Question for studio builders: What about condensation?

[seven]

I'm at the end of my studio build and I had to overcome some interesting condensation issues.

My building was a basic 2x4 framed peaked roof structure. From the outside in I have siding, tyvex, 5/8" OSB sheeting, 2x4 studs with insulation, vapour barrier, drywall.

As I was putting up the sheeting I followed the advice here and in Rod's book about making sure it was all sealed. I used that black, non drying, tar-like acousti-seal to affix the sheeting on the studs. It's all sealed nice and neat.

I live in Vancouver Canada. Our building code has us place the vapour barrier on the warm side of the insulation - between the drywall and the studs. What I'm finding is because the rest of the structure is sealed tight, condensation develops and does not go away. This is going to make quite a mess of things if I just leave it.

I'm going back around and having to put venting throughout the structure - basically wasting the time and money I spent messing with the acoutsi-seal. That said, I'm glad I caught it because if I didn't everything behind the drywall would have been a mess in a few years.

If I didn't bother with a vapour barrier, then all my condensation would collect in the drywall and create mould.

So, how did you overcome this in your studio?

How does one seal everything tight but allow it to breathe and not form condensation and mould?

[xaMdaM]

The short answer is that your HVAC system should remove the excess moisture.

I take it you don't have final power connections. If that's the case, either get some heat in the building, or get a dehumidifier and some air circulation from a small fan.

If you do have final power and the HVAC system is running... your system is WAY undersized, or there is a problem you need to get fixed NOW!

[seven]

The condensation is not in an area where any HVAC would reach. It is within the sealed walls and ceiling.

The inside has been staying a comfortable 15-17 degrees.

I was able to overcome the condensation in the attic space with a few vets and a fan. It is the condensation in the walls that worried me.

Allowing airflow into these cavities fixes the problem and returns the structure to normal building status where these areas breathe.

What I'm wondering is HOW other people managed to do this.

Or, have they not managed and just don't realize what is hiding behind their drywall?

[fabricaudio]

Do you use double doors?


Nikolas

[seven]

Yes.

At the moment the entry door goes into an entry area which is currently open to the attic and airspace.

But this should have no bearing on the sealed wall cavity.

Let's forget my studio for a moment. If someone converts their garage - without a double wall system - and seals the 2x4s to the exterior sheeting and puts up a vapour shield in the warm side of the insulation, they are going to create a cavity which is not breathable, will get condensation, and will promote rot and mould growth.

Case in point, tydbowl's thread. Granted, he is in Texas so conditions are different, but from the looks of it he is sealing his sheeting to the 2x4s using caulking.

That said, he is using backed fiberglass insulation.

Perhaps that is the difference. I used rockwool and a 6mil poly shield and created a proper continuous vapour barrier. Backing on regular fiberglass is not a vapour barrier.

[xaMdaM]

Originally Posted by seven

The condensation is not in an area where any HVAC would reach. It is within the sealed walls and ceiling.

The inside has been staying a comfortable 15-17 degrees.

I was able to overcome the condensation in the attic space with a few vets and a fan. It is the condensation in the walls that worried me.

Allowing airflow into these cavities fixes the problem and returns the structure to normal building status where these areas breathe.

What I'm wondering is HOW other people managed to do this.

Or, have they not managed and just don't realize what is hiding behind their drywall?

Oh shit... I thought you were mistaken and were really talking about condensation on the inside of your room...

Other than creating ventilation holes to the exterior, I don't see any other way to let those air cavities in the stud bays breath.

How did you find out that there was condensation on the inside of the stud cavities?

[fabricaudio]

This is why i asked for the double doors

My two walls are not attached physically, just some polyurethane, and some rockwool in the entrane of the door to look nice. Appart from that when ond door is pen the air can actually cetcilate into the gap. The moment both doors are closed everything is sealed.



Nikolas

[seven]

Originally Posted by xaMdaM

Oh shit... I thought you were mistaken and were really talking about condensation on the inside of your room...

Other than creating ventilation holes to the exterior, I don't see any other way to let those air cavities in the stud bays breath.

How did you find out that there was condensation on the inside of the stud cavities?

I was saved by being lazy. There were a few places that were trouble spots for my drywall in the server room --those places that have funny size pieces and will take a bit of extra time to get the drywall to fit nicely.

I had a handful of small patches of vapour barrier not covered yet so I could see the condensation.

Granted, there will always be a little condensation in a healthy system, but it should go away. I'd been keeping my eye on it and it wasn't going away.

In my case fixing it is fairly easy.

I have concerns for other people who DIDN'T catch it and I was also wondering if there was a way around it I didn't know about.

[seven]

Originally Posted by fabricaudio

This is why i asked for the double doors

My two walls are not attached physically, just some polyurethane, and some rockwool in the entrane of the door to look nice. Appart from that when ond door is pen the air can actually cetcilate into the gap. The moment both doors are closed everything is sealed.



Nikolas

Got ya.

Yeah, part of my space was like that. A few vents and a fan fixed that problem. Even without the mechanical air movement I've created enough airflow to never have to worry about it.

The wall cavities are another story though.

[AnthonySpinali]

I've seen similar problems in finished basements.

I'm also curious. I've considered leaving access to the airgap between the exterior wall and the inner wall. Maybe I could allow this gap to breath into a storage room that would be cooled by my AC.... This is one of my biggest concerns...
My Studio Thread

If anyone has answers I could really use it.

Thanks guys

Anthony

[naethoven]

Mainly, I just wanted to bump this b/c it needs to be answered. I am working on a solution for the same problem. I have not sealed things shut yet, just trying to plan ahead. One idea I had was to run duct work to and from the between-wall cavity as if it was just another room. To my knowledge it would remain just as sound proof as the duct work to the CR and studio, and it would be cooled the same as well.


WILL A PRO IN THE KNOW PLEASE EXPLAIN THE ANSWER!?!?!?!?!?!?

[naethoven]

bump

[naethoven]

yoohoo...anybody able to save me from getting some kind of strange mold sickness and my building falling down?

[fabricaudio]

Originally Posted by fabricaudio

This is why i asked for the double doors

My two walls are not attached physically, just some polyurethane, and some rockwool in the entrane of the door to look nice. Apart from that when one door is open the air can actually circulate into the gap. The moment both doors are closed everything is sealed.



Nikolas

Nikolas

[naethoven]

I hear ya Fabric. That's a cool idea. Do u think it's enough ventilation? How would one know? Have u checked to see if u have any condensation up there?

[AnthonySpinali]

Originally Posted by fabricaudio

This is why i asked for the double doors
My two walls are not attached physically, just some polyurethane, and some rockwool in the entrane of the door to look nice. Appart from that when ond door is pen the air can actually cetcilate into the gap. The moment both doors are closed everything is sealed. Nikolas

No offense to you but I'm not certain that's enough nor is it ideal. I will have quite a bit of cavity to ventilate. I guess I don't think that is a cure-all....

Maybe I'm wrong...

Anthony

[naethoven]

Hey guys, I've posted this question in the thread "Questions for Rod Gervais about his book..." Keep a check on it for his answer : )

[seven]

Originally Posted by naethoven

Mainly, I just wanted to bump this b/c it needs to be answered. I am working on a solution for the same problem. I have not sealed things shut yet, just trying to plan ahead. One idea I had was to run duct work to and from the between-wall cavity as if it was just another room. To my knowledge it would remain just as sound proof as the duct work to the CR and studio, and it would be cooled the same as well.


WILL A PRO IN THE KNOW PLEASE EXPLAIN THE ANSWER!?!?!?!?!?!?

What kind of structure is it? Explain the build a little better.

[fabricaudio]

Originally Posted by AnthonySpinali

No offense to you but I'm not certain that's enough nor is it ideal. I will have quite a bit of cavity to ventilate. I guess I don't think that is a cure-all....

Maybe I'm wrong...

Anthony

What is the air gap between your two walls?


Nikolas

[naethoven]

My build will be room in room construction. I am using the existing ceiling (really its the roof of my garage) for the cieling of the exterior shell, and I have beefed up the existing walls to match the mass of the roof, making an equal system for my ext shell.

For the interior shell I am building a completely seperate frame, only coupled by the concrete foundation, and of course double drywalling the inside surface that you will see from inside the room.

Rod stresses that everything must be airtight, so I am sealing the ext room and the interior room. That will create an airtight space between the 2 shells that I figure will produce condensation (mold) and extreme heat that will damage the wood.

I am trying to figure a way to keep this space btwn the shells ventilated to solve these issues, and my thoughts were to treat it just like any other room by running ducts to and from it. The air unit will be in a sound proof "closet" type room any way, so running another duct from it shouldn't change anything. I just wanted a second opinion. I see no reason it should not work.

[tINY]

Make sure you have send and return ducts in the space.

Use a muffler/plenum type set-up to prevent sound from traveling trough the ducts.




-tINY

[seven]

Naethoven: I think if you seal that structure you'll run into the same problems I did. I think your concept of creating the "air room" might work but you will rely 100% on mechanical ventilation.

Your sealed inner room will be quite insulated. I'm not sure where you live but our spingtime weather fluctuates quite a bit. The nights can be quite cold and the days sunny and warm. My space maintained 5-6 degrees colder than the outside and sometimes as much as 10 when the sun was shining. Inside was around 14, the attic space was around 26 and it was 17-18 outside. I had a duct pulling air from the studio space, through the (then sealed) attic, to the outside. The minute the temperature outside (and in the attic space) got to a particular point, water would bead up and run off the duct. In one day (the day I cut the vents) I had so much condensation it had actually ruined the drywall pieces I used for the air silencer.

I decided to put in standard attic venting and compliment it mechanically. If my mechanical system fails, I won't suffer. The good news is I don't notice a huge difference in sound coming in or out of the studio with the air vents in. There must be SOME difference because I have two "holes" in my exterior walls,. but I honestly can't tell a difference.

Take the worst case scenario - you have to leave for several weeks and during this time your system fails and the weather outside is just the right conditions. You may come back to a huge mess.

I have learned spray foam insulation on the exterior wall may solve this problem. You do not need a vapour barrier with spray foam as it IS the barrier. It is directly applied to the wall and creates a seal to the wood - no area for water, rot or mould.

I think the solution is to apply the foam to avoid condensation and cover it with rockwool for acoustic reasons.

This is only my theory though. We'd need someone in the industry to verify it.

[naethoven]

Originally Posted by seven

I had a duct pulling air from the studio space, through the (then sealed) attic, to the outside.

Thanks for all the details seven. In the quote above, did this duct actually ventilate the attic space, or do you mean it just ran thru that area to get to the outside? If it actually sent and returned air to the attic, I don't see how it could still develope condensation or get too hot.

Originally Posted by seven

I think the solution is to apply the foam to avoid condensation and cover it with rockwool for acoustic reasons.

Just a note, in the Rod Gervais book Build it Like the Pros, he says that rockwool inside the walls contributes little/nothing to transmission loss of your walls. He advises to just use regular fluffy insulation inside the walls and save the rockwool and such for the acoustic treatment inside the actual room. Just thought that may save u some money : )

[AnthonySpinali]

Originally Posted by fabricaudio

What is the air gap between your two walls?

It varies quite a bit from 2-6in. Please check out my thread:

Basement Studio Hangups

It's a basement so ventilating the ceiling is unrealistic. Maybe vent holes like in an attic are a good idea. I could drill 3/4" holes in a couple places and put up some sort of screen to keep bugs out. I'm just not sure... I would really like to hear Rod's take on this...

Anthony

[seven]

Originally Posted by naethoven

Thanks for all the details seven. In the quote above, did this duct actually ventilate the attic space, or do you mean it just ran thru that area to get to the outside? If it actually sent and returned air to the attic, I don't see how it could still develope condensation or get too hot.

The duct pulled air from the inner studio space, through the attic space, and vented outside. The attic space was the warmest and the studio space was the coolest. Condensation developed on the duct in the attic space only. I've now changed this.

I'll include a picture this time to explain what I've done.








My fresh air intake is in the server room (the long room in the lower right) The concept is the server room will contain most of the heat generating equipment. Our weather here is normally around 16 or colder. By bringing the fresh air into the server room I will use it to cool the equipment. On hot days I can cool it with an air conditioner in the server room.

This air will then vent directly into the main studio space either by negative pressure from the outgoing air flow or mechanically.

The ceiling space above the entry way (the room in the lower left) houses my attic fan and the fan to expel air from the studio.

My outgoing air from the studio space is in the ceiling a few feet from the inside door. An acoustic cloud will hide it and also act as an added noise damper - although there is next to no noise at the vent thanks to my silencer. I have changed this to vent into the attic space and the cross ventilation from the vents I placed in the peaks helps to expel it naturally from the attic. It will also help cool this space.

There is also the attic fan over the entry which is on a timer and has variable speed - right now it is running 24/7 on full while I'm still doing my construction. Later I'll change this to only run during the day.