Terra-Dome Earth Shelter Build

[lhansman]

I too have long had an interest in building an earth sheltered home but have never taken the plunge. I have thouroughly enjoyed watching your work and reading all of the posts over the last couple of hours.

I realize the discussion on floor water temperature was a couple of months ago, but as someone who rebuilt his above ground home a few years ago and installed radiant floor heat I have some thoughts that might benefit you. We live Canada about an hour north of Toronto, Ontario so we definitely get cold winter nights (-24 degrees C as I write) as well as warm summer days.

When my boiler was first installed my water temp was set at 140 F and it certainly kept our 3600 sf foor home warm. However with the high temperature of the water if the outside temperature was not really cold, the floor would continue to radiate heat for a long time after the boiler shut down. Things would then really cool down before the boiler would fire up again and warm the floor again.

I am not an HVAC expert but after doing some research and speaking to the person that installed our gas fired boiler, I learned that there was an option to install an outside temperature sensor connected to the boiler. With this connected to the boiler, the boiler then heats the water to a sliding scale depending on the outside temperature.

These values are approximate, but here is how my boiler works. You tell the boiler what the coldest expected outside temperature is (in my case -30F) and what the warmest outside temperature is (in my case 60F) that you want the boiler to operate at. In other words, if the outside temperatuer is 61F or higher, the boiler will not come on not matter what you do with the thermostat. You then set the hottest water temp you want the boiler to operate at when it is -30F outside (140F in my case) and the coolest boiler temp you want when it is 59F outside (105F in my case).

Now draw or picture a line graph with outside temp on the vertical axis and boiler water temp on the horizontal axis, plot the upper and lower intersection points and then draw a line between them. When my boiler fires, it then automatically adjusts the water output temp to the appropriate point on the line depending on the outside temperature. This means the floor is always warm on the coldest days and continues to stay warm even during the "warmer" winter days.

I hope this isn't to convoluted an explanation but I know implementing this kept the temperature in our home much more consistent and we were not running 140F water all the time. I look forward to following your work to completion Sam.

 

[patrick_g]

We may have radon problems but the internal french drain will allow gasses to escape through the path of least resistance. I don't want to install a pump unless required.

Don't let path of least resistance get you into trouble. What you have are several parallel paths. The one with the least resistance gets more of the flow but the others still get some, maybe more than you want to breathe.

I used Stego Wrap a HD moisture and gas barrier sheet under my walkout basement's raised slab floor which sits on 2 1/4 inches of figid foam insulation on top of 16 inches of washed septic gravel over the excavated grade. I have a complete perimeter loop of 4 inch perforated drain pipe at the level of the excavated grade on the inside of the foundation and another one on the outside of the foundation. All 4 ends drain to daylight. To be more sure about radon I also buried a 4 inch perforated drain in the 16 inches of washed septic gravel and brought that out of the slab to a vertical run of PVC to take it up through the main floor and upstairs to vent to the outside.

The Stego Wrap is lapped and sealed with a special (expensive) wide red tape so that nothing leaks through. I used the tape where all plumbing penetrations were made too. Any positive pressure from radon or anything else under the slab will be vented at roof level unless it goes out the perimeter drain which terminates 150 feet or more down slope toward a pond.

Pat

 

[rox]

Sam, It is cold and raining and I have just spent at least an hour in front of the fireplace enjoying so much reading about your project. I am sorry about the roofing product but I am sure you will come up with something. I see by your job that you are sensitive to water. I am sure you will figure it out, it's just one of those things.

​

 

[pwitt79]

Sam, I have read through all 20 pages of this forum and I really appreciate your willingness to show pics and talk about your experience. I live in NE and I am in the very early planning stages of a home similar to yours. I had some questions that I wanted to ask you.

Did you consider PAHS (Passive Annualized Heat Storage)? If so why didnt you go with it?

I think you said this house was around 3000 sq ft...what did you budget and how close are you to it? How many bedrooms? Baths?

Was Terra Dome extra helpful in the design phase? Or did they just sell a plan they already had? Did they do all the drawings?

Does your house face towards the south?

What was the most difficult part of this project?

Was financing on such a house easy to get?

I am super excited that I foudn this forum...I will be checking back often.

 

[SamWalton]

Sam, I have read through all 20 pages of this forum and I really appreciate your willingness to show pics and talk about your experience. I live in NE and I am in the very early planning stages of a home similar to yours. I had some questions that I wanted to ask you.

Did you consider PAHS (Passive Annualized Heat Storage)? If so why didnt you go with it?

I think you said this house was around 3000 sq ft...what did you budget and how close are you to it? How many bedrooms? Baths?

Was Terra Dome extra helpful in the design phase? Or did they just sell a plan they already had? Did they do all the drawings?

Does your house face towards the south?

What was the most difficult part of this project?

Was financing on such a house easy to get?

I am super excited that I foudn this forum...I will be checking back often.

Sure, we have four windows facing south which during the winter months while the sun is low on the horizon the low E windows will allow passive solar heat to the home and the earth sheltering will help maintain a constant temperature year round. I don't want to rely on passive systems alone and feel in order to provide better air quality the HVAC system is necessary. I also like the ideal of warm floors so we will be installing radiant floor heating.
Our plan is to use our Greenwood hydronic wood boiler and an array of solar panels in a closed loop to provide domestic hot water and both radiant and HVAC forced heat via the power of the sun and renewable energy of wood. We will eventually install some Photovoltaic's to provide 2000 watts of inverter power via battery bank.
We went over budget and won't know by how much until we get closer to moving in. We have four bedrooms and two baths.
Terra Dome answered all my questions and provided a Micro station drawing of my basic plan for $1560. I designed all details beyond the basics. There is a lot to understand and if you're not into engineering you may want to have electricians and plumbers involved to implement all details to drawings.
Our home faces south, north and a little east. We are bermed from east to west but expose all of the north side and most of the south side.

The area I have stalled in is the plumbing. I am learning the National Standard Plumbing Code and insist in being sure we have it correct before pouring the cement floors.
We were unable to get financing because I was unwilling to allow the bank to control the building process.

Good luck on your build!
Please let us know how things progress.

 

[sajurcaju]

Sure, we have four windows facing south which during the winter months while the sun is low on the horizon the low E windows will allow passive solar heat to the home and the earth sheltering will help maintain a constant temperature year round. I don't want to rely on passive systems alone and feel in order to provide better air quality the HVAC system is necessary. I also like the ideal of warm floors so we will be installing radiant floor heating.
Our plan is to use our Greenwood hydronic wood boiler and an array of solar panels in a closed loop to provide domestic hot water and both radiant and HVAC forced heat via the power of the sun and renewable energy of wood. We will eventually install some Photovoltaic's to provide 2000 watts of inverter power via battery bank.
We went over budget and won't know by how much until we get closer to moving in. We have four bedrooms and two baths.
Terra Dome answered all my questions and provided a Micro station drawing of my basic plan for $1560. I designed all details beyond the basics. There is a lot to understand and if you're not into engineering you may want to have electricians and plumbers involved to implement all details to drawings.
Our home faces south, north and a little east. We are bermed from east to west but expose all of the north side and most of the south side.

The area I have stalled in is the plumbing. I am learning the National Standard Plumbing Code and insist in being sure we have it correct before pouring the cement floors.
We were unable to get financing because I was unwilling to allow the bank to control the building process.

Good luck on your build!
Please let us know how things progress.

Hi Sam,

I definitely hear you on being over budget. Lots of non-standard stuff that is hard to predict. We're also interested in putting in solar (electric and hot water), but will be waiting on the electric until our local budget recovers.

I think this guy has done a great job discussing diy solar hot water:
BuildItSolar: Solar energy projects for Do It Yourselfers to save money and reduce pollution
You've probably been there. I'm hoping to start on a system this summer.

Our house is moving along. All of the interior walls are up and plastered, about 1/2 of the interior paint is done. We're doing tile floors and maybe 1/3 of that is done. Our contractor hopes to have the house done end of January (we're thinking a week or two later), then he will pour the shop and barn floors and finish their electrical. Getting close.

I'll post pictures next week.

Steve
Lovell, Maine

 

[sajurcaju]

Sam, I have read through all 20 pages of this forum and I really appreciate your willingness to show pics and talk about your experience. I live in NE and I am in the very early planning stages of a home similar to yours. I had some questions that I wanted to ask you.

Did you consider PAHS (Passive Annualized Heat Storage)? If so why didnt you go with it?

I think you said this house was around 3000 sq ft...what did you budget and how close are you to it? How many bedrooms? Baths?

Was Terra Dome extra helpful in the design phase? Or did they just sell a plan they already had? Did they do all the drawings?

Does your house face towards the south?

What was the most difficult part of this project?

Was financing on such a house easy to get?

I am super excited that I foudn this forum...I will be checking back often.

We're building a Terra Dome house in Lovell, Maine. If you're nearby and would like a tour, let me know.

TD is responsive during both design and build phases, much more so than Formworks who we started with.

Due to the way our site is laid out, our house faces sort of north-east, but the back side has a lot of windows with southern exposure. I may try to figure some kind of reflectors in an attempt to melt the front in winter.

We had no problem getting financing from a local bank. The key is to find a bank that will carry the loan themselves. The minute you get into a loan that might be re-sold, if you're the slightest bit non-standard there's a problem. You may pay a little higher rate, but not always. Check all your area banks, I was surprised how much variation there is in loan costs.

Steve

 

[pwitt79]

Thanks guys, i really appreciate your comments.

Sam, I am actually a mechanical engineer but only been out of school for a few years. I live in Nebraska so making a trip to Maine is definitely out the question. Maybe Oklahoma some day, there are actually lots of these in the midwest i just need to get tours from volunteers arranged. Did you consider having Earth Sheltered Tech construct your home? What about davis caves?

How did you make the big decisions like if you would have more than one side open? If you were going to build into a hill? Best floor plan for a earth sheltered house? Did terra dome do a free site visit when you were first bidding it out? Did you get competitive bids? Or was the scope not completely laid out? Did you purchase the land just for this house?

Thats what i want to do now...i will probably not build for 3-5 more years...but i want to have all the details complete so that when the time comes I will have all the decisions made.

I have micro station at work and can use it for something like this...just not during my normal hours. I am still considering a complete PAHS system with some supplementary air ventilation and probably a an outside wood boiler with a water loop. Still lots of things up in the air of course.

Did you put a skylight in every module? Would you recommend them or the suntubes?

One last question...do you think its possible to build into a steep hill that you could design a floor plan to actually be two levels? So the so you would actually walk in the bottom floor or top floor by a deck or garage on the first level? Just thinking

I guess one more...are you planning on doing all the backfilling and dirt work yourself? Did you do all the grading before you laid out footings? I would think this would be the easiest part. Are you putting the 2" foam insulation on the outside of the structure?

Have a great weekend.

 

[patrick_g]

Boy oh boy, over budget and non-standard construction... those terms sure ring a bell (way too loudly.) After spending literally years buying books and studying underground/bermed/earth sheltered residential construction I didn't follow through exclusively.

I have a walk-out basement which is totally underground on three sides with lots of glass on the south so it is in fact an earth sheltered passive solar underground SEGMENT of our home. Other segments are ICF, traditional stick, and red iron (engineered steel trusses with I beam columns and the 2x6 in the walls run horizontal not vertical like studs.

During our framing stage the cost of sheet goods (OSB, plywood, ...) doubled and tripled as did steel and concrete shot up too (not a good thing for ICF construction or our 12 inch thick cast concrete basement walls and the extensive retaining walls that hold back the world to let us have a walk out basement AND maintain original grade for a nice backyard pecan tree.

I thought I was a decent project manager (decades of experience, just not in residential construction) and thought I had ample reserve in the budget for the unforeseen little cost drivers that pop up in the best of plans and management strategies. Well, my little crystal ball was out of calibration apparently and I didn't get advance notification of the effect of east coast hurricanes on the price of sheet goods nor the effect of our military activities in the Persian Gulf on the cost of steel, cement, and (dare I say it again) sheet goods.

So, we went seriously over budget. It isn't that as two recently retired folks who had lived frugally and saved for decades that we didn't have more $ it was an issue of not wanting to spend it all on the house and then essentially be mostly broke. We retained contractor assistance long enough to mostly finish the trim work on the ground floor and left oodles of stuff undone in the walk-out basement and the upstairs. I am now personally the finish carpenter, cabinet maker, plumber, electrician, painter, and whatever else needs doing when I'm not tending to ranch business maintaining and improving 160 acres and tending a couple dozen pregnant black Angus momma cows, the bull, and calves in various stages.

Right now I have some serious issues with the ground sourced water to water heat pump that supplies heat to the in-floor, in-ceiling, and in the case of the master bath shower, in-wall hydronic heat. It seems the whiz kid that helped me design and install the in-floor hydronics was really good on theory, did a great install but suffered from lack of long term experience. Our mutual ignorance regarding long term system maintenance, especially periodic testing of the glycol solution in the hydronic loops led to a near disaster which I mention, not for anyones sympathy but to give warning in case others might be helped.

There are open systems and so called closed systems. Closed systems may in face not be so closed as you may hope, and over time the condition of the glycol solution circulating through your hydronic loops will change in its chemical constituency and balance. This can and, in my case, did lead to scaling in the coaxial heat exchanger in the ground sourced heat pump. This scaling insulates the heat exchanger rendering it ineffective. The heat pump makes oodles of heat but can't get it into the hydronic loops so it builds up until the heat pumps self protective circuitry shuts the unit down.

Luckily our heat pump can make hot air and or hot water at the same time. We therefore still have access to standard forced air heat, just not heated floors, our preference. The out of whack pH of the glycol solution ate a hole in the little bladder tank which accommodates expansion and contraction and had to be replaced. Likewise a hydronic towel heater in the master bath had a hole eaten through it. These happened the same week and served notice that not all was well right here in River City.

We are now in month two of waiting for materials to clean, flush, and restore the system to proper operation (with additives to prevent the recurrence) and a plan for periodic testing to stay on top of the water chemistry. Oh by the way... the whiz kid doesn't work there any more and they don't return my calls. I think I have a good case for litigation. They are the licensed experts who installed the system and ignorance or any other excuse doesn't matter. If they knew and didn't take proper action (never mentioned the topic to me) then my problems are their fault. If they were ignorant and didn't know any better then it is still their fault because they are the licensed experts and they should have known. Will I litigate? Most likely not. I have better ways to waste time and money. If I had more of each than I knew what to do with I would love to take them to court but time and money are not in over supply.

So, everyone planning on hydronic heat... Be sure you consider my tale of woe and take steps to avoid it. I was blissfully ignorant of the existence of even the potential for problems with the solution in the hydronic loops. I thought, gee, its like anti-freeze running in nearly all plastic at moderate temps and should last essentially indefinitely since it isn't getting contaminated or stressed. WRONG!!! It requires, as a minimum, periodic testing to see how it is getting along. Sans testing, the first indication that things are not as they should be is system failure from scaling and leaks from corrosion. I haven't fully quantified the cost of recovering from the HVAC contractors ignorance or lack of attention to detail. I may still have to replace the coaxial heat exchanger if we can't get it properly cleaned and leak free and replacement is very pricey.

Yes, the devil is in the details. Ignorance is bliss until your rude awakening. After this what do I think of hydronic heat? I love mine, and miss it dearly. I will soon get it restored and take steps to insure its long term reliability.

Best of luck to all who install hydronics and I hope you avoid my situation. Forewarned is forearmed. Learn from my mistakes and avoid repeating them.

Funny how we are setting records for low temps just now while I don't have hydronics, when it would be the neatest thing to have. Just a little bad timing, soon to be a non-problem.

Pat

 

[sajurcaju]

Thanks guys, i really appreciate your comments.

Sam, I am actually a mechanical engineer but only been out of school for a few years. I live in Nebraska so making a trip to Maine is definitely out the question....

How did you make the big decisions like if you would have more than one side open? If you were going to build into a hill? Best floor plan for a earth sheltered house? Did terra dome do a free site visit when you were first bidding it out? Did you get competitive bids? Or was the scope not completely laid out? Did you purchase the land just for this house?

Thats what i want to do now...i will probably not build for 3-5 more years...but i want to have all the details complete so that when the time comes I will have all the decisions made.

I have micro station at work and can use it for something like this...just not during my normal hours. I am still considering a complete PAHS system with some supplementary air ventilation and probably a an outside wood boiler with a water loop. Still lots of things up in the air of course.

Did you put a skylight in every module? Would you recommend them or the suntubes?

One last question...do you think its possible to build into a steep hill that you could design a floor plan to actually be two levels? So the so you would actually walk in the bottom floor or top floor by a deck or garage on the first level? Just thinking

I guess one more...are you planning on doing all the backfilling and dirt work yourself? Did you do all the grading before you laid out footings? I would think this would be the easiest part. Are you putting the 2" foam insulation on the outside of the structure?

Have a great weekend.

(this is Steve and the Maine house) Silly of me, I saw that you said you were in NE and I thought New England. I grew up in Nebraska, should have thought of that.

We have read about earth sheltered houses (use this term, not 'underground' when talking to banks, insurance, etc.) for years, but we have still been babes in the woods on this. We bought land before talking to a contractor; this is ok if you know what you're doing (we didn't). Our site dictated building the house on a sort of level spot instead of into a hill. The water table is so high that we built at and above grade, with more dirt over the top. Terra Dome did everything by email prior to sending the crew out to begin work. They came out in December and kept saying things like "does it always snow this much?" and "we saw a moose!".

Terra Dome has custom forms to cast the concrete domes, so with them you don't have the choice of getting a competing bid from another company. You'd have to do some house design both places and see what they cost.

Skylights and suntubes are nice, but you may not want them in your bedroom. Remember, in a stick frame house, the ceiling and walls aren't transparent either.

I happened to go to Colorado the week that Terra Dome was pouring a two story underground house in Ward, CO. A few pics attached. Not something that had occurred to me to do.

181 shows the forms for casting a dome
196 shows the second floor with temporary supports

Steve

ps: we were going to have more sun tubes, but ended up cannibalizing the pass throughs to the roof for ventilation instead, as we didn't have enough.