Home repair ignoramus here.
My boyfriend wants to insulate the attic. We don't intend to turn it
into living quarters. We just want to help keep the heating bills down.
He says he wants to insulate both the roof and attic floor. I say just
to do the attic floor. By the way, there is no ventilation in the
attic...no soffits, no ridge vents, no attic fan. This is something we
will be dealing with eventually, but my thoughts about insulating just
the attic floor have to do with allowing the attic to breathe a bit.
What do you folks think?
TIA for your opinions,
bonnie in Oklahoma
Well the conclusion is definitely the correct one albeit slightly wrong
in reasoning. If were to do both, would end up w/ high probability of a
condensation problem and that is almost always an issue against a roof.
You definitely need some attic ventilation and it really ought to come
sooner rather than later (the "eventually" prompted me to say that)...
Venting is not the only answer.
Take a look at The Building Science Corporation web site.
It includes work by building reasearchers.
This is a link to a series of pieces on vented and unvented roofs.
Great website. Thanks. The house was originally built in 1961. The attic
is kind of divided up in compartments. The second floor has gables with
small attic/storage spaces between and on the sides of the gables. Over
the second story room is another attic space, about 4 feet tall. There
is an A/C unit up there which is just for the second floor. It was put
in many years after the home was built.
We also need to insulate the walls. We don't think there is any thing
there. I guess you'd have to shoot that foam stuff in there. Is that a
job for a professional? We have aluminum siding which I hate. (White
stuff rubs off from it. Oxidation???)
bonnie in OK
no vents is not normal, but unless there is mold on the attic ceiling
that was its design, it worked. Only the floor should be insulated ,
and at maybe R 40-50, but then you must get sufficient venting to keep
the attic temp near to outside temp or condensation, mold and rot
There is no mold or mustiness. The attic spaces are all dry. If
(emphasis on If) the attic is presently functioning with even flow of
moisture/air and heat/cold...and I put insulation on the floor, I can
see how that would change the "balance" since air wouldn't be rising
through it. Is it possible it would reach a different equilibrium...just
base on changed circumstances? Am I making any sense?
b in OK
Unless there is clearly already a vapor barrier, be sure to install one or use
insulation with one. The vapor barrier goes between the heated area and the
insulation. This will at least decrease the moisture getting into the attic to
cause problems. Venting should still be done ASAP.
BTW in certain instances the use of ' certain oil' based (non-latex)
paint on 'interior' surfaces will act somewhat as a non permeable
A certain house here that the owner couldn't keep paint on.
Problem, outside husband was painting with non breathable (non-
permeable) marine paint. Inside wife was painting with latex paint
(easy to clean up with water etc.) No vapor barrier on warm side of
the walls and ceiling, lots of cooking etc. moisture trapped in walls,
outside paint blistering. The owner never did figure it out.
Eventually put vinyl siding on and now has some rot problems inside
Insulate ceiling only. Ventilate the attic.
It's not a matter of 'allowing an attic to breathe a bit' a rotted
roof is expensive to replace.
For example; Canada standard IIRC is 0.3% minimum percent venting
'distributed in such a way as to allow cross-ventilation. (That's a
'minimum' of three square feet for every 1000 sq. feet of attic area.
We have added soffit vents a couple of times to our approx 2000 sq.
foot attic, over the years to ensure adequate ventilation and in
summer we also open a screened hatch in one gable. Potential rot and
mould up there without venting is likely, depending in part on your
climate and life style.
Also check the vapor barrier of your ceilings to minimize warm and
therefore damp air reaching the attic.
You are completely on the right track. It's amazing how many people do
not understand the importance of NOT having moisture condensing up
there. Do some more reading on vapour barriers.
On a regular basis we even have people asking 'Is it Ok to vent a
bathroom or a dryer into the attic"! Not realizing apparently that all
those pounds of water in warm damp air will condense somewhere up
there!!!!! Mushrooms/fungus anyone?
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