humidity levels

johnnyge

Quick question. What will be considere a good % humidity level inside the house. HO here with one pipe steam system.

Brad White_137

Depends on what the goal is,

what the outside climate is, how well insulated and how permeable is the envelope...

Forgeting rare books and collections, if you are talking only comfort, ASHRAE Standard 55 has some guidelines. Yes, I know what you are thinking, blah, blah, blah..

In my experience however, 30% in winter is as high as I would go in my own house. The reason is that with spotty vapor barriers (contradiction in terms) you are inviting moisture migration in air to and through the walls, condensing somewhere therein. Single pane glass if it still exists, will condense at relatively high outdoor temperatures when humidity is too high. Even double-pane glass can drop below indoor winter dewpoints.

If you require higher RH due to health concerns, you have to have an envelope that can withstand/resist that kind of moisure migration.

By the way, it matters not what kind of heating system you have, none remove humidity unless they induce infiltration through imbalance (ie: an air system). ALL spaces heated in winter experience a drop in relative humidity, but not by virtue of the heating system itself, do they actually remove the specific humidity.

johnnyge

Brad thank you for you reply. Your explanation is clear. I hear about 30% as a good number to keep humidity inside the house in the winter. I am planning to get a home humidifier to keep moisture in the house around that 30% because the steam heat gets the air to dry. Today the humidity in the house was at 40% and was ok and it isnt too cold ouside yet, but around january and febrary. It gets really cold and dry.

johnnyge

Brad thank you for you reply. Your explanation is clear. I hear about 30% as a good number to keep humidity inside the house in the winter. I am planning to get a home humidifier to keep moisture in the house around that 30% because the steam heat gets the air to dry. Today the humidity in the house was at 40% and was ok and it isnt too cold ouside yet, but around january and febrary. It gets really cold and dry.