Senseless writes – “I was wondering if I could heat the water in my swimming pool using the heat in the house’s attic and I started messing about with a large heatsink. The water for my hotwater heater has to pass through it and picks up free calories which saves on the power bill quite a bit of the year. Even on winter days it adds some heat to the water and every calorie free is one I am not paying for…” Link.
40 thoughts on “Turn excess attic heat into hotwater”
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This is a leak waiting to happen, and why wouldn’t you make a solar collector to sit outside, which is many times more efficient?
Solar would provide you with 180+ degree water, not 90-100 degree water.
Neat as a proof of concept, but not very efficient.
Won’t this take extra energy to pump water through a longer system, driving up the electric bill and wiping out any advantage?
“and why wouldn’t you make a solar collector to sit outside, which is many times more efficient?”
If you are concerned about efficiency, adding a larger or additional hot water tank would be even more efficient, and cheaper than a solar solution.
Great idea. Not only are you taking that heat and using it to heat the water, but also you’re lowering the attic’s temperature in hot days, needing less energy for cooling the house.
I’ll have to consider doing this on my house!
Insulating your attic and putting black painted radiator on your roof will save you a lot more.
Some neighbours are using a system like that for years now to heat up their swimmingpool.
On further reflection, if you really wanted to remove heat from the attic, copper pipe would transfer the heat better than plastic.
jhurliman, adding a larger or additional water heater would cost even more, because you are trying to keep a larger amount of water at high temp, requiring more btus to maintain the temp.
Here is a link that will help justify the solar water heating process-
http://www.azsolarcenter.com/technology/solarh20.html
This is a leak waiting to happen, but so is a solar collector with pipes through the roof. Also, here in Florida solar energy is plentiful but so are hurricanes. The last thing I want on my rood is an expensive heavy object to catch wind.
To reduce the leak risk you could put a drip pan and drain pipe under the pipes as used under air conditioner air handlers placed in attics.
A leak waiting to happen
That was why I placed it over the top garage instead of over the main floor. It can be bypassed manually if it freezes or springs a leak.
180 degree water
The mass of sand averages out the tempurature so I can grab calories reguardless of the time of day. The hotwater in your house should be set around 115 degrees.
Extra Energy to pump water through a longer system.
I loop my hotwater because the house is so large. It just loops through the hotwater tank not through the block of sand. It is only when you draw in more water to make up for hotwater that is used that water passes through the loop and it does that under standard water pressure.
Hurricanes
My house is actually designed to be very hurricane resistant, but that’s another project…
This is the dumbest idea I’ve seen on this site yet.
1) What you built is not a heat sink, it’s a thermal battery.
2) It doesn’t need to be a battery, as you said your attic area is always hot. You could have left out the sand and put a plastic tray and condensate pump to collect condensation.
3) In the process of adding 2 cubic yards of sand you also add about 2500 lb of live load to your attic.
4) The live load specified in most codes is 20 lb/ft^2.
While I applaud your dedication and energy, my guess is that you have too little learning and too much time and money. Use some of the latter to get some of the former before your next project.
This is the dumbest idea I’ve seen on this site yet.
1) What you built is not a heat sink, it’s a thermal battery.
2) It doesn’t need to be a battery, as you said your attic area is always hot. You could have left out the sand and put a plastic tray and condensate pump to collect condensation.
3) In the process of adding 2 cubic yards of sand you also add about 2500 lb of live load to your attic.
4) The live load specified in most codes is 20 lb/ft^2.
While I applaud your dedication and energy, my guess is that you have too little learning and too much time and money. Use some of the latter to get some of the former before your next project.
Actually it is about 6000 pounds of sand, about 60 cubic feet I believe and my average attic tempurature is what I am after not a Peak at noon when I don’t usually use hot water.
It is a lot of weight and I thought about it before I put it up there. The house is built so I do not have to evacuate during a hurricane. The weight actually took out a slight tremor on the top floor when they were testing over at the bombing range. The mass is sitting on a shear wall and anchored in three planes to the house.
http://senseless.livejournal.com/150150.html
Why not invest in evacuated solar tubes to heat all of your water. Just google for “evacuated tube solar UV”. Thes are a series of glass tubes which contain a vacuum. They work on U.V. so it does not really matter if you have cloudy weather. You should have no problems being in Florida. Anyways, theses tubes are not like traditional solar water heaters. These tubes work by trapping UV radiation in their tubes to heat the water. Since the tubes are a vacuum they are highly efficent at maintaing heat.
6000 lb = two cars (or one Hummer). An easier and lighter solution would be to put it in an accumulator tank. The mass of water would work as the thermal battery.
My co-worker pointed out what a complete ass I sounded like in my last post, so accept my apologies. I’d just hate to see what would happen if someone tried to copy this and caved in their ceiling.
I need to have a large disclaimer made up on a sign saying don’t try this at home.
This is just something I mess around with in between trying to finish building this house. All the summer days I spent crawling in attics made me wonder obout the excess heat. It’s a lot bigger than it needs to be because I keep modifying it.
You didn’t happen to install the sprinkler system at my last house did you?
Looked pretty similar to this.
only.. in, you know, dirt and all.
There is a ridge vent thet you install all along the peak of your roof. It works wonderfully and your teperature controlled attic fan will never turn on since it never gets hot enough!. This will save cooling costs and heat stress to your roof. Cool your attic and put solar collector elsewhere.
They make a ridge vent thet you install all along the peak of your roof under the ridge cap. It is like corregated plastic with many horizontal holes for hot air to escape. It works wonderfully and your teperature controlled attic fan will never turn on since it never gets hot enough!. This will save cooling costs and heat stress to your roof. Cool your attic and put solar collector elsewhere.
I understand the concern about leaks but what really got me was the use of PVC. If you want to transfer heat go with copper pipe. A much larger heat transfer coefficient. Just my thoughts…
Netminder25,
You are correct.
I found that out after the fact and added 150 feet of 3/4 copper tubing. I spent a day trying to heat it with almost boiling water and it wasn’t transfering heat, and I realized the R value of cpvc is higher than I had thought.
If I built another I could probobly get a better result and only be one fifth the size.
I’m interested in putting a batch tank in the attic to preheat water for hot water tank. Live in PA so I will have to drain system in winter. Looking for an inexpensive tank for attic. Any ideas?