insulation between floors?

Did an inspection today on a 2 story house in which the space above the first floor (kitchen, living room, etc…) had no insulation. The attic upstairs had R-30 cellulose. What’s the consensus on insulation between the first and second floor?

It is not needed. That area is not part of the building envelope.

I suppose, for sound deadening, a case could be made.

as Larry said only used for sound as in the case of rental unit separation…

Agreed and as Jim pointed out for rental units, sometimes it is also wise to insulate the second floor to retain the heat on the first floor unit when the two apartments have seperate heating units, and responsible for their own heat.
One would be surprised at the heat loss from the first floor to the second.

Other than that, not required. :slight_smile:

Should there be insulation between interior walls?

“One would be surprised at the heat loss from the first floor to the second.”

You got that right Marcel, we actually don’t heat our second floor in my 140 year old farm house, it just sucks up the heat from the first floor and stays quite comfortable for the most part. I have to replace the heat on the first floor on a pretty regular basis though $$$:shock:

In a home I built for myself, not only did I not insulate between the first and second floor, I didn’t have any heating on the second floor at all. The second floor relied solely on the heat from the first floor rising.

While I agree you do not need to insulate between the floors you do need to have an air barrier and insulation at the end of the joists (rim board) to prevent air flow between the 2 floors.

That is correct and seldom done in older homes. IR camera is about the only way to find out.
In the winter time, you could use an IR Thermometer also and shoot the ceiling perimeters and the field of the ceiling and walls for comparison. :slight_smile:

What kind of rooms did you have on the 2nd floor. By c^de, all habitable rooms are supposed to have a source of heat.

Joe, it did, just not like you see it today. It had radiant floor heating. :slight_smile:

He also probably had floor registers to radiate heat in the space like I had in my Fathers home back in the 50’s till the mid 60’s when it got changed to oil heat.
Met code back then. If there was one. :mrgreen:

I had all bedrooms upstairs. It violated code but I didn’t care. It worked great.

Floor register to let the heat Up ???
I thought these where so the Kids could lay on the floor and hear what mom ,dad and their friends where saying .

This was great place to hear all the stories they talked about .

Yeah, you could hear if having to get a twitch in the woods was in the forecast for something you might have done wrong.
Worked great for heat too!, all the way from the wood furnance in the basement.
I got to be a pilot because of that wood furnance at a very young age. :mrgreen::wink:

Sound travels through framing. Insulating walls and ceilings makes very little difference in lowering sound transfer. A long time ago I once recommended insulating between ceiling joists to lower sound levels. It made almost no difference and they were not happy with me.

Often when we framed library and sometimes bedroom walls, in each wall we used 2x6 top and bottom plates and two sets of 2x4 studs, each set held flush to opposite sides of the plates and each set offset from each other.

An STC of 50 is a common building standard and blocks approximately 50 dB from transmitting through the partition. However, occupants could still be subject to awareness, if not understanding, of loud speech. Constructions with a higher STC (as much as 10dB better - STC 60) should be specified in sensitive areas where sound transmission is a concern.

When the mass of a barrier is doubled, the isolation quality (or STC rating) increases by approximately 5 dB, which is clearly noticeable.

Here is a floor design with insulation

And here are the same design with no insulation.

look at the STC ratings, 59 vs. 47 and 48.

+/- 10
Twice (or half) as loud

+/- 5
Clearly noticeable

So insulation does help on sound, but is usually more effective when resilient channels are installed to the framing.
There are many more scenarios on STC design ratings.
This is just an example. :slight_smile:

Resilient channel is good for reducing sound transmission, but I don’t see how installing it would effect the performance of insulation in reducing sound transmission.

All I know is, the one time I recommended installing insulation for reducing sound transmission, it didn’t make much difference and I got raked over the coals.

Ceiling insulation increases Sound Transmission Class slightly and can not be verified unless tested for such, as an assembly.
It is unfortunate that telling people insulation helps in sound transmission, but they more or less have to take your word for it.

Insulation can improve STC ratings in wood stud construction by 3 to 5 points and in metal stud construction by 8 to 10 points, depending on the complexity of the wall configuration and layers of insulation.

Sound Attenuation Batts (SABs) are lightweight, flexible fiber glass insulation batts. They are designed to deliver noise control in metal stud wall cavities of interior partitions. The friction-fit installation, light weight and longer length help speed installation and virtually eliminate acoustic performance problems.

Acoustic Benefits

Sound Attenuation Batts provide excellent in-place acoustic performance for interior partition acoustic systems. Depending on the construction method used, SABs can improve Sound Transmission Class (STC) ratings by 4 to 10 dBs.

Sound Transmission Class is measured in accordance to ASTM E 90 test methods, which measure the transmission loss characteristics of a partition. Depending on the wall construction, substantially higher (than 10dB) dB reductions can be achieved depending on what type of wall, ceiling, or floor systems are being compared. A laboratory test of a typical untreated interior wall has an STC of 35. Our 2” x 4” QuietZone® Acoustic Wall Framing when used with QuietZone® Acoustic Batts and QuietZone® Acoustic Caulk receives a rating of STC 49, a 14 dB reduction in sound transmission.:slight_smile:

Sound channel helps with noise reduction, but is a special requirement with the drywall install. It works on walls too.
Something like this, But you HAVE to know how to install it.

Being an audio tech, I can vouch that insulation DOES slow sound transfer, but it does not stop it. It works better in some applications, and less in others. Differences in framing, ceiling finish, drywall application, insulation depth and type, insulation install, all transfer different frequencies differently. (even the color of the room make a perceived difference and yes I know what I’m talking about.)

I asked my friend after building his house what he would do differently (1/2 mil suburban home) He immediatly said “*Noise reduction between floors. *”