Best Practices for Boiler, Furnace and Hot Water Heater Vent Screens

When it comes to high efficiency appliances, there’s a right way to protect intake and exhaust vents along with many incorrect ways. If you protect your PVC intake and exhaust vents correctly, your vents will be guarded from all seasonal threats while maintaining adequate airflow for clean combustion cycles during all-seasons and temperature ranges. If you protect your intake and exhaust vents the wrong way, as many consumers often do, you risk having inadequate protection, a substantial loss in energy efficiency during the winter or even more severe problems. Because so many people overlook the purpose of their vents when purchasing vent protection products, we’ve taken the time to highlight some of the most important features you as a consumer should be looking for in a vent protection product. If you have a high efficiency boiler, furnace or hot water heater, we encourage you to read this entire best practices page to better understand the importance of a debris-free ventilation system and how inferior vent protection products can cost you hundreds or even thousands of dollars in the long run.

PVS Series Vent Screens for Boilers, Furnaces and Hot Water HeatersThe Need to Maintain Adequate Ventilation

High efficiency boilers, furnaces and hot water heaters earn their superior energy star ratings because they are able to extract more heat from an efficient and clean combustion cycle. To maintain a clean flame burn, the appliance requires an adequate source of fresh air and the ability to discharge spent gas from the combustion process through the exhaust pipe to the outside of the dwelling. High efficiency appliances also utilize sensors and switches, which are monitored by the control board, to maintain both efficiency and ensure their safe operation. This is very similar to having a proper air to fuel mixture in automobiles, which is monitored by an ECM (computer), so the vehicle may run properly and achieve optimal gas mileage. Using an inferior vent protection product, especially during winter, can impact appliance efficiency that may result in higher utility bills among other more serious problems. Though inexpensive vent screens are available, in reality the cheaper vent screens often cost much more in the long run as they are so restrictive during winter that they impede an appliance’s performance (incomplete combustion) when demand is at its peak. In fact, many vent screens being sold don’t even advertise their airflow capacity because they are so restrictive. The ability of any vent protection product to provide ample airflow, especially during winter, must always be the first priority in any vent screen purchase. Because of the need for airflow, which greatly increases in below freezing temperatures, we prefer to use a two screen solution (pictured above) for trouble-free and complete all-season PVC ventilation system protection.

Understand All Ventilation System Threats

Wasp Nest in Furnace ExhaustAny large and unprotected exterior opening that leads into the inside of a home or business is a potentially expensive problem waiting to happen. While some regions of the country experience temperatures that are above freezing all year long, other regions experience frigid winters. As seasonal temperature changes occur, so do the threats to open intake and exhaust vents. During spring, summer and early fall insect activity adds to the always present risk of debris and animals entering vents. Unfortunately rodent screens do not provide protection against insects and smaller debris, though many people believe they are “safe” using just a rodent screen or that they will never have a problem with insects until they get hit with a repair bill. While an animal entering a vent can lead to expensive repair bills, insects can be even more costly to remedy. Yellow jackets, for example, can nest within furnace intake and exhaust pipes just as the nest pictured to the left. If you’re interested in watching how this nest was discovered, and the repair cost, you can watch the scope video here. Active nests inside a furnace cabinet may require remediation by a licensed exterminator and a follow-up visit from a HVAC technician, which can be quite costly. In some cases, the total cost to fully recover from insect damage can exceed $1000.00 when large active nests must be removed from inside a sealed furnace cabinet. One misconception that many have is that a fine/close mesh vent screen is needed to protect against mice, when in reality a mouse needs an opening about the size of a nickel to squeeze through. Please view Fairfax County Health Department’s controlling rats and mice PDF brochure (opens in new window) for additional details. A nickel measures .835″ in diameter while our PVS-RS series rodent screens maintain 90% airflow with a .478″ opening. Even a much smaller dime can’t fit through the openings on our PVS-RS series vent screens, nor can mice, chipmunks, birds and other animals that often invade ventilation systems.

Consider Seasonal Challenges

When temperatures drop below freezing, air becomes denser and the condensate from condensing exhaust vents can freeze on vent screen wires. Since insects are not an active threat when temperatures are below freezing, it is important to use a wide mesh vent screen on both intake and exhaust vents during winter. With a wide mesh vent screen in use during winter, the likelihood of any freeze-over is greatly reduced/eliminated while still maintaining maximum airflow even when cold air becomes dense. As a general rule of thumb, those that must turn off the outside water to their homes and businesses should also be changing vent screens for the season. While our PVS-IS series vents screens protect against insects (ants, bees, wasps, etc.) and animals when temperatures are above freezing, our PVS-RS series rodent screens provide an industry leading airflow rate of 90% for use during winter in the coldest regions of North America. On a 90% airflow PVS-RS series vent screen, it is common to lose 2-3% airflow because of condensate freezing on the exhaust screen during very cold temperatures, which then melts during the next heat cycle and the process repeats itself. Since finer mesh and thicker wire screens have more surface area for condensate to collect and freeze on, the airflow loss from frozen condensate can be more substantial and may even lead to an appliance shutting down in safety lockout.

Rust Stains on Furnace Concentric VentVent Screen Construction

Most high efficiency appliance manufacturers require that vents be terminated with a PVC hub. Vent screens that fit around the outside or extend beyond the termination hub are more likely to collect debris. Additionally, these types of vent protection products often require they be attached with adhesive or by drilling into the PVC termination hub itself. When installed, these types of vent screens likely have permanently altered the termination hub and are difficult or impossible to service. Another problem with cheap vent screens is oxidation. Inferior materials can oxidize so badly that the screens begin to disintegrate and eventually fall out, leaving the vent unprotected. As you can see in the furnace concentric vent pictured to the right, oxidation from an inferior vent screen also leaves permanent and unsightly stains on the white PVC. This oxidation process is accelerated on exhaust vent terminations since exhaust gases are mildly acidic. Vent screens are made from many materials, from highly restrictive inexpensive plastic to more costly premium grade 316 stainless steel. Since plastic screens are too restrictive for vents, and become brittle and eventually break, they should always be avoided. OEM supplied galvanized screens should also be avoided as they are known to rust, stain PVC and fall out after just a few years of use. Especially if you have children playing in the yard, you don’t want a child to find a rusty galvanized steel screen by stepping on it. Because of corrosion concerns, we utilize only non-corrosive materials in the construction of our PVS series vents screens. Both the 316 stainless steel screen, meeting ASTM E 2016-11 and UNS S31600 standards, and 6061T6 aluminum shell are both durable and are highly resistant to corrosion. Since our PVS series vent screens are designed to fit inside PVC termination hubs and couplings, the screen is hidden from view and does not protrude from a vent where debris could otherwise collect on it and create a partial or full blockage.

Ease of Installation and Serviceability

As noted previously, some vent screen models must be installed with either screws or an adhesive. Though screws can be removed, they leave permanent holes inside intake and exhaust vents. Adhesives, or cement welds, often cure with a permanent bond and the termination hub must be cut off and replaced if the vent screen needs to be removed. For this reason, we prefer using internal wire clips to secure our PVS series vent screens in place, and we provide one internal wire clip for each vent screen we sell. Not only can the stainless steel internal wire clips be reused for many years, but they also allow for easy seasonal vent screen changes between PVS-IS and PVS-RS series vent screens.

In closing, professional HVAC technicians, plumbers and pest control specialists understand the ventilation needs of high efficiency appliances are not met by just any vent screen. Because high efficiency appliances rely on sensors that monitor the efficiency and safe operation of the appliance, it is important that the appropriate vent screens are used to balance the needs of the appliance with exterior threats that include animals, debris and insects. The PVS series vent screens accomplish this balance and are universally used to protect many different OEM boiler, furnace and hot water heater installations with superior results. It is our hope the best practices we have discussed on this page serve as guidelines when you purchase or use any vent protection product. If you need help with sizing your boiler, furnace or hot water heater vent terminations, please visit this page (includes pictures and video). In our store you will find all of our stocked PVS series vent screens and SVC series vent caps.

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