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Heating & Air Conditioning Home Repair Basements

Basement Ceiling Insulation - Yes or No?

3 years ago

The previous owners of my home had installed fiberglass insulation in the (unfinished) basement ceiling between the floor joists. I assume they did this for heat purposes. The insulation is old, dirty and crappy looking at this point. I am working on an effort to reduce dampness and the presence and smell of mold/mildew in the basement and am wondering if I should remove or replace this ceiling insulation. My concern is that the old insulation has absorbed moisture and is probably home to some mold & mildew.

I will be taking additional steps to reduce moisture, including adding a dehumidifier that drains into the sump pit (set it at 50% humidity), and I'll probably add a fan or air purifier that I'll keep constantly running. Will also cover my sump pit so that the water in the pit isn't open to the air in the room.

My question for the forum is - should I replace the ceiling insulation w/ new fiberglass insulation or should I just leave it out? If I leave it out, should I expect to notice a difference in moisture or heating/cooling loss from the main floor above?

Thanks in advance-

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Comments (5)

millworkman
3 years ago
I would replace it with unfaced insulation and then cover it with poly sheeting or similar.
Steve Marshall
Original Author
3 years ago
last modified: 3 years ago
Thanks for the reply and suggestion. I'd prefer not to cover w/ sheeting because I don't want to restrict access to plumbing and electrical. I also don't want to go crazy with this effort. The plumbing and HVAC are all below the joists so that would be complicated. Would you still recommend replacing the insulation by itself?
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Insulation helps absorb sound that passes into and out of the floor cavity through cracks but it is not a substitute for a resilient surface top and bottom. The minimum treatment is for a drywall ceiling to be suspended from resilient channels that lower the ceiling .5 inche. RC8 is the tradename of Auralex Acoustics. A more effective suspension system is IsoMax from Kinetics Noise Control that uses standard hat channels held in highly resilient connectors that lowers the ceiling 1.32 inches. The minimum treatment for the flooring is one of a multitude of a thin resilient underlayments for engineered hardwood or some kind of system that allows a 3/4" hardwood floor to be floated like Soundeater from Impacta Acoustical Floor Underlayments but such systems can raise the flooring enough that the subfloor and framing must be dropped in order to align with other floor finishes.
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Not sure what part of the country you live in but typically the basement walls are where the insulation should be placed. That's where the vast majority of the intrusion from heat or cold will occur. If for some reason the basement is significantly above or below the temperature controlled room(s)above then it might make sense to insulate it.
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Spray foam is the easiest way to seal rim joist cavities. I've never understood the point of insulating between the basement and the first floor-- it is code required here and no one can tell me why, There's typically little, if any, temperature differential, it's all inside the house's conditioned envelope. Rigid foam on the basement walls would be my second step, with, as Worthy says, the top half being more important than the bottom half-- sealing the rims would be first because that's typically a source of a lot of air infiltration. In a small house it's an easy (and fun) DIY project with the spray kits available at the big box stores.
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How about a drop ceiling? Example for 64 square feet: Ceilingmax 64 sq. ft. White Surface Mount Ceiling Grid Kit Armstrong Brighton 2 ft. x 2 ft. Drop Ceiling Panel (64 sq. ft. / case)* *According to the Armstrong brochure, this tile is mold/mildew/bacteria resistant.
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ci_lantro
3 years ago
last modified: 3 years ago
Is the basement heated/ conditioned space? What general geographic area do you live?

ETA, without knowing the details of what the basement space is used for, the PO's may have installed the insulation to reduce noise transfer between levels.
Steve Marshall
Original Author
3 years ago
Thanks for the reply. The basement is unfinished and not conditioned (no heat or AC ducts open to the basement). The only conditioning item I currently have is a dehumidifer that is set to 55% and drains into the sump pit. It does a decent job of regulating the humidity however it just doesn't move the air enough to feel fresh.

Im thinking about getting an air purifier for the basement and running that regularly. Maybe see how that works before I go replacing insulation. My concern with the insulation is just that it may be a living-space for mold and mildew and I'm not sure if replacing or removing would help with that cause. Maybe the air purifier and improved dehumification would do accomplish 90% of what I'm after.
worthy
3 years ago
The insulation is pointless. Dehumidify and keep any basement windows closed year-round.

Unless the basement is sealed tightly, it is part of your conditioned space whether or not there are HVAC ducts. If the furnace is in the basement and it is not a sealed combustion unit, it is getting combustion air from the basement.

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