Insulating partially finished 1890s attic.
![](https://secure.gravatar.com/avatar/ae2b21a02a5843e9477c98553f30ec75?s=52&d=https%3A%2F%2Fimages.finehomebuilding.com%2Fapp%2Favatars%2F200x200%2Fw.png&r=g)
This post related to a large balloon frame house in Buffalo, New York, built in the 1890s. The attic floors are all finished with t&g pine over 2×10(?) joists, with lath and plaster being the ceiling material of the rooms below. In some cases the lath and plaster was subsequently covered with a layer of 1/2″ drywall.
Most of this ceiling/attic floor area has no insulation at all, but that’s obviously not a good thing, so we’d like to change that.
Because some of the wiring in the floor/ceiling is very old we would prefer not to simply blow something into the joist bays, for fear of compromising the wiring. Ripping up the whole floor to rewire and insulate is not an appealing prospect.
What I’m thinking of doing is simply laying fiberglass bats on the floor in the areas that aren’t occupied with storage. This could be about 50% of the total floor area.
1) Is there any point in that, or is it all or nothing in this sort of situation.
2) If I do do this, should I put plastic down under the insulation as a vabor barrier?
The attic rafter bays are uninsulated and there is plenty of air movement through the attic.
Replies
You have to be very carefull in how you insulate an old home. Modern insulation techniques rely on blocking vapors, and keeping vapor from intruding into the cold areas so they won't condense and cause rot within an assembly.
Your old house breathes, which is great for passing wator vapor in and out of the assemblys without condensation... but not so good for insulation.
Do some reasearch at the http://www.buildingscience.com/index_html website, you will need to understand how to insulate without suddenly rotting out your house.
Charge........
I think the only heat you'll save (generate) with partial placement of batts as you describe ..............
is the energy you expend doing it.
Wiring first, plugging all the holes in the envelope second and then you can concentrate on insulation.
It is not the easiest or cheapest option, but to do less would be more a waste of money and energy than you would save in the addition of insulation in your attic.
Revisiting this topic
I'd like to bump this topic up again, and refine the question.
My current thinking is this, especially since we had a fully vented roof installed and it will now be colder (at times) in the attic, to remove the attic flooring and do the following.
1) Replace old wiring.
2) Seal any holes/gaps/etc around wiring/pipes/etc.
3) Start at the bottom of the rafter bay (against the lath of the upstairs ceiling) with a 1"-2" sheet of rigid insulation with a foil face cut to fit in the joist bay.
4) Foam in a can around the edges of the rigid foam to create an air seal isolating "above" and "below" and radiant barrier with the foil.
5) Fill the balance of the joist bay with cellulous - either blown or simply dumped out of the bag and raked out.
In reality this would probably be done incrementally and it will be a pain, but I can't really think of a better way to accomplish as many of the desired effects as possible.
I would foam under the roof (with set-off to allow venting under the roof deck) but I am paranoid about leaks and the fact that I'd never know if they were there in that case.
Thanks in advance for any thoughts.
There are a lot of advanced techniques for insulation and those mostly are for new homes of this age. If you would like to do something for old home then check with any contractor and ask them the procedure. How are they going to do? and what are the measures they are going to take to prevent any dmages?