Metal Buildings, Condensation Vs. Insulation

 
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Old 03-21-2006, 02:25 PM   #1
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Metal Buildings, Condensation Vs. Insulation


Hi... I'm new to these forums and have a question or two I hope some of you might be able to answer, or at least shed some light on.

I have a 45,000 sq ft (metal) building that was not insulated at the time of construction. We recently insulated the building with 6" sheet insulation, and put a moisture resistant cover over the insulation. A gap of approximately 1" was left between the top of the insulation and the bottom of the metal roof.

I should mention the building is used for horse shows, and is watered heavily prior to use. It seems that when the sun hits the roof, there is a considerable amount of condensation forming on the underside of the roof, and the steel structure of the clear-span building. This is being absorbed by the insulation and causing it to sag, and, some of the water is leaking to the floor below.

Was this the proper way to insulate a building after it had been constructed?

What can be done to eliminate the condensation?

Should this have been insulated differently?

What could be done now to salvage this project?

Any thought you might have would be appreciated. Thanks in advance...

Roy

Last edited by Roy; 03-21-2006 at 02:30 PM.
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Old 03-21-2006, 05:28 PM   #2
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Re: Metal Buildings, Condensation Vs. Insulation


Did you put poly on the bottom side of the insulation or was it not required by that type of insulation?
This is my problem with metal roofing. It always sweats.
I'm sure someone will have a solution for you, but the only thing I can think of is having some power vents with humidistats. More venting of some type will be your only answer to dry this building up.

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Old 03-21-2006, 08:07 PM   #3
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Re: Metal Buildings, Condensation Vs. Insulation


Quote:
I have a 45,000 sq ft (metal) building that was not insulated at the time of construction. We recently insulated the building with 6" sheet insulation, and put a moisture resistant cover over the insulation. A gap of approximately 1" was left between the top of the insulation and the bottom of the metal roof.
I assume the 1" space is for air circulation? Is their some type of soffit and ridge vent in place?

In order for the 1" air space to be effective, there must be soffit to ridge ventilation. That would allow air to flow out through the ridge, taking with it the excess moisture.

Huge exhuast fans at each end might also draw out some of the moisture laden air. In order for that to work there must be a way to replace the air be sucked out.
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Old 03-22-2006, 06:13 AM   #4
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Re: Metal Buildings, Condensation Vs. Insulation


You have tp move the dew point to the topside of the metal. SPF or a single ply retrofit with flute fill and topside insulation would do it. Weird, though. When the the metal warms the moisture condes to it? Condensation usually occurs on te colder surface.
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Last edited by AaronB.; 03-22-2006 at 06:20 AM.
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Old 03-22-2006, 07:16 AM   #5
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Re: Metal Buildings, Condensation Vs. Insulation


Quote:
Condensation usually occurs on te colder surface.
Condensation occurs on the warm side. That's why we install vp on the WIW (Warm In Winter) side.
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Old 03-22-2006, 09:42 AM   #6
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Re: Metal Buildings, Condensation Vs. Insulation


Sure, but the colder surface is what Im saying.....Like condensation on the outside of a glass of ice water in the summer or a cold egg left on the counter for a few minutes before cooking....water expands when warm and contracts when cooled until it freezes then it expands again.
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Old 03-22-2006, 01:05 PM   #7
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Re: Metal Buildings, Condensation Vs. Insulation


You may have an even bigger problem if...
1. you're in a snow belt area
2. The building is heated
3. the 45,000 square feet is free standing, with no interior load bearing walls

Cause if those are all yes answers, The building may not be designed to hold the additional weight of unmelted snow caused by the added R-value.

Our Church is a free standing metal building, originally a roller rink, and we cannot add the insulation we would like, so says the structual engineer that analized our wants. The building, minus load bearing interior walls, wont' support the potential added snow weight
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Old 03-22-2006, 02:18 PM   #8
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Re: Metal Buildings, Condensation Vs. Insulation


Wow, thank you for the responses. To answer a few of the questions...

* We are in Kansas, and the snow load is something I wonder if the engineers thought about... Temps here can be from below 0 F, to over 100 F, although winters have been milder of late.

* The building received the long, tubular radiant heating fixtures at the same time as the insulation was installed. They are in a rectangular pattern approximately 30' in from the outside perimeter.

* We have 10 industrial sized exhaust fans to remove air from the arena, but they do not draw air from the 1' space between the underside of the roof, above the insulation. We do have more than adequate intake for those fans from overhead doors and louvers. However, trying to heat that much space AND running the exhaust fans in COLD weather is pretty counterprodutive, not to mention expensive with the price of natural gas...

* No ridge vents

What is SPC? Flute fill?

The architect is talking about installing a LOT of vent panels near the outer perimeter of the building (on the roof, of course) with solar powered exhaust fans on either side of the ridge, to draw air through the space where the condensation is taking place. I'm not sure if the insulation installer was so "accurate" in the installation process to allow for the 1" of space under the roof, over the insulation. If the insulation is touching the underside of the roof in various locations, wouldn't the airflow be impeded to the point of NOT stopping the condensation? I'm not looking forward to another 144 holes being cut in the existing roof to allow for these vent panels and exhaust fans.

Thanks again for taking the time to respond...

Roy
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Old 03-22-2006, 02:35 PM   #9
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Re: Metal Buildings, Condensation Vs. Insulation


Quote:
The architect is talking about installing a LOT of vent panels near the outer perimeter of the building (on the roof, of course) with solar powered exhaust fans on either side of the ridge, to draw air through the space where the condensation is taking place. I'm not sure if the insulation installer was so "accurate" in the installation process to allow for the 1" of space under the roof, over the insulation. If the insulation is touching the underside of the roof in various locations, wouldn't the airflow be impeded to the point of NOT stopping the condensation? I'm not looking forward to another 144 holes being cut in the existing roof to allow for these vent panels and exhaust fans.

That's what I was trying to say. The 1" space does no good if it is blocked or sealed up. Their should be some type of ridge vent along with some type of venting along the eaves so the air is drawn up from the eaves, through the 1" air space, and out the ridge. This flushes out the warm moist air that is making its way through the insulation, and replaces it with outside cold air. It creates a balance of air temps. and humidity on both sides of the roof panels.
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Old 03-22-2006, 03:51 PM   #10
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Re: Metal Buildings, Condensation Vs. Insulation


http://www.metalroofing.com
Go to 'Ask The Experts" for many questions and issues such as you are experiencing.
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Old 03-22-2006, 09:53 PM   #11
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Re: Metal Buildings, Condensation Vs. Insulation


OK, so its not only when its raining, right?
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Old 03-25-2006, 07:57 AM   #12
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Re: Metal Buildings, Condensation Vs. Insulation


Ummmm.... no. Rain is not part of the equation. This is purely a condensation problem. High humidity inside the building as a result of watering the dirt inside to prepare it for horse shows....Cold airoutside, typically a sunny day which heats the metal roof, thereby causing the condensation on the inside of the metal roof and support beams.

Hope that helps...
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Old 03-25-2006, 08:54 AM   #13
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Re: Metal Buildings, Condensation Vs. Insulation


I would think it is simply warm inside and cold outside doing this. BWDIK?
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Old 03-28-2006, 05:37 AM   #14
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Re: Metal Buildings, Condensation Vs. Insulation


45,000 square feet and you added 6 inches with an air gap? I would bet there are multiple gaps, especially with sagging. Every solution I can offer would be exensive. If an engineer says weight is not a factor, there are exterior insulation systems that seal and insulate, but you give up the architectural apeal of the building. In the event you have to remove the added insulation now, you might consider having the panels lifted and insulation installed correctly, but this won't be cheap either. If you remove the added insulation, there are EPS insulation systems that will work, but I am not sure what surface preperation on an existing building would be required. If you call someone like Arrow Insulation ( I think they alos are in Kansas), they may give you some insight. The root of the existing problem is you are I guess wetting the arena down with a lot of water, raising the relative humidity in the building, and without adequate ventilation, it sweats...if you don't get a handle on this problem, the sweating won't be as serious as the mold and corrosion or rusting...ect.
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Old 03-28-2006, 06:55 PM   #15
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Re: Metal Buildings, Condensation Vs. Insulation


Have you considered pulling the insulation up tight and eliminateing the air space? I retrofitted 6 buildings with insulation last fall but we avoided any air space above the insulation due to condensation concerns. we used using nylon strapping fished between the roofing and purlins at the ribs running perpendicular to the insulation rolls. It worked great.
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Old 04-05-2006, 04:38 PM   #16
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Re: Metal Buildings, Condensation Vs. Insulation


Thank you again for these responses. I'm printing this thread and taking it to my architect and building contractor.... let them sort it out...

Roy

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