Insulation in basement?

[Captain Cactus]

Good morning,

I have pink fiberglass insulation on the ceiling in my unfinished basement.  It was there when we bought the house.  Is there any usefulness to this?  Is it doing me any good?  What would be the impact if I removed it?

I ask the question because I believe it's providing a nice hiding spot for mice and it's starting to fall down in some areas.  It looks gross, is turning black from dust, or mold, or God knows what.  There's no moisture barrier on one side (bare fiberglass on both sides of insulation) so it's not keeping moisture out of the upstairs.

I guess theoretically it's keeping the warm air in our living area from descending through the wood floors back into the basement, but then again "heat rises", right? 

Basically I need some advice from people smarter than me on this topic. 

Thank you! 

[Askel]

Probably depends on how cold your basement gets. You could get yourself one of those cheap laser thermometers, remove the insulation in one spot and do some comparative readings both above and below to see how much difference it makes. 

For the record, we have pretty cold basements here and I have never seen this done. Insulation in the sills, yes- but never along the ceiling.   

If it turns out you need it and rodents are a problem, consider spray foam. 

[GodlessCommie]

Based on nothing but reading a lot of Greenbuildingadvisor.com, ideally, your basement is a part of your conditioned space. Insulation belongs on the outer side of it, not between the basement and the rest of the house. If mice gets in, then plenty of cold air and moisture also gets in, so some sealing seems to be in order. Spray foam is a popular choice these days, but if you are willing to pay for energy audit, you should get better advice.

[Captain Cactus]

Thanks all for the replies so far.  We live in Connecticut, so while it can be cold outside its not cold in the basement.  Not hot, either.  Probably in the low 60s year round.  We do run a dehumidifier in the summer because humidity gets high down there, but no leaks per se.  The boiler is down there too, which generates some heat when running I think.

The previous owners did some interesting things, to include putting paper over the AC vents in winter to keep heat from escaping.

I guess I'm leaning toward removal.  I'm afraid of all the crap that's going to fall on me when I do... 

[sonofsven]

Unfinished basement, but concrete floor, yes? Not dirt? If dirt then plastic vapor barrier is needed.
If the basement isn't especially drafty (and if it is then seal the drafts) then it isn't doing much except providing sound insulation between the levels.
I'd pull it, I hate that crap falling on everything, including the inside of my lungs.

[Captain Cactus]

Unfinished basement, but concrete floor, yes? Not dirt? If dirt then plastic vapor barrier is needed.
If the basement isn't especially drafty (and if it is then seal the drafts) then it isn't doing much except providing sound insulation between the levels.
I'd pull it, I hate that crap falling on everything, including the inside of my lungs.

That's right, concrete basement floor and walls.  Not really drafty at all, no drafts felt when i'm down there, but then again there are only a few windows and they're little and up high.  the door to hatchway is pretty thick and has insulation on the outside of it. 

[SunnyDays]

Seems pointless to me.  I would only insulate the basement ceiling for soundproofing (and even then would use Roxul) if I was going to drywall it.  I can't see that it's doing anything productive as is.

[trollwithamustache]

it would also depend on how cold you like your floors.

[Captain Cactus]

it would also depend on how cold you like your floors.

Do you think it makes much of a difference to floor temp?  I keep going back to why the previous owner would have done that.  He was a smart guy, engineer I think.  Must have seen some kind of value in spending the money to buy and install. 

But what does it do?  How much of a difference will I see if I remove?

[GodlessCommie]

Do you think it makes much of a difference to floor temp?  I keep going back to why the previous owner would have done that.  He was a smart guy, engineer I think.  Must have seen some kind of value in spending the money to buy and install. 

Unless the previous owner had specialized knowledge, it doesn't matter how smart he was. Building science develops slowly, and construction practices follow even slower. A lot of counterproductive stuff is being done all the time.

[trollwithamustache]

it would also depend on how cold you like your floors.

Do you think it makes much of a difference to floor temp?  I keep going back to why the previous owner would have done that.  He was a smart guy, engineer I think.  Must have seen some kind of value in spending the money to buy and install. 

But what does it do?  How much of a difference will I see if I remove?

depends where you are.  I've lived in a 1920s era house with hardwood floors and no insulation under it. It was cold, this is in California so Cold under the house maybe isn't that cold. The house could be fine and the floors friggin cold. 

Most newer construction will have the floor joists finished with drywall on the ceiling of the basement, they do this for fire safety. Its not an amazing insulator but newer places floors sure are not as cold. But my experience isn't apples to apples since old to new homes there is different under layers/ carpeting choices ect.

Your insulation sounds like the cheap/easy retrofit for an old home. If you were to re-do it right, there is probably supposed to be vapor barrier in there somewhere.

[nereo]

Simply put, the fiberglass batts are not providing you with any thermal benefit if your basement is a conditioned space and part of the building envelope. It sounds like this is the case from everything you have described.

The batts will help attenuate sound, but not terribly well and ultimately that would only matter if you wanted to dampen noise coming from your basement to your upstairs living space, or vice versa. Most people’s basements aren’t noisy without people, and unless you are hanging out there making noise I don’t see the point.

A MUCH better use of your time and some insulation would be to 1) seal and insulate the rim joists and then 2) insulate the basement walls (at least to two-feet below grade, and all the way to the floor if possible. That will make the entire basement more uniform in temperature and reduce the humidity as well. This is course assumes you have no issues with water intrusion (a ‘leaky basement’).

[Captain Cactus]

Simply put, the fiberglass batts are not providing you with any thermal benefit if your basement is a conditioned space and part of the building envelope. It sounds like this is the case from everything you have described.

The batts will help attenuate sound, but not terribly well and ultimately that would only matter if you wanted to dampen noise coming from your basement to your upstairs living space, or vice versa. Most people’s basements aren’t noisy without people, and unless you are hanging out there making noise I don’t see the point.

A MUCH better use of your time and some insulation would be to 1) seal and insulate the rim joists and then 2) insulate the basement walls (at least to two-feet below grade, and all the way to the floor if possible. That will make the entire basement more uniform in temperature and reduce the humidity as well. This is course assumes you have no issues with water intrusion (a ‘leaky basement’).

Thank you for the advice!  What do you mean by "building envelope"?  And "conditioned space"?  I don't have heating or air conditioning down there, but the furnace is located down there and its never too hot or too cold. 

[nereo]

Simply put, the fiberglass batts are not providing you with any thermal benefit if your basement is a conditioned space and part of the building envelope. It sounds like this is the case from everything you have described.

The batts will help attenuate sound, but not terribly well and ultimately that would only matter if you wanted to dampen noise coming from your basement to your upstairs living space, or vice versa. Most people’s basements aren’t noisy without people, and unless you are hanging out there making noise I don’t see the point.

A MUCH better use of your time and some insulation would be to 1) seal and insulate the rim joists and then 2) insulate the basement walls (at least to two-feet below grade, and all the way to the floor if possible. That will make the entire basement more uniform in temperature and reduce the humidity as well. This is course assumes you have no issues with water intrusion (a ‘leaky basement’).

Thank you for the advice!  What do you mean by "building envelope"?  And "conditioned space"?  I don't have heating or air conditioning down there, but the furnace is located down there and its never too hot or too cold.

Ah, those are building science terms - sorry I should have explained.

The building envelope divides “inside” from “outside”. Seems like it should be straight forward, but a lot of mistakes occur because people don’t consider whether a space is inside the building envelope or not. For example, a garage is generally (though not always) outside the building envelope. If you have a room above the garage you have three choices: make that room an unheated (or “unconditioned” space - see below), insulate and seal  the garage ceiling and stairs (thereby making the building envelope at the garage ceiling), or bring the entire garage into the building envelope and figure out how to seal and insulate the garage - including the garage door (tricky to do well)

Anything within the building envelope should be a conditioned space, which basically means that you control (to some degree) the humidity and temperature. It doesn’t need to be very precise - many basements are conditioned but the temperature can be 20 degrees different from the living spaces, as long as the relative humidity levels aren’t out of control and that you don’t have steady air leakage which would set up a problem with condensation (that is: your building envelope is “tight”).

Where big mistakes happen is when the building envelope isn’t complete (for example, an open basement with a dirt floor and no air barrier or insulation separating it from the rooms above) and/or when a space within the building envelope isn’t conditioned (think about a sealed basement but that had no airflow, heating or dehumidifier).

Make sense?

[MasterStache]

it would also depend on how cold you like your floors.

Do you think it makes much of a difference to floor temp?  I keep going back to why the previous owner would have done that.  He was a smart guy, engineer I think.  Must have seen some kind of value in spending the money to buy and install. 

It doesn't make much of a difference. The floor joist provide a thermal bridge anyways as they have a lousy R-value. The batts aren't doing anything.

As other's have pointed out, insulating your basement properly is the way to go.   

[ysette9]

Hijacking this thread to ask a related question. Our finished basement doesn’t have insulation between the floors and I want to add it mostly for sound reasons. The basement is/can be a separate apartment so I can see a future of people being down there and not wanting to listen to my elephant-footed children. Is blow-in cellulose or fiberglass the best I’ve got?

[nereo]

Hijacking this thread to ask a related question. Our finished basement doesn’t have insulation between the floors and I want to add it mostly for sound reasons. The basement is/can be a separate apartment so I can see a future of people being down there and not wanting to listen to my elephant-footed children. Is blow-in cellulose or fiberglass the best I’ve got?

Nope!

First you have to understand what kind of sound-transfer you are trying to dampen.  If it's elephant-footed children, that's harder to do than if it's just muffling the sound of voices and music and what not.

For dampening the sound of footsteps you need to de-couple the floor upstairs from your basement downstairs. Just as the joists act as a 'thermal bridge' bypassing batts stuffed in-between, the wooden joists also act as an accoustic bridge transferring the stomping of feet or clack of high-heels to the ceiling below.

Solutions range depending on how much time you are willing to spend and how much money.  Blown cellulose and/or fiberglass batts will muffle conversations but not do much else in terms fo sound dampening. If you are redoing the upstairs floor for whatever reason it would help to put an underlayment (basically a rubber mat) before laying the floor down on top.
But short of that, you are limited to what you can do from below.

The easiest* (IMO) is to add a second sheet of drywall right under the existing drywall, but to use a de-coupling adhesive like "green glue" between the sheets.  This creates a tiny gap that stops most of the accoustic bridging. They cost roughly $5/tube bought in bulk, and you need about one tube per full sheet of drywall.
OR you can use isolation clips/channel on your ceiling and then hang your drywall from that.  I find that a bit more finicky and it will further lower your ceiling heigh by another ~1" over the green-glue option.

If you want to go whole-hog, blow cellulose (or use mineral wool if you are feeling $$pendy), then two layers of drywall with either green glue or clips in between.  But that's a complete tear-out job, whereas you could just add a second layer of drywall without all the demo and dust.  For many basements the ceiling height is already pretty low, so losing an inch or two can be considerable.  If you've got "full height" you are in luck.

If you are fortunate enough to have HIGH basement ceilings then I'd do a suspended ceiling with accoustic tiles. It only works when you are willing to loose at least 8" of ceiling height, but it will serve as decoupler, sound absorption and easy-access to utilities which can be important.

[Frugal Lizard]

Hijacking this thread to ask a related question. Our finished basement doesn’t have insulation between the floors and I want to add it mostly for sound reasons. The basement is/can be a separate apartment so I can see a future of people being down there and not wanting to listen to my elephant-footed children. Is blow-in cellulose or fiberglass the best I’ve got?

  There are some really good articles in Fine Home Building about sound transmission.  What I learned: Insulation doesn't alter vibration transmission through the structure. I swear our son uses a pogo stick after dark and the sound /fire dampening insulation does nothing. 

Our next door neighbour built a new house with a completely acoustically isolated walk out basement apartment.  The fire door between the apartment and her basement portion is actually two doors because one is hung on her wall and the other is on the apartment framing. Nothing bridges the framing around the "envelope" of the apartment including the ceiling of the apartment. It is independent of the framing of the floor joists.  The apartment is heated with radiant floor heating so no transmission on air ducts. Plumbing is has insulation and rubber pads.  Neighbour has a rambunctious standard poodle. Her tenants can hear the dog barking through open windows but not the prancing above their bedroom.

[ysette9]

I appreciate the advice. I think we are going to be pretty limited in what we can achieve then. The basement ceiling is already low and I’ve gone to the trouble of installing ceiling lights and repairing approximately a bazillion holes in the drywall so I am reluctant to open things up. On thé top side We will likely be redoing the flooring but best guess it will be putting LVP over existing hardwood. Some LVP samples I’ve grabbed have a rubbery back so perhaps that will add a bit of damping.

[SunnyDays]

Hijacking this thread to ask a related question. Our finished basement doesn’t have insulation between the floors and I want to add it mostly for sound reasons. The basement is/can be a separate apartment so I can see a future of people being down there and not wanting to listen to my elephant-footed children. Is blow-in cellulose or fiberglass the best I’ve got?

Find elderly and/or hard of hearing tenants!

[Uturn]

I may be way off base because I always lived in non-basement areas, but when I read this I did not think the insulation is the problem. How are the mice getting in?  I would guess that if mice can get in and out, so can air and possibly water.