Research. Metal building condensation help

Hi Everyone, I came across this forum a few weeks ago, and have been very impressed with the knowledge here. We have started clearing out a metal shed at the bottom of our garden, in the UK, with the hope of transforming it into a studio. The dimensions are around 10m X 2m (I will be more specific when I finally ask for design advice) At the moment the main thing bothering me is condensation. The walls and ceiling and constructed out of trapezium shaped corrugated metal. The Idea is to build a wooden room inside this to separate the space, and insulate between the internal and external walls and ceiling. However I am concerned that the insulation is going to get damp from the condensation. Does anyone know how we could cure this issue? Thanks in advance

AlexHoward wrote:

We have started clearing out a metal shed at the bottom of our garden, in the UK, with the hope of transforming it into a studio. The dimensions are around 10m X 2m (I will be more specific when I finally ask for design advice) At the moment the main thing bothering me is condensation. The walls and ceiling and constructed out of trapezium shaped corrugated metal. The Idea is to build a wooden room inside this to separate the space, and insulate between the internal and external walls and ceiling. However I am concerned that the insulation is going to get damp from the condensation. Does anyone know how we could cure this issue? Thanks in advance

I take it from your post that condesation is an issue right now? Which would suggest that you have some heat inside the building and are finding that the inside face of the exterior wall are the point of the condensation? This would be expected on a standard metal building without insulation (and vapor barrier) installed inside of the siding. Commercial buildings designed and constructed by professioanl steel manufacturers don't usually have this problem - but the homeowners kits are not constructed to those same standards. In the case of a metal building - the problem should go away if you take care with the installation of a proper vapor barrier covering all faces of the inner most surface - this will probably require some dehumidification on your part as well as sufficient fresh air supply and a barometric release directly to the outside world from within the new room as well. you might also have to install some ventilation within the wall cavities, forcing outside air to circulate within the space (between the 2 wall assemblies) to lower the inside temperature (again - just between the 2 walls) below the level of dewpoint. This might be tricky while still maintaining sound isolation - but is doable as long as you wourk your way through it completely before putting the mechanics into place. I probasbly wouldn't duct the work - but would install the fans mounted directly outside of the building face and into a baffle system between the walls - with a fan installed high on one end of the wall and a low inlet baffle on the other end. This would have to be done 4 times for the walls and once for the roof (this because it's a dangerous fire hazzard to leave everything open around the inner rooms - they should have fuire stops at each room corner and at the top of walls in the very least. If you do that - then for all intent and purpose the wall itself becomes invisable from the point of view of the inside and outdside worlds - it is the same as if you removed it ( although it still keeps out the rain and the sound.). Could you see what I was describing? Sincerely, Rod The trick in this case is going to be to make certain that the

What Rod said - I would add that you could add a new inner layer of drywall and then build an inside room. Let the air circulate between the outer iron face and the inner drywall layer. When you add the inner room it will create a triple leaf but the iron won't contribute and you won't get a loss in TL because of it IMO. I hope I've interpreted your construction correctly.

John, I know I'm sometimes the bad guy, and it's often easier to be silent (:) maybe you can't imagine that from me ...) I sometimes have the feeling some of your own guys know, but hesitate to disagree with you. I've heard you say that more already. But it isn't true. Also with corrugated steel you will create a triple leaf system, which depending on the situation will be more or less limiting. In the combination you draft I shouldn't use it. As you possibly know I'm/was mainly an industrial acoustician. I've insulated complete power stations. Hence I'm not unfamiliar with steel building. We tried to avoid this as much as possible and when having no choice we screwed the corrugated steel directly against insulating panels in order to get resonance as high as possible where it didn't harm anymore. I know your reasoning. There is a shortcut with the environment at the bottom and top (underneath roof), further these panels overlap one another to make them rain tight. And last they are relative lightweight. This shortcut only weakens the spring stiffness somewhat but will not prevent the triple leaf effect. Now you told that you have experience with studio builds like that. Hence you have some practical experience I don't have. I mainly have experience with larger industrial steel buildings (which must comply with very strict environmental (including sound) rules, in what you know to be a small country here with relative little space and a dense population). I do have the impression that too easily you assume the triple leaf effect to disappear. That's why, in order to make sure for high insulating studios, as e.g. Paul Woodlock's door, we minimize that cavity as much as possible and than glue it with hard thermal spray foam. Even gluing it with larger cavities and such spray foam will bring resonance dangerous low to the mids. I should build that inner room, that ventilation feels OK, and respect Rod's description of the vapor barrier. To improve that steel shell for impact noise spraying it inside with bituminous material or gluing strips on them, is a possible, but likely not only solution.

John, I agree with Eric on this - and I have dealt with steel structures with commercail skins as the starting point of a super isolated building (an example being Building [removed] - the 15,000 s.f. studio Steven Spielburg shot the Amistad courtroom scenes in) and I wouldn't approach it from the perspective you are for a couple of reasons. I don't know about the rest of the world - but they can't be all that different from the US in the general concept of construction even if they do generally use different materials. Venting in the manner that you show is verboden here - a big sin........ All building construction has to be compartmentalized - thus with a simple room within a room you would have a minimum of 5 compartments 1 for each wall - and then a compartment for the roof. The flow of air as you indicate would create a vertical chimmney effect that is a very big sin........ a minimum 1 hour fire stop is required at that wall to ceiling juncture. That is a very basic code required in all 50 states even in the most simple residential construction. If you want to beef up the existing in order to maximize isolation - then I would create a larger air cavity and beef up directly at the inner face of the exterior skin............. thuis avoiding the triple leaf effect in it's entirety....... Sincerely, Rod

I don't know about the rest of the world - but they can't be all that different from the US in the general concept of construction even if they do generally use different materials. Venting in the manner that you show is verboden here - a big sin........

Rod - if that's the case every home in my country is illegal. I'll wait and see how this building is constructed. cheers john

Hi Guys, This is excellent; I didn’t expect so much response so quickly. In response to a few points: The building is not heated as yet, I assume its just being heated through the day, and cooling at night (at the moment it's empty, would you like me to post a picture?) Thanks John for your design for the air-gap. This is kind of what we were thinking, however, as the room is fairly narrow already, and has a flat ceiling standing at around 2m (I’m 6ft 4) I'm not sure how much room we could sacrifice. Apologies for the rough measurements, we will get accurate measurements tomorrow and I’ll post a diagram Does the Air-gap have a minimum depth; i.e. would an inch or two inches be enough to circulate the air? Thanks again to everyone

yes - pics and a plan would help. cheers john

John Sayers wrote:

I don't know about the rest of the world - but they can't be all that different from the US in the general concept of construction even if they do generally use different materials. Venting in the manner that you show is verboden here - a big sin........

Rod - if that's the case every home in my country is illegal. I'll wait and see how this building is constructed. cheers john

John, WOW......... are you serious? That framing is called balloon framing here in the states - and it was outlawed back in the 60's due to the manner in which it creates a potential chimney from the floor into the attic within the wall frame. A ton of homes frame pre-60's were constructed in that manner - and I am very familiar with the construction technique. In the states they require a complete fire block (1 hr min) at each floor level - plus over the top of every bearing partition - and smoke stops over the top of all non-bearing partitions separating rooms. And (in case you are wondering) yes this is nation wide. They take these fire stops very seriously - (and I am talking about one family residential here - not commercial) forcing the use of fire caulk to seal around every pipe - duct - conduit or wire penetration passing from one floor to another or into the attic ............. The only way they would let us do what you show would be if it was hard ducted ( galv metal duct meeting a 1 hr rating) and sealed at each floor level (around the penetration) - which would sort of make it not work for our purposes being discussed here. In the case of some loans - the Govt won't even let you run a soffit vent outside a window - but make you break them 4 feet away......... Amazing some of the differences around the world........... :) Rod

AlexHoward wrote:

The building is not heated as yet, I assume its just being heated through the day, and cooling at night (at the moment it's empty, would you like me to post a picture?)

Alex, it amazes me that the building is not heated and yet is experiencing dew point inside of the building - the outside would make sense - -but inside is strange.......... Is this really taking place - or do you just aniticipate its happening? Rod

rod gervais wrote:

That framing is called balloon framing here in the states - and it was outlawed back in the 60's due to the manner in which it creates a potential chimney from the floor into the attic within the wall frame. A ton of homes frame pre-60's were constructed in that manner - and I am very familiar with the construction technique. Rod

Balloon framing got its bad rap due to continuous stud length from bottom floor level to top of the second wall at the second floor level. With this open cavity between studs, from one floor to the next, above to below or vice-versa, this helped many an apartment building to burn down due to an unrestricted path for fire to move around in. Blocking at floor to floor intervals has corrected, or at least, slowed down the fires unrestricted path. I have had my hands on a balloon framed wall as recently as 1986 on Sugar Mountain in North Carolina. It(balloon framing) has lost favor for many reasons, I am sure:) Another still widely accepted practice is called platform or western platform framing. John is suggesting a wall inside a metal building. That is called stick framing.

Rod - sorry I was being flippant ;) it wouldn't work here because our standard stud wall MUST have horizontal studs, (noggins) at 4' spacings. But our brick veneer constructions do have a vent in the bottom of the brickwork to the airspace between the brick and the inner stud frame and it's open through to the truss cavity above. As was just pointed out - we are talking about a steel framed building here.

[quote="xSpaceJohn is suggesting a wall inside a metal building. That is called stick framing.[/quote] Regardless of how the chimney makes it into the attic - there is nothing in John's drawing to stop the spread of flame fromone floor to the next within the stud bay. Sincerely, Rod

John Sayers wrote:

Rod - sorry I was being flippant ;) it wouldn't work here because our standard stud wall MUST have horizontal studs, (noggins) at 4' spacings. But our brick veneer constructions do have a vent in the bottom of the brickwork to the airspace between the brick and the inner stud frame and it's open through to the truss cavity above. As was just pointed out - we are talking about a steel framed building here.

John, I didn't think you were being flippant - that's not your style.... 8) Neither am I for that matter............ :wink: Here in the states nothing is allowed to do what you indicate - regardless of the structure - there must be a hard fast disconnect between floors. Here in the states - a brick veneer is generally installed with a minimum 7/16" sheathing installed between the outer face of the wall and the inner face of the brick. A building paper (not capable of passing water molecules but capable of passing vapor molecules) is then installed over the sheathing and the brick is installed with an air space between the 2. If the brick space is to be vented (this is NOT a requirement of our codes) then it is vented in both instances directly through the brick to outside air. All that IS required in the case of a veneer finish is that weep holes be installed above grade to handle the condensation that will take effect within the air space. But under no circuumstances - for any type of construction - is there an allowance for the passage of free air from floor to floor. In the case of your detail - should a fire break through the interior wall surface - it would have a direct route into the attic. The only time we can get away with anything resembling this would be in the case of a chase - the walls of which would have to exceed the required floor to floor rating of the building - and even under those circumstances the chase has to end either outside of the building above the roof- OR it has to end within the attic with the same assembly rating at the top of the shaft as it has in the walls. It can never just dump into the attic with free open air. Any ducts passing through the shaft would be required to have fire dampers installed at the point of passage through the wall of the shaft (there are a couple of exceptions for this where special designs are implemented which afford the same effective rating as the installation of a fire damper would - but those are very specific in nature and few and far in between. Amazing........... Sincerely, Rod

Rod - in our Brick Veneer construction there is foil lining the studwall. (optional) and metal ties are used to link to the brickwork. The brickwork goes up to just above the eave. The airspace between the studwall(foil) and the brick work is open to the ceiling cavity and open to the outside air via vents below. It is not a requirement to seal off the air connection between the two areas. Anyway - let's wait for the pics. ;)

John Sayers wrote:

Rod - in our Brick Veneer construction there is foil lining the studwall. (optional) and metal ties are used to link to the brickwork. The brickwork goes up to just above the eave. The airspace between the studwall(foil) and the brick work is open to the ceiling cavity and open to the outside air via vents below. It is not a requirement to seal off the air connection between the two areas. Anyway - let's wait for the pics. ;)

Awww.......... :cry: You went and spoiled the fun.......... Actually - I find it fascinating to learn about the different construction techniques used around the world. But - OK - we'll wait for pics........ Rod

cheers for the replies so far, I am hoping we can get this sorted between us before we start buying materials etc and actually getting started. To help you visualise the space here are some pics and the dimensions. The drum kit is pictured in what we envisage being the control room so pretend you can't see it for now :wink: thanks in advance for your wisdom and effort. It might be worth noting that condensation was present on the uninsulated internal surfaces when we were busy clearing this shed out. While we were taking these pics today there was none so possibly the heat of our activity contributed?

and here are those dimensions :D

AlexHoward wrote:

It might be worth noting that condensation was present on the uninsulated internal surfaces when we were busy clearing this shed out. While we were taking these pics today there was none so possibly the heat of our activity contributed?

Alex, I doubt it - but seeing what I'm seeing I am not surprised........ any sun at all and the small air pockets between the inner board and the exterior skin can raise the temp enough to cause condensation on the outer skin - and you can see that moisture inside this space is quite high - everything looks pretty wet - including the inner sheathing under the window - the black rafter that it wolls like there's a lot of mold on it - the same with the stud you gave us the close-up of. It looks to me as if you might have some active leaks in this room- possibly that is why the empty spots (where you have no inner skin) exist? So a question - does this room stay bone dry when it rains? Rod

As far as I can tell it stays bone dry inside apart from directly under the window (the chipboard is stained wet) in very heavy rain because the seal isn't good enough. the roof and walls don't leak at all. The floor is dry and dusty at all times.

AlexHoward wrote:

As far as I can tell it stays bone dry inside apart from directly under the window (the chipboard is stained wet) in very heavy rain because the seal isn't good enough. the roof and walls don't leak at all. The floor is dry and dusty at all times.

So the black rafter and the exposed stud that looks like it has mold on it are actually both bone dry? And the room is very low humidity? If that's the case I am very puzzled by the whole condensation on the inside of an unheated building thing that's going on - that is very unusual compared to anything I've experienced. I might be able to explain it if I was there to examine the building - but not from a distance. As far as the building itself goes - I would probably invest a few more dollars and take apart the remainder of the building - carefully so that I could reuse the siding and roofing and begin with a whole new frame that I could work some proper isolation into........ I wouldn't want to start with what exists right now.......... Sorry, Rod

but if you do rebuild it on the same foot print, then this might work. having the drums in a booth, middle room for the rest of the band, and the CR on the other end. doors with windows allow visibilty from end-to-end.

AlexHoward wrote:

As far as I can tell it stays bone dry inside apart from directly under the window (the chipboard is stained wet) in very heavy rain because the seal isn't good enough. the roof and walls don't leak at all. The floor is dry and dusty at all times.

Clearing out the brush and undergrowth around the outside of this building will help in your inspection Alex. One thing it will do is to allow free movement of air under the building. Another thing it will do is allow you to determine if there "is" any free movement of air under this building. If no movement of air is able to get in under the floor, coupled with the saturation from rain penetrating the wall and going to the ground underneath the wooden floor, this is most likely a large part of the condensation concern.

Hi Guys, Thanks for all you help so far, this is quality. Thanks also to Gullfo for an excellent design, very nice :D I think the next step will be to strip off all the old panels, and seal or probably more ideally remove and fill the windows. Then see what we're left with. i generally believe the structure to be in good condition, and a little work should make it water tight (under the window for example) Thanks again Alex

Here's a rough idea of how we propose to insulate the walls. We also have some Tyvek Vapor Barrier Material, which could go against the outside wall... Does this look ok? Cheers Alex