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OK, I have been reading Rod's book and have a couple of questions about how to retrofit an existing space in regards to Mass Air Mass concept and keeping it airtight.

Situation: 1925 Craftsman House of shiplap construction with a walk out basement/garage that is not insulated to be turned into a recording area. There are two small rooms with low ceilings that I have to work with. One room is on a slab, and the other has wooden floor joists. Plan to use one room for tracking and the other for a control room.

Problems: Part of the walk out basement wall has no insulation and also has cracks in which I can see daylight coming from outside. (Also has some type of animals, squirrels possibly, living in the ceiling of the closet which is another problem altogether) Low ceilings. A wooden floor in one room that doesn't have a slab.

Questions: In making the outside wall airtight and a greater mass, what should be the preferred order of layers of the wall, and what role will vapor barrier come into play? (i.e. outer wood/rigid foam board/vapor barrier/insulation) I've been watching some YouTube videos from the HouseImprovements channel and was wondering about the use of rigid foam board and vapor barrier in the outer wall. I don't know that vapor barriers were mentioned in Rod's book. What is the recommendation for the order of layers for adding mass economically and effectively to this outer wall? I'm considering adding (from the outside to the inside) rigid foam board with expanding foam spray caulking, then a layer of vapor barrier with acoustic caulk, two layers of 5/8" drywall, and then some fiberglass insulation for the outer wall of a double wall. Does that sound right?

I'm also thinking about taking up the decking, and filling in the space below with dry sand. Will I need to use vapor barrier between the sand and the ground? What problems might come into play with the wood floor and sand interaction such as moisture/mold/etc?

Due to the low ceiling in the room for the proposed control room, I'm planning on incorporating a cloud into the whole ceiling/floor joists overhead. (saw this in a Ethan Winer video as well as Rod's book) Is it better to fill the whole space in the ceiling with insulation, or leave a small air gap between the insulation and the bottom of the floor above? There is about 7.5" to work with in this space. What would be the most bang for the buck type of insulation for treating this ceiling area?

I know that this is not an ideal situation, but it is what I have to work with. I'm not looking for perfection, just direction on improvements that I can make on a small budget. I can do the work myself, and have a father-in-law that is a contractor for some other advice and help. Thanks for any advice and recommendations that you can give! I am already anticipating using some spray foam to plug some holes! My father-in-law also has an animal control business. I guess he's a good guy to know.

Much appreciated,



KurtFoster Wed, 10/25/2017 - 11:06

it sounds as if your ready to spend a lot of money.

you probably don't want to hear this but imo don't invest any more than you have to. low ceilings are a deal breaker and any room with them will exhibit excessive peaks, nulls and the resulting cancellations or reinforcments. there's nothing you can do other than to mitigate early reflections and perhaps do some bass trapping but you will never get even close to "right" only a little "better".

learn to work the room as it is. regardless of what you do or spend, you will never hear what is really happening. so you will be forced to learn what adjustments need to be made by listening on other systems in different environments and then returning to make the appropriate compensations. a lot of folks have been doing it that way for quite some time.

also, what you do record will be plagued with uneven broad band amplitude and frequency response. absorption does not remove a boundary, only a reflection. close mic'ing and gobos / baffles/ blankets / tents can help but don't count on doing any room mic'ing techniques with any success.

on the other hand, you never really know until you try. serendipity can pop it's head up in the most unexpected places. you might just wind up with a great sounding room just by chance. best laid plans of mice and men stuff ..... best of luck.

kmetal Thu, 10/26/2017 - 15:14

I would tend to think out to in would go rigid foam, drywall, r-value fluffy insulation, then the poly vapor barrier. There should be some sort of vapor barrier between the houses sheathing and the outer layer (shingles siding ect) so you may be able to omit the rigid foam if you’ve got the outer shearing patched up properly.

I would avoid the use of foam spray as it has a tendency to crumble fairly quickly, and will be tough to get at once it’s buried. Acoustic caulking isn’t necessary either. Non hardening silicone or butyl caulking are perfectly acceptable for acoustic use. Silicone is easier to work with than butyl.

Sand filled decks are worth it if it can afford it. Depending on your situation it may be cheaper to just do a 3/4”-1” layer of self leveling concrete on top of the deck, as opposed to trying to get underneath.

I can’t say for sure what the vapor barrier would be for your sand filled deck. When I did them for Triad recording, it was a pressure treated wood deck, sand filled, on concrete foundation. I use the standard vapor barrier/padding that was typical for the laminate wood flooring. No issues over 8 years later, and we’ve been flooded 3 times. We do run dehumidifiers as to keep things controlled day to day.

As far as your ceiling goes. If you don’t need isolation there you could leave the bays open (no drywall) and use standard building insulation in the bays. Then cover w plastic to contain fibers, and cover with fire treated fabric. You could also use 1” rigid fiberglass (in front/below the fluffy stuff to give a nice clean look. Then cover w plastic and fabric. Just way it doesn’t look all puffy.

You can always add concrete to the floor above if you need the isolation.

I’d check with what standard building codes call for as far as fire treatment, and vapor barriers. Usually there’s a relatively simple way to maintain isolation.