Calgary winters are brutal on your home. The cold, dry air drives humidity levels down, leaving you with cracked skin, sore throats, and static shocks every time you touch a doorknob. A humidifier seems like the obvious fix, and for your comfort, it often is.
But there is a side to humidifiers that most Calgary homeowners do not think about: what all that extra moisture does to your roof. As a local roofing company that has seen the damage firsthand for years, we want to walk you through the risks, the root causes of dry indoor air, and smarter ways to solve the problem without putting your home at risk.
4 Ways Humidifiers Can Harm Your Roof
When you run a humidifier, that moisture does not just stay in your living space. Warm, humid air rises and finds its way into your attic through gaps, light fixtures, plumbing penetrations, and attic hatches. Once there, it meets the cold underside of your roof deck. Here is what happens next:
- Attic rain and roof damage: Excess humidity condenses and freezes on the underside of your roof sheathing. When temperatures rise, that ice melts and drips down, a phenomenon Calgary homeowners know as attic rain. Over time, this causes rot, mould, and structural damage to your roof deck.
- Increased risk of leaks: Repeated moisture exposure degrades shingles, flashing, and other roofing materials from the inside out. This accelerates the risk of roof leaks and water damage to your ceilings and walls.
- Insulation damage: Wet attic insulation loses its effectiveness. Fibreglass batts that absorb moisture compress and clump, drastically reducing their R-value. That means higher energy bills and a less comfortable home, which is the opposite of what you wanted from the humidifier in the first place. Proper insulation and ventilation is essential.
- Shortened roof lifespan: The freeze-thaw cycle caused by excess attic moisture accelerates the aging of your roofing materials. What should have been a 25-year roof can start failing much sooner when it is constantly exposed to moisture from below.
The Health Benefits Are Real, But Balance Matters
Before we go further, we want to be clear: humidifiers are not the enemy. Dry air in Calgary winters can aggravate respiratory issues, dry out your skin, cause nosebleeds, and make sleeping uncomfortable. A humidifier can genuinely improve your quality of life during the coldest months.
The key is balance. You can maintain healthy indoor air without cranking humidity levels up to a point where your home starts to suffer. With proper maintenance and the right settings, a humidifier can be a helpful addition to your home without compromising the integrity of your roof.
The question is: why is it so dry in the first place, and can you address that root cause instead of just treating the symptoms?
Why Calgary Homes Get So Dry in Winter
Do you find yourself constantly dealing with dry skin, chapped lips, and nosebleeds? Are you getting static electricity shocks around your home? These are all signs of low humidity levels.
Calgary’s winter climate is one of the main culprits. As temperatures drop well below zero, the outside air simply cannot hold moisture, and humidity levels plummet. When your furnace kicks on to heat the home, it further dries out the indoor air. This is especially true if your home has poor air sealing, allowing cold, dry air to constantly infiltrate and replace warmer air.
Instead of just masking the problem with a humidifier, it makes sense to understand and address why your home is losing moisture in the first place.
Address the Root Cause: Improve Insulation and Air Sealing
The most effective long-term fix for dry indoor air is to stop cold air from getting in. When your home is properly sealed and insulated, your heating system does not have to work as hard, and the air inside retains more of its natural moisture. Here are the most common areas where cold air infiltrates Calgary homes:
- Doors and windows: Check for gaps around frames, worn weatherstripping, and failing seals.
- Attic: Look for gaps or holes in the attic floor, around plumbing stacks, and in the insulation itself. This is also where proper roof ventilation plays a critical role.
- Basement: Check for gaps in the foundation and around pipes and ducts where they penetrate walls.
- Wall outlets and light switches: These are often sources of air leakage, especially on exterior walls.
- Fireplaces and chimneys: Open dampers and unsealed surrounds let cold air pour in.
Finding the Leaks
A thermographic camera or professional energy audit can pinpoint exactly where cold air is entering and heat is escaping. If you are buying a home, having a professional inspect the building envelope before purchase can save you from inheriting expensive problems.
By addressing these root causes, you can improve your indoor air quality and humidity levels naturally, without relying on a humidifier. If you still want the comfort of a humidifier after air sealing, you can safely set it much lower.
The Real Danger for Calgary Homeowners: Attic Rain
The biggest risk for Calgary homeowners running humidifiers is attic rain. It is a well-documented problem in our climate, and CBC has reported on its growing prevalence across Calgary.
Here is what happens: moisture from humidifiers, cooking, showers, and everyday living rises into the attic. In Calgary’s extreme cold, that moisture freezes on the underside of your roof sheathing. When a warm spell or chinook hits, the ice melts all at once, and water drips through your ceiling. The result is stained drywall, damaged insulation, mould growth, and potentially costly structural repairs.
Many homeowners do not realize the connection between their humidifier settings and the water stains appearing on their ceiling weeks later. The damage often goes unnoticed until it becomes a major problem. This is also one of the most common winter roofing problems we see in Calgary.
How to Protect Your Calgary Home from Humidity Damage
You do not have to choose between comfort and protecting your roof. Here is what we recommend to Calgary homeowners:
- Fix the air sealing first. Address gaps and insulation issues before relying on a humidifier. This solves the dry air problem at the source.
- Keep humidity at 20 to 25 percent. If you do use a humidifier, keep it at this range. According to the Alberta New Home Warranty Program, this is the recommended level for Calgary’s cold climate. Going above 30 percent in winter significantly increases your risk of attic rain.
- Use exhaust fans properly. Run bathroom and kitchen fans during and after showers and cooking. These are major sources of indoor moisture that many homeowners overlook.
- Check your attic ventilation. Make sure your soffit vents, ridge vents, or roof vents are not blocked by insulation or debris. Good roof ventilation allows moisture to escape before it causes problems.
- Get a roof inspection. If you have been running humidifiers at high settings, it is worth having a professional check your attic for signs of moisture damage. Getting your roof winter-ready includes checking for these issues.
Frequently Asked Questions
Can a humidifier cause mould on walls?
Yes. When indoor humidity is too high, moisture collects on cold surfaces like exterior walls, window frames, and corners with poor air circulation. This creates the ideal conditions for mould growth. In Calgary, where the temperature difference between indoors and outdoors can be extreme, even moderate humidity levels above 30 to 35 percent can lead to condensation and mould problems.
Can a bad roof cause high humidity in my home?
It can contribute to it. A roof with poor ventilation traps moist air in the attic, which can work its way back into your living space. Damaged or missing shingles can also let rain or snowmelt seep in, raising moisture levels. If you suspect your roof is contributing to humidity issues, a professional roof inspection can help identify the problem.
Should I use a furnace humidifier in Calgary?
Whole-home furnace humidifiers can be effective, but they need to be set carefully. The same rules apply: keep humidity between 20 and 25 percent during cold snaps, and ensure your attic is properly ventilated and insulated. A furnace humidifier set too high will push moisture throughout your entire home, including into the attic, making the risks even greater than a single-room portable unit.
What humidity level should I set my humidifier to in Calgary?
During Calgary winters, aim for 20 to 25 percent relative humidity. When temperatures drop below minus 20 degrees Celsius, you may need to go even lower. The colder it is outside, the less moisture your home can safely hold without condensation forming on windows, walls, and in your attic. A basic hygrometer (available at any hardware store for under twenty dollars) can help you monitor levels.
Need Your Roof Inspected?
If you have been running humidifiers in your Calgary home and want to make sure your roof has not been affected, we can help. Our team inspects attics and roofing systems for moisture damage, condensation issues, and early signs of attic rain. Contact Whalley’s Four Seasons Roofing to schedule an inspection.
