House Humidity w/ Wood Finishes

[treillw]

Finished building a house in the summer. We have a pretty large area of wood floors and some timber frame bents as well. Nothing too crazy - drywall, carpet in bedrooms, and tile bathrooms. It is very dry here in the summer and even dryer in the winter. I'm worried about the wood getting too dry and going crazy - warping and cracking. I have a small humidifier pumping out moisture for the time being, but I'm considering getting one put into our heating system. Don't feel like filling humidifiers for the rest of my life. Currently the humidity ranges from 27% to 40%, depending on how much the liquid propane furnace is running. I've had people tell me that the humidity in the house should be 60% with all our wood. I've also had people tell me that it doesn't matter what the humidity is and that the wood is going to do what it wants to do (which likely holds a lot of truth). There is also the consideration of condensation getting on the wooden windows and ruining them when it's bitter cold outside. It seems like the floor began creaking more once we turned the heating system on. I went crazy with three humidifiers initially, but have tapered off from that a bit since then. Kiln dried lumber is supposed to be 15% internal moisture content with regular lumbar being around 19% - don't know if 20% humidity would even effect it.

Anywho, what humidity would you shoot for? Any other advice?

Thank you!

 

[Squirrels]

Anyone that tells you the humidity isn’t going to affect the wood and what it’s going to do is pumping sunshine up your backside.

 

[DanimalW]

Humidifiers on the cold air return work pretty well. If you have 60% humidity in your house though, living in a cold climate, you’re going to have water dripping down your windows. Our house was built in the 70s so it’s not wrapped tightly, and probably breathes too well. I just crank up the humidifier until I get window condensation, then adjust it down incrementally until I don’t get any. We still get some gaps between hardwood planks, but nothing that’s ridiculous. You’d rather have that than mold growing in your walls.

 

[Squirrels]

I agree with @DanimalW that 60% seems high. We keep ours around 40-50%, anytime it creeps above 50 I can tell it soon as I walk in the door.

 

[treillw]

Anyone that tells you the humidity isn’t going to affect the wood and wood will do what it’s going to do is pumping sunshine up your backside.

What humidity would you suggest?

 

[DanimalW]

I think 40s sound about right, but that might not even be manageable humidity if you’re dealing with -40F outside. HVAC running will dry the house, and cold, dry air tries to suck the warm, humid air out when it gets super cold.

 

[Squirrels]

What humidity would you suggest?

I’d shoot for around 45, but as @DanimalW stated above that might be hard to achieve if your heat is running a lot with super cold temps. I live an area that is humid in the summer and winter till it gets cold.

 

[fishslap]

I’d get a whole house humidifier installed in your hvac. I think we notice the wood floors creaking and shrinking when we drop below 25% for too long. I’ve developed allergies and some breathing issues and the dry air makes it way worse. We shoot for 40-45%. The wife complains if it gets above 45%.

 

[tdot]

Adding humidifiers into your HVAC system should definitely be researched and approached with caution. I've seen it work well and I've seen it fail miserably. I would also suggest that you add an ERV system into your research. I prefer to have those installed into homes.

Most Kiln Dried lumber should be between 6% and 8% when it leaves the mill. Your wood should stabilize at roughly 1/5 of the Relative Humidity. So if your house is held at 30% RH, the wood will stabilize at roughly 6%.

What I typically recommend for my clients is to match the summer humidity. Around here in coastal BC, no one is running AC. In the summer the windows and doors are open and our Relative Humidity (in homes) is typically 40% -45% so about 8% moisture content in the wood. In the winters everything is closed up and the heaters go on. The RH will usually drop to about 30% unless we add moisture back. I'd suggest a similar line of thinking. Though if the wood was acclimated and installed at a different RH, then you will notice the difference. Personally I ensure all wood is installed on our projects is in that 7-8% range which is fairly easy for us to maintain. Also, I'd rather wood dry out and shrink, vs increase its' moisture content, and then swell and buckle.

 

[Esq]

I have represented a client that had his hardwood fail within 1 year of install. He made a warranty claim and the manufacturer hired and "independent" expert to do an evaluation. The experts conclusion was that higher than allowable indoor humidity caused the failure. If I recall the max allowable by the manufacturer spec was 58%. Measured humidity on the day of inspection was around 65%. They denied the warranty claim and blamed the homeowner. This was a very expensive custom home. Here in the Willamette Valley it would be hard to keep your house under 58% year round. In any case, every manufacturer will state the max % allowed. I believe there is a national association of flooring manufacturers that states a standard %. You could probably find that fairly easily online.

 

[treillw]

Is there a good way of figuring out what the humidity would be in your house based on how much water volume you are adding to it?

I played around with some numbers and by adding 17 gallons of water per day to my house volume of 32851 cf, you get a humidity increase of 70%. Obviously some of that is eaten up by the furnace etc, but I'm not sure how much.

I would imagine somebody has already put a good amount of thought into this and developed something......

 

[mtnbiker208]

Do you run a wood stove?

 

[treillw]

Do you run a wood stove?

Gas forced air

 

[DenverCountryBoy]

Set the humidity to a comfortable level. Let the wood adapt for a year, then make any adjustments needed to address movement.

 

[mtnbiker208]

I only ask, because wood stoves bring the humidity down.

 

[Esq]

I would get a measuring device and just play with the variables while you monitor the moisture.

 

[GotDraw?]

Aprilaire humidifier!
JL