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Metal Roofs and condensation???


Bryan
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I am looking for some solid information to back up my findings from a recent progress inspection. The building is a pole structure with metal siding and roof panels installed directly to the framing. On the interior of the side walls they used 1 1/2" spray foam, however; no foam or insulation on the bottom of the roof metal. All heat ducts are in the attic space and the plans indicate 16" of blown cellouse for the attic. Also the soffits have continous vents around the building, the contractor indicates the ridge of the building is vented and this will provide adiquate air flow to prevent condensation. I have been around these buildings in the past and have never seen one with a vented ridge and the ridge filler appears to be solid foam. Therefore, I believe that this building will be soaked from condensation as soon as the structure is conditioned on that first cold morning. Furthermore, the insulation contractor does not see anything wrong with the system.

Thank you in advance Bryan

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Originally posted by Bryan

I am looking for some solid information to back up my findings from a recent progress inspection. The building is a pole structure with metal siding and roof panels installed directly to the framing. On the interior of the side walls they used 1 1/2" spray foam, however; no foam or insulation on the bottom of the roof metal. All heat ducts are in the attic space and the plans indicate 16" of blown cellouse for the attic. Also the soffits have continous vents around the building, the contractor indicates the ridge of the building is vented and this will provide adiquate air flow to prevent condensation. I have been around these buildings in the past and have never seen one with a vented ridge and the ridge filler appears to be solid foam. Therefore, I believe that this building will be soaked from condensation as soon as the structure is conditioned on that first cold morning. Furthermore, the insulation contractor does not see anything wrong with the system.

Thank you in advance Bryan

Even if the ceiling vapor barrier is perfect, the underside of the roof metal will still sweat. If the ceiling vapor barrier is imperfect, the underside of the roof metal will sweat a lot.

Why didn't they spray the underside of the roof?

BTW, what do the plans & specs say?

- Jim Katen, Oregon

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I'm with Jim. I can't imagine it not condensing. I wonder if the builder has built a few like that and because he hasn't ran into any problems he thinks it's OK. It's not. Eventually he will build one that has a major problem.

If he's counting on lots of ventilation openings to control (dilute)and prevent excessive moisture vapor in the attic then he better think again. That's not the way to approach the problem and in fact could become the source of a problem. I would insulate the underside of the metal roof deckid="blue">.

On a cold windless day or night where the hell is his ventilation going to come from? If it was a wood structure durring those periods the wood would load up with moisture and hopefully not saturate before some heat and air movement returns but with metal there's no loading phase, it's going to condense immediately and profusely.

The best source on this subject is William B. Roses book "Water in Buildings: An Architect's Guide to Moisture and Mold". There has long been this idea promugated that humidity is based on air temperature. It is not! What controls humidity are the bounding surfaces and their temperatures! You can in theory (and temporarily in real life) exceed moisture vapor levels beyond those in the tables.

Your builder should get himself educated and consider the surfaces not the air!

Chris, Oregon

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Originally posted by Chris Bernhardt

I'm with Jim. I can't imagine it not condensing. I wonder if the builder has built a few like that and because he hasn't ran into any problems he thinks it's OK. It's not. Eventually he will build one that has a major problem.

If he's counting on lots of ventilation openings to control (dilute)and prevent excessive moisture vapor in the attic then he better think again. That's not the way to approach the problem and in fact could become the source of a problem. I would insulate the underside of the metal roof deckid="blue">.

On a cold windless day or night where the hell is his ventilation going to come from? If it was a wood structure durring those periods the wood would load up with moisture and hopefully not saturate before some heat and air movement returns but with metal there's no loading phase, it's going to condense immediately and profusely.

The best source on this subject is William B. Roses book "Water in Buildings: An Architect's Guide to Moisture and Mold". There has long been this idea promugated that humidity is based on air temperature. It is not! What controls humidity are the bounding surfaces and their temperatures! You can in theory (and temporarily in real life) exceed moisture vapor levels beyond those in the tables.

Your builder should get himself educated and consider the surfaces not the air!

Chris, Oregon

Very interesting. I've got a pole barn that I just installed a new metal panel roof on. Now, the discussion has been finishing the interior space, and I'm on the front end of researching how to insulate.

http://www.foam-insulation.co.uk/metal- ... lation.htm

Does this sound reasonable?

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Thank you for the input so far. Our firm is working for the lender on this project doing the draw and progress inspection regarding the building. This is a 10,000 square foot wooden pole structure (barn) being constructed as a church building. The church had the shell and exterior finishes completed by a contractor and they are finishing the rest of the building themself. The plans are minimal with the rest being complete on a design and build bases. Truely I am not sure how they recieved there state plan release with the available prints and lack of details. I do believe that there will be a great moisture problem due to the fact a vapor barrier is rearly installed correctly, especially at penetrations for fixtures and duct work.

Kurt,

IMHO the spray insulation is the only way to when you have an exsisting roof in-place. I built metal building for a while and on rehab work we always had problems with condensation due to the purlins and other penetrations.

Bryan

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Bryan,

The builder should be required to document that his vendor/manufacturer for the metal panels specifies the installation procedure he used. (I don't think he can)

I had a client with a house roofed this way. A local insulation contractor did the foam application and guaranteed his work to solve the problem.

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Originally posted by Bryan

Thank you for the input so far. Our firm is working for the lender on this project doing the draw and progress inspection regarding the building. This is a 10,000 square foot wooden pole structure (barn) being constructed as a church building. The church had the shell and exterior finishes completed by a contractor and they are finishing the rest of the building themself. The plans are minimal with the rest being complete on a design and build bases. Truely I am not sure how they recieved there state plan release with the available prints and lack of details. I do believe that there will be a great moisture problem due to the fact a vapor barrier is rearly installed correctly, especially at penetrations for fixtures and duct work.

Kurt,

IMHO the spray insulation is the only way to when you have an exsisting roof in-place. I built metal building for a while and on rehab work we always had problems with condensation due to the purlins and other penetrations.

Bryan

If you are lucky you might get the ear of the bank to listen to your concerns. The majority of the time the banks are only concerned with the quantity and not the quality. Sounds like you might be getting into more of a quality inspection than a draw inspection. Now if the bank is asking for you to look at the quality this is great, but be sure you are being paid for it as well.

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Hi,

I think you've got a right to be concerned, but this isn't the best place to go to get answers. You need to go to the horse's mouth, so-to-speak; the Metal Roofing Alliance. You can even post the question on their Ask the Experts Forums.

Check them out. Once you get the answer, please stop back by here and edumakate all of us codgers.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by Bryan

. . . The church had the shell and exterior finishes completed by a contractor and they are finishing the rest of the building themself. . .

For years, I've given people the same three rules to follow when they ask me for advice about hiring contractor:

1. Never go with the lowest bidder.

2. Always get references, preferably from someone you know.

3. Never hire anyone from your church to work on your house.

An entire building being build by folks from the same church sounds like a nightmare to me.

- Jim Katen, Oregon

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I believe the only effective way to insulate the structure is to apply foam directly to the bottom of the roof deck.

Normally, I'm a proponent of icynene, but for metal roofs closed cell urethanes are the clear choice.

I've seen several failures with each style of foam...roofs rusting through from the inside out. The failures with the icynene appeared to me to be the result of the product allowing some conditioned, moisture laden air through causing rust around every area where the protective coatings on the metal had been violated..screw holes, scratches and chaffs where the material met metal purlins etc.

The urethane failures looked to all be installation error. Pockets of uninsulated roof connected to conditioned space by crevice, nook and cranny.

A modest applied cost for urethanes in this area is 1.50 a board foot installed and about .90 a board foot if you rent the equipment and install the product yourself.

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Thanx. That's about what I was figuring. I've never seen urethane done this way, but it makes sense.

What would you do to treat the penetrations or other finish defects to keep it from rusting?

Church work should always be the last job you take, and never, ever work for your own church.

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  • 1 year later...

Yea I try and shy away from the church jobs. Shame ain't it.

I'm a Deacon at a 2500+ Baptist Church and I don't advertise what I do for a living. The Sunday school director still owes me $475.00 for a home inspection that I did for her over 6 months ago. I see her every week as the wife and I teach a class. I just smile and nod.

Kinda chaps my butt though.

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Originally posted by Bryan

I am looking for some solid information to back up my findings from a recent progress inspection. The building is a pole structure with metal siding and roof panels installed directly to the framing. On the interior of the side walls they used 1 1/2" spray foam, however; no foam or insulation on the bottom of the roof metal. All heat ducts are in the attic space and the plans indicate 16" of blown cellouse for the attic. Also the soffits have continous vents around the building, the contractor indicates the ridge of the building is vented and this will provide adiquate air flow to prevent condensation. I have been around these buildings in the past and have never seen one with a vented ridge and the ridge filler appears to be solid foam. Therefore, I believe that this building will be soaked from condensation as soon as the structure is conditioned on that first cold morning. Furthermore, the insulation contractor does not see anything wrong with the system.

Thank you in advance Bryan

Get the specs from the manufacturer. With a few notable exceptions, home inspectors aren't really qualified to engineer pole barn roofs. In the HI business, we're mostly on the lookout for homeowner/handyman/builder screwups. It's best, I think, to get your info straight from the horse's mouth.

I'll offer this: Sooner or later, the exposed metal roof will sweat.

Good luck,

WJ

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No solid information here, but I have seen a lot of pole barns with double-bouble insulation applied to the purlins before the roof metal is put on. The insulation would reduce the condensation, and any drips would run to the end of the roof so long as the insulation is lapped properly. Commercial steel buildings use vinyl backed batts.

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Originally posted by davidlord

Yea I try and shy away from the church jobs. Shame ain't it.

I'm a Deacon at a 2500+ Baptist Church and I don't advertise what I do for a living. The Sunday school director still owes me $475.00 for a home inspection that I did for her over 6 months ago. I see her every week as the wife and I teach a class. I just smile and nod.

Kinda chaps my butt though.

I chased an inspection fee for about 9 months from one of our new associate pastors (we had 6 of them) in a church of 9,000 at our old church in Jackson MS. When he and I finally spoke about it he said the he was not happy with my inspection because after four months in the home his 10 year old dishwasher died as well as the 10 year old water heater. I told him in the report that they needed to be replaced.

Funny thing is that he paid a month or so later. This was also not long after I became a deacon and I was placed as the chairman of the pastoral review committee.

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Like others have said, I don't chase work at church. We have about 6000 attenders that are in the community. Of the many I have done, there has never been a problem with collections or expectations. Done three of the senior staff's homes. I still hold my breath when one comes up and says "I've got a question".

If you have to look someone in the face weekly, it helps to ensure you do your best! I did have a seller in the area whine "I took care of my church people" and no one should behave that way. Her deal imploded. Turned out she refused my client's new offer when her home did not appraise for enough. Always the HI's fault.

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