Well, last year I was hell-bent on saving money on heating and insulated
EVERYTHING. I tucked insulation up between the sill plates & the floor. I
wrapped all the steam pipes in the basement to direct the heat upstairs. I
put plastic over every window. I insulated every hot AND cold water pipe
where they were accessible. I put plastic over every transom and the lites
on the sides of the front door.
Lo and behold: today I walked over to the window bumpout to dust and my
stocking feet were instantly cold. I realized: where my old house has a
sort of bay (the 3 front windows and the floor under them jut out so the
room isn't square, it has a sort of built-in bay--I don't know what to call
it!), THIS part of the floor actually is part of the porch! And there is NO
INSULATION under it. The dining room does the same thing! YIKES! I must
be just pouring money through those floorboards!
So tomorrow I'm crawling under the porch to see how the joists run and what
I can do to insulate.
What would you recommend for this application? Would fiberglass or rigid
foam be better? Should it be foil backed? I am worried that anything I put
up that is outside will be a haven for bugs and wood rot. Is there anything
I should do to prep the area first? How do I get it to stay in place?
Thanks for any help/advice.
What's under the area? Dirt? Is the area underneath enclosed with
concrete or blocks like the basement? Or sheathing of some sort? Or
open to the air or latticed? Is this area open to the basement or
separated from it by the house foundation? Describe it. This could
make a difference in ways to insulate. I have a dirt-floored crawl
space under my kitchen, for example, but it is connected to the
basement by an opening at the top of one wall (there is a huge boulder
in the crawl space -- about as big as a couple of station wagons, I'm
thinking. When the house was put up in 1921, they simply left it there
and built the kitchen bump-out over it). Anyway, I was able to
"insulate" by simply laying several heavy sheets of plastic over the
dirt and weighting the edges along the foundation walls with bricks. I
could have also laid insulation on top of the plastic. In my case,
because the basement opened into the space, it was a lot more
effective to isolate the dirt floor than to attempt to insulate the
basement ceiling (the floor of the kitchen).
The living room portion extends out onto the porch portion, which runs the
length of the house. Under it is dirt. Lattice needs replacing, so it is
exposed on 2 sides now, but unlikely to get wet, unless a hurricane or major
flood comes through.
The dining room portion is exposed, just hangs off the side of the house.
I've planted azaleas up close around it, but they are still rather small.
I have a 9 by 12 foot bumpout laundry room with four feet of clearance under
it, and no side walls under that space. I filled it with 6 inch fibreglas
batts, then screwed on 1/4 inch exterior plywood to hold it in place. I
didn't vent the area, since there are crosswinds under there, and
overhanging roof eaves keep rain and moisture out, but I didnt caulk the
seams so some air would get inthere. If there is any chance of rain or
moisture getting trapped , you could use zig zagged wire, or chicken wire
stapled to the joists, to hold the batts in.
I would if it were my house. The reason is that air infiltration might
be a big issue, since floor boards are not exactly air tight. In my
old house, drafts and air infiltration are more of a problem in many
areas than actual lack of insulation.
Here's my solution: Put a vapor barrier against the floor. Add
fiberglass or rigid foam insulation per Roger's suggestion. Then put
some sort of sheathing over it -- plywood would work, as Roger says.
To hold the insulation between the floor joists until you can put the
sheathing over it, use flexible wire holders that fit between the
joists, available at home centers and lumber yards (are there still
any lumber yards???), or use the cris-crossed wire method.
Since the interior areas do not cover the entire porch, you would
either have to block off the edge of the outside wall under the porch
to enclose the newly insulated area (I would cut 2 x 6 blocks to put
between the joists) or insulate under the entire porch. I think
blocking off the area would be easiest and cheapest and most
Personally, I think you've located a significant source of heat loss
that's worth fixing, and good on ya for it. I'm not a contractor or
anything (as everyone can probably tell) but just another homeowner
who went through this kind of thing around 20 years ago. It's sort of
fun. I liked the challenge, and I did save quite a bit on heating
bills and improved our living environment.
I would suggest that as soon as practical you find more permanent
solutions to some of your "plastic" insulating. For example, I found
that putting up plastic storms in a couple of spots every fall got old
pretty quick, and it wasn't long before I was skipping it. I just had
other things to do, like making a living. Adding real storm windows or
replacing the windows made life easier, got the job done permanently,
and looked a whole lot better. Just my experience.
Thanks for your reply. I think I'll do it just as you described.
Regarding the plastic on windows:
I do have storms, but this is quite an old house (more than 100 yrs) and the
windows are just not tight, so I started doing the shrink wrap thing. Then
I found these plastic channels that you can apply to the window, put up the
plastic sheeting, and snap another piece of plastic into the channel to hold
it. It looks really nice, and is a great way to cheaply insulate things
that don't have storms, like the window lights around the front door.
Someday when I'm rich I'll get replacement windows. I'll have to be rich
because I'll need every one of them custom made--the house has sunk & sagged
so much over the years that a good many windows are visibly crooked!
I've seen these and they are easier I'm sure. This house had
combination storm windows on most windows already. All I had to do was
repair some of the screen portions and fix some of the slides.
Seven larger windows had aluminum storm inserts -- not sure what you
call them, but they had frames into which one puts a glass pane on top
and a screen on the bottom. In winter, you take out the screen and
replace it with a second glass pane. They work great, but it's manual
work every fall and spring. But only seven windows.
I hear you. We practically went nutz trying to fit 10 of our windows
with Roman blinds. I thought I would have to put my wife in a Home.
We replaced all the windows on the second floor (all the windows were
pretty much ruined with moisture, warping, and 50 layers of flaking
paint) with aluminum windows with double pane glass. Not as expensive
as I thought it might be (but this was 25 years ago). Frankly they do
not work as well as the original windows with storms on them, which
are now 83 years old.
On third floor we had new, larger windows installed, vinyl-clad wood
double pane. They work great and look good. More expensive, naturally.
>> is NO INSULATION under it. The dining room does the same thing!
>> YIKES! I must be just pouring money through those floorboards!
This is basically what I did with a small dinning room overhang.
I filled the floor joist area with fiberglass (faced toward the floor
above) insulation and nailed 1/4 inch exterior grade plywood to hold it
and close the area. Then it got a good primer and house paint coat
over the bare wood. --Phil
Phil Munro Dept of Electrical & Computer Engin
mailto: email@example.com Youngstown State University
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