My townhouse has a partial lower level and partial crawlspace of dirt. Rooms with crawlspace under get pretty cold in winter. There is some un-faced (I think) fiberglass roll insulation tucked up between the joists, although some has come down.
The crawlspace is fairly dry and has good airflow. I'm not able to encapsulate or whatever. Local weather goes from just below freezing to hot and humid. I can manage to lay on my back in there and staple up some 4x8 foot sheets of half inch or so insulation board if it will help. I think that the floors will be warmer because winter air won't blow right against the joist spaces.
the lower level ends in a concrete block wall which supports the middle of the building. There is one too-small opening which we are going to permanently close and seal, in a closet. The crawlspace runs all the way under this six unit building, with access at each end and plenty of vents. The water heater is under there too (HVAC got too big, I guess). There is some poly on the dirt, but it's mostly pushed all over by some past work or something (I'm new here). Radon inside in lower level tested about 1.5 twice. We own our unit but not the building so we can't do major work.
Is rigid insulation board a good idea? I can't get it air tight due to pipes and wiring on underside of joists. Would board cause moisture issues in the floor joist area, and is there a better idea? If it is good, should I get the silver faced board, and which side up? This is super helpful to me, with not much money to spend and willing to get filthy under there... Again!
