Condensation and mold

[Tube_shuttle]

Hey! I just moved to the Pacific Northwest and I didn't realize the problem condensation and mold would cause in the skoolie. I thought that the walls were completed. My bf and I didn't have time to treat the wood furring we installed except a few pieces with polyurethane. Originally my bf and I cut plywood then screwed the 3inch plywood to the metal ribs. Literally every piece of metal gets wet including the screws attaching the wood to the metal which then create mold on the untreated wood. The poly furring strips look great, but the untreated wood is horrifying.

My question is how do other prevent mold on their furring strips? What do people cover the exposed metal with to prevent condensation? I need lots of ideas on preventing condensation. I am about ready to spray foam every window lol.. We were originally thinking to polyurethane all the wood furring so we could wipe the moisture off. However, painting poly takes a lot of time and I know people don't normally poly their furring. Also where does the moisture go if not into the wood? It's also winter here and I want to continue to work on the bus right now. Another thought was putting moisture wicking insulation (r1) between the wood furring strips and metal ribs and then putting more r-1 insulation over the wood furring then put whatever we will use for our walls on top of that. If you have any questions or want pics, let me know! I would love to hear what other people have done.

 

[DeMac]

We'll need a good prognosis to diag and treat the condensation.

Increase the amount of water the air will hold and/or decrease the amount of water in the space.

Are you using propane for your source of heat?
1lb of burnt propane releases 1.6lbs of moisture.

Some folks paint every splinter of wood in their build and touch them up if they're drilled or cut after installation. Primarily for the reasons you state.

Seems like you're considering conduction, and that's probably most of it. Also consider convection, the cold air from the door crack meeting the warm air on the metal surface in contact with the cut edge of the ply. In the top pic, the mildew is heavier at the edge, more so near the corner where there are two edges.

 

[cntryby]

The screws in the ribs provide a thermal bridge from the outside coolness to the inside warmer air. The water molecules in the warmer air stick to the cooler metal... condensation.

The fir strips need to be secured to a wood or plastic stand-off that is in turn secured to the ribs. This is easiest to achieve this is with a short stand-off mounted to the sides of the metal ribs of the bus. Then the fir strips attached to those. This means no screws contact outside metal will contact inside warm air. The screws holding the stand-offs should be sealed under spray foam.

In fact, any metal which touches or is bridged to the outside should be seal with something, Spray foam is the best for areas needing insulation. I like bed liner for areas like around the driver and dash...etc.

Of course, something like a mini-split will pull the moisture out of the air and will greatly reduce, if not eliminate, condensation.

 

[Rucker]

Hey! I just moved to the Pacific Northwest and I didn't realize the problem condensation and mold would cause in the skoolie. I thought that the walls were completed. My bf and I didn't have time to treat the wood furring we installed except a few pieces with polyurethane. Originally my bf and I cut plywood then screwed the 3inch plywood to the metal ribs. Literally every piece of metal gets wet including the screws attaching the wood to the metal which then create mold on the untreated wood. The poly furring strips look great, but the untreated wood is horrifying.

My question is how do other prevent mold on their furring strips? What do people cover the exposed metal with to prevent condensation? I need lots of ideas on preventing condensation. I am about ready to spray foam every window lol.. We were originally thinking to polyurethane all the wood furring so we could wipe the moisture off. However, painting poly takes a lot of time and I know people don't normally poly their furring. Also where does the moisture go if not into the wood? It's also winter here and I want to continue to work on the bus right now. Another thought was putting moisture wicking insulation (r1) between the wood furring strips and metal ribs and then putting more r-1 insulation over the wood furring then put whatever we will use for our walls on top of that. If you have any questions or want pics, let me know! I would love to hear what other people have done.

relevant thread:

https://www.skoolie.net/forums/f13/insulation-vapor-barriers-and-moisture-35983.html

 

[Simplicity-SKO]

So, good information from other posters, yet they appear to be assuming you're understanding how the problem is created. If you understand things like air moisture content, thermal bridging and such, cool.

If not, I'd recommend you watch a couple of videos on condensation and read about thermal bridging.

Per the idea of screwing a piece of wood (cross member) between the ribs of the ceiling, then screw the firing strips into those into the cross member, you still have a screw going into the metal and into wood...it's just that it's going into the cross member versus the firing strip. So, you can still have condensation form.

To address this, you might consider using a really good construction adhesive to glue the wood cross members in place, then screw the firing strips into the cross members. This way, you have no screws into the metal of the bus.

I screwed my firing strips directly into the ribs and coated the screw head with silicone caulk. This insulates the screw head from the air.

Of course, you have to insulate all the metal from the inside air, so whatever medium you choose (spray foam, rigid foam, wool, etc.) is key.

Once the insulation is in, it's time to combat the real culprit of condensation....the amount of moisture in the air.

If you're using any propane appliances, make sure they are vented to the outside of the bus.

When taking a shower, isolate the steam as much as possible and exhaust it to the outside of the bus.

When cooking, exhaust the moisture to the outside of the bus.

Keep the air moving! It's harder for condensation to form when air is flowing.

Absorb the moisture out of the air....dehumidifier or a wood stove are probably your best bet.

Bottom line, keep the humidity low. The colder it is outside, the warmer it is inside and the more moisture in the inside air, the more condensation you'll have.

Hope this helps.

 

[Ella72]

Hello, im here from North Vancouver Island, I'm having the same issue, Didn't know to treat the metal studs with some kind of material or a rubberized sealant. Now the walls from bottom windows are molding, pooling water on floor. I can not rip every thing out and start again. I was think to rubber coat (rock gaurd) outside the bottom half of bus to stop cold transfer to inside. Any thoughts?

 

[mmoore6856]

a dehumidifier is a must as you built it you should have used sill insulation between any wood to metal. also we painted every piece of wood to seal it. unless you can disassemble it to put the insulation make sure you run the dehumidifier 24/7

 

[Rucker]

Hello, im here from North Vancouver Island, I'm having the same issue, Didn't know to treat the metal studs with some kind of material or a rubberized sealant. Now the walls from bottom windows are molding, pooling water on floor. I can not rip every thing out and start again. I was think to rubber coat (rock gaurd) outside the bottom half of bus to stop cold transfer to inside. Any thoughts?

No amount of coating will prevent condensation-those metal surfaces need to be isolated from the inside air.

The problem you are trying to solve is not the problem creating your condensation. Water vapor in the air inside your bus is condensing on cold surfaces. Your options are:
1. Reduce the water vapor inside the bus; or
2. Raise the temperature of all internal surfaces exposed to the outside air temperature to above the dew point.

For #1: dehumidifier is the most commonly referred-to option. This works better if the temperature differential between inside air and outside air is not large. For colder environments, it may not be sufficient.

Vent all propane appliances. If you have a buddy heater, find an alternative heating source and use the buddy for backup or auxiliary heating.

When you exhale, your breath is about at 100% relative humidity. We put out a lot of that condensation ourselves!

For #2, better air circulation might make a difference. Stagnant air in contact with cold surfaces squeezes out the moisture.

But even with those recommendations I can't emphasize how valuable education is in this space; and with just a little more understanding through reading and research you'll be able to tackle the issues you need to treat specifically.

Don't get discouraged! Condensation can be conquered--it's just another bump in the road many have encountered (perhaps after they thought they were done!)

 

[Ella72]

Thank you mmoore6856 and Rucker for the reply.
I will be ordering a few small fans for bunk area to push heat. Add a few more vent holes to these areas. With more reading I have been leaving windows open on either side of bus. Main heat source is a wood stove. Insulation is the original foam that came with the bus. I did paint and caulked everything which helped the pooling water stay put, which I did not know it would do,
before the inside wall builds wish I had seen this post... our fault for not doing enough homework.. I also have a wet dog most days, lol, and a cat.. Makes sense on the breathing and cooking.
Thank you both. ��

 

[Veloc]

Hello, im here from North Vancouver Island, I'm having the same issue, Didn't know to treat the metal studs with some kind of material or a rubberized sealant. Now the walls from bottom windows are molding, pooling water on floor. I can not rip every thing out and start again. I was think to rubber coat (rock gaurd) outside the bottom half of bus to stop cold transfer to inside. Any thoughts?

Mold is a health hazard, and it can kill. You'd really be better off pulling it apart to eliminate the mold and fix the problem.

 

[VinHay]

In my opinion, there is no better resource than the videos on you tube by Chuck Cassidy. Even if you don’t agree with all of his opinions, you will learn a ton from his experiences and knowledge.

 

[Hutchy-SKO]

In my opinion, there is no better resource than the videos on you tube by Chuck Cassidy. Even if you don’t agree with all of his opinions, you will learn a ton from his experiences and knowledge.

Spelling is Chuck Cassady, but I totally agree and I'm not one of the people who necessarily "loves" Chuck but I think he's super smart and helpful. The information he contributes to the skoolie community is invaluable.