ice build up

What to Do if Ice Builds Up Around Your High-Efficiency Furnace Intake and Exhaust Vent

Calgary homeowners know that the wintertime requires some diligence to avoid costly and inconvenient maintenance issues. If your furnace quits when it’s -25°C outside, it’s not only uncomfortable and inconvenient – it can pose a danger to residents and damage household infrastructure.

One of the most common causes of winter high-efficiency furnace shutdowns is the build-up of ice and snow in-and-around your furnace intake and exhaust vent terminations outside your home. Luckily, with a little know-how, you can handle this situation with ease.

What is furnace intake and exhaust venting?

All high-efficiency furnaces have an exhaust vent pipe that moves the exhaust gases generated by your furnace outside your home (learn exactly how your furnace works in our Furnace 101 blog). Also, some high-efficiency furnaces have a combustion air intake pipe that draws fresh air from outside directly into your furnaces for combustion. If your furnace has a combustion intake in addition to an exhaust vent, they will be located side by each on the exterior of your house.

In most cases, the furnace exhaust and intake terminate on the side of your home, usually on the same side of your home as your furnace room. In some cases, these intake and exhaust pipes vent up through an existing furnace chimney chase and can be seen on the roof.

The intake and or exhaust will be easy to spot on the side of your house. They are 2-3” diameter plastic pipes, in most cases white in colour, and will have a short section (the termination) exposed outside, to direct the furnace exhaust gas away from your home.

During cold weather, you will notice water vapor and exhaust gas coming from the exhaust vent pipe while the furnace is running and there will generally be a large piece of ice directly under the exhaust vent. The intake vent pipe (if your home has one) will generally not have any ice build-up directly under it but on cold and snowy days you may notice snow forming around the vent termination.

The dangers of exhaust and intake vent ice build-up

If the intake or exhaust vent is partially blocked with snow or ice, airflow will be restricted to/ from your furnace. Sensing reduced airflow your high-efficiency furnace has integrated safety devices, called Pressure Switches which will prevent the furnace from starting up (if you notice that your furnace is down and can read the furnace error code as ‘Pressure Switch’ related, the first thing to check is for a blockage in your furnaces intake or exhaust venting).

The impact to you is that your furnace will stop working wither periodically or entirely, depending on the degree of blockage.

The causes of ice build-up and how to prevent them

Condensation is the number one culprit for vent freezing. As warm air and steam exits from the exhaust port, a cone of ice can begin to form under it from the ground up. This is usually harmless and can be quickly fixed by knocking the ice down before it connects with the exhaust port.

When a furnace combustion intake vent is located immediately beside an exhaust vent, a portion of the moist exhaust gas can be drawn back into the furnace through this intake pipe. Over time, this moisture can condense and form faceted snow inside the intake vent pipe, eventually blocking it.

Heavy snowfall or blowing snow accumulations can also build up, and cover the exhaust and intake vent terminations.

In other cases, regular and more serious freezing can occur from improperly installed or compromised exhaust pipes (the pipes that carry the exhaust air from your furnace to your exhaust port). To prevent this, your furnace installer should ensure that intake and exhaust vent pipes are properly sloped with grade back toward the furnace, supported, and installed with as short a distance between your furnace and the intake/ exhaust termination as possible with the fewest number of elbows. The exterior vent placed must be placed at a minimum height of 18” above the ground – allowing adequate space in the event of heavy snowfall. All new furnaces must be installed and vented to meet current Canadian building code requirements, which require System 636 Vent Pipe. Early high-efficiency furnace installation may have older PVC vent pipe and not meet today’s code, and therefore may be more prone to cold-weather venting issues.

Another cause…uninvited guests

Another reason a vent may become blocked is due to animals seeking refuge from the cold. Occasionally birds or squirrels are attracted by the warmth. They’ll build nests or take shelter in your vent during the summer months when your furnace is not running. When the weather changes and your furnace fires up for the first time in the fall, the restricted airflow from animals and nests, which prevents the furnace from operating.

How to handle blocked intake and exhaust terminations

A furnace vent that has been blocked by snow or ice can usually be fixed by clearing the opening. Intake vent pipes are usually not fully frozen, rather just clogged with snow and can be cleared with hands or a flexible rod. Remember, it is unlikely that the blockage will extend further than the point at which the venting penetrates the side of your house.

If ice is frozen in the pipe, you can also try using a hairdryer to heat the intake or exhaust terminations to melt the blockage and clear the obstruction. The best advice is to call a furnace professional. This way you avoid the risk of accidentally damaging the exhaust.

If blockages and full pipe freezes happen regularly, it may be a sign that a vent exhaust was improperly installed or requires replacement. Contact a professional furnace installation company to help.

Make an inspection a regular part of your week

One of the easiest ways to prevent ice build-up and the difficulties that come with it is to make regular checks a part of your weekly winter routine. Put a reminder in your calendar to check your pipes every few days during winter months or make a mental note during cold snaps to check on your exterior furnace vent terminations.


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Furnace & Duct Cleaning Checklist




Quote guarantee

When we receive an online furnace or air conditioning quote request and the customer accepts the initial quote, we’ll send a comfort advisor to confirm the provided information and quoted price in person. 


If the comfort advisor finds any inaccuracies during the in person visit, we’ll revise the quoted price on the spot. After the quoted price is confirmed with an in person visit, the price is set. 


If there are unforeseen complications on the date of install, Advanpro will not pass the additional costs along to the customer. (See exceptions in Terms below.)



The guarantee is not valid if the customer provides inaccurate information when Advanpro seeks to confirm any information about the quote. This also applies to the on-site confirmation visit. 



In the exceptional circumstance that the chimney liner required for most furnace installations cannot be installed or gets stuck during installation, the guarantee no longer applies and we will provide a supplementary quote to complete installation. 


We do not warranty or guarantee customer-supplied thermostats.

Repair guarantee

If the diagnosed issue is not fixed by our initial repair, we will dispatch the first available service technician to return and fix it at no additional cost.


If we determine that there is an additional unrelated issue, there may be a charge for the additional repair.

Correct A/C sizing guarantee

If the air conditioner Advanpro installs is determined to be improperly sized for your home, we will supply and install the correctly-sized A/C condenser at no additional cost. 


Advanpro must be immediately notified of any install issues. The guarantee applies for 3 months, starting from the installation date. The guarantee no longer applies if, at any time after the quote or installation, modifications are made to the home that impact cooling requirements.

Correct furnace sizing guarantee

If the furnace Advanpro installs is determined to be undersized for your home, we will supply and install the correctly-sized furnace at no additional cost. 


Advanpro must be immediately notified of any install issues. The guarantee applies for 3 months, starting from the installation date. The guarantee no longer applies if, at any time after the quote or installation, modifications are made to the home that impact heating requirements.

Hot water tank types

Natural draft or atmospheric vented hot water tanks have a 3″ – 4″ steel vent pipe, which runs to a vertical chimney. The chimney is usually shared with standard or mid-efficiency furnaces.


Power vented hot water tanks have one or two black or white plastic vent pipe(s), which are 2″ – 3″ in diameter. The vent pipes usually exit from the side of the house.

A/C Tune Up

Regular preventative maintenance improves efficiency and extends the lifespan of your air conditioning system, with the following benefits:


  • Reduced electricity bills and operating costs. When the unit operates as designed, electricity usage is reduced.
  • Maximized cooling capacity. Home comfort on the hottest of days with minimum run time.
  • Minimized repair bills. Detect and fix small problems before they get worse.

HRV Cleaning

In Calgary, all homes built in 2016 or later have a Heat Recovery Ventilator (HRV). Some homes built or renovated after 2013 may also have an HRV. 


An HRV efficiently replaces stale indoor air with fresh outdoor air, all year round.


As with any other air-handling equipment in your home, your HRV should be cleaned regularly to ensure the best possible indoor air quality.


If you aren’t sure if you have an HRV, call our team to find out how you can tell.

Duct Work Sanitizing

If you or your loved ones suffer from respiratory issues or allergies, or you’re concerned about the quality of the air that you are breathing, then our sanitizing treatment will give you the reassurance that your ductwork is sterile and free of debris that could negatively impact your respiratory and overall health.


Microban is our hospital-grade sanitizing solution, which kills 99.99% of germs, viruses, funguses, molds, and other pathogens.


We also offer Benefect, an all-natural sanitizer made from plant extracts, which also kills 99.99% of germs, viruses, funguses, and molds. ​

Exhaust Flu Stack Cleaning

Mid-efficiency furnaces produce a sand-like, mildly-corrosive byproduct. This substance condenses in the exhaust flu stack and collects over time near the inducer/venter motor, restricting exhaust gas flow. Eventually, it enters the inducer motor and causes premature wear on the furnace.


Exhaust flu stack cleaning removes the build-up to reduce the chance of motor failure and maximize the life span of your furnace. Preventative maintenance ensures your furnace runs efficiently all Winter long — without costly no-heat emergencies. 

A/C + High-efficiency Bypass

The secondary heat exchanger in a high-efficiency furnace or A/C coil has delicate, closely spaced fins that must be protected during your furnace and duct cleaning.


For furnaces that require a bypass, we temporarily install a filter above the heat exchanger or A/C coil, and position our duct vacuum above the filter.


This bypass procedure prevents damage by ensuring all dust and debris in your supply duct work is collected before reaching the heat exchanger or A/C coil.


Standard furnaces without A/C don’t have secondary heat exchangers or A/C coils and don’t require the bypass procedure.

Furnace Tune Up

Regular furnace tune ups are essential to maximizing the lifespan and efficiency of your furnace, so you can rely on it to keep you warm all Winter long.​


During our 30+ point inspection, we check all furnace systems to identify components that are worn out and need replacement. Replacing parts before they break — preventative maintenance — maximizes heating efficiency, avoids no-heat emergencies, and saves on costly service calls. 


Home furnaces can last for 20 years or more if well-maintained. A professional furnace tune up every two years helps to preserve your investment for decades.

Reverse Octopus Whip Tool

The reverse octopus whip has eight 16” flexible tentacles, which whip around blasting high-pressure air in all directions as it moves through your duct work.


The tool agitates and dislodges the most hard-to-reach dust, debris, and contaminants, moving them toward our duct vacuum for collection and disposal.

Brush Cleaning Method

Our high-speed rotary brushing equipment sweeps the entire interior surface of your duct work, ensuring that all dust, debris, and pet hair are vacuumed away.


Physically cleaning the entire length of your duct work ensures that no contaminants are left behind, increasing your indoor air quality and peace of mind.

Dryer Vent Cleaning

Dryer fires are a top-five cause of house fires. Cleaning your dryer vent regularly greatly reduces the chance of a dryer fire, plus the following benefits:


  • Reduces clothes drying times
  • Lowers utility bills through greater efficiency
  • Extends the life span of your dryer
  • Lessens the amount of allergens in your house

Back Skipper Tool

The back skipper is a 1” diameter rounded ball connected to a long, flexible high-pressure airline.


The 1” ball has jets that discharge high-pressure air, pulling the tool and airline through the length of your duct work.


The high-pressure air moves the dust and debris toward our duct vacuum, where it is collected for disposal.​