bath exhaust fan venting material

[ramsy]

Current codes require that the vent exit through the roof or exterior wall. No place to put the board.

Under the fan-unit output, intercepting drips from puddling on drywall.

Residential structures often use roof jacks with 3" openings, so over-sizing the duct during fan replacements wont reduce back pressure.

 

[goldstar]

That all sounds fantastic for commercial, new construction and even a remodel where other trades are involved.

I doubt you'd ever get a residential job adding a vent fan to an existing bathroom if you excluded the vent.

I'm with you on this. Can you imagine bidding on an existing residential job and telling the HO they have to hire an HVAC guy to do the duct work ? You'd never get any remodel work.

 

[jxofaltrds]

I'm with you on this. Can you imagine bidding on an existing residential job and telling the HO they have to hire an HVAC guy to do the duct work ? You'd never get any remodel work.

So the HVAC should wire a new fan?

 

[mjf]

So the HVAC should wire a new fan?

No, it means I dig out my 4 1/8" hole saw!!

 

[goldstar]

So the HVAC should wire a new fan?

New fan - no, replacement fan - maybe. Here in NJ some of the trades (like plumbers) are permitted to disconnect wiring from a boiler, replace the boiler and reconnect the wiring, including wiring up any new zone valves. He does not have to be a licensed electrician to do so. In addition they are now permitting HVAC guys to do the same with forced hot air units. They are not permitted to run a new line and tie into the breaker panel (unless they are licensed) but they are permitted to disconnect/reconnect any existing wiring.

Again, putting yourself in the shoes of an HVAC guy, if you had to give a HO a price to replace an AHU in the attic wouldn't it seem ridiculous to have to bring in another trade making one trip to disconnect the existing unit then another trip to reconnect the new ?

 

[kwired]

I'm with you on this. Can you imagine bidding on an existing residential job and telling the HO they have to hire an HVAC guy to do the duct work ? You'd never get any remodel work.

Some of us don't necessarily see that as a bad thing

 

[ptonsparky]

Yup, I buy and install a good fan with enough CFM to do the job...HVAC comes in and puts that insulated flex duct in with no care as to what they just did to the airflow.

 

[kwired]

Yup, I buy and install a good fan with enough CFM to do the job...HVAC comes in and puts that insulated flex duct in with no care as to what they just did to the airflow.

And on top of that you bought a more expensive model that is supposed to be quieter than other models, and by restricting the airflow it is not as quiet as it could be. Then customer eventually says "I thought this was supposed to be a quiet fan?"

 

[goldstar]

And on top of that you bought a more expensive model that is supposed to be quieter than other models, and by restricting the airflow it is not as quiet as it could be. Then customer eventually says "I thought this was supposed to be a quiet fan?"

Most of the self-contained units I've seen (i.e Panasonic, Broan/Nutone) come with a 4" air outlet port. Hasn't the engineering been done on the product so when they claim that it's x # of sones and 110 cfm that it's quiet enough the way it was designed ? Do you really have to increase to a 6" duct to get it more quiet than what they claim ?

BTW, I just installed a Nutone 110 cfm exhaust for (if you can believe it) an engineer. He did all his own research on-line, purchased all the fixtures and devices for his newly remodeled bath room and I installed them in accordance with his directions, including the EXACTLY marked out locations of each device and fixture. Among the devices he purchased was a Miesrto s/p dimmer that he wanted used for the fan speed control. Talk about being loud - it's loud on high speed and even louder on slower speed. Go figure !! Why would you buy a 110 cfm fan and want to slow down the speed :?

 

[GoldDigger]

Minimum size vent will depend on the length. For a short run ( e.g. straight out through the wall) 4" could be fine. Maybe even 3"?

Tapatalk!

 

[renosteinke]

This thread is a good reminder that there are more codes than just the electrical code.

It's reasonable to expect an electrician to have a weak grasp of other codes. Most of the issues raised here - CFM, ducting methods, vent location condensation - are addressed by codes. I do not see a single person supporting their assertion with a code citation.

Such citations would help others to know where to look.

It's my practice to look to what has already been decided, before I go about re-inventing the wheel. That's why sites like Bulk Resource - and the various state agency postings of their codes - are critical to the safe practice of the building trades.

I've had to address these bath fan issues a umber of times. I've looked up the rules. It's not for me, though, to delve into the minds of others and report on their thinking. I invite them to post their authorities for their claims.

 

[kwired]

Most of the self-contained units I've seen (i.e Panasonic, Broan/Nutone) come with a 4" air outlet port. Hasn't the engineering been done on the product so when they claim that it's x # of sones and 110 cfm that it's quiet enough the way it was designed ? Do you really have to increase to a 6" duct to get it more quiet than what they claim ?

BTW, I just installed a Nutone 110 cfm exhaust for (if you can believe it) an engineer. He did all his own research on-line, purchased all the fixtures and devices for his newly remodeled bath room and I installed them in accordance with his directions, including the EXACTLY marked out locations of each device and fixture. Among the devices he purchased was a Miesrto s/p dimmer that he wanted used for the fan speed control. Talk about being loud - it's loud on high speed and even louder on slower speed. Go figure !! Why would you buy a 110 cfm fan and want to slow down the speed :?

Just because it has a 4 inch outlet doesn't mean you don't need a larger duct. Look at how many furnaces/air handlers have a smaller outlet on the unit then the duct connected to it, all has to do with factors in the duct system and desired air flow. If you ask a HVAC guy (that knows how to size duct) what size you need for 110cfm he will not suggest a 4 inch duct he is probably going to suggest minimum of 6 inch duct, but will also factor in length, number of bends, and also will consider flex to have more air flow resistance than rigid duct. One 90 deg elbow adds about as much resistance to air flow as an additional 10 feet or so of straight duct from what I recall.

Now you can get 110 CFM through a 4 inch duct, but will probably require a bigger blower, will operate at more static pressure to achieve 110 CFM, and will make more noise when it reaches 110 CFM level - and that is just the duct itself - the fan will probably make more noise as well.

You can slow down these types of motors usually shaded pole motors, but a dimmer switch is not the best way to do it. I also do agree with the question of why would you want to slow it down on most bathroom type exhaust fans.

I have installed Panasonic fans that are supposed to be quiet, as well as the Nutone/Broan QT series, they are quiet, but put some restriction in the duct and they become louder. This is just a general property of centrifugal fans. If you put the fan on the other end of the duct, it may still have same issue but the sound in the room is dampened because the fan is not so close, but that only happens with remote blowers and not the typical units where the fan is in the room being exhausted.

I have had some installed with very little duct at all before exiting the building that you just about can not hear the fan at all, and have had some with 4 inch flex duct that was maybe up to 10 feet long (same model of fan) and there is definitely a difference in sound performance. Change the 4 inch duct to 6 inch and it gets quieter, eliminate elbows or length if possible and it gets quieter. The QT series fans use a bigger fan but run at a lower speed which helps with noise coming directly from the blower itself, but the less static pressure in the duct at the desired delivery rate the easier it is to push that delivery rate through the duct and the easier it is to do it quietly.

 

[goldstar]

This thread is a good reminder that there are more codes than just the electrical code.

It's reasonable to expect an electrician to have a weak grasp of other codes. Most of the issues raised here - CFM, ducting methods, vent location condensation - are addressed by codes. I do not see a single person supporting their assertion with a code citation.

Such citations would help others to know where to look.

It's my practice to look to what has already been decided, before I go about re-inventing the wheel. That's why sites like Bulk Resource - and the various state agency postings of their codes - are critical to the safe practice of the building trades.

I've had to address these bath fan issues a number of times. I've looked up the rules. It's not for me, though, to delve into the minds of others and report on their thinking. I invite them to post their authorities for their claims.

I respect your opinion and your position is well taken. IMHO, if I had to do that much research in order to install a bath fan I'd just as soon not install it. I'm also not one to turn away work but I figure if I don't do it some unsuspecting EC will come along and install it and most assuredly not to the specs suggested by some in this thread.

 

[jxofaltrds]

Example why you should always verify where you get your facts.

From Ohio's website:

SECTION M1506 MECHANICAL VENTILATION

M1506.1 General.
Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.
M1506.2 Recirculation of air.
Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit.
M1506.3 Ventilation rate.
Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1506.3.
TABLE M1506.3 MINIMUM REQUIRED EXHAUST RATES FOR ONE- AND TWO-FAMILY DWELLINGS

Now compare to what I downloaded from the state (PDF):

1507.1 General. Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.
1507.2 Recirculation of air. Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be
exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.
1507.3 Ventilation rate. Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with
Table 1507.3.

 

[kwired]

I respect your opinion and your position is well taken. IMHO, if I had to do that much research in order to install a bath fan I'd just as soon not install it. I'm also not one to turn away work but I figure if I don't do it some unsuspecting EC will come along and install it and most assuredly not to the specs suggested by some in this thread.

That very well may happen, next the customer may want to know why his QT series fan is louder than his friend's same model QT series fan, did you know how to answer that or solve the problem before reading content in this thread? What if he doesn't want to pay you extra for the "quiet series" that is not all that quiet?

Example why you should always verify where you get your facts.

From Ohio's website:

SECTION M1506 MECHANICAL VENTILATION

M1506.1 General.
Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.
M1506.2 Recirculation of air.
Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit.
M1506.3 Ventilation rate.
Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1506.3.
TABLE M1506.3 MINIMUM REQUIRED EXHAUST RATES FOR ONE- AND TWO-FAMILY DWELLINGS

Now compare to what I downloaded from the state (PDF):

1507.1 General. Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.
1507.2 Recirculation of air. Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be
exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.
1507.3 Ventilation rate. Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with
Table 1507.3.

What if I don't plan to install any bathroom ventilators in Ohio?

What if I install one in a neighboring state and run the outlet of the exhaust into Ohio?:lol:

 

[goldstar]

1507.2 Recirculation of air. Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be
exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

I would violate this code section if the guy in the next apartment was keeping me up at night playing his drums. What better way to express my dissatisfaction with his performance than with an exhausting performance of my own.

 

[jxofaltrds]

That very well may happen, next the customer may want to know why his QT series fan is louder than his friend's same model QT series fan, did you know how to answer that or solve the problem before reading content in this thread? What if he doesn't want to pay you extra for the "quiet series" that is not all that quiet?

What if I don't plan to install any bathroom ventilators in Ohio?

What if I install one in a neighboring state and run the outlet of the exhaust into Ohio?:lol:

Kinda like our power plants?

 

[electricmanscott]

Here in MA electricians are not allowed to do duct work.

Life is good.

Life is good unless you work with incompetent contractors who are too cheap to hire the right people to do the job properly and ruin a kick ass fan install. :rant:

 

[glennspark]

I'm installing several bath fan vents using a Fantech dual vent remote fan using 6" ducting, and two 110 cfm Panasonic units using 4" venting, multiple switching in two bathrooms. I'm not sure if two 4" pipes in one 6" roof vent will open the flapper if one 4" is pushing air. I'm also told there's a building code requirement to install a 8 R rating insulated pipe from these vents directed to the roof. Is hard pipe, aluminum soft, or ridged flex still permissible even though it doesn't meet r value requirements?

HR...

well for a start....ridged (or flexible) ducting is going to reduce the airflow....

 

[kwired]

Originally Posted by howardrichman I'm installing several bath fan vents using a Fantech dual vent remote fan using 6" ducting, and two 110 cfm Panasonic units using 4" venting, multiple switching in two bathrooms. I'm not sure if two 4" pipes in one 6" roof vent will open the flapper if one 4" is pushing air. I'm also told there's a building code requirement to install a 8 R rating insulated pipe from these vents directed to the roof. Is hard pipe, aluminum soft, or ridged flex still permissible even though it doesn't meet r value requirements?

HR...




Since OP was quoted again i noticed his concern over insulating the duct - HVAC guys insulate hard pipe all the time so if you choose to use that it can be insulated in the field. This becomes more of a necessity in areas that get pretty cold as it helps reduce condensation in the duct and should only be necessary where the duct is outside of non conditioned spaces and beyond the general building thermal insulation.