Bathroom heat/vent return

[Mainiac]

We have noticed that when the bathroom vent is on, and the door is closed, the vent struggles to get air, unless the window is open. It creates what amounts to negative pressure in the bathroom. You can open the bathroom door and hear the fan relax. By the same thinking, or reverse scenario, when the heat is on, it must create a positive pressure in the bathroom. As the air will take the path of least resistance, it will flow out the two vents in the main cabin (if those vents are open), and that is where the thermostat is too, the bathroom will stay noticeably cooler. This is especially true if the door is closed.

So, what we did, is cut a 3 1/2" hole up high in the wall between the two rooms. We cut it up high so no shower water should show up there. Without the furnace running there was no airflow through the hole. When the furnace came on, the airflow through there would almost blow the candle flame out. We put an adjustable SS vent cover over the hole in both sides so the the airflow could be restricted from either side, if ever needed. It will let the airflow coming into the bathroom have a path back to the furnace return vent. The easy way of course is to leave the bathroom door open, but that is an inconvenience when we are sitting at the dinette. I have pictures but this new device is hiding its secret on how to release them.

 

[SeaDawg]

That mod makes a lot of sense.

[Mike and Carol]

That’s a good idea. We keep the bathroom door open as much as possible, especially during cold weather. 

[Mainiac]

One picture came through. I'll try another.

[John E Davies]

Can you post a product link? What kind of stainless is it made from?

Neat mod, I like it. I have been thinking of putting a big hole there, but intended it for off season natural airflow. I had not considered its use with the bath fan sucking air out the roof.

John Davies

Spokane WA

[Mainiac]

My invoice is filed away, but it looks like the one from; 'Point Supplies + Outdoors', sku #77417. Described, funny I thought as: 4" Sea Dog SS Butterfly Vent, center knob. Price was $ 6.99. It is described as 304SS.

I was going to put the butterfly one outside, and a standard louvered vent inside. That way any stray shower water would be reflected down and away. What I found was that the holes didn't match up. Luckily I had ordered two of each, because of another project. I picked up 4 each SS machine 6 -32 X 1" machine screws and locknuts at a local hardware.

 What I didn't have was a 3 1/2" hole saw. What I found was around $ 33.00 for a hole saw and then $18.00 for a mandrel, at the big box lumber and hardware stores.  Hmm, for a one time hole did I want to spend over $50? What I found was a whole kit of many many different sizes that I might never use( including mandrel and case) for $18.00 at Harbor Freight ( also had a coupon for 20% off and a free flashlight). It worked extremely well and left a very crisp edge on the back side, and I still have the saw if I need or want to cut another hole. I used a small round file (chain saw) to notch slots for the screws, as they are just outside the 3 1/2" . The wall is actually 7 /16" cored with 5 layer plywood. We did coat the exposed wood with some white oil base paint, that we happened to have, to prevent any possible moisture intrusion. 

Edited March 6, 2020 by Mainiac

[John E Davies]

1 hour ago, Mainiac said:

The wall is actually 7 /16" cored with 5 layer plywood. We did coat the exposed wood with some white oil base paint, that we happened to have, to prevent any possible moisture intrusion. 

Thanks for the info. And a huge THANKS for mentioning the wood core! Sealing the exposed wood is really important for a bathroom divider wall to prevent ROT! Especially a vent like this that could suck moisture laden air through it whenever the shower is used without the bath fan running....  I discovered the wood when I mounted a clothesline support there. I was dismayed since Oliver says there is NO wood in the hull construction, though I suppose one could argue that technically the wall is not part of the hull - it is a separate piece that is glued in place.

BTW the rear overhead “wall” which forms the big storage compartment has a bonded honeycomb structure, no wood, like the rest of the molded hull and interior..... I would love to ask an Ollie engineer why they cheaped out with the front bulkhead. There must be a reason for the wood. But I would smack him along side his head anyway, it is a stupid design.

Has anyone had the bathroom door frame off, and can you tell us if the wood is exposed or sealed?

John Davies

Spokane WA

Edited March 6, 2020 by John E Davies

[Mainiac]

Just guessing here, but I would think the 5 core ply would have a flatter appearance. Less deflection, and easier to attach hooks and towel racks in the bathroom, hooks in the main cabin, and a door and trim pieces. The core I cut out looked at least like cabinet grade, and hopefully a marine equivalent glue. The Oliver family of companies appears well versed in the use of fiberglass and it's possible limitations...

[Mainiac]

An inside close-up view.

[SeaDawg]

That looks great, Maniac. Nice that you used an adjustable vent, so you can close it while showering, and running the exhaust fan.

 

[WhatDa]

The sealed body aspect of the Oliver and bathroom are important to note.  Any of the fans will create positive or negative pressure.  The path of least resistance with the composting toilet seems to be the vent for said toilet.  Bathroom fan on and window closed (whoops) for a few hours seemed to pull the outside moist air in over our compost, making it wetter/smell a little.   I don't think that little nature's head fan can keep up with either of the other two in a tug of (air) war.

 

[Mainiac]

Not familiar with how the compost toilet is vented, but if it is a 1 1 /2" pipe, you might well be right. I also think the vent might indirectly help a little with the ac circulation. Thinking a main cabin window could be opened a little, allowing the frosted bathroom window to stay closed. I think the vent location should minimize any fancy gyrations from putting water up there. Hopefully. ..

[SeaDawg]

We also get negative pressure if we forget and leave the bath fan on, and bath window closed. And, we have an older elite, without ac ducting.

I think Maniac' s retrofit is a great idea. Like jump vents or undercutting doors in a stick and brick house without a return in each room, it allows for pressure equalization. The adjustable vent allows airflow when you want it, seals moisture from the main cabin while showering. Might be mod of the year. Imo.

 

Edited March 16, 2020 by SeaDawg
Spelling correction

[Mainiac]

Thought I would see how the flame looked with the furnace running and the exhaust vent on. Without any windows open it drew the flame towards the vent. The best part the fan didn't appear to be struggling for air.

[Overland]

Our maxx fan really struggles if we run it without a window cracked, so I think that you’d want a window open somewhere with this mod. Otherwise, like whatda said, make up air is going to come from somewhere you don’t want. Nonetheless, there are obvious advantages to not having to open the privacy window and being able to get conditioned air from the main cabin. Personally, I’m fine opening the bath window and running the fan a bit after a shower, but I have a shower curtain for privacy and don’t mind a bit of cold air. But my wife would probably want this if she saw it. 

Edited March 28, 2020 by Overland

[Mainiac]

We are talking the bath exhaust fan, and the heating/cooling of the bathroom space. The Maxfan is another issue, with it's own set of circumstances. We primarily put the extra vent in to increase the airflow efficiency of the heating system to the bathroom. With the shower going, vent closed and the window open that is the way to go. Opening that window for a little ways I can't imagine would comprise anyone's privacy.

[Overland]

True that the maxx fan pulls more air than the bath exhaust, but what I meant to convey was that the trailer is pretty tight all around, so even with the vent, I think you’d want to open a window in the main cabin for makeup air, which I think is what you’re saying.

I’ve definitely got this mod on my list.  Even if it doesn’t bother me to open the bath window, your idea is a definite upgrade, and my wife will certainly appreciate it.

Edited March 28, 2020 by Overland

[topgun2]

Quote

1 hour ago, Mainiac said:

Opening that window for a little ways I can't imagine would comprise anyone's privacy.

I would have agreed with this statement up to the point when a couple of years ago I was taking a shower after a day of fishing in Yellowstone.  As I was drying off, I looked out my partially opened bathroom window and there was a young boy of about 8 or 9 years old staring back at me.  While he was NOT tall enough to be able to see "anything", I could not help but to think about this kid going back to his parents and telling them that some old guy had just "flashed" him.  So, I immediately got to work on making a curtain for that little window!

Bill

 

[Mainiac]

21 hours ago, Overland said:

True that the maxx fan pulls more air than the bath exhaust, but what I meant to convey was that the trailer is pretty tight all around, so even with the vent, I think you’d want to open a window in the main cabin for makeup air, which I think is what you’re saying.

Actually the outer bottom hull might not be as tight as we might like to think. There are a few strategically drilled holes to let any "extra" water escape. You can spot them with the little SS caps. I was surprised to see a couple, but they are designed and installed to avoid forcing air into the cabin while underway. The return air vent opens directly into the inter hull space. It may not get much air through there, but some. I have wondered if they were closeable, would it be easier to heat the whole unit and keep tanks warmer?

21 hours ago, Overland said: