Hell all. Did a search on here and found some answers but not all. So
here goes my questions.
The house was built in the 1860's. Doing an attic where I will be
insulating the walls and ceiling (cathedral I think it is called). It
will be against the old clap board siding with it's many tiny holes in
it. So how would I go about making it air tight before I put the
insulation in the walls? Or should I?
Live in the Indianapolis area so any special needs? Vapor barrior?
Also someone said something about putting in soffet? And something
about the bottem 12" remaining free of the insulation for venting.
Anyways I am looking for all information I can get since I am doing
this for an older lady from my church and don't want to screw it up.
Oh and if you have some link that would be great.
Unless the attic is living space there is little value in insulating the
walls. Ditto the roofline.
The number one heat loss factor is through the ceiling. R-38 in this area
and some caulk for air infiltration could easily cut her heating bill in
half. If you insulate the living space below from the attic above that is
your greatest payback. Sometimes with a floored attic this is hard to do.
Is that you situation?
It is important to allow for airflow for the roof in situations where the
roof rafters have insulation added between them in a true cathedral ceiling
situation. I doubt you have that in pre 1900 construction. Also, I think
you have not clearly understood something that someone has posted about
soffitt and the bottom 12".
Post again with more info and myself or one of the regulars will try to
answer you questions.
And thanks in advance for helping the old folks.
Is it a heated attic, unheated you insulate the floor, if heated and do
the roof deck you need an airspace between the deck and insulation with
venting, a soffit and ridge vent. You better learn before you mess up
her houses design.
The soffit will be a horizontal panel (vented) between the lower edge
of the roof and the wall of the house. You'll also need a ridge vent
on the roof as others have mentioned. Then, with a cathedral ceiling,
you need to provide a space on the underside of the roof
sheathing/boards for air to travel freely from the soffit all the way
up to the ridge vent. There are styrofoam baffles that can be easily
stapled in place against the inside surface of the roof. Then you can
fill the remaining cavity between the rafters with insulation. If this
is living space, get the insulation batts with a vapor barrier and
install with the vapor barrier down (towards the living space). Then
you can finish the ceiling with drywall or whatever you feel like
If this is not heated living space - then as others mentioned, you
still need the soffit and ridge vent, you'll want at least a row of the
same baffles down near the soffit. Then you can insulate the floor of
the attic space (ceiling of the room below). The baffles will ensure
that air can get past the insulation and flow up into the unheated
attic then out through the ridge vent.
On Fri, 16 Dec 2005 04:19:13 GMT, "Colbyt"
I should have said that the woman had three attics. Two she had blown
insulation put in and likes the savings on heat. But she needs to keep
the third for storage. So it has a wooden floor to walk on (nothing
solid just plywood). But it is the backside of the clapboards and has
some little holes all over the place.
The room isn't a true cathedral but I do need to do the walls and the
roof. It sorta looks like this:
| || \\
This is a rough look but the left side is the wall to a room. The
right is the roof. And the || is a window where the clapboards are. I
was wondering how to keep the small holes in the clapboard area from
blowing in (some type of fiberglass sheathing like I see on the
outsides of houses?). And Also I sorta see what is meant that I need
baffles on the bottom. But the ridge vents. Do I need to cut out the
top of the roof to put them in?
Also I didn't look but I think that the roof continues on past the
wall to the room on the left. so how would I put in ridge vents?
While I am still ready to help the woman out I am seeing that I need
alot more information. I am going to follow one guys advice and look
at the how to book but any advice that people have is still needed by
One other thing. The soffet. It is an old style house. Wouldn't
putting aluminum soffet kinda ruin the look?
Insulating the wall on the left makes sense using standard fiberglass batts,
vapor barrier turned to the heated side. Insulating under the existing
plywood floor makes sense if it can be removed and replaced. If these two
things are done no soffitt or vents are required the roof will have the same
airflow afterwards as before. Another option would be just to roll
fiberglass batts out over the existing floor but you lose the storage space.
Frankly trying to insulate the entire attic in my opinion is a waste. It
might help a little but the payback is no where near what it would be if the
above is done. The heat is still going to leave the home and move to the
If you choose to disregard this advice, you need to maintain 1.5" of
clearance between the bottom of the roof boards and top of the insulation.
This greatly reduces the R-value you can install. The old house is most
likely leaky enough that if you do that you can avoid adding soffitt vents.
That is just an opinion not a know fact.
As for your holey clapboards you could use house wrap in one big piece
folded over the studs, into the stud cavities and back out before you add
your fiberglass batts.
IMO the little old lady needs to choose warm and cheap or storage for junk
she doesn't need.
Look at Building Science Corporation web site.
Lstiburek says in part: In general, in cold climates, air barriers and
vapor retarders are installed on the interior of building assemblies,
and building assemblies are allowed to dry to the exterior...
I'd see if the local historical preservation society wouldn't be
interested - you could probably get architectual advice for free. If you can
CLAIM U.S. Grant slept there or the house was a way-station on the
Underground Railroad, you might be able to get grant money from the
======*Years ago, my city wanted to give a little old lady $200 each for five old
oak trees whose removal was necessary to widen the road. She asserted the
trees were hand-planted by King Gustav V to commemorate the city's Swedish
citizens who lost their lives in the Great War of 1917. And the trees WERE
on the National Historical Registry (due to an earlier claim). The city
didn't get out for a paltry $1000. I think they moved the road.
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