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Old 11-25-2016, 05:24 PM  
Snoonyb
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The reason I use smooth wall vent is the noise reduction, noted in the link in post #6, because any ribbed vent will affect the smooth air flow, as well as the efficiency.

Before you compose the "jig", and start cutting, what kind of roof material do you have and what size is the existing roof jack? Also mentioned in the link in post #6.

Because warm air has a greater ability to contain moisture in suspension, having that "after run" feature on the fan will allow a greater volume of moist air to be evacuated and lower the potential for condensation.


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Old 11-26-2016, 01:49 PM  
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Alright got a chance to do some digging after getting home from the holiday. Found a few more sticking points.

1) Roof vent appeared sized large enough from on top of the roof. When I removed the existing duct to check it out from underneath, however, the jack has a metal base with a 4inch round hole cut in. Meaning 6in would not fit through the hole. Would this require a replacement jack to get to 6? My main concern doing that is the roof only has about 2-3 years left on it so shingles are probably brittle. For what it is worth the vent flap gets stuck in the open position when I open it (was closed when I got up there though)

2) The exiting hole in the roof is directly above the base units exhaust. Meaning from the unit to make the exsting roof hole there would be no horizontal run and a pretty sharp bend. Both of which I understand to be no-nos.


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Old 11-26-2016, 03:37 PM  
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You have some alternatives as eventualities; You can budget for the eventuality of the eventual roof being replaced, or the asphalt shingles softening in warmer wether and using 6" material, as you had planned, and several "L's", with a 6" too 4" reducer and with the understanding that the volume will only be that of a 4", or with the 4" and several "L's".
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Old 11-26-2016, 05:16 PM  
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I agree, run the 6" to the jack and adapt to 4", change the jack or not when the roof is replaced.
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Old 11-28-2016, 12:31 AM  
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Got the fan installed, wired, and ducts placed to try them out. I ended up doing a 6in rigid run reduced from 4 at the ceiling. There is an L from the ceiling at a 45 tilt, into a 2 foot run into a 45 elbow and then a 90 after to come back to the fan. Meant to take pictures but ran out of time.

So took a long hot shower after and while the fan seemed to be working at first, condensation heavily built up on the ceiling to the point that it dripped on the bath mat multiple times.
Couple of potentials. I did not add insulation yet while trying it out to avoid potential double work.

Also while working up there I moved a lot of the bat insulation out of the way and haven't been able to get that back.

I do live in MN and it is 29 degrees out.
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Old 11-28-2016, 06:43 AM  
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When showering with a partner you tend to ignore the condensation.
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Old 11-29-2016, 07:45 PM  
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Haha nice Snoonyb.

So I got a chance to do a couple of dry runs and not sure if either of them are actually acceptable. I also have a couple of 4in elbows I was thinking could come off the roof too. Thoughts?



This would require a short length of straight cut to size
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Old 11-29-2016, 07:56 PM  
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Go with the shorter route, every 90* bend is like adding another 5 ft to the length.
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Old 11-29-2016, 09:01 PM  
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Anything I can do for the social wellbeing.

Yep, shorter is better, and more in keeping with the "KISS" principal.
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Old 12-05-2016, 06:11 PM  
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Yeah that definetly looks like a 1st year installed that. Its cute. Instead, Install a 90 right off the bath fan outlet aimed at the jack. Then aim another 90 from the jack to the bath fan 90. Add another elbow (<90) to make up any difference needed. Foil tape or duct seal pipe joints. Wrap with 1-2 layers of 1" fibreglass foilback insulation.


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