What type of shingles, if any?
What does the roof look like?

Vic

the roof looks like a conventioanl built roof.

Manfred,

Your talking about 3 more componates. Please explain more as I planning geothermal.
You have my attention as you claim the costs are affordable.

Vic

vmg, so far we have talked about the energy storage underneath the house for heating, hence "hot-circuit". What about the cooling of the house in the summer or "cool-circuit"? In this case the cooling is provided by seperate pex loops outside the house perimeters where the earth temperature is a constant or 50-55 degree Fahrenheit. These are seperate loops that get included in the ICF construction and the slab on grade. If the temperature inside the house are rising above a certain point the cooling circuit jumps into action.

Manfred,

So you have a hot, and cold circuit. Now would you care to let us know how you draw off these circuits into the house?
How does it jump inta action? are you holding back on something here?

Vic

I worked on a sip house next to a river so it had high ground water levels that had a 30 inch dia culvert for a well casing and black poly pipe plumbed into the mech room. I didn't see the finished installation but they said they were going to have a heat exchanger to use for the in slab pex system.

By the looks of all the mini storage places around, seems a lot of people could use the crawlspace as secure, conditioned storage.
In our area of Wyoming, (with neccessity of 48 inches of frost protection) the "short basement" is non taxed space but provides options for storage, retrofit, and ease of construction scheduling. We leave an access from the garage without stairs, therefore it is not appraised as living space. One guy I know rebuilds engines down their in his spare time....


Kevin

vmg, sorry for the late response to your last question, you know, holidays and all. Ok, so.... the hot and cold circuit are being used as thermal barrier. The actual draw, as you call it, comes from the 3rd. element not talked about yet. That is a "pipe-in-pipe" air-exchange duct. Through this system you expell stale air and draw in fresh air. Since you are using stainless steel the thermal exchange efficiency is rated at 98%. You don't have to worry about condensation in the pipe, since this pipe is again burried 6-10 feet in the ground.

Bob Ramlow of Artha Renewable, author of Solar Water Heating, made a plan for my house to use 24" deep sand beds under my slab as a high mass heat energy storage. He wanted to insulate the ground and walls and compact sand with PEX tubing run through it then pour the slab on top. We would then heat the sand with solar collectors. The idea was that the sand would take 8 weeks to heat up but could provide heat for 4 weeks of cloudy days.

I scrapped the plan because I was worried that an ICF house would overheat in the mild climate of San Francisco.

eco-hammer, you made the right decision! The system that you describe would have only pumped energy into the sand. In a cooling climate like San Francisco there would not have been enough use for this alone. I also think that without the perimeter sand bed insulation the heat would have dissipated enough not to cause a heat sink overload.

There are substantial differences between your system and the one that I describe. Aside from using the "hot circuit" underneath the house there is also a "cooling circiut" beside the house. Then there are thermal barriers inside the walls and the ground slab. The "hot circuit" is also used to pre-heat the hot water requirement in the house. And laslly there is the pipe in pipe technology which provides the necessary air-exchange in the house.

The whole system is based on all elements working together in concert. The "hot circuit" in the summer gets used all the time due to circulation, hot water use, and thermal barrier gradiency where the hot water "area" by-passes the cold water "area" in the thermal barrier wall and floor assembly. THis flow is controlled by sensors.

I agree with you, that if you install one system without the other the effects could be very minimal or in your case detrimental.

Manfred,

Please correct me if I am wrong, but I think a summary of your plans as I understand them so far is as follows:

A.  A cooling loop deep in the ground outside the perimeter of the house. 

B.  A heating collecting loop under the roof (using the roof tiles as sort of a solar collector) that will store heat in soil (sand?) below the footprint of the house.  This mass of soil is insulated (thermal barriers) around the perimeter and from the slab.

C. Ventilation air is provided through an underground coaxial air-to-air heat exchanger.

Now the questions:

1. Are you using the heating/cooling water directly (i.e., not as the "condensor" side of a heat pump) for heating/cooling.

2. How are you harvesting the heating and cooling?  Do you envision to use PEX in the floor(s) or slab(s)as radiant heating and cooling?  If so, would this be a single circuit system (one embedded pipe that would either heat or cool as needed)?

3.  If you are using radiant heating/cooling as noted in 2, will you have multiple zones for different exposures?

4. Do you plan to insulate under the heating soil mass?  If so, how are you calculating the quantity of the soil mass?

5.  For the heating side, will you have a single circuit that connects the "solar collector", soil mass, radiant heating and domestic HW preheat?......or will there be separate circuits, i.e., a circuit between the solar collector and the soil mass, another connecting the soil mass to the radiant heating and another connecting the soil mass with domestic HW preheat?

6. How are you approaching the calculations for the amount of pipe to use outside and inside?

7.  I assume you will be superinsulating.  What is your target R or u value?

8.  Will you also use passive heating through windows?

Sounds like a really interesting concept!

Bruce

 

Bruce, thank you for your interest in this concept. You have summarized this system very nicely, with minor details left out.
I'll answer the questions in sequence:

1. The water is used directly for each respective circuit and hot water pre-heat. This geothermal concept eliminates the use of a heat pump!

2. Actually you need to think differently here. The heating and cooling is not harvested as such as it provides a thermal barrier from the outside. Yes, you have the cooling "and" the heating circuits inside the wall. Works great with ICF, whereas you install the circuits alternatively as you go up.

3. Yes, this system allows for multiple zones. The actual comfort level (Temperature) is controlled via the air exchanger.

4. No insulation "under" the soil mass. It will take about a year for the temperatures underneath the slab to achieve a stable permanence.

5. The big picture is a single circuit with branches. Branches are controlled by valves with sensors.

6. Civil engineer conversant with thermo-dynamics.

7. This system works best with an ICF build. The concrete in between the styrofoam now becomes a thermal barrier, rather than a thermal mass. It will work effectively as well as a retro-fit for stick-build houses. Calculations and pipe requirements change from situation to situation.

8. This system will allow you to install regular windows (2 pane, argon filled) and still achieve a "zero-energy" house. Passive heating through the windows is not a requirement for this system to work.

I know "zero-energy" is a terminology that is interpreted differently by different institutions and people. Some institutions say "if you use less than" you can call it "zero-energy". Most people think "zero-energy" should be "no" energy at all, period. This system is of course not a "no" energy solution. Electricity is used to run the valves, the computer, the air pumps. Electrical current consumption, depending on where you live would be around $10 - $20/month.

I think I am getting the concept.  I assume this is a mild climate project.

You will run the PEX tubing INSIDE the ICF walls, heating or cooling the concrete core of the ICF as a "thermal barrier" ......sort of "virtual" or "reactive" insulation that will change the thermal gradient across the wall.

The complications I see to this are: 1) Facade area will be critical - you will want to optimize the facade/floor area ratios (the shape of the house); 2) unless you use "lopsided" ICF, you are heating/cooling with only ±R10 between the concrete and the outdoor condition; 3) because it would be hard to do a serpentine PEX layout in an ICF wall, you will probably need to do a manifold type piping arrangement that has a supply manifold(s) around the base and a return manifold(s) at the top.  Water balance will be a challenge.

How will you control the temperature with the air exchanger?  Temperature control implies that it will also have a water coil capable of using the heating/cooling water.

Bruce

Bruce, this system is good for any climate or temperature extremes. It works well in cold climates as it does in very hot climates.

I don't understand your facade/floor-area-ratio. In this design the ratio is irrelevant.

Your point #2 is a non-issue with this design. As a matter of fact the thermal barrier gradiant is controlled according to the temperature present in the concrete. If more heat is needed the hot water circuit will kick-in more. If more cold is needed the cold water circuit kicks in more. There is always a balance between the flow of the hot circuit and the cold circuit that is reactive to what is going on thermally insdie the concrete.

It is not hard to construct a serpentine inside the ICF walls. At the end, or the stop of the wall you will cut the PEX and connect to a connector PEX which will take it to the next level. The meandring way of placing the PEX of course needs to be thought of before starting the construction with the ICF forms. You are right about the manifolds. This design will require a mechanical room with enough space for all the manifolds, valves, gauges, and so forth. Water balance is not a challenge at all.

The temprature coil (pipe) is placed outside the perimeter of the walls and inside the perimeter of the walls. So the air goes through a cooling circuit and a heating circuit. Air velocity is handled through an air exchanger and also the dampers in the individual rooms/areas.

To make sure I have the concept correct:

You will have PEX in the ICF that will heat/cool the concrete core of the walls to eliminate any heat gain/loss from the inside.  This essentially give you an "effective R value" of infinity, since the interior space should see no heat gain/loss through the walls (theoretically).

Heating/cooling loads from doors, windows, roof, people, etc. and any load that does make it through the walls will be handled with heated/cooled air from the air exchanger using variable air volume dampers.

Is that correct?

Since you will be heating/cooling the walls, it seems to me that optimizing the wall area would be a bit more important than normal.  It shouldn't necessarily drive the design, but it will minimize costs and the amount of heating/cooling (the length of your coils in the ground) that will be required. 

In a cold climate it seems to me that the walls will require a lot of heat, hence my mild climate comment.

Is this a project that you are building or still in the concept phase?

Happy new year!

Bruce

Bruce, by "importance of optimizing your wall area", do you mean the percentage ratio between the wall and window/door opening? Happy New Year.

For a given floor area, a round building will have the least amount of perimeter walls.  A square building is the next most efficient.  The "more rectanular" the building, the greater the amount of perimeter walls for a given floor area.

A square box is not very architecturally exciting, but it is efficient.

An example......The EU is mandating that all new commercial and multifamily residential buildings (I am not sure about single family) have "Energy Performance Certificates" rated A-F.  While the calculation metodology is left to each country, the "shape factor" of the building is an important calculation consideration.  It is harder for a building with an extreme shape to get a good grade when the comparison is based on w/m².

Bruce

I am with you on the shapes. But I think it is important to understand the difference between a wall in EU and USA. Minimum standard practice in the US is 8' tall walls. This does not cut it in the EU. Depending on the country you are looking at, a minimum of 9'-10' tall walls (inside room measurments) are the requirements.

Here in the US you are looking at upgrades if you want a wall to be 9' tall or higher, hence you are getting into the custom home market. So, while you do have a point about the floor area/wall ratio it is also important whether these walls are 8' or 10' tall. So then to better understand how much wall area is available I usually use the percentage ratio of wall vs. openings. While they are at 20%-25% in the US, they usually are between 13% - 20% in EU.

Having said that, the calculations will change regarding the percentage of your wall available. And you are right - a shoe box building with no windows is much easier to calculate and takes less pipe installation than a more complex design with openings in the 20%-25% range. In the EU they consider a "passive-energy house to be less than 12KwH/m2/a. That is 12 kilo watt hours per square meters per annum (year). Translated to dollars and cents that is less than $40 per month for a 3000sqf house @ $0.15 cost per Kwh.

Cupolex ventilated slab system?

May be able to reduced the slab thickness, to reduced efficiency sink?

I'm all for crawlspaces (if possible) most definitely a site specific consideration.

GB, can you explain of why the Cupolex ventilated slab system would be a benefit to a "zero-energy" house considering my elaboration of an integrated system discussed in this thread?

Reduce slab thickness from what to what and reduce efficiency sink why?

Crawl spaces are an inefficient use of real estate. Harbours dead space, creepy crawlers, disease agents, moisture overload, mold and mildew etc. There are people who approach this cons intelligently and propse a non-vented space within and insualted perimeter area etc. I am of the opinion if you were to convert the cubic air space of a crawlspace into a mechanical room you'd much further ahead. The pluses of a mechanical room vs. a crawl space are obvious.