Originally Posted by Dennis Erskine
Foamed walls are excellent for energy use reduction, thermal insulation, and air penetration. What most consumers are not told is the most benefit per inch from these products comes in the first 2". After that the benefit per inch falls off a cliff. From an acoustics perspective, fiberglass insulation is far better. (Foam will also couple the interior and exterior walls to each other). When foam is used (for all the right reasons), I suggest no more than two inches. That is followed by fiberglass, isolation clips and HAT channel, then drywall. In a 2x4 framed wall that leaves just over 5.5" of total depth. With two inches of foam, you have enough remaining depth for fiberglass batts...the acoustic wall remains decoupled. FWIW
I hate to chime in on a thread that I've just come across when I know the build is probably too far along to use the suggestions. However...
Closed cell or "2 pound" foam, is usually sold as the better foam because of it's higher R-value, but like any material there are situation when it should be avoided. In this case in favour of open cell (1/2 pound) foam. As Dennis points out the 2 lb sound couples. A cathedral ceiling filled with 2 lb sounds like you are under a tin roof when it's raining! In the same situation with 1/2 lb the rain is just audible. The problem with either foam in the basement is that the walls must not have moisture problems. The 2 lb, being closed cell is a "vapour barrier". As such, if sprayed directly on the concrete, it will try to keep water back. Hydraulic pressure will win. There is a potential for mold. It is best to install tar paper (foam won't stick to plastic) against the wall (shingled up on the back side of a stud wall section before you stand it up) and deal with drainage at the floor by using Delta membrane on the floor covered by T & G plywood plus finish (this also creates a thermal barrier, making the floor warmer). Also, not mentioned in the tour guide is that the 2 lb is less stable, losing about 15% of it's R-value in the first 5 years because the gas in the bubbles expands in the heat and breaks the bubbles. 1/2 lb is open cell and is more stable, so the diminishing difference in R-value between it and 2 lb makes you wonder if it is worth paying the higher price for 2 lb. They both seal air movement. 1/2 pound holds water like a sponge, again creating a potential mold problem if the walls get moisture through the wall. So again tar paper should be used. A proper waterproofing and drainage system on the outside of the foundation wall should of course alleviate water problems and the best solution.
I would ask Dennis of his thoughts about filling the stud space with 1/2 foam as opposed to fiberglass...all wiring, except for the stuff you forgot would be done before the foam is sprayed.
You had a concern about sounds from the 4" drain. Speaking of mass. Cutting the pipe where it comes through the floor and replacing the plastic 90 and pipe with two 45's and pipe both made of cast iron using a rubber Fernco coupling to the plastic and MJ clamps between the pieces of iron will kill most of the noise, then spraying it with 1/2 lb foam will make it barely noticeable. The horizontal needs a 1/4" per foot fall, so start close to the joist at the 45's to gain maximum head space.
The PEX tubing eliminates water hammer, but tends to expand when the hot water starts heating it up. Make sure you dab a bit of silicone caulking between it and anything it gets fastened to or touches. If it goes through a hole, fill the hole around the tube. This will eliminate squeaks.
The 10" flexible heating/ventilation duct should go to a 12" rigid duct with an internal 1" rigid fiberglass liner to kill the sound. This is available from commercial HVAC suppliers. The insulated section should be at least 3' long, 5' is better. If you have ever seen Space Pac A/C; each port has a 3' "sound attenuator" on the end of the 2" duct to deaden the sound. Same idea.
Thank you for defining "IB". Is there some place that this jargon is listed to help us nubies?
Great name! I haven't been able to come up with one yet. So I can't start the build out.
Some have suggested, "The Bomb Shelter", because it has poured concrete walls and ceiling, but it just doesn't have that roll-off-the-tongue sound appeal. I have a 1907 money pit and have been flip flopping between Arts and Craft (which is what the house "kind of" is), Art Nouveau (I love) and Art Deco (the beginning of movie theatres). I too have a file of Deco buildings.
Maybe you'll shift the balance. So the pressure is on!
I promise I won't skip a page on this one.
...have to get back to reading...