James Terry
07-02-2010, 8:18 PM
I wanted to experiment with a way to jet my exhaust straight up while maintaining rain proofing. Apparently that is exactly what stacks do. I was amazed at how little information there is online about stack heads. I finally found what I was looking for in a home coffee roasting forum as apparently they run into similar exhaust issues that we might with lasers vaporizing substrate. Now that I know about this magic mojo, I am seeing them all around; trucks, buildings, restaurants...
No-loss stack heads are designed to eliminate back-pressure on positive-pressure exhausting equipment while still protecting the equipment from the rain. This allows your equipment to operate as efficiently as possible and also allows the exhaust to blast unhindered straight up with full velocity which is exactly what you want in residential or business areas to avoid complaints.
No other stack termination will give you the positive effects for pollution control that the no-loss stack head will. Most other solutions drastically reduce exhaust velocity and some actually force the exhaust down where it can linger, build up and get drawn into HVAC or fresh-air makeup systems.
The no-loss design additionally drafts fresh air from the bottom of the outer cap and mixes as it rises to dilute the exhaust, so with better dilution and dispersal rates, your effluent becomes less offensive, and you will be less likely to receive a complaint. It is always better to actively try to reduce your chances of getting complaints than it is to deal with neighbors or city officials after a complaint has been filed, regardless of the final outcome.
It works. I just tested this in a downpour and I was looking straight up the tube and just getting a tiny bit of random splash mist hitting my eye while cars were floating down the street. Unfortunately my roof boot didnt fare so well. Those "no caulk" boots dont seal too good around a snap-together vent pipe seam. I figured as much but I was unable to find a storm collar or a cover boot at the home store, so I guess I'm off to the roofing store to find that finishing fix. Perhaps I should have used PVC for the riser.
So I now have my upblast exhaust and I like it. There were various formulas floating around for calculating dimensions but I chose to use a 12" length of 4" pipe and a 24" length of 6" pipe for the outer cap. I overlapped the two tubes by 6" and used four lengths of 3/4" flexible poly pipe with an outer dimension of 1" as support brackets. I used rivets to fasten to the inner pipe and then inserted all of that into the outer. Super easy with minimal parts needed.
The magical jist for this design is simply that you extend a larger tube beyond where your smaller exhaust tube ends. The larger tube rises such that 99% of all moisture that falls in hits its walls before reaching the inner tube and then is gravity drained away outside to the roof. The design can be extended to any size of pipe, so if your exhaust is 6", you can build using 8" for the outer cap. The cap length should be 4 times the diameter of the main pipe. So if the exhaust is 4 inch diameter, you should have a minimum of 16" long cap extending from the end and also allow for 6" to mount them together. I used 24" of 6" for my cap since I could buy it that way.
Now the burning question is if I should spray paint all of my roof vents flat black?
http://www.webglider.com/laser/2010/no_loss_stack_head_small.jpg (http://www.webglider.com/Laser/20100700/)
Click the image below to see all my photos:
http://www.webglider.com/Laser/20100700/DSC07177.JPG (http://www.webglider.com/Laser/20100700/)
No-loss stack heads are designed to eliminate back-pressure on positive-pressure exhausting equipment while still protecting the equipment from the rain. This allows your equipment to operate as efficiently as possible and also allows the exhaust to blast unhindered straight up with full velocity which is exactly what you want in residential or business areas to avoid complaints.
No other stack termination will give you the positive effects for pollution control that the no-loss stack head will. Most other solutions drastically reduce exhaust velocity and some actually force the exhaust down where it can linger, build up and get drawn into HVAC or fresh-air makeup systems.
The no-loss design additionally drafts fresh air from the bottom of the outer cap and mixes as it rises to dilute the exhaust, so with better dilution and dispersal rates, your effluent becomes less offensive, and you will be less likely to receive a complaint. It is always better to actively try to reduce your chances of getting complaints than it is to deal with neighbors or city officials after a complaint has been filed, regardless of the final outcome.
It works. I just tested this in a downpour and I was looking straight up the tube and just getting a tiny bit of random splash mist hitting my eye while cars were floating down the street. Unfortunately my roof boot didnt fare so well. Those "no caulk" boots dont seal too good around a snap-together vent pipe seam. I figured as much but I was unable to find a storm collar or a cover boot at the home store, so I guess I'm off to the roofing store to find that finishing fix. Perhaps I should have used PVC for the riser.
So I now have my upblast exhaust and I like it. There were various formulas floating around for calculating dimensions but I chose to use a 12" length of 4" pipe and a 24" length of 6" pipe for the outer cap. I overlapped the two tubes by 6" and used four lengths of 3/4" flexible poly pipe with an outer dimension of 1" as support brackets. I used rivets to fasten to the inner pipe and then inserted all of that into the outer. Super easy with minimal parts needed.
The magical jist for this design is simply that you extend a larger tube beyond where your smaller exhaust tube ends. The larger tube rises such that 99% of all moisture that falls in hits its walls before reaching the inner tube and then is gravity drained away outside to the roof. The design can be extended to any size of pipe, so if your exhaust is 6", you can build using 8" for the outer cap. The cap length should be 4 times the diameter of the main pipe. So if the exhaust is 4 inch diameter, you should have a minimum of 16" long cap extending from the end and also allow for 6" to mount them together. I used 24" of 6" for my cap since I could buy it that way.
Now the burning question is if I should spray paint all of my roof vents flat black?
http://www.webglider.com/laser/2010/no_loss_stack_head_small.jpg (http://www.webglider.com/Laser/20100700/)
Click the image below to see all my photos:
http://www.webglider.com/Laser/20100700/DSC07177.JPG (http://www.webglider.com/Laser/20100700/)