For the attic, they just feed insulation bales into a machine
outside, which grinds them up and blows them through a large hose
all over the attic. For walls, they drill holes into each stud
space and blow it in through a tapering nozzle into the stud
space. The holes may be from the inside or through the siding. If
through the siding, they often then plugs them with plastic
covers. The insulation is often "cellulose", which is basically
ground up newspaper treated for fireproofing.
The basic machine for blowing cellulose into the attic is often
provided free by the place you buy the insulation from. I don't
know if they can provide the attachments to blow it through 1"
holes in the walls. Call insulation contractors for estimates,
which should cost you nothing.
My 1926 house had the walls done this way before I got it, and
some, but not enough insulation blown into in the attic. I chose
to cover that with fiberglass batts, which I can move easily if I
need to work on anything in the attic.
On Wed, 10 Dec 2003 13:23:28 -0500, Jeffrey Silverman
My (non-professional) experience is that insulating the attic of an
old uninsulated home is always worth it and insulating the "rim joist"
(runs around the top of the foundation) is helpful. Sealing up obvious
air leaks in doors and windows with various insulating materials and
caulk is effective. Storm windows are effective. Insulating the walls
may or may not be cost-effective depending on the climate and the cost
of installing the insulation.
We live in a 1921 house which had not a bit of insulation in 1981 when
we bought it. We added insulation strategically after calling the
local utility and getting a free site evaluation -- which was
surprisingly thorough and informative.
It may be that blown in insulation will suit your needs. But I would
do a little reading on insulation methods and insulation materials
before running out and picking one method over another, because it
depends on your house and climate. There are 1000s of books and
pamphlets on this subject.
You are right that insulating the walls will save money, cut down on
drafts, make the house easier to heat, etc. I fully agree. But whether
or not it is cost-effective in terms of your gas or oil bill depends
on where you live and the type of house you have. Here in NJ, a
relatively moderate climate, the payback on retrofitting walls with
insulation in my three story brick house with plaster walls was
multi-decades in 1982. I'd be dead or living elsewhere before payback.
Insulating the attic was a different deal entirely -- highly cost
The storm windows I was speaking of are for my (handsome) original
1920s wooden single-pane double-hung windows. I don't know if the
storms are cost effective today or not, but I cannot imagine living
with the incredible drafts that blow through without them. Fortunately
for me, the house came with most of them already installed, and I
added only a few and repaired about 8. The house has 18 windows on the
first floor alone! Certainly other homes with different types of
windows might fare better than mine without storm windows or
Anywayz, my point was that before spending on any kind of insulation
project for an old house, a competent evaluation is called for. Making
a blanket rule for all houses in all climates is risky. And as I say,
I'm only speaking from personal experience. I did do a lot of reading
on insulation however.
I lived in an 1930's farm house in Iowa, Dad and I did the attic, he hired a
contractor to blow the walls.
I would do the same. Check new homes in your area and see how much they use
in the attic. Use that as a guide.
I'd suggest a look at the Building Science Corporation web site.
It might give you some background on insulation needs and methods for
There are a lot of foam, cellulose, glass fiber insulations and it is
well worth research.
I used a "new" insulation a number of years ago.
I opened a wall today as part of a project and found it had
go to home depot. they have this cellulose insulation that you blow in a
space using a machine. thye rent the machine and might even give it free for
a day with a minimum purchase.
if you have enough space between plaster and the wood behind, you can make
holes in the plaster and blow the insulation in. it's certainly better than
ripping out the walls completely.
On Wed, 10 Dec 2003 13:23:28 -0500, Jeffrey Silverman
Someone in another post mentioned that there is now a substitute for
the old urea-formaldehyde insulation that was available in the 70's.
It had a high R-value, around 5 as I recall, but it suffered from
outgassing formaldehyde and some people couldn't tolerate that. The
big advantage, however, was that not only did it not expand, but
actually shrunk something like 1 %. If this new stuff doesn't outgas
and the R-value is as high, it would be a lot better than blown
cellulose which tends to settle in the walls. (fine for horizontal
surfaces, however). You might look into it a bit. Sorry I don't have
How do you sell the shrinking as an advantage? The whole point of
it was that it filled the wall cavity. The shrinking left spaces &
voids, so your R-5 was suspended in the center of a cavity surrounded
by cold air. It was also evidence of the gasses that the homeowners
were breathing. The old foam insulation was a great example of
something that would work very well in a lab, but in real life was a
It was a couple years before anyone figured out that the old Urea
Formaldehyde stuff was outgassing. I'd be slow to jump on a new
bandwagon. [and wouldn't jump at all if there is a chemical reaction
on-site that depends on temperature, humidity, or whatever other
substances might be introduced to the mix inside a wall cavity]
Cellulose, properly installed will not settle in a wall cavity. It
also has the advantage of fairly easy removal.
I insulated my house with cellulose-- then 10 years later I renovated
& needed to take down the old lathe & plaster walls. In 10 years,
there were only two runs that had settled at all. I removed about
500 square feet of cellulose easily with a shop vac. [and spread it
out in my attic].
The things to remember with installing cellulose in the walls are-
A. Inspect the cavity before you start to blow. [I remove a strip of
siding 1/2 way up the outside and inspected up and down with a
flashlight & mirror. Some 'pros' just use a snake to poke in the
cavity to be sure there are no firestops.]
B. Know how much cellulose it should take to fill that cavity-- if
you 'fill' it too soon, you need to find what is blocking the flow.
If you put 3 bags in one cavity, you need to go inside and clean up
Fun places in really old houses are where the walls reach the basement
in balloon construction-- sometimes you need to plug that with
Another spot where I've made an incredible mess was in a house that
had built in dressers in the bedroom. The builder hadn't used any
sheetrock behind the dresser. So after we used *way* too much
cellulose in one cavity we went inside to inspect & found that we had
nicely filled the homeowner's dresser with cellulose.
After that mishap we always checked behind cupboards & dressers to be
sure there was some sheetrock.
Good point-- I'd forgotten that that is one reason I used to take
off a strip of siding in the center of the wall. It allowed you to
check up & down *and* across. We would put a batt of fiberglass in
that cavity about an arm's length in. Then we'd fill the lower half,
dropping the hose right down to within a few feet of the bottom and
withdrawing it as we filled; spray a bit to loosely fill that little
bit of ceiling; move on to the next cavity until that wall was done.
Then we'd replace the siding and fill the top half from holed drilled
up within a few feet of the eaves.
If you can get to a gable end in your attic, tie a heavy sinker on a
piece of string and drop it down the wall. Measure how far down it
goes. If it goes to the basement without obstruction, you have
balloon framing. Check several spaces [you'll need to do every one
before you insulate whether you use cellulose or foam] as sometimes a
cross-brace, or some floor boards will obstruct a couple cavities.
In Baltimore you're insulating as much to keep summer heat out as to
keep the winter heat in. With that in mind you should look closely
at your options.
You need to be more concerned with getting some reflective insulation
in your attic, and insuring that you have excellent ventilation up
there. The money you spend on your attic might have a payback of a
year or two. Your walls are going to take longer to reach the
Was it this:
Looks like I can do it myself. Good thing I haven't painted yet.
High R value also (important when you only have 4 inches to work
with). I also have an uninsulated home.
With regard to the do it yourself foam, our son just checked on it and it
was going to cost over $3,000 to do the side walls of his house, blown in
cellulose cost less than $200. I would say it will be a lot of years to make
up the difference in savings, even with the increasing NG prices.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.