Do Crawl Spaces Need Dehumidifying Year Round in North Carolina?

Matthew Jackson

Oct 13

2 min read

Updated: 6 days ago

In the Piedmont and the coastal region, yes. Run it all year. In the mountains it matters less, because it gets cold enough in winter that dehumidifying is not as important.

North Carolina needs three different answers because it is really three different climates, and most advice you will read online is written for none of them.

The three regions

Coastal, the Piedmont in the center, and the mountains in the west. Crawl space performance genuinely fluctuates by season, but which season and by how much depends entirely on which part of the state you are in.

The mountains

It gets much colder in the winter out there. Cold air holds less moisture, so the humidity problem eases off on its own for part of the year. Dehumidifying is not as critical in that season as it is in the rest of the state.

The Piedmont and the coast, which is most people reading this

Here is the actual reason I tell people in central and eastern North Carolina to leave it running.

We might have a winter day where it is seventy or even eighty plus degrees with high humidity. And then the next day it is in the thirties with really low humidity.

That swing is the problem. A dehumidifier that is off on the warm humid day is not protecting anything, and by the time anyone notices, the moisture is already in the wood. Running it year round is not about the average. It is about the days that do not follow the average.

What about the power bill

A properly sized unit is not running at full tilt all the time. It runs when humidity rises and rests when it does not. On the cold dry days you are worried about, it is barely working.

The comparison that matters is not the dehumidifier against nothing. It is the dehumidifier against replacing insulation, treating mold, and dealing with rot in your joists.