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Stupid idea? Using attic heat?

Started by Old Greenhorn, September 09, 2020, 09:13:54 AM

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Old Greenhorn

 SO I am working up in the attic of my shop to prep for installing a chimney and you know, it gets hot up there during the day. The other day by 11am it was only around 70 outside but way too hot to work in the attic. So even though I know it can be dangerous, I got to thinking.
Many of us use house fans to suck air from the living space into the attic and keep the place cool in summer, so why not reverse the process?
 I am wondering if it would be helpful to suck the heat out of the attic in the fall and spring and perhaps even a few milder spells during the winter, and blow it down into the shop to augment the building heat. If it works, and I add some basic filtering, I could set the fan on a thermostat and just have it blow down when the temp hits 70° in the attic.
 It seems practical, but I have never heard of anyone doing this. The cost of heat in the shop is a big issue for me and if this helps keep it comfortable I am will to try it. I just ordered a remote probe thermometer to put in the attic so I can monitor the temp and humidity and get an idea of how dumb this idea might be.
 What do y'all think? We have some smart folks here, I'd like to beat this around a bit.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

mike_belben

So theres an old man who has spent his life building houses that supposedly take no heat or very little depending on region and other factors.  I cant recall his name.. I think he called the technology something like stored geothermal or passive geothermal.  And i remember the term "capers" being used alot in his writings.  

The idea was to take the attic heat all summer and blow it by fan into tubes buried under the slab.  Obviously a new construction only sort of thing.  Capers was the term he used for all sorts of freecycled insulation to go in the dirt around the home perimeter to prevent the heat from radiating out to the cold atmosphere. Pool liners, roofing rubber and so forth.  (Not a bad idea to keep runoff from frost heaving under your slab either)  

Anyway the earth is a mass that acts as a long term heatsink. The caper made a big corral of dirt to park heat in. This stored energy supposedly would travel back under the slab and keep it warm/er without any heating system. And supposedly by the 3rd yr or so it stabilized and worked better. Idk.  


My issue was the ducts were dead ended.  You dont get much flow down a dead end pipe. Like a gascan with no vent.  If they were open ended pipes and snaked around then came back up to atmosphere i could see a flow exchanging substantial heat to the dirt.  University of colorado i think it was, did a greenhouse where two buried 55gal plastic drums acted as plenums in opposite corners.  They had a ton of 4" perforated plastic pipes buried in raised beds that started and ended at a drum, and a big industrial fan in one drum to recirculate the same air.  They said if the cfm was suffiencient to fully exchange 5x the cubic air volume of the space [iirc] that it created a substantial drop in temp and a very large one in humidity.  The moisture in the air was being fed through the raised beds which acted like a dessicant and sucked up the water.  The plants continually absorbed the moisture and removed it.  I guess the temp drop was from 90 to 80 but with the humidity removed walking inside it on a hot colorado desert day felt like air conditioning.



So anyway.  Yes you can blow your attic heat down into the house but whatever air you blow out must be replaced with some other air or you wont be doing much. Do you have vented gable ends or vented ridge?  Or are you thinking about venting ceilings of the living space into the attic to let the air circle from attic to living space to attic?
Praise The Lord

mike_belben

they make fans that go inside a piece of 8" ductwork.  And they make temp switches that look at temp differential across 2 probes.  grainger probably stocks them. 

The laziest way to do this is probably duct one of those from the shop attic to the lower level of the house somehow and set it on a switch that blows anytime the attic temp is say 10* above interior temp.  Youll probably lose 5* in the pipe before it gets there. A variable differential would be handy.  I have a pump controller from a solar water system that works exactly that way.  Just on off switching based on differential temp.
Praise The Lord

Old Greenhorn

OK, so maybe not a stupid idea. I will collect some data and see what it shows. I have no intention of getting as carried away as the fella you refer to, but anything that might help would be worth a little effort, commensurate with the ROI of time and materials. It's worth looking into. BTW, this is strictly for the shop. Now if it turns into something really worthwhile, I would look into doing something in the house after I collect a year's worth of data and run the numbers.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

doc henderson

lots of good and fun info on passive solar.  the challenge will be making something automated that does not allow transfer of heat when you do not want it.  Our living room is concrete floor and a wall of south facing windows, and an overhang that shades them in the summer and not in the winter.  one of the solar kilns designs I reviewed had big air valves made out of rigid foam.  spring and fall is great and winter and summer needs to not compromise keeping the heat where you want it.  could also make a separate actual solar panel like for the roof or along the south wall.  basically building a small enclose well insulated attic.  I know you prob. want to keep it simple.   If it is a vented attic with an insulated ceiling, the difficulty will be the switching from daytime to night time, and maintaining your ventilation so you do not have condensation that ruins you insulation.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

mike_belben

Well, the mudhut hippies have pretty much tried it all in the last century so that takes a lot of the pioneering out of it for you.  Today theyre splitting carbon hairs about how much evil was expelled in the production of the duct tape and gorilla glue you use to build the project over on permies.net or org or whatever it is.   

You dont necessarily have to pump the actual attic air and fiberglass and mouse poop down either.  You can use an air to air exchanger so that the lower level air is being contained and circulated inside a sealed conduit up through the warm attic and back down.  This could be as simple as a few lengths of 4" dryer duct that goes up through the ceiling, hangs from the ridge beam via wire ties to collect heat and then re-enters the shop.  Little solar circulator fan can kick it on when the sun is shining.  


Or.. Theres liquid storage. Water is 800x more times denser than air and it stores a tremendous volume of BTU comparatively.  Plenty of hut nuts have made well pumps powered by old exercise bikes with chain and sprocket driving the pump that fills the tank up in the attic every few days for gravity fed domestic water. U could pump water up for day then drain it down by ball valve to a drum in the shop by evening.  Rooftop solar hot water [parabolic trough concentrators] were all the rage in the 80s.  Subsidized by the almighty dotgov before it even had a dot mind you.


Is it worth it?  I dunno. Thats up to you.  If you spend more than you save by doing it then its officially a hobby.
Praise The Lord

Southside

One thing you need to be very careful with on system like that is creating condensation puddles in the piping which can lead to the conditions for growing the bacteria which causes Legionnaire disease. Just plan accordingly. 
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

Old Greenhorn

Well, the attic is already vented with gable vents at both ends. Not getting complicated here, just want to grab the heat out of there, if there is any. So at this point a simple 8-12" diameter riser pipe up in the attic to be away from the insulation and other 'stuff' with a simple filter and a round duct fan or 'something' to pull that air down and discharge it into the air space of the shop. Nothing more complicated than that. The ceiling fan in the shop should do the rest. It's just a little extra free heat to take some of the burden off the woodstove is all I'm thinking. But the data collection should tell the story once the temps start to drop a bit. Right now, the last thing I want is more heat in the shop. ;D
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

doc henderson

at least gable vents especially if louvered can be manipulated.  ridge with soffit vents would be tough.  if you just suck air into the living space, it may facilitate pulling outside air in and rapidly cooling the attic space.  i was thinking you might have to "un-vent"  the attic during the day to circulate shop and attic air to heat it.  great concept.  @GeneWengert-WoodDoc i know has mentioned attic spaces for drying wood.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Old Greenhorn

SO I quit early today, had to take the wife to the farm co-op for our weekly pickup (she is feeling poorly) and drop off a double pane window for repair ($115 bucks!), so i got home and did a little web surfing, turns out it is NOT a stupid idea and a lot of folks have worked on it. Found a page with a fella in MT that tracked his attic temps from fall thru late spring and he had an impressive number of days over 80° and even some days over 90 in January! But most of these folks get carried away and make it complicated with computers, processors, special hardware and lots of it. That ain't me. :D
 I am not looking for a miracle here, just a little extra help. If I put an 8-10" straight pipe near the center of the building with the suction end near the top sheathing, I figure any air sucked in through the vents will have time to get heated before it reaches the duct to be sucked down. A variable speed fan may help with this, and thermostatic control as Mike suggested to turn it on and off based on temp. Keeping it very simple and cheap until it is proven more time and money is worth it.
 Funny, you mention using it as a kiln. I might try that. First I need stairs up there and I have been searching CL for a setup. Just missed one, but I keep looking. With all the loft space I have up there now, it's an easy install. 3 years ago it was impossible. Right now, with the little hole I am limited getting lumber up there, but the stairs will make it easier. (would make the chimney work a dang sight easier too!)
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

doc henderson

you could set a thermostat to run the fan if the attic temp is above your target temp.  have to make sure you do not loose hot air after the stove gets going and the fan is off, up that pipe.  If you could "non vent" the attic during the time you are harvesting heat, it will help, so it reheats the partially heated shop air and not pulling in cold air from out side.  you will get it figured out, esp if you throw some remote thermometers up there and come up with a plan.  have fun!
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Old Greenhorn

Yeah, that's pretty much the target plan for now. This is just something that popped into my brain when I let it wander off. I will play with it. When the remote temp probe shows up, I will install it and start watching and maybe moving it to find the best pick up point. Then after the stove and chimney are done and the weather starts to get less hospitable and I spend more time in the shop I will start messing with it. It's a cross between curiosity and something useful. For now, as Mike says, just a hobby, but we shall see where it goes. Knowledge is power. I have lost track of all the improvements I've made to the shop and 'operation' here over the last 10 months, but I know there have been a few. This might be another one, or maybe not.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

doc henderson

you have got a crap load done.  some are one and done and then you move on to making stuff to support your habit!  so you are building the infrastructure for the rest of your life.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Old Greenhorn

DANG! you figured out my plan. Lets just keep that our little secret OK?
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

Don P

I think the full boat way would be to insulate the underside of the roof surface, bringing the attic inside the insulated envelope. Then circulate that stratified heated air either mixing it back with the downstairs air or expanding the heated area by using it in the shop. In other words I don't think there is a free lunch, that's those pesky laws of thermodynamics, but there might be more efficient ways of moving and using that warm air. 

Old Greenhorn

Don I am not following your logic. The attic floor is very well insulated now and the roof is not. The sun hits the roof and the attic becomes an oven. If I move that insulation up on the roof, the attic will no longer get the radiant solar heat and at the same time it becomes parts of the envelope I will have to heat through 'artificial means.'
 As it stands now I have what I think you are calling 'stratified heat' at the ceiling of the shop (below the attic insulation). Except that I don't, because I have a ceiling fan in there that has been running for 33 years straight. This is how I have kept the shop from freezing for all that time without any heat running. (Well, there were 2 winters where it froze for a time, but...). The sunlight enters through the windows in the front of the shop during the day, warming the slab floor and the fan keeps churning up that air all night long smoothing out the building temps.
 I wasn't looking for another major project that will likely only save me a little money or effort, just thinking I might be able to get a little extra help by pulling that heat down on those days where it is a benefit. I am just half way through my first cup of coffee, so maybe I missed it, but right now I am not seeing the benefit of what you propose. None the less, I appreciate the discussion. You are a construction whiz, so I am trying to figure out what it is that I don't understand. There have been a LOT of times I have no clue what you are talking about and then later it becomes very clear. That's why I read all your stuff and keep my mouth (and fingers) shut until the whole thing plays out. Then it makes sense. That's how I learn.
Thanks,
Tom
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

Crusarius

Sounds like an interesting experiment for sure. I cannot repeat this enough times. After the carbon monoxide scare I had a couple years ago, I highly recommend you add carbon monoxide detectors (more than 1). Remember carbon monoxide is lighter than air so it is going to be higher concentrations up high. 

I would add at least 2 up high and 2 down lower. Since you will be circulating the air, no telling where it may concentrate.

Old Greenhorn

Thanks Crusarius, it's a good safety point I have been meaning to add those in the shop but keep forgetting. I am wondering where you think the CO might be coming from in an open shop? (except of course vehicle work, which is rare and during winter months I have an exhaust hose I use for those short periods.)
 I am trying to keep this as a wood and fab shop and keep the vehicles out. But 'stuff happens' as we all know. ;D You do what you have to do.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

Crusarius

if you continue to recycle air, and not replenish, eventually the CO levels will begin to rise. Whether you have running cars in there or not.

It may be an inconsequential rise but I feel it is still worth noting.

Another thing that raises CO levels alot more than you would think is an idling car outside. If that happens to be a place air gets into the shop it can get bad fast. I do not know what you have for square footage or air volume but still worth noting. 

Alot of factors can add to CO.

QuoteCarbon monoxide is produced when fuels such as gas, oil, coal and wood do not burn fully. Burning charcoal, running cars and the smoke from cigarettes also produce carbon monoxide gas. Gas, oil, coal and wood are sources of fuel used in many household appliances, including: boilers.

Old Greenhorn

OK, I get it now.  The attic is vented at both ends so it is not a closed loop. As I blow air down fresh air will be sucked in through the vents and heated (I hope). That is the starting plane anyway.
 As a former firefighter I have done many CO jobs and seen all kinds of strange things happen through 'poor thinking' or 'planning with disregard to physics'. It's fairly intuitive to me but your reminder is timely and good for everyone to keep in mind. 
 I am abundantly familiar with how the CO poisoning patient presents, I have had several, from mild to severe and one very acute (a fellow firefighter). Scary stuff indeed, especially if you don't recognize it quickly.
 I just added CO monitors to my shopping list, thanks.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

Crusarius

yup. I knew you had experience. This was more for everyone else :) 

and a gentle reminder to myself to not do that again.

thecfarm

I worked for the state for a couple years working on low income houses. Seem like I remember the cold roof. The attic should be about 10° difference from the outside temperature, during the winter,  to have a cold roof so no ice is formed outside on the eves or inside either. They showed pictures of attic not vented correctly. Icicles was hanging from the rafters!!!
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

doc henderson

so the theory is that energy is neither created or destroyed.  so all you can hope for is to be efficient.  at the risk of "preaching to the choir"  I will go on to say that insulation just serves to slow down heat transfer, so we can condition a space by increasing the efficiency of retaining the heat.  in summer we have an air-conditioner (if we are lucky) that pumps the heat out and insulation to slow how fast it comes back in.  so if you insulate the roof, the attic will no longer get hot.  if the hot air from the uninsulated attic is pushed to the shop, it will simultaneously pull the outside cold air in. It may be heated some.  as we add heat, to be efficient, we would want to start with warmer air to achieve a higher overall temp.  I am afraid if it is cold outside (the point), the the air in the attic will quickly become colder than the air in the shop.  If we create a closed loop from the shop, we can add heat to the warm shop air, and make it warmer.  so the trouble is changing from daytime to night time.  and from seasons or bouts of weather change.  great discussion.  so the conundrum is both getting some free heat, and keeping it simple.  If we solve this, we all agree to give 5% to the forestry forum :)
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

just had another thought.  not sure of how you shop is positioned, but if you build a solar kiln on the south facing wall, when it is empty you could exchange air from it with the shop, during the day, and close it off at night.  basically a free standing solar panel.  or If you do get some cheap foam insulation, and glazing, it would be easy with a mill for lumber to build a solar panel for heat.   popcorn_smiley smiley_sun :P
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Old Greenhorn

Ah Doc, you are starting to make my head hurt! ;D
 But I do like that idea of using the solar kiln. Problem is getting it closer to the shop than I had planned and the angle it needs to get the sun right. It would wind up at a 30° angle to the shop wall approximately. DO-able, but the kiln would then be in the back yard proper and I don't know how that will float with 'she who is to be obeyed'. Still, I will keep it in mind as those plans firm up. First lets see how the simple experiments go before we jump in with both feet.
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

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