bathroom return air

[paul42]

My understanding is that a return air duct is typically not allowed by code in a bathrooom.

Is a transfer grill between the bathroom and another room permitted?

[Gunnery Sergeant Hartman]

Do you want to smell ass all through the house?

[paul42]

If you put a supply vent in there, the air is going somewhere. Do you assume that it all goes out the bathroom exhaust fan - whether it is running or not?

[icenup]

There should be no return or transfer in the bathroom
The rest of the has will smell what your doing in there

[byrdsa/c]

I dont know about permited. But why would you want to put a return in a bathroomthats not the best quality of air comming out of there better put a uv light in the duct to kill the smell.lol

[amickracing]

In addition to the smell you likely wouldn't want the humidity that a long hot shower would produce either.

[icyflame]

Sounds like someone is trying to justify spying on someone!
What other reason would one consider putting a tranfer or return in a bathroom!:D

[paul42]

Planned new house.

225 sq. ft. master bathroom with three exhaust vents. The one over the shower and the one over the tub are humidistat controlled. The one in the small closet that actually has the toilet is motion controlled with a timer. You walk in and the exhaust kicks on - a few minutes after you walk out, it kicks off.

So, the smell (not counting my wifes foo-foo stuff) is confined to the small closet with its own exhaust fan.

The humidity from the shower and tub are somewhat controlled by their respective vents.

At least half of the time spent in the bathroom involves things other than sitting on the toilet or taking a shower.

The bathroom is large enough to need at least one supply vent, probably two. Is the answer to always leave the door open when we are in there?

[pstu]

One thing is for sure. You have supply vents in the bathroom area and the air supplied is going to have to get back to the main house through some kind of return path. Is it all supposed to flow through the master bedroom? Is that *really* better than the rest of the house? Do you have doors which will obstruct this flow and create regions of positive and negative pressurization in the house? Who wants that?

There is always an issue about bathroom smells and it looks like you have it pretty well covered with exhaust fans and having the toilet itself behind a door.

I myself put a transfer vent in the bathroom, with a house similarly configured to yours. I was fully prepared to cover it back up if something bad happened, but the results were perfectly good in my case. One benefit was seeing relative humidity in the bathroom suite go down measurably.

I understand a return in the bath is against code, but some rules are more important than others. One way or another the air is going *somewhere* as a result of those supply vents. It's not clear to me that asking it all to go under the door, is superior.

Best of luck -- Pstu



P.S. I wonder how well the humidity controlled fans will do their job, as the humidity controllers I have seen are somewhat imprecise.

[perel]

You may want to think about putting a single central fan in instead of the individual fans - no noise in the bathroom that way, and you can use an ERV as the central fan. That way with a new tight construction house that needs fresh air ventilation anyway, you can pull the stale air from rooms that MIGHT be smelly (kitchen, bathrooms, utility room / janitor closet, etc) keeping them under negative pressure with air you'd have to remove anyway. Better than pulling the ERV stale air from the return air duct or putting return air ducts in the smelly rooms.

[lmnop]

We have a return right near our master bathroom. Its between our bathroom and closets, so it may not be techniqually in the bathroom, but it definitely pulls the air from there. We dont have any issues with humidity or smells throughout the house. I'm not sure about code in our area, but neither home inspector nor HVAC pros said anything about it. And we had the HVAC pros come out and specifically look at that duct work.

[paul42]

The plans already included one central fan and using seperately controlled vents at each location.

In a cooling dominated climate, I'm not convinced that an ERV will recover enough energy from the humid air pulled out of the bathroom to make it cost effective.

[hvac1000]

BOCA, CABO, do not allow return air from kitchens and baths with a toilet. You can dump all the supply air you want in these areas but no return.

[comfortdoc]

The bathroom should be slightly negative pressure anyway so the air cannot move from there to the rest of the house (humidity, smell whatever). The exhaust fans should be designed to accomplish that. When the fans are not on the supply air will passively exit through the exhaust fans as well as under the door and anywhere else it can find to move.

Return is prohibited by code. Some of the foo-foo stuff your wife uses will also permeate the house and if it is perfumed powders and hair spray you do not want it drawn through the A/C system and distributed through the house.

[pstu]

HVAC1000, I appreciate your professional information but I would like to ask a couple questions. If you DID increase supply air in bathrooms which I believe is common practice, won't you expect a problem with overcooling those rooms?

In my own house I have had supply airflows measured and when I compared them to room-by-room Manual J requirements, they were far in excess of heating or cooling requirements. I observed the summer overcooling really did happen, so it is not just theoretical. Made me ask "why are we overcooling an inherently humid room like this?".

A couple of times I have heard the argument that you don't want to spread the bathroom humidity into the main house. To that I want to ask, is it better to concentrate it into a small room instead? Won't that potentially lead to the kind of localized high humidity which might create a mold garden?

It seems like we are looking at a taboo based on a worst case scenario, and I am not quite comfortable with that. The law is the law, but I see individual homes which appear not to be exposed to the worst case outcomes. Maybe you can offer some insights on the rules which I don't yet have.

FWIW I am becoming fond of the idea of putting a dehumidifier in or near the bathroom itself. That will combat the bath humidity at its source, rather than ask the whole-house system (either AC or dehu) to treat it in a diluted form.

Thanks in advance -- Pstu

[comfortdoc]

The humidity is supposed to be removed by the exhaust fans. They should be sized properly and run long enough after a shower to do the job. The "oversized" supply is to bring enough conditioned air into the room to keep it comfortable, since so much is being exhausted. If the bathroom is designed like this from the start and the sizing of all components is done properly you will have a comfortable room.

You are building a new modern house. By the description of your bathroom it is a high-end home and at least semi-custom. You cannot compare the design to older tract homes. Industry standards have and codes have changed over the years. Some during the last year as has been stated by other posters.

[dash]

Originally posted by paul42
The plans already included one central fan and using seperately controlled vents at each location.

In a cooling dominated climate, I'm not convinced that an ERV will recover enough energy from the humid air pulled out of the bathroom to make it cost effective.


Consider using the ERV as the ducted bathroom(s) exhaust.

[paul42]

I looked into an ERV, but could not justify the expense. ERVs just are not very efficient at transfering latent heat. I ran the math and it would add about $800 to the cost of the house and save me about $30 a year in cooling and heating bills. The more efficient the air conditioner, the less money you save with an ERV.

[davo]

All we deal with is custom homes on a island in SW fl.
I recommend the use of a whole house dehumidification system to help. We install them with a motorized outdoor air damper and link the damper and fan to the central exhaust fans and kitchen exhaust fan.
When any exhaust fan is turned on, dehumidified makeup air is supplied. Under regular operation by the electronid humidity control, it keeps the homes under 50% RH year round, helping the home owner raise the t-stat setting.
Thermastore is the best system I have found and very energy efficient. On retrofit, most all customers report no increase or a lowering of their electrical usage. Nerver had a unit fail yet, a testament to their quality. In fact, a house we remodeled had one in it I installed 10 years age right on the beach, and I put it in my own house 2 years ago. Working great. We have installed 100+ systems like this.
Unit is not much mor than a ERV, and does the de-humidification you need.

[paul42]

The thermastor unit is the answer I was planning on using as well. Have you used the DEH 2000 digital control panel and are you happy with it?

[davo]

All we use is the digitat control, as they look much nicer.
I have been pleased with their performance and reliability.
Make sure to choose the size wisely. By the way, the outdoor air damper can also be controlled by the controller, and you can program fresh air times as well.

It's a great system!

[dash]

I checked the Florida Mech Code ,which is based on the International Mech code,can't find where returns are prohibited in baths and kitchens.

Any one have the IMC code ,to quote chapter and versus on returns in baths and kitchens?


It was in the older Florida code, Southern Mechanical.


I was taught that NO returns in baths and kitchens ,was code ,to prevent over powering the exhaust fans.Now I know there is an odor thing,but is that why it's in some or all codes??

[curiousgirl]

I sure wouldnt want a return in my bathroom after my husband gets thru crapping haha. We'd have to evacuate the house for hours.

[comfortdoc]

A kitchen return can draw grease and cooking odors into the ducts.

[dash]

If you look at the Original Posters master suite you can see the concern about proper return air.

Our home is the same,separate exhaust in the small toilet room,and over shower and tub.Our walkin closets ajoin the master bath ,and that's where I placed the returns.We use an ERV for the bath exhaust,which in turn provids some make up air.No odor problems ,in the home,don't ask my wife about the toilet room!LOL!

[pstu]

deleted post

[Edited by pstu on 08-22-2006 at 06:50 PM]