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.
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.
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.
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.
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.
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.
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.
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."
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.