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.
Felix Weiner wrote:How does this affect the "heat" up there in winter when its cold?
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,
Matt McSpadden wrote:Hi Ken,
I always assumed that a cupola was the short cousin of what you are describing.
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.
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.
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.
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.