45-50% Humidity is generally accepted as too high. 30-40% is a more commonly recommended range during winter. (It is currently 28% right now in my 45 year old home with original windows here in MD.)

About 40% is the happy medium you want to be with hardwood floors in a cold zone like IL.

thanks Stax. We have been in this house (new construction) for one year and have finished on site hardwood. Someone told me and now I can’t remember who...to keep my humidity between 45-50%. So that is where we aim for and usually it’s easy.

smh at 30-40%. Are you sure? I appreciate the advice..just doubting myself here.

As a general rule, the National Hardwood Flooring Association recommends 30%-50% RH.

The EMC (equilibrium moisture content) is the point at which the flooring neither expands or contracts. It varies with geographical location and the wood species.

EMC sounds ideal Worthy. We have White oak Floors. Lots of painted trim that I would like to not see moving.

dh turned off the erv and the rh rose to 40% fairly quickly and we haven’t checked it again tonight. Will check it again in the morning. Have not had to turn off erv in the past to keep humidity up. Puzzling.

it sounds like 40% should be fine. But why did it take turning off the erv/HRVs to bring it up to this?

Weather is often drier (less humidity) in the winter time. ERV/HRV's bring in that drier less humid air, cycle out the humid air from the structure.

So that mix, tends to lower your indoor humidity levels.

I live in a very humid climate, it's a hard stretch to get indoor humidity here below 50% most of the time. Winter time though can vary this... it all depends on the outdoor weather.

More dry air from outside could be more infiltration. Is a window slightly open, is a weather stripping out of place? Is it very cold - like unusually cold?

The 1st year in a house is usually a little wet as products are still drying out.

But that doesn't explain a sudden drop of course.

I would wonder perhaps about the ERV but I would think most problems would let in less air and keep you humidity higher. But I suppose if it has a plugged filter and then air bypasses the ERV portion that could be an issue.

Wow - I just checked Chicago weather and it is warmer than we are in Raleigh and with 61% humidity. I realize that it is a big state but St Louis is really warm also.