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<div class="moz-cite-prefix">On 4/24/2013 7:05 AM, Alan Abrams
wrote:<br>
</div>
<blockquote
cite="mid:CADj3_s7eKhXXAFxc-aW4iR4dMhaORTkM4GjLk8xkTdXtcSTZ_Q@mail.gmail.com"
type="cite"><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><The
'time to heat' a high mass house can be an order of magnitude
longer than a light house, and its return to ambient is
similarly long.></span>
<div>
<span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br>
</span></div>
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">to
what extent is that a factor, assuming more or less continuous
occupancy and forced air heating? if it were a troublesome
issue, it would be a disincentive for moody climates.</span></div>
</blockquote>
<br>
Forced air heating wouldn't be my first choice; one would need to
transport a <i>lot</i> of air to heat the building should it cool
down. Time to heat is only a concern if the temperature is setback
for some extended time. With continuous occupancy, the issues
diminish, as the house is always close to optimum temperature. I am
not sure what you are implying with a 'moody climate'. If
inhabitants like to adjust the temperature based on weather outside,
high mass is not recommended.<br>
<blockquote
cite="mid:CADj3_s7eKhXXAFxc-aW4iR4dMhaORTkM4GjLk8xkTdXtcSTZ_Q@mail.gmail.com"
type="cite">
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br>
</span></div>
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">but
the subtext of all this is whether an AAC wall is sufficient
on its own, as its proponent put forth. my position was
simply that in a 4000-5000 HDD climate, with long periods of
low temps and no sunshine, additional exterior insulation is
advised. </span></div>
</blockquote>
<br>
I would suspect that it would depend on the details of that AAC
wall. The steady-state R-value touted seem to vary wildly, from
around 1.1 per inch to 3.9 per inch, I would want a pretty thick
wall of the former. A 12 inch thick wall giving R-13 would be R-20
with the dynamic benefit of massive wall (from ORNL study for
Minnesota), given my experience, I would want to discount that for
my climate, to perhaps R-18. Just not enough, in other words.<br>
<br>
Adding insulation on the outside not only increases the R-value, but
also puts the wall into the more advantageous category of 'exterior
insulated' massive wall.<br>
<br>
I have no data on it, but I suspect that the massive wall benefit is
not linear with respect to R-value. Once you get to the point where
loses are a few degrees over the course of a cold dark day, any heat
input is getting stretched out over more time.<br>
<br>
<blockquote
cite="mid:CADj3_s7eKhXXAFxc-aW4iR4dMhaORTkM4GjLk8xkTdXtcSTZ_Q@mail.gmail.com"
type="cite">
<div><span
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Under
such extreme circumstances, peak load would still be a
function of "steady state" R-values, even though it might take
hours or even a day to reach that point. the lag provided by
the thermal mass might reduce annual demand; then again, this
"time to heat" might actually increase annual demand.</span></div>
</blockquote>
<br>
I don't see how 'time to heat' can possibly increase annual demand
in a more or less continuously occupied building (intermittent is
another thing altogether, of course). Maintaining 68°F 24/365 is
just a matter of heat loss * heating degree days. High mass means
that one is computing that on daily or even multi-day average HDD,
as opposed to hourly computed HDD. Which is<i> always</i> going to
be lower.<br>
<br>
Thank You Kindly,<br>
<br>
Corwyn<br>
<pre class="moz-signature" cols="72">--
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
<a class="moz-txt-link-freetext" href="http://www.GreenFret.com/">http://www.GreenFret.com/</a>
<a class="moz-txt-link-abbreviated" href="mailto:topher@greenfret.com">topher@greenfret.com</a>
</pre>
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