I have two 90 year old two flats with balloon construction and lathe and plaster interior walls. The exterior walls are stucco and vinyl siding. I want to insulate the walls to increase the energy efficiency. I'm planning to do it myself using blown in insulation. Can I do this from inside the units? What is the technique for cutting through lathe and plaster without compromising the integrity of the walls? How do I close the walls when I'm done insulating? Should I keep the plugs from cutting the holes? Help. Thanks

It's been a long time since I worked on lath and plaster. You could try saving the plugs and reusing them but I'm betting most of them will just crumble apart. You can glue and or screw a piece of lath a couple of inches longer than the holes, on the back side, then use that to back a sheetrock plug.

This site has a recipe for mixing plaster. I've never used their product, but it sounds good to me, especially if you need to make other repairs as well, while you're at it.

http://www.plastermagic.com/faq.php

Also, if you've been needing to add some wall outlets or relocate some light switches, it's easier to go ahead and do it now before insulating.

While it is possible for you to DIY on the blown in insulation, It is really a job that should be left to the pros.
There are many pitfalls that you will run into while doing it yourself.
1. Seeing its a old home, do you still have Knob and Tube wires that are used? This type of wiring must not be covered with insulation. Even though the blown in stuff is fire resistant, by covering it with the insulation you risk overheating of the wires which you can understand its not a good thing.
2. Ideally the insulation should be done from the outside of the house. Its going to be a messy job. Regardless of what you would think. The blower device used will cause the insulation to blow out of the holes you cut into the walls. You will need many holes in each cavity to get the insulation packed properly in order for it to do any good. Doing it from the inside may seem like a good idea, being on each floor is easier then climbing a ladder outside, but think of all the patches that will be easily seen on the interior walls.
Although you will also see these holes on the outside of the house, proper patching and re-painting will cover them.
3. Using blown in insulation for walls has been done for many years. Its a great method of saving energy. But for the insulation to properly provide its insulation power and to prevent moisture from building in the walls. It must be packed in the wall properly. Not doing this correctly risks mold and lack of insulation R value.
4. I do not want to convince you not to attempt this, but some jobs are better left to the pros, You may find it will end up costing about the same if they do it, rather then you. They have greater purchasing power,thus material cost them less, The labor and experiance of course cost some money, but in the end if something is not right, you can call them to fix it. They have the tools necessary to check walls for blocking which is often found in this type of construction. Tools necessary to remove vinyl siding and to put it back up. Pluggs to place into the wall to seal off the insulation access points.

Last but not least. Many folks spend countless dollars in an attempt to insulate a wall but do not consider where the heat loss is really taking place. Hows the insulation in the attic? Do you have energy saving windows, doors? What about proper ventilation in the attic? Also what about the rim joist in the basement? A lot of heat loss goes through this point in the basement. Those are areas in which DIY projects pay off big time.

Lathe & plaster walls are "rock hard" and are ideal for blowing in cellulose. I have done this to several old homes from the inside before renovating, it's the perfect time.

Use a good 2.5" carbide tip hole saw made for stucko/plaster to drill your holes. If you use a steel hole saw you'll get about three holes before you have to throw it away.

One hole per stud cavity is fine, but make sure you use a tube and "dense" pack the cellulose. If the house is balloon construction you will need to block the joist space between floors or plan to pack a lot of extra cellulose into the floor/ceiling joist cavity.

There are great videos of all of this stuff at http://startinsulating.com

Here is the video collection: http://startinsulating.com/forum/viewforum.php?f=12

quote:

Originally posted by mk1000:
One hole per stud cavity is fine, but make sure you use a tube and "dense" pack the cellulose. If the house is balloon construction you will need to block the joist space between floors or plan to pack a lot of extra cellulose into the floor/ceiling joist cavity.

Hopefully I can revive this thread a bit...

As for blocking the joist spaces between floors, how does one go about this? There's no apparent way to stuff anything in there from the outside through 2" holes. Spray foam would probably work great, but economically out of the question.

I'd thought of removing the base trim along the inside of the 2nd floor. There, a few rows of exposed lath could be removed, giving plenty of room to get to the joist space underneath.

Any advice?