In this episode of Building with Metal, McElroy Metal’s Stephen Knight unpacks the science behind managing moisture and sound in metal roof systems. Learn how underlayments, insulation, and design details minimize condensation, reduce noise, and improve overall comfort, turning great performance into lasting satisfaction.
Notable Quotes
- "The roof is not really to blame. It's more of a problem with the system as a whole, with whether or not you've got adequate ventilation or insulation for the system and the components that exist inside of it." - Stephen Knight, Engineering Manager, McElroy Metal
- "Every winter, when I look up at frost on asphalt shingle roofs, you can see the rafters in people's roofs. That is thermal bridging there, and that assembly has no metal in it." - Stephen Knight, Engineering Manager, McElroy Metal
- "Projects typically go wrong with corner-cutting, honestly. And corner cutting can happen at any phase of a project." - Stephen Knight, Engineering Manager, McElroy Metal
What You'll Learn
- Why condensation happens in any building assembly, not just metal roofs
- How the dew point drives moisture issues and what controls it
- Three proven ways to manage moisture: reducing humidity, ventilation, and insulation
- What thermal bridging is and why it shows up in every type of roof, including asphalt shingle
- How Above Sheathing Ventilation (ASV) works and why it pairs well with standing seam
- Why an apples-to-apples comparison of metal vs. other roofing systems matters for noise
- Which insulation types absorb sound best and how standing seam clips help
- How vapor barriers, sealed penetrations, and proper detailing prevent moisture intrusion
- The specific phases of a project where corner-cutting causes the most damage
- Which McElroy panel systems are ASV-compatible
Key Timestamps
- [00:00] Episode introduction and welcome to the Building with Metal Podcast
- [01:00] Why metal buildings "sweat" and why the roof isn't actually to blame
- [03:30] The science of the dew point and how humidity drives condensation
- [06:00] Three ways to control moisture: reducing humidity, ventilation, and insulation
- [09:30] Above Sheathing Ventilation (ASV) explained, how it works and why Stephen prefers it
- [13:00] Thermal bridging: what it is, where it hides, and why it affects every roof type
- [17:00] Apples-to-apples roof comparisons and why metal performs as well as other systems
- [20:00] The truth about rain noise on metal roofs and how to mitigate it
- [24:00] Where projects most often fail: design, installation, and the cost of corner-cutting
- [28:00] McElroy panel systems with ASV capability, contact information, and closing thoughts
Mentioned Resources
- 138T Shingle Recover System
- Maxima Standing Seam Panel
- 138T/238T Standing Seam Roof Panel
- Trap-Tee Panel System
- Stephen Knight, Engineering Manager: sknight@mcelroymetal.com
- Connect with host Kathi Miller on LinkedIn
Episode Deep Dive
In 30 Seconds
- Metal roofs don't cause condensation or noise. Building assemblies do.
- Control humidity, ventilate the system, and insulate properly to handle both.
- Above Sheathing Ventilation paired with standing seam is one of the most cost-effective fixes available.
Most complaints about metal roofs being "sweaty" or "loud" come from comparing the wrong things. A drafty old farm shed with a single metal skin is not the same animal as a finished home or office with proper insulation, ventilation, and detailing. When you put the two in the same conversation, metal roofing takes a beating it doesn't deserve.
In this episode of the Building with Metal Podcast, McElroy Metal's Engineering Manager, Stephen Knight, walks through the science behind why moisture and sound show up in any roof system, and what contractors, designers, and owners can do to control them.
What causes condensation on a metal roof?
Condensation happens when humid air meets a surface colder than the dew point. The moisture has to come out somewhere. That same physics is why a bathroom mirror fogs after a shower and why dew forms on grass overnight. The metal panel isn't producing the water. The assembly is allowing humid interior air to reach a cold surface.
"The roof is not really to blame. It's more of a problem with the system as a whole, with whether or not you've got adequate ventilation or insulation for the system and the components that exist inside of it." - Stephen Knight, Engineering Manager, McElroy Metal
That distinction matters. If you treat condensation as a roof problem, you'll keep replacing roofs. If you treat it as a building science problem, you can actually fix it.
How do you control moisture in a metal roof system?
The big-picture goal is keeping humid air away from cold surfaces. You can do that by reducing the humidity inside the building, by ventilating the air out before it has a chance to condense, or by insulating so that the cold roof surface never meets warm interior air. Most well-built projects use a combination of all three.
Ventilation is the workhorse. Stephen's favorite approach is Above Sheathing Ventilation, or ASV. With ASV, a half-inch to two-inch gap sits between the deck and the metal panel. Cold air enters at the eave, warm air exits at the ridge, and any moisture that does form has a clear path back out of the system before it can cause damage.
Insulation does the temperature-equalizing work. Over several inches of insulation, a cold metal panel never reaches the interior air. Pair good insulation with a properly sealed vapor barrier, and you've cut off the path that humid air would otherwise take into the roof cavity.
What is thermal bridging in a metal roof assembly?
A thermal bridge is any place where insulation thins out, gets compressed, or where a conductive material like a metal purlin connects the outside of the roof directly to the inside. Even a well-insulated roof can develop condensation problems at these weak points.
This is not a metal-only issue.
"Every winter when I look up at frost on asphalt shingle roofs, you can see the rafters in people's roofs. That is thermal bridging there, and that assembly has no metal in it." - Stephen Knight
Same physics, different material. The difference is what gets blamed when something shows up on the ceiling.
Catching thermal bridges is a shared responsibility. Architects and engineers should design for them. General contractors and roofers should call them out when they spot one in the field. The best contractors, Stephen notes, do more than show up and install. They help the owner understand what they're really buying.
Are metal roofs really louder than other roof types?
Standing under a carport in a thunderstorm is not how metal performs on a finished home or office. Most metal roof assemblies built for habitable space include insulation, a deck, and proper ventilation. With that build-up, rain noise is comparable to any other roof type.
If quiet is a priority, the material choices matter. Fibrous insulation like mineral wool absorbs sound better than closed-cell foam. Standing seam clips also help by holding the panel slightly off the structure, which reduces sound transmission compared to a through-fastened roof. Tall clips bring an added bonus: they create the gap needed for ASV at the same time.
Where do metal roof projects most often go wrong?
When asked where projects most often fail on moisture and sound, Stephen didn't point at design or installation specifically. He pointed at corner-cutting. Skipping vapor barrier tape at a penetration. Compressing insulation over a purlin. Substituting a cheaper material at the last minute. None of these decisions look serious on the day they're made. All of them show up later.
"It's human nature to get in a hurry to get x number of squares installed every day. There's all of these little tasks that eat up your time, and those are the areas that take more concentration than anything else to get done correctly." - Stephen Knight
The details are where roof performance is won or lost.
Why does the full roof assembly matter more than the panel itself?
The takeaway from this conversation is that condensation and noise are building assembly problems, not metal panel problems. A good contractor adds real value not by installing faster but by helping the owner think through the full system: insulation, ventilation, vapor barriers, deck choice, panel system, and detailing. That conversation isn't a line item on a budget, but it's the difference between a roof that performs for decades and one that becomes a callback.
As Stephen puts it:
"Get all of your suppliers involved in this process. Really take your time on the design phase and you'll have a great building and product that'll last for many years to come."
About McElroy Metal
McElroy Metal manufactures metal roofing and siding products for residential, commercial, agricultural, and industrial applications. Headquartered in Bossier City, Louisiana, with plants and service centers across the U.S., McElroy supplies contractors, architects, designers, and building owners with metal panel systems, accessories, and the engineering expertise to use them well.
Comments on this article:
Scroll down to the bottom to submit a comment and join the conversation. Need help or have a question? Please contact us. Looking for a distributor or contractor? Please click here to get started.