Someone with your spelling and grammar skills calling anyone else
dummy is funny.
If it is bad advice, explain why. Do you know anything about the
subject matter or do you just like to spew your ignorance as a part of
You need good ventilation under the roof deck to cool the roof. Otherwise, the
shingles will die early.
Insulating the roof will require more insulation for the same job.
Why foam? You can probably use fiberglass for way less $, and it can be removed
if you need to work on the wireing. In an unused attic, you can have as much
insulation as you want.
Will you really have an attic space, or just a bunch of gaps between trusses?
A layer of plastic will be just as good of an air barrier.
How does the foam survive over time when subjected to the extreme heat a metal
roof will transfer? Especially if there is not a ventilated airspace between
Your builder and wife are both correct but I don't think you
understand that they meant doing both the ceiling and the roof. Your
logic is also correct given your apparent misunderstanding of what
they meant. The roof insulation must be installed properly with an
airspace between the roof and insulation providing an air duct from
the eve to the ridge. If you don't do this the life of your shingles
will be greatly reduced. I suggest you don't let this attic space go
Either method will work well if done properly. Heat loss (in the
winter) or gain (in the summer) depends on the surface area of the
thermal envelope and insulation values. The actual volume of the
conditioned space does not matter directly. Since the roof is a
larger area than the ceiling, if you make the roof part of the thermal
envelope you will have somewhat more heat loss/gain, unless you
insulate it to a correspondingly higher R-value.
But it is not a large effect, and there can be good reasons to
condition the attic space. For example, if your HVAC equipment will
be in the attic space, then there are advantages to having all the
ductwork in conditioned spaces.
As others have mentioned, if you do insulate the roof, then the roof
deck can get quite hot in the summer unless you take measures
otherwise. Depending on the roofing material, this can be a problem
(e.g. with asphalt shingles). But I believe you mentioned using a
galvanized metal roof; I don't think roof deck temperature would be an
issue for that material.
On Fri, 5 Mar 2010 00:20:25 -0800 (PST), Alim Nassor
Not a Psychologist.
We live in the Mojave desert. A friend's new construction a few years
ago had the attic ceiling sprayed with ICYNENCE tm foam.
See this page: _Insulating an attic ceiling_
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