Insulating the Kitchen

Our house is a standard “older than World War II, younger than World War I” that you find in the midwest. From what I can determine by the various types of foundations (I count FOUR in less than 1200 sq ft, old cast concrete basement (coal window and storage evidence exists, along with the base of a gravity furnace), expansion on a block basement, expansion on an insufficient crawlspace, and a slab) the kitchen was a relatively early addition to the back of the house.

We had major foundation sinkage on the crawlspace part (kitchen) which we got fixed by a foundation lifting company (costed about $14k, worked well). The kitchen had been “cheaply/flip” redone on the sag, so leveling it made it clear that a redo was called for.

So far we’ve removed the ceiling and insulation (it was very old and non-asbestos) and found that the ceiling “joists” are clearly not very load bearing (they reach most of the way across the 13 feet and then are nailed to a shorted joint that is resting on … the drywall!) - so I’m going to put in new crossmembers (the roof is raftered and those are supported well at the edges, the new joists will tie into them) and reinsulate.

I’ve been looking around and reading/listening/watching to various discussions (for example Vapor Barriers: Do we REALLY need them? - YouTube) and I think I’m going to go with a “smart vapor barrier” on the inside, with very thin LED lights sealed with tape to the barrier (currently looking at INTELLO INTELLO PLUS - intelligent vapor variable, airight smart vapor retarder and densepack netting - ProClima or SIGA SIGA Majrex 200 Membrane · OTG Supply ) and then using rock wool as the insulation. I can get R-15 between the joists and then overlay it with two layers of R-30, and then similarly smart barrier the walls and at least get R-15 in there.

Part of the goal with the wool is getting something that won’t catastrophically fail because we are NOT redoing the entire building envelope, just the relatively small kitchen. I want something that’s better than what we had, but also is “vapor open” at least somewhat.

Everything I’m finding above the ceiling is exceptionally dry so I do not think I have leaks to deal with.

Anyone done similar? Tips/tricks I should be considering? My goal is to make an air barrier on the room as best I can, and insulate before we throw drywall and redo the cabinets/floor.

The lights I have are Juno® 6" LED Flat Wafer™ Downlight - 6 pack - they are thin enough that you can mount the power pack above the insulation and slip the cable through the insulation and vapor control layer and then put the lamp in, removing the recessed can light “hole”.

Interesting - I’ve been talking with some people about “aggressive re-insulation of ancient homes” recently, so certainly interested in what you work out.

What’s your climate? The short answer with vapor barriers seems to be, “If you’re stupidly dry, it doesn’t matter, and if it’s stupidly wet… don’t bother.” So I remain slightly uncertain as to what actual problem they’re solving.

We’re in 6 but just below zone 7. My research for now seems to agree with the vapor barrier - the good they did was because they were an air barrier which is the key - air moving through the wall will bring gallons and gallons of water with it - for example: Breathing Walls? - Green Built Alliance

If I were doing the whole house it’d be pretty simple, really, tear down inside walls, reinsulate and use a smart barrier (these pass code but also allow the walls to dry, some of them are “one way” which is even better; will allow moisture out of the wall but not into it) and then use an air seal and external insulation on the outside of the structure below the eventual sheathing.

As it is, I’m going to try to duplicate as much of that as I can from the inside only - I want to get something better but certainly don’t want to make it worse.

My understanding is that it’s reducing condensation build-up inside the insulation itself. Thermal difference, and thermal swings throughout the day cause the density to change, bringing in moist air and then permitting it to condense inside the insulation. The vapor barrier goes on whichever side faces the highest humidity (although I’ve heard it makes no real difference and most builders I had interaction with seem to put it on the outside), reducing the condensation possibility and permitting a one-way breath-back action which tends to dry it out effectively. If it’s got two-way breathing action (no barrier) then it’ll just suck more humidity in from the other side which doesn’t help dry it out. Exactly why or how this works, I don’t know, but I do know that in climates in which I’ve lived, at least, if you don’t have it or you put two, you end up with wet soggy black-mold filled insulation over a surprisingly short period of time, and if you have the requisite one-side-barrier, you don’t. That’s about all I know, and I’m not a building expert, wish I could explain it better.

Of course, it also does help prevent breath-through which blows out the insulating air layer and reduces the effectiveness of the insulation, too.

And yes, even in dry climates trapped condensation is a problem - there’s always a cool side and always a temperature swing through the day, You can run condensation units in the driest deserts known to man and get water out of the air, so just because it seems dry to you doesn’t mean it’s not a risk.

Yeah, you either design away the condensation layer or you move it. The BSC stuff has lots on the science but you can control a lot of it with controlling air movement.

The two sheets is the worst possible because you get a “dirty diaper” setup. This is why you want to be careful when redoing a wall or an outside cover because if you add vapor block and there already is one you’re in for a bad time.

Moisture Control for Residential Buildings | Building Science Corporation I might get this book but the info is on the website for free, too.