Natural home cooling

[Nitack]

I could use some thoughts/input into a home cooling project that hopefully will eliminate the need for using the air conditioner in my house. We live in Virginia, so the sun exposure is from the south and the

 

My wife and I bought a house six months ago. It became immediately apparent that there are two climate zones in the house. The foyer and upstairs are the first climate zone. The foyer is the entry point, and the entire length of the room is southern (solar) exposure, which means it gets very warm. The foyer has vaulted ceilings, and is completely open to a good portion of the upper level. It gets a lot of heat and passes it all on to the upper level of the house. The upper level has its own southern exposure, and just by the nature of warmer air rising, it gets HOT! Right now we spend basically all our time on the upper level. The kitchen, living room, dining room, bedrooms, bathrooms, office, and washer/dryer are all on this level. We hit 90+ degrees this last weekend on the upper level of the house.

 

The downstairs has no southern exposure at all. Most of the southern exposure is under ground level. This level is probably a good 15-20 degrees F cooler than the upstairs. There are three large rooms and a crawl space down here (under the foyer, you can walk if you stoop a little). The furnace/fan is located in a room that is open in back to the crawl space. This last weekend the downstairs felt wonderfully cool compared to the upstairs, and that is entirely due to the nature of shedding heat to the underground areas and lack of southern exposure.

 

I hate using the air conditioner. It is a nasty energy hog and there are many natural alternatives if you plan well. I have found some inspiration in the Earth Tube concept. I think I can use the floor in my crawl space for a closed loop design. I want to install an air intake in one of the lower level rooms that backs to the crawl space, and install a low power fan connecting to duct/piping that I will bury under the ground in the crawl space. the duct/piping will be run back and forth all the way to the furnace. There are three air returns in the house, two at high points and one at a low point. I want to re-rout the duct that draws air from the high points in the house into my earth tubes so that the fan will push cold air to the highest points inside the house using those return vents.

 

Here is a schematic of what I am thinking. The new piping is in blue.

 

 

Those high point returns are only needed when air conditioning the house because you want to cool the warmest air, so if i cut them off it should not affect the home heating during the winter months because you want to draw the low point cool air at that time of year anyway. I will also need to make sure that condensation can drain out of the duct/pipes in order to prevent moisture from building and mold from growing. I plan on laying the duct/pipe on top of a gravel bed and making drainage holes all along the underground portion. I think that will provide enough drainage to keep any condensation from creating mold issues.

 

My questions/request for input:

1. Is there something I am not thinking of?
   
2. What are some possible unintended consequences?
   
3. Should my fan push cool air to the high point of the house or pull hot air from the high point and cool it?
   
4. Is my drainage/condensation solution adequate?
   

 

If this works right the AC should no longer be needed at all so cutting off those upper level return vents should not pose a problem. I might use copper pipe ( $$$) for the germicidal and heat conducting properties despite how expensive it is. I'll also be using anti-microbial air filters at the output of the system, whether that be at the upper points or lower points. I will lose efficiency, but I have a 5 month old and will take no chances when it comes to mold/fungus growth.

 

So, what are the thoughts on this?

[Moontanman]

If your area is as humid as mine is, NC, then one potential problem i see is humidity in the house. Lowering the temps via a heat sink would also bring up the relative humidity in the air, at least that the way i see it. where I live lowering the humidity is often as important as lowering the temps. When you are at 72 degrees and 90% humidity it's amazing how hot the air "feels" and how much cooler it feels if you simply lower the humidity. a more efficient Air conditioner would probably be much easier and cheaper than all the changes you are thinking of making. where I live it's already far to hot to be comfortable, especially at night, with out the AC. We are so humid that even in the winter when the temps are in the low 70's or hight 60's you can sit and sweat. turning on the AC and lowering the temps by 1 degree will make a huge difference because the AC removes much of the humidity as it lowers the temp. You set up would lower the temp but it wouldn't remove much humidity, An AC is very good at removing humidity due to the high temperature gradient in the unit. Your heat sink wouldn't have a big enough temperature gradient to remove much humidity, a dehumidifier might make a difference on your idea but then you would be using power to run the dehumidifier, not sure if it would pay to do both as opposed to just having an efficient AC.

[Nitack]

Humidity is a problem here in Virginia too. However, just as water condenses on a cool glass of water, it should also condense along the pipe walls as the warmer air passes through. Is this not so?

 

This was why I put the gravel drainage bed into the design. The piping will have drainage holes drilled into it in order to shed the water. Am I missing something?

[freeztar]

Humidity is a problem here in Virginia too. However, just as water condenses on a cool glass of water, it should also condense along the pipe walls as the warmer air passes through. Is this not so?

 

This was why I put the gravel drainage bed into the design. The piping will have drainage holes drilled into it in order to shed the water. Am I missing something?

 

What is your house's foundation like? Most newer houses are built on top of concrete slabs. Is your house one of the older designs that has direct access to the ground beneath it?

 

I like moontan's thoughts on this. I'd like to add that I'm currently renting a split level home where the majority of the windows have SE exposure. Since the cold is finally gone for good (until the fall), I shut off the heat and fans and opened up almost all the windows. The house stays very comfortable with no energy use despite temperatures above 90 degrees F outside. So, when I was reading your first post, I began to contemplate the reasons why my situation is so different from your own. It's really only one reason I think...shade. The same shade that inhibits me from playing with my fresnel lenses encapsulates the house a large portion of the day.

 

If you plan to stay there a long time, it would be wise to plant some trees to strategically block that harsh southern exposure. Of course, this may mean higher heating bills in the winter. Those pesky trade-offs. :shrug:

[Nitack]

What is your house's foundation like? Most newer houses are built on top of concrete slabs. Is your house one of the older designs that has direct access to the ground beneath it?

The majority of the house is on a slab, but there is just one area that is a crawl space and has access to actual dirt. I'm guessing the builder figured that that part of the ground was not going to have direct contact with the room above so why bother. The house was built in the 1980's though, so not that much older.

 

I like moontan's thoughts on this. I'd like to add that I'm currently renting a split level home where the majority of the windows have SE exposure. Since the cold is finally gone for good (until the fall), I shut off the heat and fans and opened up almost all the windows. The house stays very comfortable with no energy use despite temperatures above 90 degrees F outside. So, when I was reading your first post, I began to contemplate the reasons why my situation is so different from your own. It's really only one reason I think...shade. The same shade that inhibits me from playing with my fresnel lenses encapsulates the house a large portion of the day.

 

If you plan to stay there a long time, it would be wise to plant some trees to strategically block that harsh southern exposure. Of course, this may mean higher heating bills in the winter. Those pesky trade-offs. :shrug:

Well if you plant deciduous trees in front of the house you won't have the winter problems because there are no leaves in the winter months. That being said... we already have two huge oak trees that block as much of the sun as possible. The only way I could get another large tree in there would be to take up the driveway and plant there.

[freeztar]

Well if you plant deciduous trees in front of the house you won't have the winter problems because there are no leaves in the winter months.

 

Except for the trunk and branches, but I see your point.

 

That being said... we already have two huge oak trees that block as much of the sun as possible. The only way I could get another large tree in there would be to take up the driveway and plant there.

 

Hmmm...well then why are you getting so much heat?

If it's from intermittent light coming in through the foyer windows, then perhaps getting double paned glass or even UV coating would be cheaper? How much do you figure this project will run you?

[Moontanman]

Humidity is a problem here in Virginia too. However, just as water condenses on a cool glass of water, it should also condense along the pipe walls as the warmer air passes through. Is this not so?

 

This was why I put the gravel drainage bed into the design. The piping will have drainage holes drilled into it in order to shed the water. Am I missing something?

 

I think what you are missing is that the air coming our of your system will be very high humidity due to the temperature gradient being so small. The coils on a AC are very cold, almost freezing and much of the humidity condenses on them Your cooling pipes will not even be close to freezing or even as cold as a glass of cool water so much less water will condense and more of it will be left in the air. You wil be lowering the temp but not so much the moisture so the reletive humidity will go up in your house.

[Nitack]

Hmmm...well then why are you getting so much heat?

If it's from intermittent light coming in through the foyer windows, then perhaps getting double paned glass or even UV coating would be cheaper? How much do you figure this project will run you?

I'm figuring this project will be a couple hundred $$$ at most. You would pay that much for one energy efficient window. We have 7 windows on the southern side of the house that would need to be replaced.

 

I think what you are missing is that the air coming our of your system will be very high humidity due to the temperature gradient being so small. The coils on a AC are very cold, almost freezing and much of the humidity condenses on them Your cooling pipes will not even be close to freezing or even as cold as a glass of cool water so much less water will condense and more of it will be left in the air. You wil be lowering the temp but not so much the moisture so the relative humidity will go up in your house.

 

That is a very good point, and exactly why I posted here before starting this project. I am sure that the duct/piping will get down to the 50's range, and it will condense water, but perhaps not enough. It might still be worthwhile to run this in conjunction with the AC in order to reduce the amount of time the AC is running... :shrug:

[Moontanman]

Nitack, where in Va do you live? under ground temps of 50 seem far too low for Va. In NC were I live temps underground are in the low 70's. I think you would have to go much farther north than Va to get temps in the 50's.

[Nitack]

Nitack, where in Va do you live? under ground temps of 50 seem far too low for Va. In NC were I live temps underground are in the low 70's. I think you would have to go much farther north than Va to get temps in the 50's.

 

I am in Manassas, so northern Virginia. However, the research I have found shows ground temps in my area of Virginia to be in the low to mid 50's at the depth I would be going to.

 

Here is a table from Virginia Tech with geothermal information at various drill depths. My house is pretty much in between either of these regions, but the data from either would put me in the mid-50's range.

http://rglsun1.geol.vt.edu/usgs1.html

http://rglsun1.geol.vt.edu/usgs5.html

 

Now weather or not water will condense in the system will be determined by the dew point for the specific conditions. The farmers almanac keeps some pretty detailed data on weather data and my area seems to have a high enough dew point on a good majority of days for my system to condense water.

Weather History for WASHINGTON DC DULLES, VA - The Old Farmer's Almanac

 

You might want to look into the data that they have for North Carolina as well.

North Carolina Wells

Although your underground temperatures do get into the 70's, that appears to only be the case when you get hundreds of feet underground. At 3-30 feet underground it appears to be in the same 50's range as my area. Although there will obviously be some areas that might have higher temperatures than others.

[Moontanman]

According your info the temps near my house should be about 75 degrees F, that's a little warmer than I thought but still within reason. I think you are reading the info backward, the temps are higher near the surface not deep under ground.

[Nitack]

According your info the temps near my house should be about 75 degrees F, that's a little warmer than I thought but still within reason. I think you are reading the info backward, the temps are higher near the surface not deep under ground.

 

That depends entirely on the specific location and the geological activity of the location. However, the majority of the locations that I have looked at get warmer the deeper you go. However, the temperature drops after 3-5 feet below ground and then climbs.

http://rglsun1.geol.vt.edu/data/kn1bnc.well

Temperature (deg C) Depth (m)

 

 

11.272 1.300

11.361 1.809

11.568 2.318

11.904 2.827

12.323 3.336

12.872 3.845

13.090 4.354

13.442 4.863

13.770 5.372

14.263 5.881

14.656 6.390

15.085 6.899

15.238 7.408

15.458 7.917

15.643 8.426

15.808 8.935

15.875 9.444

16.008 9.953

16.140 10.462

16.215 10.971

16.262 11.480

16.301 11.989

16.334 12.498

16.366 13.007

16.388 13.516

16.409 14.025

16.429 14.534

16.445 15.043

16.463 15.552

16.487 16.061

16.512 16.570

16.542 17.079

16.577 17.588

16.604 18.097

16.630 18.606

16.666 19.115

16.690 19.624

16.713 20.133

16.735 20.642

16.756 21.151

16.777 21.660

16.798 22.169

16.814 22.678

16.834 23.187

16.852 23.696

16.866 24.205

16.881 24.714

16.894 25.223

16.907 25.732

16.922 26.241

16.933 26.750

16.945 27.259

............................

23.085 310.263

23.093 310.772

23.101 311.281

23.109 311.790

23.114 312.299

23.119 312.808

23.128 313.317

23.137 313.826

23.145 314.335

23.150 314.844

23.159 315.353

23.166 315.862

23.173 316.371

23.180 316.880

23.187 317.389

23.197 317.898

23.203 318.407

23.212 318.916

23.222 319.425

23.227 319.934

23.232 320.443

23.246 320.952

23.254 321.461

23.261 321.970

23.268 322.479

23.274 322.988

23.282 323.497

23.290 324.006

23.294 324.515

23.306 325.024

23.313 325.533

23.321 326.042

23.331 326.551

23.337 327.060

23.342 327.569

23.350 328.078

23.360 328.587

23.367 329.096

23.375 329.605

23.383 330.114

23.392 330.623

23.399 331.132

23.406 331.641

23.413 332.150

23.422 332.659

23.429 333.168

23.436 333.677

23.443 334.186

23.448 334.695

23.457 335.204

23.465 335.713

23.477 336.222

23.482 336.731

23.489 337.240

23.496 337.749

23.502 338.258

23.509 338.767

23.516 339.276

23.520 339.785

23.533 340.294

23.542 340.803

23.550 341.312

23.559 341.821

23.565 342.330

23.572 342.839

23.579 343.348

23.586 343.857

23.592 344.366

23.600 344.875

23.609 345.384

23.615 345.893

23.624 346.402

23.632 346.911

23.634 347.420

23.643 347.929

23.657 348.438

[Moontanman]

Interesting Nitack, evidently the temperature gradient is quite different where you than where i live. It drops here until about 12 or 13 meters then begins a very slow rise and doesn't equal the surface temps until about 230 meters much deeper than any local wells go. How deep will your system be? Here is the depth vs temp in my area

 

 

24.1758 2.1000

23.2576 2.6037

22.5935 3.1074

21.8717 3.6111

21.2999 4.1148

20.7954 4.6185

20.3075 5.1222

19.8425 5.6259

19.4874 6.1296

19.1454 6.6333

18.8681 7.1370

18.6333 7.6407

18.4578 8.1444

18.3079 8.6481

18.1953 9.1518

18.1035 9.6555

18.0463 10.1592

18.0065 10.6629

17.9818 11.1666

17.9771 11.6703

17.9804 12.1740

17.9883 12.6777

18.0023 13.1814

18.0201 13.6851

18.0398 14.1888

18.0613 14.6925

18.0824 15.1962

18.1346 15.6999

18.1534 16.2036

 

 

23.8951 225.2391

23.9043 225.7428

23.9276 226.2465

23.9392 226.7502

23.9699 227.2539

23.9877 227.7576

24.0074 228.2613

24.0277 228.7650

24.0486 229.2687

24.0689 229.7724

24.0856 230.2761

24.1053 230.7798

24.1245 231.2835

24.1461 231.7872

24.1591 232.2909

24.1696 232.7946

24.1913 233.2983

24.2025 233.8020

24.2248 234.3057

[Nitack]

Interesting Nitack, evidently the temperature gradient is quite different where you than where i live. It drops here until about 12 or 13 meters then begins a very slow rise and doesn't equal the surface temps until about 230 meters much deeper than any local wells go. How deep will your system be? Here is the depth vs temp in my area

 

Well the table I posted before was actually a North Carolina location. My table follows:

USG-1 A RESTON lat 38 49.50 long 77 42.13 11/29/79 MCCL

 

Temp © Depth (m)

 

12.912 4.300

12.942 4.809

12.944 5.318

12.923 5.827

12.896 6.336

12.851 6.845

12.827 7.354

12.771 7.863

12.717 8.372

12.639 8.881

12.591 9.390

12.533 9.899

12.465 10.408

12.434 10.917

12.373 11.426

12.327 11.935

12.273 12.444

12.249 12.953

12.229 13.462

12.196 13.971

12.180 14.480

12.171 14.989

12.157 15.498

12.149 16.007

12.150 16.516

12.144 17.025

12.146 17.534

12.146 18.043

12.149 18.552

12.151 19.061

12.149 19.570

12.156 20.079

12.164 20.588

12.164 21.097

12.173 21.606

12.177 22.115

12.185 22.624

12.195 23.133

12.201 23.642

12.210 24.151

12.216 24.660

12.217 25.169

12.232 25.678

12.239 26.187

12.249 26.696

12.250 27.205

12.264 27.714

12.271 28.223

12.276 28.732

12.281 29.241

12.288 29.750

12.294 30.259

12.304 30.768

12.310 31.277

12.320 31.786

12.327 32.295

12.335 32.804

12.345 33.313

12.354 33.822

12.360 34.331

12.367 34.840

12.379 35.349

12.388 35.858

12.395 36.367

12.406 36.876

12.419 37.385

12.429 37.894

12.437 38.403

12.446 38.912

12.458 39.421

12.469 39.930

12.479 40.439

12.484 40.948

12.496 41.457

12.504 41.966

12.514 42.475

12.521 42.984

12.531 43.493

12.539 44.002

12.548 44.511

12.554 45.020

12.565 45.529

12.572 46.038

12.581 46.547

12.590 47.056

12.598 47.565

12.607 48.074

12.616 48.583

12.625 49.092

12.634 49.601

12.642 50.110

12.651 50.619

12.657 51.128

12.665 51.637

12.674 52.146

12.682 52.655

12.691 53.164

12.697 53.673

12.704 54.182

12.711 54.691

12.716 55.200

12.757 57.745

12.766 58.254

 

As you can see, it is pretty constant for at least the first 200 or so feet. The crawl space that I will be using is actually below ground level for the outside walls by seven feet or so, with no windows or southern sun exposure walls. I plan on dropping my system an additional 5 feet. That should get me definately to the stable temp zone. If I were to continually circulate air from these earth tubes to the air return I'm thinking that it will mitigate both the temperature and humidity of even the hottest days. And running a low power fan continually will require much less electricity than running the AC intermittently and we will have a more pleasant home temp level.

 

If this does work, I may use it as the jumping off point for incorporating a solar chimney design, and try to perfect an electricity free design. Or I was thinking of using something like this: Solar Fan with 10 Watt Solar Panel. The fan will only run with the sun is out though, so that may not be optimal for warmer nights. Perhaps I can build some batteries into the mix though.

[Moontanman]

Obviously not my NC location, your data was for Kinston NC a significant distance from me, about a 2 hour drive if I recall correctly, my old employer had a Plant there and i visited it on company business frequently. I provided a link to my location in my earlier post. I hope your idea works, My idea of a problem you might face was just a possibility due to factors about how an AC works but it might not apply to what you are doing.

[lawcat]

Theoretically, the heat transfer from air in underground pipes to ground is possible.

Practically, as Moontanman pointed out, moisture removal is the problem, as well as pipe sizes, and air quality.

 

What you are trying to do is essentially geothermal system.I would suggest researching water cooled geothermal system. See, e.g., http://www.climatemaster.com/index/res_geothermal_index?utm_source=YBadwords&utm_medium=CPC&utm_term=geothermal+cooling+system&utm_campaign=Geothermal+Heat.

 

Instead of running loops of 18" steel pipes to supply 1750 CFM of air, underground; you may want to run 1" copper water loop. It is much cheaper.

 

If indeed the ground temp is 53deg F, then the system may work. The water coil in the fan will remove moisturesufficiently , I believe. (Instead of collecting moisture in underground pipes.) Water system is also less susceptible to bad air quality, since air is controlled within the house environment.

 

(Hire an Engineer to design it, whatever you decide to do.)

[Nitack]

Well I have continued to do a lot of research, and this is by far not a new idea. Apparently this was a buzz worthy idea in the 70's and 80's but ended up busting due to environmental concerns. Mold, fungi, and bacteria ended up creating environmental concerns. The gravel drainage bed that I incorporated was specifically mentioned as having become choked with air quality hazards. Given my six month old child, I will not be doing anything that could reduce the air quality in the house.

 

Back to the drawing board I guess... however I am not ready to give up on the idea entirely. Perhaps an indirect system like what lawcat suggested. It would lose efficiency, but perhaps be safer.