Does you need cold air return with high efficiency furnace?

This goes to say that high efficiency furnaces have an inbuilt fresh air intake and do not use the air inside your home. They are designed to draw air from the outdoors. That said, you will still benefit from installing a fresh air intake as these intakes improve indoor air quality and also wick excess moisture.

Do you need a fresh air intake for a high efficiency furnace?

Since high efficiency furnaces draw air directly from outside, the furnace itself does not require a fresh air intake in order to replace inside air that otherwise would have been drawn from the room the furnace is located in.

Do all furnaces need a cold air return?

No furnace can adequately operate without sufficient return air supply. We can think of a furnace as lungs. It 'breaths out' hot and it 'inhales' cold air. Air return vents are necessary for the 'inhale' process.

How should a high efficiency furnace be vented?

Proper sidewall venting requires installing separate vent pipes horizontally so that they vent to the outdoors through a wall of your home. These ventilation pipes should be isolated from the furnace combustion chamber and made airtight to eliminate the possibility of combustion gas leakage.

Why do furnaces need cold air returns?

The return registers draw stale air into the ductwork, where it's pulled through the filter to capture dust and debris and then delivered back to the HVAC equipment for reconditioning. However, the most important function of the cold air return registers is ensuring ample airflow through the HVAC system.

Learn about Cold Air Returns

Are return air vents necessary?

Return air vents are an important part of your HVAC system. These vents allow the air that is in your home to return to the system for heating or cooling in order to maintain the proper temperature in the home.

Is it OK to block return vents?

It's important not to block your return air vent because your HVAC system needs constant return air to work properly. Blocked air return ducts will cause your system to lose energy efficiency and cause premature failure of your HVAC system.

What type of venting is used on a high efficiency furnace?

High-efficiency furnaces use sidewall vents for “breathing” in outside air for fuel combustion, and “exhaling” cooled exhaust gases nearly depleted of heat.

How far can you vent a high efficiency furnace?

The maximum vertical distance you can run a furnace exhaust vent is about 15 feet. If there is a forced air inlet within 10 feet of the exhaust vent, the exhaust gas ventilation terminal should be positioned at least 3 feet above it.

Can you vent high efficiency furnace through chimney?

These high efficiency units use PVC pipe to pull air in for combustion and vent the by-products to the outdoors. Your furnace won't exhaust gases into your chimney anymore. Instead, an HVAC contractor will install the system to expel the exhaust directly outside your home.

Does furnace need a return line?

In the rooms (except for bathrooms and kitchens), there should be a return duct for the “return air.” This is air that completes the circulation and returns cool air back to the furnace in return ducts.

What happens if there is not enough return air?

If there is not enough return air available, your HVAC system will not heat or cool properly. They must be properly sized — Return air ducts must be large enough to carry a sufficient amount of expended air back to your furnace, air conditioner, or heat pump.

How many returns does a furnace need?

Having several return vents (ideally one in every room, but even two or three is better than just one) creates consistent air pressure. If you have one return vent, your home is fine. Keep the doors to each room open so air can properly circulate.

Can I add a fresh air intake on my furnace?

Adding a fresh air inlet to most systems is typically a simple and relatively inexpensive proposition. Outside air enters the system through a roof or sidewall vent inlet that collects air from a clean outside location. The air is pulled into the system through a filter, and then a duct connected to the return plenum.

Can you install a high efficiency furnace with only one pipe?

It's perfectly acceptable to have a high-efficiency furnace installed with one pipe.

Can high efficiency furnace be vented through the roof?

If your furnace has an AFUE rating below 90 percent, it will most likely have a flue pipe that goes up through your roof. That's because the combustion byproducts are in a gaseous form, so the gases can float up through the flue pipe and out of your roof.

Can you vent a furnace out the side of a house?

An 80% efficient furnace CAN be side wall vented per National Fuel as Code 7.3. 4 with the use of a “mechanical draft system of either forced or induced draft design”. So what does this mean? You CANNOT just take the vent off an 80% efficient furnace and run it out a side wall.

Can a high efficiency furnace be installed in attic?

High-efficiency furnaces shouldn't be installed in attics because they can get damaged easily when exposed to extreme temperatures.

How many elbows can a furnace vent have?

The design tables for flue sizing assume the flue will have two elbows. If there are more, this could be a possible red flag. Flues can have more than two elbows, but this should be taken into consideration in the design stage.

Why do high-efficiency furnaces use PVC pipe?

Some high-efficiency furnaces also include a plastic pipe for the intake area, and all types use a third plastic pipe to drain away the corrosive condensation resulting from the combustion process.

Does each room need a return vent?

While it is a myth that air return grilles are required in each and every room in the house, it is definitely necessary to have more than one of these grilles installed at strategic places in the house. The most important place to have these would be the bedroom.

What happens if you block cold air return?

In the heating cycle, blocked cold air returns can cause the heat exchanger inside the blower compartment to store too much heat and eventually crack. If the cracks are too large, the furnace can emit carbon monoxide into your home's air.

Can I use flexible duct for cold air return?

Yes, you can use flex ducts for your return air. However, to maximize its usefulness, it needs to conform to technical specifications such as its insulation rating, pressure checks, dust filters, duct sizing and placement, and lastly, the installation requirements.

Where do you put cold air returns?

Cold air returns are located on interior walls in a home, typically close to the floor or low on the wall. You want to make sure that cold air return vents are not blocked or covered by furniture so that your home can get proper air circulation.