some poles into the ground and erecting a house made of metal sips.

You may need to start over again.
In suburbia its much harder to build what you had in mind, availability of soil being one issue.
You may need to think pole house, Sydney, Australia  has a lot because of the cliffs etc they have as building sites.

I'm not understanding the need for soil.  One needs to excavate the soil for the house, put the PSPs in, and  then back fill with the soil.  If anything I'm going to end up with too much soil as i need to leave the rear patio free to create the microclimate for a small greenhouse.

I realise that this post is in the earthship category, but it's not an earthship.  From what I can see earthships are built at ground level, but integrated earth buildings are built below grade.

Graham Chiu wrote:From what I recall from reading Mike Oehler's book, he also didn't believe in the thermal storage idea.  He just wanted to take advantage of the earth sheltering that provides a base temperature higher than ambient air temperature that reduces the heating cost to raise it to a comfortable level in winter.

Yeah for Mike and I, who live in cold climates, just having a home at a constant 57 degrees would be a benefit (ground temperature here in Maine). I think thermal Inertia is possible, it is just not free. It would take a lot of work, or a change in lifestyle, comfort level, and serious investment to make happen.

It is kind of like when i looked into heating with compost. I concluded that it was possible, but it would take less time, money and effort just to keep heating with wood. It is NOT that it compost heat wouldn't work, it was just not as effecient as other methods. I think Thermal Inertia is like that, it can be done, but why not just put in active solar, and pump the heat into the WOFATI when and where you need it?

From the brief description I read of Hait's Geodome, it really needs full sun heating the interior of the house for any significant heat storage to occur.  And I'm at best going only to have clerestory windows admitting some light.  So, the passive heat store is out of the question.

So, for heating I was thinking of using something like the Walker stove at the bottom of the house, and heat sent to a stratification chamber that runs the length of the building.  The stove would be used for serious cooking but "instant" cooking would be electric or a TLUD fan assisted stove using pellets.

The thing is, this is the near worse sort of land for traditional housing being both on a steep slope and facing away from the sun.  I am wondering if something like this could be prototyped to build housing on this type of unwanted land for the really poor.

Building on a steep slope like this is not for the really poor, at least if safety is a consideration. All the construction needs to be stronger than on a flatter site, and takes more skill. Someone experienced would need to be in constant control of the building process.

The slope being much too steep for mechanical excavators might actually be a benefit in this case, making it more cost-efficient to use manual labor employing poor people for excavation. As long as the cost of the land is low enough to largely offset the added expense of building, it may be feasible.

Is the slope actually 45 degrees? (1' rise for 1' of run?) That is near or beyond the angle of repose for most soils, and landslides could be a real danger without proper engineering. Such a steep slope might also be close to bedrock, which would inhibit digging below grade. What is your latitude? A 45 degree slope would not just limit winter sun, there could be no winter sun at all depending on how far from the equator you are, making the microclimate much colder than average for your locale.

A major question would be the building restrictions in the locality. Many suburban areas in the US have restrictive codes dictating land use and building methods.

The site has already been surveyed by geotechnical engineers and penetrometer testing carried out. Solid is 2 m below the surface.

Building consent had already been granted for about 5 houses to be built at the top of the ridge but the developer is moving to a different project so is selling up. He lacks the capacity to do both projects.

Lots of houses on stilts are built on such sites but building $600,000 houses doesn't help solve our housing crisis.

One way of building that might work might be to start from the top. Drive micro piles into the hillside for the first house, and then use a digger to reach the piles from below. But it's about $1k per pile. The digger should be able to pull itself up the site. And then use it to place the posts needed for the PSP.

I had a look at the site on the last day of winter and there was Sun light falling on the hillside vegetation so I suspect the houses won't be completely  in shade.
This is a fairly old development site and there are no restrictions on the site except those applied by the building code.

I've come across Don Stephen's annualized geo-thermal storage system which is causing a bit of a rethink.  I could have some flat plate or vacuum solar collectors to pump hot water into the ground under the house in summer.  So depending on how deep the rock is below the house I could insulate the perimeter of the "earthern" slab.  If the water table is too high, I'll need to insulate below the slab as well.

My experience with vacuum tubes tells me I should look at flat plate collectors instead.

More brainstorming. If I were to consider using AGS then I'd likely reposition the RMH/stove in the centre of the building with the stratification chamber running the length of the building. I'd remove the insulated bottom of the RMH so that it would also pump heat into the AGS core. But I'd need to decide if that's too extreme and I should keep some fire bricks at the base of the fire box so that enough energy is reflected back to the combustion chamber so ensure that gassification occurs.

What is an AGS please?

Annualized geo-solar thermal storage.

https://permies.com/t/11604/Annualized-geo-solar-AGS-passive

Bumping this - also curious if anyone has had success with a Wofati/Oehler structure in a temperate climate getting 20-50 inches of rain/year.  Separate question - what is more efficient/cheaper in such a climate; a strawbale home or a wofati?