Heating the basement in the summer to lower humidity would be very ineffective and costly.
- Heating the air does not remove humidity it only allows the air to hold more humidity. The warmer the air the more moisture the air will hold.
- Heating he basement in the summer would also heat the air on the upper levels (since warm air rises).
Central air conditioning
If you have central air conditioning you can effectively remove excess humidity in the house. If the basement doesn't have HVAC supplies and returns the air conditioner will not be effective in removing excess humidity.
If you have central air conditioning it should be sized properly so that it removes moisture from the indoor air. Oversized AC units typically have short run times which prevents the air conditioning from effectively removing interior moisture.
The stand alone dehumidifier is the other effective option in reducing indoor humidity. Purchase a model that has the ability to remove 40-50 pints of moisture per day.
- If possible route the dehumidifier drain hose to an accessible floor drain so you don't have to constantly empty the unit when it gets full.
- After a few days of operation the basement air should dry out and run less often.
Bathroom exhaust fans
You should also run the bathroom exhaust vent fans, making sure they discharge outdoors rather than into the attic.
Bath fans should be run for at least 40 minutes (electronic timer) or be controlled with a humidistat to remove excess moisture from the home.
For more information:
Read "What can I do to lower the humidity level in my home?" a Q&A answered by Stillman Jordan.