Tag Archives: I.C.C.

Decisions, Decisions – Vapor Barrier for a Post Frame Steel Reroof

Decisions, Decisions – Vapor Barrier for a Post Frame Steel Reroof

There are few reasons to replace an existing post frame building’s steel roof, as properly installed it should last a lifetime. Among these reasons could be:

Tired of Existing Color
Old roofing was nailed on
Tree fell through roof

This last one actually occurred to our shouse (shop/house) when I lived in Northeast Washington!

Loyal reader and Hansen Pole Buildings’ client MIKE in COUPEVILLE writes:

Reflective Insulation“I am currently re-siding/re-roofing an existing pole building in order to match the exterior of the building I recently purchased from you.  This building is roughly 32 x34 and the roof purlins are 2×6 on end roughly every 2 feet.  I’m using Fabral’s grand rib 3 29ga for the roof and it will have fully vented soffit overhangs and a vented ridge cap.  I am trying to figure out what I’m going to do for at least a vapor barrier under the roof steel, I see you seem to recommend foil faced bubble insulation but that is not very common in my area.  I am seeing a lot of people using lamtec wmp-vrr (fiberglass insulation with a poly backing)  3″ thick and I believe they lay these wide rolls on top of the purlins and then place the metal roofing on top of that then screw down the roofing compressing the fiberglass insulation between the metal roofing and the purlins.  Have you seen this style of insulating before?  Do you think it is an acceptable way of doing it?  I see as killing two birds with one stone.  I may be insulating this shop in the future so if I do then the roof is already insulated plus I believe it acts as a vapor barrier which is the main reason to do it as I don’t want any condensation dripping down on the inside of the shop.  I live in the Seattle area if that helps to know what my climate is like.  Thanks in advance for your input.” 


Mike the Pole Barn Guru responds:

Our recommendation would be to order your roof steel with factory applied I.C.C. (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/).

Metal Building Insulation (fiberglass with a vinyl facing) is a decent condensation control, provided all of the seams are tightly sealed. It is a pain to work with, provides very little effective insulation value and makes your roofing pucker outwards between purlins https://www.hansenpolebuildings.com/2011/11/metal-building-insulation-in-pole-buildings-part-i/.

If it is too late for an I.C.C. then the radiant reflective barrier (https://www.hansenpolebuildings.com/2017/05/effective-reflective-insulation/)

 is probably your best option.  Order in six foot width rolls to minimize seams and make sure to get a product including a tab along one edge with an adhesive pull strip attached.

Integral Condensation Control

With steel roofing for barndominiums, shouses and post frame (pole) buildings comes condensation.

When atmospheric conditions (in this case temperature and humidity) reach dew point, air’s vapor is able to condense to objects colder than surrounding air temperature. Once vapor condensing occurs, droplets are formed on cool surfaces. This is partly why warming a vehicle’s windshield with a defroster can prevent glass ‘fogging’.

When a building’s interior air meets these conditions, air vapor will condense to cool surfaces. Steel roofing cooled by exterior air temperature often provides this surface. Droplets formed will combine as they contact one another, continuing to do so until they are too large to be supported by surface tension. At this point, dripping will occur, essentially raining on your structure’s contents. 

Commonly (when addressed at all during construction) solutions to this problem have often involved creating a thermal break. A thermal break reduces contact between a structure’s warm interior air and cooler metal roofing, thereby reducing or eliminating overall condensation. Installing a reflective radiant barrier, often termed Vapor Barrier, involves laying rolls of faced ‘bubble wrap’ across your building’s purlins prior to roof steel installation. Ideal weather conditions are required for this as even a slight wind can make this a challenging or altogether impossible task. This can cause jobsite delays and may bring progress to a halt while a structure remains unprotected to weather. Even when ideal weather conditions are present, installing a reflective radiant barrier can be a very dangerous task, requiring builders to expose themselves to awkward material handling on a building’s bare roof framing. These risks and delays often generate additional costs for both owners and builders, but have often been necessary with reflective radiant barrier being the only relatively affordable option to prevent interior dripping. 

New materials and production methods offer a better solution. Utilizing polyester fabric’s absorption characteristics and their integral application during roll-forming, most better quality steel roofing roll formers offer a ready-to-install roofing panel with integral drip-protection. I.C.C. is a pre-applied solution reaching jobsites ready for immediate installation. Delays and increased jobsite workload caused by problems associated with radiant reflective barriers are eliminated by this product. Also, due to this solution’s simplicity, panels with I.C.C. install using the same methods, fasteners and time similar panel-only installations require. No changes to installation processes are necessary, with an exception of time and effort saved. 

It works because this polyester membrane simply retains liquid until atmospheric conditions allow it to be re-evaporated. This is because polyester is hydrophilic, meaning water is attracted to it. It acts as a wick, harmlessly absorbing condensing vapor. Rather than preventing condensation, it provides an absorbent layer to detain condensing vapor until it can re-evaporate as temperatures increase and humidity decreases.

Integral Condensation Control

Integral Condensation Control (I.C.C.) products are manufactured and distributed with trade names such as Condenstop (which I have written about previously: https://www.hansenpolebuildings.com/2014/07/condenstop/) and Dripstop.

Here are a few words on Dripstop, recorded live at the NFBA Expo held recently in Nashville, Tennessee:

I.C.C. provides drip prevention which is integral to steel roofing and is aimed at saving installation time and labor. I.C.C. is comprised of a polyester fabric with an adhesive glue layer which allows it to be adhered to the washcoat (the underside) of steel roofing panels. The fabric is attached to the sheet metal as it is being unwrapped from the coil and is roll formed with the panel, allowing the steel roofing to arrive on the jobsite ready for immediate installation.

Steel roofing with I.C.C. addresses drip prevention in a new way. By providing a wicking material to retain the moisture, condensation is no longer the enemy. This product works with the natural condensation cycle to prevent dripping and is far more durable than barriers. No additional products or inventory are necessary, and because I.C.C. is factory-applied, no additional jobsite labor is required. No need to worry about dragging around rolls of reflective or metal building insulation, just install the roof and get the job done.

To better understand how this product works, we must first discuss why condensation and dripping happen in the first place. When atmospheric conditions reach the dew point, air contains the maximum amount of moisture it can retain at its temperature. This is known as 100% relative humidity. Since cool air is unable to retain as much moisture as warm air, any drop in temperature from contact with a cooler surface essentially “wrings” the moisture out of the air. This is why fogging (condensation) is caused by the warm, moist air in our breath hitting a colder pane of glass. As the glass cools the warm, moist air contacting it, the moisture in our breath is “wrung” out.

As noted above, where warm air meets cool surfaces, the moisture in this air will often condense to the surface and form droplets. When exterior air cools steel cladding below the building’s interior temperature, the steel can provide this surface. Once condensation begins to take place, the droplets formed will combine as they contact one another, continuing to do so until they are too large to be supported by the liquid’s surface tension. At this point, dripping will occur, essentially raining on the structure’s contents.

Because some people are unaware of this process, many steel roofed post frame building owners are convinced all metal roofing leaks – a make believe ‘fact’ which can deter them from an otherwise superior product as well as cause headaches for both builders and post frame building kit package suppliers. In the past, the solution to this has been to provide a thermal break between the structure’s interior and the steel roofing to isolate the warm moist air inside the building from the underside of the cooler roof steel.

In theory, this is an excellent idea. In practice, it requires additional inventory and a large amount of additional labor. Meanwhile, the steel roofing waits to be installed. These problems are compounded by the fact barrier products are generally hard to handle and install in even mildly inclement weather.

Steel roofing with I.C.C. eliminates these delays, reduces inventory and simplifies construction without sacrificing drip-preventing performance.

The core of I.C.C. is a polyester fleece. When this material is adhered to steel panels, it greatly increases the surface area from moisture to cling to after condensing. The fleece provides hundreds of fibers per square inch for droplets to stick to, thereby greatly increasing the “grip” they have on the interior of the cladding. Because of this, a twelve foot panel can retain over half a gallon of condensed moisture.

 Steel roofing with I.C.C. is well suited for a wide variety of applications. Similar products have been available for over 15 years in Europe and have provided successful service on every continent and in nearly every climate in countless applications. Steel roofing with I.C.C. is well suited for self-storage, animal confinement, garages, grain storage, car ports, barns, aircraft hangars, stadiums and literally any other place where condensation and drip prevention are of concern.

The I.C.C. fabric requires contact with air to function properly, therefore it is not recommended for closed-decking applications. Also, it is not meant to function as insulation due to its low R-value.

In closed wall applications, any edges exposed to the exterior of a structure (i.e. the eaves), should be sealed to prevent moisture from seeping into the structure through the fabric.

The additional thickness of the I.C.C. fabric changes the roll-forming characteristics of steel panels, giving panels a slight “barrel-roll”. This effect is limited to an inch of curl up at the sides when the panel lays color up on a flat surface and provides no additional challenges for installation. Another effect is the reduction of smoothness at all bends in the panel. Again, this has no effect on performance of either panel or fabric. The barrel-roll is imperceptible after installation and the bend texture is indiscernible at distances greater than an arm’s length.