Cold Floors?

A homeowner in upstate New York wrote in about cold floors in a 1970s two-family house with electric heat and an unheated basement. He's already done a lot of upgrading: spray foam on the basement rim joists, foil-faced polyiso on the basement walls, new attic air sealing with R-60 cellulose insulation, and new windows, doors, and R-20 wall insulation. He also swapped a garage door for French doors and chose to add solar panels rather than a heat pump to offset his energy use. Even with all this work, the basement stays around 50 degrees in winter, and the floors above it are still cold.

His open questions: whether to insulate the basement ceiling, add electric heat to the basement itself, or insulate the concrete basement floor with rigid foam board. He's also dealing with a second problem created by all this air sealing — the house is now tight enough that one side has a humidity issue, since the occupants don't use their bathroom fan regularly. He wants to add whole-house ventilation and dehumidification, but can't run ductwork through the basement (too damp, risk of condensation) or the attic (blocked by the thick cellulose layer).

This is one homeowner's post to a building-science forum, not industry news. If you have a similar setup — an older house over an unheated basement, recent tightening or insulation work, and cold floors or a lingering humidity issue — this thread is a useful case to watch for people's suggestions, since it lays out common trade-offs: how to insulate a basement, whether to condition it, and how to plan ventilation once a house is sealed tight.