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Tom,<br>
<br>
2 cents worth:<br>
The usual rational for limiting the thickness of spray foam is based
on a payback calculation. Foam is expensive; more is more so. The
first half inch or so is usually enough to achieve an adequate air
seal - assuming that they covered the critical joints. <br>
<br>
It would help for you to know the length of time and energy costs
that the insulation company used in their calculation. I would
guess that it's based on current energy costs and the "average" time
before a homeowner sells. The turnover rate is still wildly skewed
by the collapse of the housing market; utility costs are very likely
to keep climbing, unless you are going off the grid.<br>
<br>
If you are going to stay there a while, or if effective
insulation/lower utility bills are a perceived added value in you
area.<br>
It is more cost effective to add insulation now, assuming that the
ceiling hasn't been installed yet, because you have access at no
additional cost. Any insulation will work the fill the remaining
space. Batt material, usually fiberglass, is easiest but must be
carefully fit to fill the space without gaps or compression. (You
can actually compress it slightly but it's inadvisable to add
downward pressure on the ceiling.) Other materials are available as
batted insulation in some areas.<br>
<br>
If the ceiling is up, a skilled installer can still blow cellulose,
or special fiberglass, in through relatively small, easily patched
holes - at least one per cavity. It should be lightly "dense
packed" so it doesn't settle and shift over time.<br>
<br>
I hope this helps. <br>
Bob Klahn<br>
<br>
<br>
On 5/10/2011 4:07 PM, <a class="moz-txt-link-abbreviated" href="mailto:tom@honeychrome.com">tom@honeychrome.com</a> wrote:
<blockquote
cite="mid:20110510130734.829494f83a1efe767477bcfea0b8f9b3.bafbfcaab2.wbe@email02.secureserver.net"
type="cite"><span style="font-family: Verdana; color: rgb(0, 0,
0); font-size: 10pt;">
<div>Asked this once before but didn't get any answers, so I'll
try again...</div>
<div>Had spray urethane insulation installed in the cathederal
ceiling of a small house being renovated (upstate NY). The
rafters were only 2x6 and the installers sprayed in 4",
claiming that anything more wouldn't be of benefit. So, there
will be about 1.5" of space left between the urethane and the
ceiling. I'm wondering if it is worth filling that space with
insulation (fiberglas or rockwool) or is that possibly asking
for moisture problems? In fact the house is pretty tight and
pretty easy to heat, but I'm about to install the ceiling
paneling and wonder if I might regret not filling all the
space with insulation later...</div>
<div>Thanks<br>
</div>
</span>
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