Why Changing Your Air Filters Matters — And Why MERV 11 is the Smart Choice for Ottawa Homes By Clockwork HVAC | Indoor Air Quality Experts in Ottawa

Apr 12

Your HVAC system does more than just keep your home warm in the winter and cool in the summer—it also plays a major role in your indoor air quality. One of the simplest and most important things you can do to maintain your system’s performance and your family’s health is to change your air filters regularly.

At Clockwork HVAC, we recommend MERV 11 filters for most Ottawa-area homes. Why? They strike the perfect balance between filtration and air flow—especially in a city where we deal with everything from winter dust and dry air to summer pollen and smog.

Why Changing Your HVAC Filters Matters

Your furnace or air handler circulates air through your home several times a day. Every time it runs, it pushes air through a filter designed to capture dust, dirt, allergens, and other airborne particles.

When that filter gets clogged, a few things happen:

🧾 Your energy bills go up — A dirty filter makes your system work harder to pull air through.
⚠️ System strain increases — Over time, restricted airflow can cause overheating or early breakdowns.
🤧 Air quality worsens — A full filter can’t trap allergens or pollutants, which recirculate through your home.
🦠 Mold and bacteria can build up — Especially in damp basements or older ductwork.

When to Change your Filter

Our standard recommendation is that standard 1” inch filters should be replaced every month, and 5” filters should be replaced approximately every 6 months, however, this is just a guideline.

Use a felt tip marker to write the date you changed the filter on the cardboard side of the filter. This way, when you go back to change your filter, you know exactly how long it has been. Every home is different, some homes have more dust, some homes have less. Especially if we children tracking mud and crumbs all over the home, or pets shedding hair everywhere. We may have a drier home or a more humid home. So these guidelines may be different for your individual family and home.

When you remove the filter, hold it up to a light. If light can pass through, air can pass through. If no light is able to pass through than you are not getting adequate air flow and this can lead to furnace failure. If the filter was significantly dirty since the last time you changed, you should replace your filter more frequently. On the flip side, if your filter was very clean, you can wait a longer period before replacing your filter again.

Don’t Forget to Check Your Filter Size

Not all filters are created equal. Be sure to check the size of your current filter (it’s usually printed directly on the side of the existing filter) before buying a replacement. If you're unsure what size or MERV rating is best for your system, give Clockwork HVAC a call—we’re happy to help.

What Is a MERV Rating?

MERV stands for Minimum Efficiency Reporting Value. It’s a scale from 1 to 16 that rates how well an air filter captures particles of different sizes.

Lower MERV (1–4): Basic filtration (large particles like lint, dust)
Medium MERV (5–8): Captures mold spores, pet dander, and some pollen
MERV 11–13: Traps finer particles like smoke, bacteria, and smaller allergens
MERV 14–16: Hospital-grade filtration, but may restrict airflow in residential systems

Why We Recommend MERV 11 Filters

MERV 11 filters are ideal for most Ottawa homes because they offer superior filtration without blocking air flow for your HVAC system. They’re a great middle ground between performance and airflow.

Here’s what MERV 11 filters remove:

✔️ Dust mites and household dust
✔️ Pollen and mold spores
✔️ Pet dander
✔️ Smoke and smog particles
✔️ Some airborne bacteria and viruses

When you have fluctuating air quality and large climate changes throughout the year, MERV 11 filters help protect both your indoor air and your HVAC investment.

Who Should Definitely Use MERV 11 Filters?

We especially recommend MERV 11 filters if:

✅ You have pets
✅ You or a family member suffers from allergies or asthma
✅ You live near high-traffic areas or construction zones
✅ You want cleaner, healthier air throughout your home

Even if none of these apply to you, using a MERV 11 filter will still improve air quality—and you’ll notice less dust buildup on surfaces, too.

Final Thoughts: Small Change, Big Impact

Changing your HVAC filters is a small task that has big benefits. It improves energy efficiency, extends the life of your heating and cooling system, and helps everyone in your home breathe easier.

And if you’re looking for the sweet spot between filtration power and system performance, MERV 11 filters are hard to beat—especially in a variable climate like Ottawa’s.