Vacuuming hot air from attic . . . without electricity!

The hottest air in your attic collects/gathers at the very highest point of your roof.  If you make a hole at the highest point of your roof, it acts as a heat relief valve.  If you add a chimney (PVS, stove pipe, whatever) that extends upward from that hole, the chimney becomes a vacuum that sucks hot air from your attic. It is that simple,  requires no electricity,  works day and night, wind or calm.  
Check out this video that shows the hot air being sucked out is 31 degrees hotter than the ambient air above the roof:  https://www.youtube.com/watch?v=_pObw2FEly8
When I mentioned that the roof was the easiest place to prevent water from leaking, I meant to say the highest point of the roof. Lol
The greater the difference in temperature between the air at the highest point in your attic, and the air outside, the faster the air will flow. It will continue working all night long as the outside temperatures drop, bringing your attic temps closer and closer to the lowest ambient temp of the night.  Once the sun comes up and starts hitting the roof, the attic chimney will work increasingly harder as the attic temperatures increase.

If you want to go all out and try a 20' chimney, it would be very inexpensive to anchor it(from the top) with galvanized cable to four points on the outer edge of the eves of your roof.
Of course this can be taken down, and the hole easily covered, once you are no longer running AC or fans in your building.
This can be used on any building with a pitched roof, including sheds, garages, and even on porta potties.

Great that you mentioned porta-potties.. a solar chimney consisting of black pipe with good southern exposure to the sun can work wonders in mediating odors from composting toilets. The sun heats the pipe, and the air in it, which rises and creates a draw, pulling stinky poo air from your collection chamber.

Ted Abbey wrote:Great that you mentioned porta-potties.. a solar chimney consisting of black pipe with good southern exposure to the sun can work wonders in mediating odors from composting toilets. The sun heats the pipe, and the air in it, which rises and creates a draw, pulling stinky poo air from your collection chamber.

Yes indeed, great way to minimize odors for a compost toilet.  And for porta potty rentals, it doesn't have to be a transport issue, because it can be stored inside during transport, and raised once the potty arrives on location. It could even be telescoping.   Remember, BSF larvae do an excellent job of minimizing odors if they can be utilized in a composting toilet system.

When we lived in the big city, our house had a turbine on the roof.

It is a non-electric type fan that allows hot air to escape.

I check and these are still sold at the big box stores.

Anne Miller wrote:When we lived in the big city, our house had a turbine on the roof.

It is a non-electric type fan that allows hot air to escape.

I check and these are still sold at the big box stores.

Yes, and when is the last time you've seen one located at the top of the roof where the hottest air collects?  And there is a big difference between air "escaping" as it does with said turbine vents and ridge vents, and having it essentially vacuumed out by the draft of a chimney. Yes, they do draw more air out when the wind is blowing, but when it isn't, the heat simply escapes/leaks.  Oh, and let's not forget that where they are typically located part way down the roof, they are far more susceptible to leaking because of the multiplied amount of water that hit the roof above them flowing past.

Here code requires 1square inch of roof opening for each square foot of roof surface give or take. Between the vented eaves and the continuous ridge vent we don't get horrible levels of heat build up. I do like the use of the chimney effect though. You would have to make sure you had an air intake though.

Ken Carman wrote:

Anne Miller wrote:When we lived in the big city, our house had a turbine on the roof.

It is a non-electric type fan that allows hot air to escape.

I check and these are still sold at the big box stores.

Yes, and when is the last time you've seen one located at the top of the roof where the hottest air collects?  

I am sorry if I sounded like I was challenging you.  I was just stating my experience.

Anne Miller wrote:

Ken Carman wrote:

Anne Miller wrote:When we lived in the big city, our house had a turbine on the roof.

It is a non-electric type fan that allows hot air to escape.

I check and these are still sold at the big box stores.

Yes, and when is the last time you've seen one located at the top of the roof where the hottest air collects?  

I am sorry if I sounded like I was challenging you.  I was just stating my experience.

Haha, it is funny you say that, because I was concerned that I was coming across defensive. I actually appreciated your example, and  was using it to reinforce my point on two or three counts.  Most importantly is that I have never seen one of those at the highest point where the hottest air collects.  Plus, they may be fairly effective when the wind is blowing, but the fan blade that draws hot air out when it is turning, also blocks a significant amount of air from escaping, anytime it is not turning.

David Baillie wrote:Here code requires 1square inch of roof opening for each square foot of roof surface give or take. Between the vented eaves and the continuous ridge vent we don't get horrible levels of heat build up. I do like the use of the chimney effect though. You would have to make sure you had an air intake though.

Yeah, I'll admit I hadn't dug into national building codes on the subject, and state/local codes follow that to an extent. And you are absolutely correct on reminding folks that the chimney will not draw unless there is a way for the air to be replaced from somewhere else inside the attic.  I have always been amused at the thought that when it comes to an attic, it can be extremely beneficial to be drawing outside air in that may be 100 F or more, as long as it is replacing air that is much hotter.  That also reminds me of those big whole house to attic fans like the one my parents had put in when I was growing up.  What makes them so stupid (IMO) is that you should never run them when the outside temperature is warmer than your inside temperature. Translated, that means that you should never run one during the hottest part of the day, only after the outside temps have fallen below your inside temps, because like you wrote, the replacement air has to come from somewhere.

Interesting that you say "we don't get horrible levels of heat build up".   That makes me wonder where the line is drawn at what would be considered horrible, how close you are to that line, and whether or not adding an attic chimney might further reduce your attic temps enough to be worthwhile. ???  When I share these ideas, My mind is mostly focused on those that they will help the most, but I so often here from folks to whom they may not apply.

Hi Ken,
I always assumed that a cupola was the short cousin of what you are describing.

Matt McSpadden wrote:Hi Ken,
I always assumed that a cupola was the short cousin of what you are describing.

Well, a cupola is definitely a place where hot air would collect, but I am not certain if they always or even ever have an opening of sorts at the highest point.  I would think that they would certainly help increase the draw of any chimney extending above them.  What's cool/fun is that you just got me to thinking that on top of a church roof, a "chimney" could essentially be hidden inside a cross, and not diminish the aesthetics of the building at all.

That is an interesting idea. Essentially steeples were cupolas with a tall top. I could totally see a cross design with a chimney up the middle.

Ken Carman wrote:

David Baillie wrote:Here code requires 1square inch of roof opening for each square foot of roof surface give or take. Between the vented eaves and the continuous ridge vent we don't get horrible levels of heat build up. I do like the use of the chimney effect though. You would have to make sure you had an air intake though.

Yeah, I'll admit I hadn't dug into national building codes on the subject, and state/local codes follow that to an extent. And you are absolutely correct on reminding folks that the chimney will not draw unless there is a way for the air to be replaced from somewhere else inside the attic.  I have always been amused at the thought that when it comes to an attic, it can be extremely beneficial to be drawing outside air in that may be 100 F or more, as long as it is replacing air that is much hotter.  That also reminds me of those big whole house to attic fans like the one my parents had put in when I was growing up.  What makes them so stupid (IMO) is that you should never run them when the outside temperature is warmer than your inside temperature. Translated, that means that you should never run one during the hottest part of the day, only after the outside temps have fallen below your inside temps, because like you wrote, the replacement air has to come from somewhere.

Interesting that you say "we don't get horrible levels of heat build up".   That makes me wonder where the line is drawn at what would be considered horrible, how close you are to that line, and whether or not adding an attic chimney might further reduce your attic temps enough to be worthwhile. ???  When I share these ideas, My mind is mostly focused on those that they will help the most, but I so often here from folks to whom they may not apply.

You get into diminishing returns. My temperature differential with venting at it's worst is probably about 20 degrees Fahrenheit so the heat gain is not that great a deal so not worth additional measures. I believe attic ventilation would be of most benefit to those with poor attic insulation and for those people your suggestions are dead on. I chuckled when you mentioned you hear most from those who would not benefit from it. I have found myself in the same position often enough both receiving and offering...
Cheers,

David Baillie wrote:

Ken Carman wrote:

David Baillie wrote:Here code requires 1square inch of roof opening for each square foot of roof surface give or take. Between the vented eaves and the continuous ridge vent we don't get horrible levels of heat build up. I do like the use of the chimney effect though. You would have to make sure you had an air intake though.

Yeah, I'll admit I hadn't dug into national building codes on the subject, and state/local codes follow that to an extent. And you are absolutely correct on reminding folks that the chimney will not draw unless there is a way for the air to be replaced from somewhere else inside the attic.  I have always been amused at the thought that when it comes to an attic, it can be extremely beneficial to be drawing outside air in that may be 100 F or more, as long as it is replacing air that is much hotter.  That also reminds me of those big whole house to attic fans like the one my parents had put in when I was growing up.  What makes them so stupid (IMO) is that you should never run them when the outside temperature is warmer than your inside temperature. Translated, that means that you should never run one during the hottest part of the day, only after the outside temps have fallen below your inside temps, because like you wrote, the replacement air has to come from somewhere.

Interesting that you say "we don't get horrible levels of heat build up".   That makes me wonder where the line is drawn at what would be considered horrible, how close you are to that line, and whether or not adding an attic chimney might further reduce your attic temps enough to be worthwhile. ???  When I share these ideas, My mind is mostly focused on those that they will help the most, but I so often here from folks to whom they may not apply.

You get into diminishing returns. My temperature differential with venting at it's worst is probably about 20 degrees Fahrenheit so the heat gain is not that great a deal so not worth additional measures. I believe attic ventilation would be of most benefit to those with poor attic insulation and for those people your suggestions are dead on. I chuckled when you mentioned you hear most from those who would not benefit from it. I have found myself in the same position often enough both receiving and offering...
Cheers,

And I had no intention of throwing you under that bus, but was thinking more about past experiences over the years.  I greatly appreciate that you mentioned being able to relate to what I said.  One can share an idea that absolutely does not apply to everyone, but would be life changing for some . . .  and then get negative feedback from those few that it doesn't apply to.  Oh well.  Keep pressing on. Lol

How does this affect the "heat" up there in winter when its cold?

Felix Weiner wrote:How does this affect the "heat" up there in winter when its cold?

It would definitely need to be closed/inoperable when not needed. At the most basic level, that would involve making a trip up on the roof or up into the attic twice per year.   I am working on coming up with a way to open/extend it and retract/ seal it from down inside the house.  Picture a two chimney system where the first chimney extends from an opening in your ceiling, to six inches below the underside of the highest point of your roof. The second chimney extends from the roof upward (the attic chimney).  I have some ideas on how it would be open and closed from down inside the house, but have not yet solved the challenge of dealing with unexpected rain events. I will post an update when I come up with a satisfactory way to make it operable and closed from inside the house with water not being an issue at all.   The water problem is easy to address if it only extends from the top of the attic upward, and you don't mind going up into the attic to open or close it.  But I am all about make things that help, but are also easy and convenient to utilize.

As far as the heat is concerned, I'll bet you could make use of those wax/oil based vent openers they use in greenhouse. When it gets hot enough they open, and when it gets cold enough they close. No timers or electricity needed.

For the rain events, why not a double pyramid shape. One sheds the rain coming down to protect the chimney, and one side facing downward to direct the air to the side.

Matt McSpadden wrote:As far as the heat is concerned, I'll bet you could make use of those wax/oil based vent openers they use in greenhouse. When it gets hot enough they open, and when it gets cold enough they close. No timers or electricity needed.

For the rain events, why not a double pyramid shape. One sheds the rain coming down to protect the chimney, and one side facing downward to direct the air to the side.

Both awesome points and potential solutions . . . thank you!!!  I was just thinking about my own version of the double pyramid, and at first was willing to settle for just a cap without something underneath it to allow the air to move up and out with less resistance. I just took a glance at the wax auto opening system idea, and it looks VERY promising. I had not heard of it prior.  Of course I would have to create a modified version of it (utilizing the principles), but my mind is already humming.  I'll continue to share my thoughts and progress, and as always totally appreciate positive thoughts, ideas, and perspectives of others . . . as well as constructive and useful criticism, provided it isn't founded on negativity and closed-mindedness. Lol.