we have an old victorian house and we are about to replace the gutters and
insulate the roof. Is there a web site where I can see the different
approaches? Do we have to ventilate from the soffits up to a ridge vent or
is there an alternative? I really don't want to cut a slit in the roof right
now, I would prefer a solution where we could spray something into the gaps
in the rafters and just put up dry wall over it BUT I read somewhere that
you have to have ventilation for moisture. This implies to me that when we
get the gutters replaced and they throw away all the old crappy wood planks
its hanging off, that we hang the gutters from aluminum with air slots in
them. These slots vent air into the gap between the insulation and the roof.
up to the ridge and out the ridge vent. I would prefer to A) not have the
ventilation gap at all b) have the ventilation gap and have it go to a tube
at the top that gets vented out of the sides of the house. Please help me
the house is north south orientated and the attic will be heated as we are
converting it into living space. The floor will be bare wood with living
accomedation below. We do not intend to insulate the floor as it tops our
bedrooms and we don't see the point.
Harry, I refer you to the following article:
The Building Science website has a wealth of information, based on
actual research and scientific principles.
this seems to be exactly what I need to read and I will also contact them to
see how to approach this. Thanks to all of you who replied and helped me out
have a really great new year
Conventional approaches also include venting at the ends of the roof and
having a small attic space at the top using collar ties. There are foam
baffles that you can place against the roof where you will have insulation
and wallboard directly on the inside. They provide a space for air flow
from the soffits to the attic space. Lowes has them.
Yes, they do have some good stuff here and they have some questionable
stuff, and I think this is an example of the latter. As someone has
already mentioned, there are drawbacks to having a roof of this type.
One is the heat issue for the roofing materials. With insulation right
under the sheathing material, the heat from the sun has nowhere to go
except into the shingles and then be radiated or convected to the air.
Conduction through the sheathing will be minimal. Depending on your
roofing materials, this may or may not be an issue.
I had to laugh at the "advantage" of the foam insulation providing an
extra layer of leak protection. I agree that it likely will do that,
but I see this as a major disadvantage, not an advantage. Sure, a leak
will cause damage to interior drywall in a conventional design, but it
also lets you know RIGHT NOW that you have a problem that needs
attention. A roof with spray-on foam insulation could leak until the
sheathing is rotted and structurally unsound and you might never know
you had a problem ... until someone walks on the roof and falls into the
attic. Trust me, that will cause more damage to interior materials than
will a small water leak, not to mention the damage to the person who
falls through you roof.
I am amazed that anyone would write that as being an advantage.
Yes, I agree. Let someone else find out what happens to those ideas
in 20 years. Converntional constrution techniques allow for ample
insulation and attic ventilation.
If you have 2x10 roof joists then that is deep enough. If they are
less then build them out where you expect to put wallboard. Install
baffles and create a small attic space above. Vent at the ends.
Insulate and finish.
I meant what is existing set up. An air space and R7" foam of a high R
value near R60 would be best. Foams go from R5-R7.2". How much you
use is most important, Codes are minimums, not optimal values. Im Zone
5, my local code is R35, here R 60 is considered optimal. But since I
used Fiberglass and it Looses R value when real cold and it settles I
used R 100 - 110 . To be optimal I bet R 60 is a good objective if you
live in cold area, what are the beams, 2x6. 2x8, 2x10? shimming down
should be connsidered for more foam. This is the most important area
to insulate, do it right. www.energystar.gov is a place to research.
right now there is nothing but a 14' attic 25' wide and 60' long. 2' knee
wall. not sure what the beam size is but will make sure I measure. Thanks
for the advice and I agree R60 would be great BUT I will make the
measurements to see what I can achieve in the space allowed. thanks for your
great help it really has been useful
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