Shawn Marshall is passionate about the art of venting tankless water heaters.

As East Coast Academy Trainer for tankless water heater manufacturer Navien, Marshall loves to coach contractors on tips and techniques that make their tankless installations safe and fast while ensuring the units perform at their peak.

That training is becoming increasingly relevant as demand for tankless water heaters shows no signs of slowing. With both pros and homeowners becoming more aware of the energy-efficiency benefits of tankless technology, the U.S. tankless water heater market is expected to grow 8.7 percent per year over the next decade, according to Persistence Market Research.

That growth means more contractors and builders are adding propane tankless water heaters to their offerings and installing more units than ever before. For pros who aren’t able to travel for in-person training, Marshall highlighted four key tips pros can use to optimize their tankless water heater venting in our latest how-to video.

1. You don’t have to vent through the roof.

Tankless water heaters have flexibility with both where they draw their combustion air and where they send the exhaust. Power-vent units can draw the combustion air from inside the conditioned space, but they require plenty of free space to draw from. Direct-vent units can save space by drawing combustion air from outside the home, allowing the units to be installed in smaller spaces like a closet or utility room.

And while traditional tank-style water heaters had to use B-vent to send exhaust through the roof of the home, tankless water heaters can vent through a side wall as well because the combustion fan blows exhaust from the units horizontally. That option can save builders and contractors significantly on material costs and installation time.

2. Condensing units can use less-expensive venting.

Condensing tankless water heaters are best known for their efficiency benefits. By using a second heat exchanger to transfer more heat to the water, condensing units can achieve efficiency levels up to .96 in Uniform Energy Factor. That efficiency also carries benefits when it comes to venting. Because condensing units extract more heat from the exhaust, the temperature of the exhaust gas is lower. That means they can be vented with less-expensive plastic materials such as PVC or polypropylene.

Noncondensing tankless water heaters are typically less expensive, but they typically require metal venting to handle their higher exhaust temperatures. Be sure to evaluate whether the savings of a noncondensing unit are offset by the more affordable cost of plastic venting materials.

3. You can reduce penetrations with concentric or common venting.

Reducing penetrations through the wall is a worthy goal of any tankless water heater installation. It can save time for the installer while creating fewer gaps in the building envelope that must be sealed or insulated. One way to reduce penetrations is by switching to a concentric vent pipe, which nests an inner exhaust vent within an outer intake pipe. The result is a faster installation with a more aesthetically pleasing vent termination on the wall.

For projects with multiple tankless units installed together, common venting combines the intake and exhaust pipes into a common header so that each unit doesn’t require its own vent to the outside. These banks of tankless water heaters can also be set up to communicate with each other to ensure they have equal run time — and to ensure the remaining units take over if one unit goes down for maintenance.

4. Outdoor installations can be fast and attractive.

If you’re in a state where freezing temperatures are rare, consider installing the tankless water heater outdoors. Most models designed for exterior installation include freeze protection in cases where winter temperatures do get frosty. Installers can make these installations more attractive with recess boxes designed to hide the tankless water heater out of sight.

With outdoor installations eliminating the need for venting, they can be an option that saves space on the interior, reduces material cost, and saves on installation time.

Check out the entire video below and share with your construction team to ensure you’re taking full advantage of tankless water heating’s flexible venting capabilities.