We have a bungalow that's 28 years old, we moved to this house last summer. The problem is high humidity mainly in the bathroom (wet toilet). The bath fan is exhausted into the attic, near the perforated aluminum soffit. Is it OK to terminate the vent through the soffit? I prefer not to go through the roof, since it's steel.
Same question is regarding the kitchen venting. Can it be vented through the soffit? Right now it's recirculating.
The bathroom fan can be vented into the soffit, but be aware, ice will build on it and possibly freeze solid over the winter temperatures. make sure it is covered well with insulation and ensure it runs for a minimum of 30 minutes to help dry the inside of the tubing.
Your kitchen should not be vented through the soffit as the fumes, smoke, and grease will clog the soffit, oil will gather and bugs, ants, and rodents may come to infest the newly found food vapour.
While not ideal, sometimes you have no choice but to vent through the sofits. Make sure you block the Sofit vents for at least 4 feet on either side of the exhaust. You don't want the fumes and especially the moisture to get into your attic space.
If you were in B.C., the answer would be simple. The code is that we cannot vent through the soffitt. We can vent through gable ends as in other areas, but otherwise it is throught the roof. Your local roofer has special vents and seals for metal roofs.
The main problem as explained by the others, is condensation caused by improper insulating of exhaust tubing in the attic space.
Your problems may be cause not only by lack of insulation, but by how many elbows are in the exhaust tubing. Make sure that your runs are as straight as possible. The other is that the fan may be too powerfull, especial;ly if you have only a 4 inch tube. That can create a backlash. We have experienced this, and although the tube from the fan is only 4 inches in most cases, you may have to go to a 6 inch tube for greater airflow.
As for the recirculating range hood fan, they were great in some particular instances, but are 90 % less efficient than normal ones. The Broan super efficient with halogen lights are great and are relatively quiet. However, it should be exhausted with a 6 inch pipe. If you have a cupboard above the stove, vent it vertically and through the roof.
The other thing that you should do is put a dehumidstadt on your bathroom fan. If there is moisture in the house it will automatically come on and extract the moisture. This is code in B.C. for one bathroom fan to have a dehumidistadt, unless you have a HRV system.
Sounds complicted, but really is quite simple.
I hope that this helps.
The answer for both bathroom and kitchen is the same:
Straight up or straight out the side.
Straight up is the best since hot air rises therefore carrying the moisture/condensation straight out. It is not that big of a deal to go through metal roofing, it just has to be done right. Whether it is not against code in your area does not mean that running it out the soffit is a good idea. The cost to you should be minimal difference running it out the roof versus the soffit.
With that being said if you are set against going through your roof you should go straight out the wall.
Up through roof. The roofers should have at least gave you a heads up. Even if it's metal the right way is usually through the roof for bungalows. Just make sure the pipe is wrapped all the way to the roof and have a properly installed vent cap for both the kitchen and bath exhausts.
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