Unit Heater Ventilation: Dos and Don'ts

Forced air unit heaters, while they do not attach to central heating ducts, still require proper ventilation. HVAC ventilation is important for creating a safe and comfortable indoor environment. Gas fired unit heaters, especially, need vents that lead outside to expel combustion byproducts.

Combustion, the process natural gas heaters use to create heat, produces toxic gases like carbon monoxide. Excess carbon monoxide buildup can have harmful effects, such as air quality contamination and health issues. Properly dispersing it with exterior ventilation is important to avoid these harmful effects.

Consulting a professional HVAC technician for unit heater installations is always the best course of action. However, if you are doing it yourself, here are a few dos and don’ts that will make the ventilation process smoother.

The types of ducts you use to ventilate your unit heater have a major effect on its performance. Different types of ventilation ducts work better in different environments, and certain materials have more benefits than others. The two main types of HVAC duct systems are rigid ducting and flexible ducting.

Rigid Ducting

Rigid ducting is more durable, ideal for larger or more industrial applications. Most rigid ducting uses sheet metal made from either galvanized steel or aluminum. Sheet metal ducts made from aluminum are easy and lightweight to work with and install. Galvanized steel is also popular because it is resistant to rust and corrosion.

Fiberglass and fiberboard ducts are also types of rigid ducting. However, they are porous in nature, meaning mold and bacteria can grow in them. Sheet metal, on the other hand, is nonporous, meaning it is more resistant to contaminant buildup.

Flexible Ducting

Flexible ducting is more lightweight, inexpensive, and easier to install than rigid ducting. Most flex ducting consists of steel wire spirals wrapped in bendable plastic and insulation coating. Their adaptability makes them resistant to corrosion and extreme temperature changes. If you have a more compact space or lots of obstacles to duct around, opt for flexible ducting.

However, flex ducts are susceptible to bends and kinks which can obstruct air flow. Proper installation is important to avoid sharp turns or sagging sections that could cause crumples or cave-ins.

When choosing which type of air ducting you want for your space, it depends on factors such as space availability and size. Larger spaces like warehouses and factories would likely need rigid ducting. Flex ducts are better for more cramped spaces like garages.

Where you place unit heater ventilation, specifically the exhaust fans and ventilation fans, is important. For garage unit heaters especially, the fans need to have open space to expel heat and exhaust properly. Any blockages could disrupt the air balance of your space and even cause those toxic gases to not fully dissipate.

Generally, installing unit heater vents near the ceiling is better for space management. However, because heat rises, putting vents nearer to the floor will circulate heat better throughout a room. But as long as you do not constrain your ducts in a way that could wear on them over time, you can place vents high or low for nearly equal results.

As with all forced air systems, you should make sure that the air flow creates a proper circulation and temperature balance. Especially if you're concerned about the performance of your system, an air balance test will tell you how well it's working.

To conduct an air balance test, all you need is an air flow measuring tool, such as an anemometer or manometer. You can acquire these from most hardware stores and HVAC manufacturers. If you get insufficient readings, install dampers to adjust air flow as needed. Dampers function like valves for your ventilation ducts, controlling the amount of hot air that travels into your space.

Installing an air filter for your ventilation fan is paramount to maintaining clean indoor air quality. Filters catch any dust, debris, or other contaminants that may accumulate in your heater. Regardless of how coated and clean your ducts are, a filter is always a necessary failsafe. If your unit heater ventilation system does not already contain a filter, investing in one is worth the cost.

Oftentimes, ventilation for HVAC systems suffers from inadequate sealing or insulation. This may be because of cost constraints, rushed installations, or faulty materials.

Without sealing and insulating your unit heater ventilation, you will likely face air leakage and heat losses. When you experience leaks and losses, your unit heater will work harder to compensate for it. This uses up excess energy in an endless cycle and will drive up your energy expenses.

Making sure you properly seal your unit heater ducts can save you on wasted heat and energy bill costs. Properly insulating your ducts will also make sure none of that harmful exhaust overheats or leaks into your space.

HomElectrical offers a wide selection of unit heaters with easy-to-ventilate systems. Purchase a unit heater for your garage, warehouse, or workshop and get to installing today!