For years I have battled with this dilemma myself. Is there something wrong with my floors? Thankfully, for most hardwood floors the answer is “no”. Wood is a natural product that reacts to the environment it’s in. Gapping and associated noises in hardwood flooring usually occurs when the flooring dries significantly from its summertime higher moisture levels. So, to reduce winter gapping, reduce the annual range of moisture levels. More specifically, don’t let the indoor Relative Humidity (RH) drop too much in the winter months. A good annual range suitable for hardwood flooring is no more of a change than 15% RH annually (i.e. 32% winter; 47% summer). Ideally, here in Ontario, you do not want to let your Relative Humidity drop below 30%-35%, even in the winter months. Aside from the adverse health effects of low humidity, it will cause issues with all the wood products in your home.
The moisture content of your hardwood floor will change depending on the Relative Humidity of the surrounding air in your home. The moisture content of the wood will increase as the humidity level in the air increases, this process will make the wood expand. In the same way, when the humidity level in your home drops, the woods moisture content decreases and it starts to contract and cause gaps and creaks. Don’t be alarmed, you are not alone. This is a natural process and your hardwood should expand back to the same size it was prior to shrinking.
What causes low humidity in your home in the winter? The short answer: You’re bringing in too much outdoor air! COLD air is DRY air. In Ontario we experience frigid temperatures for several months at a time. Without a perfectly air-tight home, this cold air comes in through cracks, doorways, old windows, inadequate insulation, etc. And, fundamentally, the more your furnace has to work to heat the air inside your home, the lower your RH level will be.
Ok, so now you realize you have low Relative Humidity in your home, your flooring is starting to gap, and you don’t want to wait until summer for it to expand, what’s the answer? Although there isn’t a simple “do this and it will solve all your problems” type of solution I have found, there is certainly some options to increase your homes Relative Humidity both mechanically and naturally, without breaking the bank:
- Install a whole home humidifier on your furnace. Taking into consideration the pints/hour rate to ensure the unit will provide adequate moisture for your homes specific RH requirement. Every home is different, it is best to consult with your HVAC technician for more details. Typically, you’re looking at around $600-$700 to have one of these installed.
- Purchase a large portable humidifier. A simpler solution however not quite as effective as above, but it’s close! Most decent units have a timer or even a sensor allowing you to set your RH level to your preference. The downside of these types of humidifiers is that most require manual filling. You can pick up a good unit for $200-$300.
- Boil water on the stove. This is a great way to get moist air into your home quickly but requires constant filling and maintaining. Don’t let the pot run dry!
- Air seal your doors and windows. In the case of most homes built prior to say the 2000’s, the windows were likely installed with fiberglass insulation stuffed around them between the jamb and framing. If you are somewhat handy, pull the window trim off, remove the old insulation, then spray foam and tuck tape the gap. If your windows are just old and no longer seal properly, perhaps consider replacing them or at the very least sealing them with plastic for the winter. Preventing air loss and cold air penetration is a major factor in low RH.
- Add more insulation to your attic. The less warm air escaping from your home, the less your furnace has to cycle to heat up the cold dry air coming in to replace it.
- Limit exhaust & bath fan usage to a minimum. Don’t forget to shut it off or better yet, install 15-minute timers on them. Let the humidity from your bath have a chance to get outside your bathroom to the rest of your house, rather than sucking up that already conditioned warm and wet air right outside through the vent.
- Place containers of water on your heat supply vents. Your furnace will heat this water up causing it to evaporate into the air slowly adding RH to your home.
Using these tips and tricks will certainly increase your homes Relative Humidity. As with anything in life, be careful not to overindulge, excessive RH can cause mould and other damage to your home. A suggestion would be to purchase an inexpensive indoor humidity monitor to aid you in your fight with RH. You can pick one of these up from your local hardware store for around $30.
The Conclusion: Wood is a natural product and is susceptible to expansion and contraction with varying relative humidity. Maintaining similar RH in your home throughout the different seasons is crucial to minimizing gaps, cracks and creaks in your flooring. When installing hardwood, it is best to place it in the respective rooms a minimum of 1 week prior to installation, this will allow the hardwood to acclimate to your home’s environment. Hopefully, using these tips will ease your mind and help keep your floors looking beautiful for many years to come.