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Dmurr33
Basement Ceiling

Hi,

I'm preparing to finish my basement and can't decide whether to insulate the ceiling. Even in the winter with the heating vents closed, the basement doesn't get much colder than 58 degrees. So I'm not sure how much I'll be gaining by putting up insulation, other than some noise reduction. I've also heard that insulating a basement ceiling might trap moisture in the basement rather than let it pass through the floor into the upper level of the house where it can escape more easily in the summer.

There appear to be some conflicting opinions on whether to insulate the ceiling of a finished basement, and I would appreciate any thoughts on this.

Thanks,

Dave

Timothy Miller
Re: Basement Ceiling

Howdy a R/22 insulated basement ceiling will keep the main floor warmer as uninsulated it is a heat sink. Continually drawing heat out of the heated rooms above. The next issue is if you ever have anyone sleep in the basement if you insulate the ceiling have to consider not having a fiberglass shower onto any bedding.
I am insulating a ceiling using the plastic wrapped fiberglass that home depo sells and taping the butt joints. Owens rep assured me by phone-it is neither a vapor or moisture barrier- the plastic wrap on the fiberglass.
that way i do not have to sheet rock the ceiling where we will sleep during tornado alerts .....

canuk
Re: Basement Ceiling
Timothy Miller wrote:

Howdy a R/22 insulated basement ceiling will keep the main floor warmer as uninsulated it is a heat sink. Continually drawing heat out of the heated rooms above. .....

I'd have to disagree ---- there is little to no benefit as to the cost of thermal insulating between one conditioned space and another.

Dmurr33 wrote:

Hi,

I'm preparing to finish my basement and can't decide whether to insulate the ceiling. Even in the winter with the heating vents closed, the basement doesn't get much colder than 58 degrees. So I'm not sure how much I'll be gaining by putting up insulation, other than some noise reduction. I've also heard that insulating a basement ceiling might trap moisture in the basement rather than let it pass through the floor into the upper level of the house where it can escape more easily in the summer.

There appear to be some conflicting opinions on whether to insulate the ceiling of a finished basement, and I would appreciate any thoughts on this.

Thanks,

Dave

Dave --------- you're spot on.
There is really no benefit as far as thermal insulating the basement ceiling of your finished basement.

Any heat that migrates from this conditioned space up into the conditioned space above is a plus . In other words it's adding to the conditioning of the space above and is not wasted energy compared to escaping into a cold unconditioned attic or crawl space.

Consider there is never insulation used for thermal resistance placed in interior walls or the ceilings between first and second floors of your main living areas.

As you mentioned ---- the only justification as to the cost would be for sound insulation.

As for moisture or vapor ----- you're correct ----- vapor within the conditioned spaces needs to freely pass throughout these areas. This why you should never apply a vapor barrier or faced batts on the ceiling of the basements. This includes the ceilings of basement bathrooms.

Again consider how the interior walls and ceilings between conditioned spaces of your main living area are constructed ----- no vapor barriers.

Hopefully this helps. :)

Timothy Miller
Re: Basement Ceiling

I have been reading a few books on solar and super insulated homes as i am afraid that our energy costs are going to get much more $$
The super insulated homes with tiny heating and cooling costs all have insulated basement ceiling cavities in the books. An thermal camera showed the heat sink of the wood framing members at the floor level of uninsulated basement ceilings.
Any body got more information as i am always wanting to learn more to help save and conserve...

canuk
Re: Basement Ceiling
Timothy Miller wrote:

I have been reading a few books on solar and super insulated homes as i am afraid that our energy costs are going to get much more $$
The super insulated homes with tiny heating and cooling costs all have insulated basement ceiling cavities in the books. An thermal camera showed the heat sink of the wood framing members at the floor level of uninsulated basement ceilings.
Any body got more information as i am always wanting to learn more to help save and conserve...

If you read up on some basic thermal dynamics this can help better understand heat gain / loss .
One of the basic rules is heat from one zone will migrate ( with some mechanisim )to a colder zone to give up it's energy components to try and reach equilibrium. The differential ( Delta T ) between these zones ( T1 .... T2 ) is the amount of heat loss / gain.
In other words -------- the less differential between T1 and T2 the less heat loss / gain.

Consider the environment within your main living space ------- unless you are trying to maintain micro-environments between one space and another ------ it's beneficial to allow the heat to freely circulate between areas.

Living here in a part of Canada where the winters reach deep sub-zero temperatures ( and for too long ;) ) we have plenty of research and experience with what works for insulating.

Quote:

An thermal camera showed the heat sink of the wood framing members at the floor level of uninsulated basement ceilings.

Was the basement insulated and heated ?

If you simply insulate the basement walls you are raising the temperature of this space ( T1 ) ---- by preventing heat loss . If you included conditioning the sapce with a heat source you further raise the temperature of this space ( T1 ). So --- the higher the temperaure of basement ( T1 ) and the closer it becomes to the temperature of the living space above ( T2 ) you will have minimul or no heat loss between the spaces.

Besides ---- as mentioned earlier if heat migrates from one conditioned space to another conditioned space ---- this is not a negative.

The floor temperature can be negatively affected by inadequate insulating and air sealing the perimeter rim joists and the bottom plates of the walls.

There shouldn't be much difference measuring the temperature at the floor between a insulated and heated basement compared to the uninsulated floor/ceiling between a first and second levels of a 2 story home.

Timothy Miller
Re: Basement Ceiling

Howdy, Canuk thanks for the information. The thermagraphy was showing an non insulated basement including the walls and the floor. If the basement was insulated and heated and sealed the dead air space of the basement would reduce the heat sink of the floor above but heck why not throw a tiny bit more of $ to insulated the ceiling too? I think we can assume Dmurr33's question was for an non insulated basement.

Have you any experience with installing 2" foam board 2 feet wide outside the foundation on grade to shift the heat sink of the soils away from the foundation instead of insulating the foundation? An what type of spray foam insulation do you use in the rim joist bays in Canada? Just saw a homes on homes show where they spoke briefly of the foams shrinkage verses bonding to the framing members.

canuk
Re: Basement Ceiling
Quote:

Have you any experience with installing 2" foam board 2 feet wide outside the foundation on grade to shift the heat sink of the soils away from the foundation instead of insulating the foundation?

I'm not clear on your question about the foam board.

Are you suggesting laying the foam board flat on the ground next to the foundation?
If so ----- this will do absolutely nothing.

If a slab on grade is to be poured then the foam board would lay flat on the ground with the concrete poured over top.

Otherwise for a vertical foundation wall the foam board needs to have intimate contact with the foundation. The foam board would be applied vertically isolating the foundation from the heat sinking soil preventing any thermal briding.

Quote:

An what type of spray foam insulation do you use in the rim joist bays in Canada? Just saw a homes on homes show where they spoke briefly of the foams shrinkage verses bonding to the framing members.

Spray foams have been around here for about 40 years or so. Earlier uses were for commercial applictions. In the 70's the infamous Urea-Formeldehyde found it's way into residential ( that's another story ) which halted the use of any type of spray foams for a short time.

Then along came Poly based foams which had undergone intense scrutiny because of the previous issue with spray foams. Once the governing agencies were convinced that the recent incarnate foams were safer they were once again being used in commercial applications.

It was difficult for companies to regain the residential market for awhile because of the negative stigma of foam insulation. That did eventually change and spray foam eventually made it's way back into the residential market.

Both the open cell and closed cell foams are used here.
Around the mid 80's a Canadian company ----- Icynene Inc. developed an open cell foam which is widely used. Another type of foam developed by the huge multi-national company BASF had developed a closed cell foam and is also widely used. Of course there is now a myriad of different brand names and types available.

As for the shrinking issues --- usually these are associated to the open cell ( 1/2 pound ). These types of foams rapidly expand 100 times the volume. There is a condsiderable amount of heat generated from the chemical reaction which causes the expansion. If the ambient temperature is too cool or if there is an improper chemical mix this may cause an issue when the foam is curing and may not bond with a surface. Normally there really isn't an issue with shrinkage when properly applied ------ at least with Icynene.

Dmurr33
Re: Basement Ceiling

Guys, thanks for your replies. It's great information and I appreciate it! That's a few hundred dollars I'm glad I won't have to spend.

Dave

Timothy Miller
Re: Basement Ceiling

Howdy, the 2" 24 " wide foam insulation board is laid onto the soil and easily covered with mulch or stone etc. It makes not having to insulate the walls of the basement as it moves the freeze/ frost zone away from the foundation. The book i was reading was making the point that it brings the average 58* earth temp at 8' below grade up for lack of a clearer explanation and moves the heat sink away from the outside wall of the foundation.
Some are using with crushed stone shallow foundations ....
Thanks for the information about the spray foam too.

canuk
Re: Basement Ceiling

Dave , you're welcome and yep saving those $$$ on something with little benefit will help going toward other materials for finishing the basement.

Good luck. :)

canuk
Re: Basement Ceiling
Timothy Miller wrote:

Howdy, the 2" 24 " wide foam insulation board is laid onto the soil and easily covered with mulch or stone etc. It makes not having to insulate the walls of the basement as it moves the freeze/ frost zone away from the foundation. The book i was reading was making the point that it brings the average 58* earth temp at 8' below grade up for lack of a clearer explanation and moves the heat sink away from the outside wall of the foundation.
Some are using with crushed stone shallow foundations ....
Thanks for the information about the spray foam too.

Huh ?!?!
Sorry ---- there's no way that simply laying a 2 inch thick by 24 inch wide sheet of rigid foam flat on the ground beside the foundation is going to prevent the frost penetrating below that sheet of foam.
You would need a vertical thermal break from the rest of the soil the entire 8 feet down.

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