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Humidity & Your House

By Mike Holmes

Mike’s Advice / Home Safety & Maintenance

Monday, March 18th, 2019 @ 12:11pm

You’ve done your research on the best builder in your area. You’ve checked out their work, you have had many, many conversations with them and you know that they believe in using the best materials. They build above minimum code and they build energy efficient, healthy homes. CONGRATULATIONS! Sounds like you bought a home that will last. You’ve made the right investment.

If you’ve purchased a Holmes Approved Home, your home was built to be strong, healthy, sustainable and energy-efficient. This Holmes Approved Homes Certification Binder is proof of that. It’s your record of the investment you made and the true value of your home.


The Importance of Home Maintenance

When problems start happening in the home most people want to blame something or someone else. ‘Oh, it’s because no one knows how to do anything anymore,’ ‘They used cheap materials,’ ‘They didn’t do this right.’ I’ve said those a few times myself. But sometimes the source of the problem isn’t a bad contractor, sub trade or builder—it might be a little closer to home.


A Home Maintenance will check more than what you see on the surface but what’s happening behind the walls

Nothing lasts forever unless you make sure it does. That means it is your responsibility as a homeowner to understand how the systems in your house work together and ensure you are doing the proper maintenance.

MHI Heating do you know whats in your furnace room mike holmes advice

It’s also important to know how your furnace room works.

A Well-Sealed House

I always say the things you don’t see in a home are more important than the things you do, and by addressing these critical details the moment you decided to purchase your dream home, you have protected your investment—saving you time, trouble and money tomorrow.

Here’s the thing about well-built homes-they are airtight. That’s great for energy efficiency, because a home can lose up to 30% of it’s heat due to drafts. But airtightness also means that although air can’t get in, moisture also can’t get out.


You need good air movement in your house for your HVAC system to work. Never block a cold air return with furniture.


TIP: Clean or vacuum the vents and grilles throughout the entire house. It’s not a huge task and has major benefits for your furnace.

Watch below to see Mike Holmes Inspector Mark Diplock talk about how to control your humidity.


Why Should I Care About Excess Moisture?

MH-FurnaceWithout letting fresh air in, there’s no road out for the air inside our homes — air that becomes thick with moisture. That moisture can start to do damage. It can get inside your walls and lead to problems with mold and rot in your building materials.

If the condensation gets inside your walls or attic space that could lead to mildew, mold and rot, which we know isn’t safe or healthy. If the moisture and rot gets into structure, you’re looking at big problems. That’s why you need an efficient air exchange system. HRV units exchange indoor air with fresh outdoor air, and as the indoor air goes out it pre-heats the fresh air coming in.

Read more about your mechanical room here.


Don’t Underestimate Your Exhaust Fans

Your kitchen and bathroom exhaust fans work to keep moisture from building up in these heavy use spaces – and that keeps the mold away. Have you checked your exhaust fans lately to make sure they’re in proper working order? When I check my exhaust fans I like to do the tissue test. It’s simple to perform, just turn on the exhaust fan and hold a tissue against it. You want to see that the fan is strong enough to hold the tissue in place. If it can, your fan is probably in good shape.


Turn your extractor fan on in the kitchen to prevent the moisture build-up, and leave it on for longer than you are cooking. Same goes for when you are showering.


Why Are My Windows Leaky?

The issue is condensation — in other words, wet, “leaky” or “weeping” windows. This happens when condensation builds up on the inside of the windowpane. It’s pretty common during winter. Have you noticed your windows fogging up? There are a few reasons for that:

  • Not enough ventilation
  • Bad windows (which hopefully is not the case if you’ve found a great builder)
  • Humidifier set too high
  • Too much moisture in your home. Do you know what the main sources of moisture in your home are? Cooking, showering and even breathing creates moisture.

I mention windows specifically because they are a good indication of the humidity levels in your home.



If you have triple pane windows, your home will have a higher relative humidity during the winter.


Do You Need a Dehumidifier?

A dehumidifier helps pull excess moisture out of the air, like a vacuum cleaner. It sucks in air from your home at one end, removing the excess moisture, and blows it back into your home again. The moisture collects into a container that you’ll have to empty from time to time. A dehumidifier is a good idea in the summer, but for winters I recommend installing an ERV (Energy Recovery Ventilator). A dehumidifier also usually only draws moisture out of a specific area, not your full house.

Getting the right balance of moisture in your home can sometimes feel like Goldilocks—it has to be just right. If there’s too much or too little your hardwood floors will tell you. Too much moisture, they’ll start to swell and buckle. Too little, you’ll start to see gaps and cracks.

To find the right balance use the guide below.

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