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Posted by on January 7, 2009, 2:03 pm
> Astro wrote:
..
> >>>> Hi all
> >>>> we have an old victorian house and we are about to replace the gutte=
rs
> >>>> 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 v=
ent
> >>>> or
> >>>> is there an alternative? I really don't want to cut a slit in the ro=
of
> >>>> right
> >>>> now, I would prefer a solution where we could spray something into t=
he
> >>>> 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 w=
hen
> >>>> 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 slo=
ts in
> >>>> them. These slots vent air into the gap between the insulation and t=
he
> >>>> roof.
> >>>> up to the ridge and out the ridge vent. I would prefer to A) not hav=
e 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 he=
lp me
> >>>> out
> >>> Without air circulating up standard shingle roofing on the S side can
> >>> go bad in 5-7 years from excessive heat in summer. Is it a heated
> >>> attic, or is it open to air and the floor insulated.
> >> 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 livi=
ng
> >> 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:
> >http://www.buildingscience.com/documents/digests/bsd-149-unvented-roo...
> > The Building Science website has a wealth of information, based on
> > actual research and scientific principles.
> > -Ted
> Yes, they do have some good stuff here and they have some questionable
> stuff, and I think this is an example of the latter. =A0As someone has
> already mentioned, there are drawbacks to having a roof of this type.
> One is the heat issue for the roofing materials. =A0With 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. =A0Depending 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. =A0I agree that it likely will do that,
> but I see this as a major disadvantage, not an advantage. =A0Sure, 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. =A0A 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. =A0Trust me, that will cause more damage to interior materials tha=
n
> 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.
> Matt- Hide quoted text -
> - Show quoted text -
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.
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>>> >> 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
>>> >> out
>>> > Without air circulating up standard shingle roofing on the S side can
>>> > go bad in 5-7 years from excessive heat in summer. Is it a heated
>>> > attic, or is it open to air and the floor insulated.
>>> 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.