Everything you need to know for maintaining your home.

Maintenance Manual


Navigating Calgary’s weather can be complex – that’s why we crafted a guide to help prepare your home for Calgary’s
unique winter season. Included is a comprehensive winterization checklist for both the exterior and interior of your home, furnace maintenance protocols and much more.

Understanding Attic Rain and Its Occurrence in Alberta:

Attic rain is a natural occurrence, especially in regions like Alberta, where temperatures can swing dramatically between cold and hot conditions. This phenomenon happens when heat and moisture from everyday activities in the home rise into the attic and turn into frost in freezing temperatures. When it warms up, this frost melts, potentially causing attic rain. While it’s impossible to completely prevent attic rain due to these natural temperature fluctuations, homeowners can take several precautions to minimize its impact and prevent damage to their homes.

Possible Solutions to Avoid Attic Rain:

  • Adjust Humidifiers: Keep indoor humidity below 20% during freezing temperatures.
  • Use Ventilation Fans: Reduce window condensation by using ventilation fans.
  • Utilize Bathroom Fans: Always turn these on during showers or baths.
  • Open Drapes or Blinds: This helps warm air circulate and prevents ice buildup.
  • Manage Window Ice: Wipe off any ice or moisture on your windows.
  • Turn On Kitchen Fans: Use these when cooking to control moisture.
  • Promote Air Circulation: Keep doors open throughout the house for better airflow.
  • Avoid Indoor Air Drying: Don’t air dry clothes indoors in cold temperatures.
  • Maintain Adequate Heating: Keep your home warm, especially at night.
  • Extra Measures in Extreme Cold: Below -25°C, YOU MUST continuously run your home’s ventilation, bathroom, and kitchen fans.

In Alberta, where temperature shifts are common, these steps are particularly crucial to mitigate the risk of attic rain and protect your home from potential water damage.

What is Attic Rain?

During periods of extended cold weather, frost accumulates in the attic as a result of holes and pressures allowing air to enter the attic. Once the weather becomes warmer causing the air to be warmer and/or the sun to be able to shine on the bare shingles, the accumulated frost melts rapidly, in the attic or walls raining down into the insulation and on occasion leaving stains and water dripping from lights. This is known as Attic Rain.


• Frost can be seen accumulating around the air leakage area in your attic during cold weather

• Most commonly occurs throughout the entire attic
• High interior relative humidity exacerbates the issue

During times of extreme temperature swings Attic Rain can occur. It is not to be of a concern if small amounts of condensation or frost are present in attics and inside walls as they sublimate prior to melting, this is a common occurrence. This can be identified most commonly by exterior cladding stains but will also cause leaks inside lights or windows and ceiling stains.

In older homes chimney’s which acted as “B” vents to allow hot combustion gases to exit can be found in older homes which is why this problem rarely occurs for those old homes, unless they have a new furnace or additional insulation added, but can be seen more frequently in newer homes, renovated homes as well as homes with upgraded furnaces. While exiting through the B vent warm gases create negative interior pressure allowing cold, low vapour, outdoor air to be suctioned into the building drying any moisture. As a result, older homes would be able to have big holes because of the moisture being able to dry with the furnace running.

Newer homes use a seal combustion system which does not require a chimney. This system does not allow for any pressure change due to there being a sealed pipe connecting to the furnace for combustion air and a sealed pipe for exhaust. This new system creates positive pressure and with the added insulation in new homes it eliminates radiant heat loss needed to absorb the moisture, this excess warm air is required to absorb the moisture in the attic. To eliminate the moisture in new homes you will need a fresh air intake in the returning air ducting for the home to be ventilated, which will allow for negative pressure change inside the home while the furnace is running, forcing the air outward.

Due to this new homes can only have a limited number of holes as they would otherwise require the switch under the thermostat labeled “Ventilation Fan” to be always running. The Ventilation Fan allows for the movement of air to be equal coming inside and exiting the home stabilizing the pressure created and in most cases being able to help mitigate the issue of attic rain. All new homes have Heat Recovery Ventilator (HRV) that operates by balancing the pressure inside the home as a regular ventilation fan, but also heating the new air entering allowing you to save the extra money.

It is important to note is not a result of having lack of ventilation or roof vents, VENTILATION WILL NOT STOP ATTIC RAIN, BUT VENTILATION WILL HELP DRY THE ATTIC AFTER. If the attic is over ventilated it can become more damaging as a result of more air being transferred into your attic from your house by the wind.

How To Fix Attic Rain

The first step to resolving the attic rain issue would be identify the areas allowing air leakage in the attic. This can be done by using an infrared camera. You will be able to spot the areas allowing cooler air by depressurizing the home and as a result of the negative pressure the movement of air will display the colder air on camera. The areas can than further be verified by wetting the back of your and having it placed next to the suspected area of opening. During the warmer seasons the air entering may be warmer as a result of the weather conditions. Once identified the holes can be sealed. No issues of concerns should be present if the total openings into the attic can be kept less than 4 square inches in total as long as interior pressures not
abnormally high. Pot lights and bathroom fans are the most commons areas leaks will be present in any case of attic rain. The second step will be to, with the help of a diagnostician, identify and stabilize any unequal interior pressures. You will need to test the mechanical system as the furnace runs both with the ventilation fans off and on. Each room will need to be tested to see if there is insufficient air return to the furnace and measures will need to be taken to adjust pressure accordingly such as a using a undercut door or a transfer grill.