How to Vent a Garage Heater?

A natural gas garage heater is one of the most efficient models that you can buy to keep your garage comfortably warm for years to come. Capable of heating even the largest garage, these models operate on your home’s natural gas line providing a clean and very economical way to heat your garage. Since you are tackling with gas lines, most regions require a licensed contractor to make the gas line connections but in order to help you understand how these models work, this article will discuss how to properly install and ventilate your gas-powered garage heater.

Ceiling-mount Garage Heater Installation

Most natural gas garage heaters come with a mounting bracket and are capable of wall or ceiling installation. For safety, you want to select an installation location that is at least 3” from the ceiling and ensure that all objects are at least 3 feet away from the unit. If you are installing a forced-air model, you want to make sure that the blower is aimed at the area of maximum heat loss, usually the garage door, and also ensure that the placement will allow for the air to circulate throughout the garage without any objects blocking the flow path.

Use the mounting bracket to install the heater and allow room to for the gas connection, electrical cord, and vent outlet to feed out of the unit on either the right or left side, depending on your model’s specifications. Since these models run on gas, you’ll need to connect the heater to your home’s gas line. Choose the right sized gas pipe according to the garage heater’s manual. This will ensure that the proper gas pressure is supplied for optimal performance.

Then make the pipe connections, using pipe compound to secure the connections. Once connected, test the line for leaks prior to operating the heater. With your gas connections in place, you’ll now make the electrical connections according to the instructions supplied in your user manual.

You can run your garage heater with a thermostat by running sheathed electrical cable from your circuit breaker box to the thermostat and then from the thermostat to the heater, or you can bypass the thermostat and run the cable directly to the garage heating unit. Once the garage heater is connected to your electrical system, you’re ready for the final step, ventilation.

Venting a Garage Heater through a Roof

Natural gas heaters need to vent their exhaust gases from the units to the outside of your garage. While you might be using a professional to install the actual heating unit and make the required connections to the gas line, you can save some money by installing the vent yourself. One of the most common methods of venting your garage heater is by running the vent through the roof.

To do this, you need a duct that is the same size diameter as the vent flange on your heater. Once you determine the size, you need to calculate the length of duct needed. You can do this by measuring the distance from your heater to the spot in your roof where you’ll be installing the vent. You’ll also need some roof flashing and a vent cap to finish the job, as well as a few tools such as a hammer, reciprocating saw, ladder, metal snips, screwdriver, and plumber’s tape.

To connect the vent to the unit, place one end of the 90-degree duct elbow on the vent flange of your unit and aim the other end towards the underbelly of your roof. Mark where the duct will be inserted into the roof sheathing with a marking pencil and make a circular outline that is the diameter of your duct work on the exposed portion of your roof sheathing. Next, make another circle around this outline that is 1” to 2” larger in order to allow for obstruction-free clearance when inserting the vent duct.

Next, you’ll use your power drill to make several ¼” to ½” pilot holes along the perimeter of your guiding outline. Now, you can use your reciprocating saw to completely cut out the hole in your roof sheathing followed by removing the roof shingles around the hole. Make a hole that is the same diameter in the roof flashing. Next, you’ll install the upper flange of the roof flashing beneath the line of shingles that are over the hole towards the peak of the roof.

Align the hole in the flashing with the hole in the roof to allow for a straight run for the duct work. Once the job is finished, the flashing will be permanent and the seams will be patched. You will now insert the long portion of your duct through the hole in the roof from below until it’s about 24” above the roof shingles. Place the vent cap on the top end of the duct and tighten the set screws with a screwdriver. With the exterior complete, you can finish the rest of the job inside your garage.

You’ll need to measure the distance between the rafters where the duct will go through the roof. Then add about 16” to this measurement. Cut some plumber’s tape and screw one end in on one side of the rafters, wrap it around the duct and adjust the duct until the bottom end aligns with the top end of the duct elbow that is coming out of your heater. Once aligned, secure the other side of the plumber’s tape to the opposite rafter with a deck screw.

Now you’ll measure the distance left between the suspended piece of duct and the open port on your 90-degree elbow. If needed, add another portion of duct and trim it with a hacksaw. Make sure that you are attaching male to female ends so that the two pieces of duct can correctly snap together. Now, you’ll simply pop off the elbow piece, insert the suspended duct into the top port and connect the bottom port back into your heater’s flange.

Then just secure the 90-degree elbow to the flange on the heater by using 1” self-tapping screws along the rim of the elbow. Venting a Garage Heater through a Wall The other solution to ventilating your garage when installing a gas heater is to run the vent duct through the wall of your garage. Some people prefer this method since this option allows you to maintain the integrity of your roof.

You’ll need to same tools as the ones required for a roof vent. The only difference is that you’ll now measure the duct from the heater to the wall you’ll be running the vent duct through, most commonly the wall directly behind the unit.
You’ll follow the same steps as you would if you were installing a roof vent. First, you attach the 90-degree elbow onto the flange of the unit, only this time, you will position it so that the top port of the elbow is aimed at the wall.

Then you need to trace the outline of the vent on the wall and make a larger outline, around 2”, around this tracing in order to allow for easy clearance. You need to cut out the wall next. This means using a drywall cutting knife or reciprocating saw to cut out the circle, clearing out the insulation directly behind the hole, and then smoothly cutting through the exterior of your garage. Next, you’ll insert the vent pipe through the hole from the inside and attach the vent cap.

Some regions require a vent pipe to extend for a certain number of inches, so check with local building codes prior to finalizing this step. You can then seal up the exterior of the wall surrounding the duct or install flashing to ensure that it is weather-resistant. After that, you’re ready to move inside for the rest of the project. Once back in your garage, simply follow the steps outlined in the section above that highlighted how to install a vent through a roof.

The only difference being that now you’ll be running the duct pipes horizontally to the hole instead of vertically through the roof. Natural gas garage heaters are extremely efficient and are perfect for keeping any sized garage warm and comfortable. While the process of installing one of these impressive heaters might seem complicated, once you know how to go about the project, it’s relatively simple. Best of all, once you’re done, even the coldest winter days won’t be enough to keep you out your garage workshop.

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