[LTParis]

I have a circa 1930's home in the cold northeast that lacks virtually all insulation. The walls are lath and plaster so insulating from the inside is almost a show stopper, there is also no outside house wrap.

One thing that intrigues me is the spray insulations like WALLTITE, however I am unsure if you can essentially "spray blindly" since it would be applied in the wall gaps.

If possible this seems more effective than blown cellulose since it creates a seal, and also acts as a vapor barrier. I am just unsure if this is really a viable option in my case.

 

[Windows on Wash]

Vapor barrier recommendations are dependent on location.

CC SPF is a better air seal and will serve as a vapor barrier (class 2 at 2" in most cases)

The SPF will require a bunch more demo to get to everything whereas the cellulose will allow you to dense pack via more surgical installation locations.

If you are doing and exterior cladding change out, the insulation schedule changes dramatically as does the interior demo.

What are you going to do to the home?

 

[LTParis]

Well still planning things out. Originally I wanted to dump the lath and plaster but it's in general very good shape being 80+ years old. The amount of demo that would need to be done to take it out would likely be staggering.

The goal is to change out some things on the home, while keeping the character and the quality of the house. For instance I would not put in vinyl siding just to cut costs, I'll replace old/damaged clapboards with new ones. Same with windows, either a refurb of the current counter-weighted wood windows or replacement wood windows.

However a big concern right now is it looks like I will be spending $400/mo on oil fired forced air heat and hot water. The hot water tank is pretty mizerly, and sipped through ~50 gallons of oil in from April (when we bought the house) till October. However now that it's getting cold and the heat is on, the lack of any real insulation in the house, combined with it being oil, is sticking me with $400+ month oil bills. The tank is new, and the forced hot air heater is pretty new and efficient. So my goal is to swap out with gas and insulate where possible.

Thanks to a bonus room in the attic, getting the roof insulated looks to be a real challenge, so I was thinking the spray insulation like WALLTITE. The walls though look to be an even bigger challenge so I was wondering if blown cellulose would be the best application for that, or if things like the lack of a vapor barrier, combined with likely poor sealing around gaps would make blown cellulose less attractive to shoot for.

 

[Windows on Wash]

Air seal and insulated first. That will be your biggest return on investment.

 

[Fix'n it]

The amount of demo that would need to be done to take it out would likely be staggering.

if you are doing it "by yourself", yes it will be staggering. ask me how i know.

but, if you have some friends (or hire good helpers), it will go A LOT faster and easier. if you could muster 10 good helpers, and have things preplanned = place to put the waist, buckets, hammers, etc. 1000sf house, walls and ceilings could be done easily in one day. ask me how i know this.

do it on a windy summer day.

 

[LTParis]

Any other tips if I were to rip out the old lath and plaster?

 

[Fix'n it]

Any other tips if I were to rip out the old lath and plaster?

search plaster and lathe on this forum, and also youtube. also have your insulation plan finalized = what you plan to use, have it in place. plan on doing wiring = more outlets, removing the old wiring, whatever. try to secure helpers to help you reinstall all that stuff.
check you ceiling joists = are they flat enough ? perhaps you will need to sister new ones. ask me how i know this.


its not hard, just a lot of work. i didn't want to do it myself. i was only going to do the outside walls, for the insulation. but these guys talked me into doing all of it. and i did new windows. in the end, i KNOW i will be MUCH happier doing it this way. and the value of the house has gone way up.

oh, and here is a BIG ONE = hope and find out if you have metal lathe in the wall. this makes it tougher, in my experience.