Originally published in the April 2018 issue of Sweeping Magazine
Question: I've heard that recent changes in the IRC now allow fasteners to penetrate the inside of dryer vent/duct. Is this true, and is it a good idea?
by Mike Segerstrom
Yes, it's in the IRC. The 2015 edition of the IRC has language that states: M1502.4.2 "Exhaust duct joints shall be sealed in accordance with section and 1601. 4.1 and shall be mechanically fastened. Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8" into the inside of the duct.
If we are going to consider this, we have to check with our local Authority Having Jurisdiction (AHJ) to confirm if they enforce the IRC for the NFPA 211 for dryer vents, as the NFPA 211 still prohibits screws and fasteners from penetrating the pipe. The local AHJs may also be unaware of this change so if we are going to do it, we may want to have a friendly conversation with them about it pointing out the code change. And whether or not they are aware of the change we're support it, they do have the authority to still prohibit the use of screws or rivets.
So is it a good idea? Dryer vent service technicians throughout the country have seen where long screws catch lint and create obstructions and clogs, and hazardous dryer venting conditions. Will 1/8" penetrations cause the same problems? They may, and there are several factors to consider.
In a short dryer vent run with air moving at high speeds, there is less likelihood that lint could get caught and build up on a 1/8" screw penetration. A part of that will also depend on frequency of dryer use and frequency of dryer vent cleaning. A longer dryer vent run, with at times significantly lower air flows near the outlet, could be more prone to catching lint on short screws near the exhaust end.
If the vent serves an older dryer, or there is a lack of maintenance and frequency of use issue, even 1/8" penetrations could potentially cause a problem. It could start as a small amount of lint caught on the fastener, and over time it could become larger.
There are variables to consider and though 1/8" penetrations are now permitted, clamping systems at the pipe joints are the best practice. Dryer duct and vent systems are also now available, that come equipped with gaskets and clamps. However, we connect pipe sections, annual dryer vent maintenance will increase the performance of the venting system and reduce the risk of fire or damage.