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]

Originally Posted by 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?

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.

[Nitack]

Originally Posted by freeztar

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.

Originally Posted by freeztar

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.

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]

Originally Posted by Nitack

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]

Originally Posted by 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?

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]

Originally Posted by freeztar

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.

Originally Posted by Moontanman

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...

[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]

Originally Posted by 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.

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.