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<p><font size="+1"><font face="Gill Sans MT">So well said, Lauren!</font></font></p>
<p><font size="+1"><font face="Gill Sans MT"></font></font><br>
</p>
<br>
<div class="moz-cite-prefix">On 2018-01-07 6:35 PM, Laren wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAFJG_1CPUZXYz1GzVDNVrra3nF4Y_dh+X8U+4jOnUtdCTLRhAg@mail.gmail.com">
<div dir="ltr">
<div><span style="font-size:12.8px">Reuben wrote:</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<span style="font-size:12.8px">> I have a line on 3-1/2"
rigid foam panels</span>
<div><br>
</div>
<div>> My house ha<span style="font-size:12.8px">s 2x4 walls
into which I've blown dense pack cellulose.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">> </span><span
style="font-size:12.8px">was going to add a Larsen truss
(another 2x4 wall with a big </span><span
style="font-size:12.8px">cavity</span></div>
<div><span style="font-size:12.8px">> between inner and outer
walls) and blow cellulose into the rest for</span></div>
<div><span style="font-size:12.8px">> </span><span
style="font-size:12.8px">an eventual 11" thick wall.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">Hi Reuben;</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"> Seems excessive for your
re</span><span style="font-size:12.8px">latively mild
climate. Do some payback</span></div>
<div><span style="font-size:12.8px">calc</span><span
style="font-size:12.8px">ulations, but not just </span><span
style="font-size:12.8px">comparing the absolutes of </span><span
style="font-size:12.8px">doing it or not doing</span></div>
<div><span style="font-size:12.8px">it. Also </span><span
style="font-size:12.8px">look at the </span><span
style="font-size:12.8px">paybacks </span><span
style="font-size:12.8px">for each inch of insulation. </span><span
style="font-size:12.8px"> I anticipate that</span></div>
<div><span style="font-size:12.8px">the </span><span
style="font-size:12.8px">last few </span><span
style="font-size:12.8px">inches will save less energy than
was required to produce</span></div>
<div><span style="font-size:12.8px">and </span><span
style="font-size:12.8px">install the cellulose. Overkill is
UN-GREEN, and</span><span style="font-size:12.8px"> simply
wasteful.</span></div>
<div><span style="font-size:12.8px">Dimi</span><span
style="font-size:12.8px">n</span><span
style="font-size:12.8px">ishing returns hit </span><span
style="font-size:12.8px">pretty severely </span><span
style="font-size:12.8px">when it comes to insulation.</span></div>
<div><span style="font-size:12.8px">So, do a few calculations to
determine the optimal strategy. </span><span
style="font-size:12.8px">It might</span></div>
<div><span style="font-size:12.8px">be greener to spend a little
more on 100% renewable electricity, </span><span
style="font-size:12.8px">than</span></div>
<div><span style="font-size:12.8px">on redundant insulation. </span><span
style="font-size:12.8px"> With extreme</span><span
style="font-size:12.8px"> walls like that, you would</span></div>
<div><span style="font-size:12.8px">likely </span><span
style="font-size:12.8px">be </span><span
style="font-size:12.8px">looking at </span><span
style="font-size:12.8px">nearly all your heat loss </span><span
style="font-size:12.8px">going out </span><span
style="font-size:12.8px">windows,</span></div>
<div><span style="font-size:12.8px">doors, and </span><span
style="font-size:12.8px">ventilation, </span><span
style="font-size:12.8px">and the last few inches of
cellulose simply</span></div>
<div><span style="font-size:12.8px">not having </span><span
style="font-size:12.8px">any payback, </span><span
style="font-size:12.8px">at all, </span><span
style="font-size:12.8px">for the time and money they cost</span></div>
<div><span style="font-size:12.8px">you.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"> </span><span
style="font-size:12.8px">BTW, with adding </span><span
style="font-size:12.8px">that much foam on the outside of
your</span></div>
<div><span style="font-size:12.8px">existing </span><span
style="font-size:12.8px">walls, you </span><span
style="font-size:12.8px">are very safe in terms of
condensation,</span></div>
<div><span style="font-size:12.8px">with or without more
cellulose outside of it.</span></div>
<div><span style="font-size:12.8px"> </span></div>
<div><span style="font-size:12.8px">></span><span
style="font-size:12.8px"> I'm wondering </span><span
style="font-size:12.8px">if there are reasons not to place
these as the</span></div>
<div><span style="font-size:12.8px">>middle </span><span
style="font-size:12.8px">layer of a cellulose </span><span
style="font-size:12.8px">sandwich?</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"> My recommendation is to a</span><span
style="font-size:12.8px">dd the foam as the outer insulation</span></div>
<div><span style="font-size:12.8px">layer, without the
expensive </span><span style="font-size:12.8px">additional
layer of cellulose and</span></div>
<div><span style="font-size:12.8px">and framing,that would </span><span
style="font-size:12.8px">not save hardly </span><span
style="font-size:12.8px">any energy. For instance,</span></div>
<div><span style="font-size:12.8px">you </span><span
style="font-size:12.8px">live in (IIRC) a climate with
maybe </span><span style="font-size:12.8px">4500 annual </span><span
style="font-size:12.8px">HDD (Heating</span></div>
<div><span style="font-size:12.8px">Degree Days) </span><span
style="font-size:12.8px">not considering so</span><span
style="font-size:12.8px">lar </span><span
style="font-size:12.8px">gain </span><span
style="font-size:12.8px">and interior generated</span></div>
<div><span style="font-size:12.8px">heat </span><span
style="font-size:12.8px">(which together may reduce the
effective </span><span style="font-size:12.8px">HDDs </span><span
style="font-size:12.8px">by a lot).</span></div>
<div><span style="font-size:12.8px">So if we look at a </span><span
style="font-size:12.8px">worst case, assuming </span><span
style="font-size:12.8px">just R13 </span><span
style="font-size:12.8px">for your total</span></div>
<div><span style="font-size:12.8px">existing walls</span><span
style="font-size:12.8px">, only R12 </span><span
style="font-size:12.8px">for the foam (you didn't </span><span
style="font-size:12.8px">say </span><span
style="font-size:12.8px">what kind)</span></div>
<div><span style="font-size:12.8px">and another R2 outside the </span><span
style="font-size:12.8px">foam, we get a total of </span><span
style="font-size:12.8px">around R27,</span></div>
<div><span style="font-size:12.8px">So, an </span><span
style="font-size:12.8px"> annual </span><span
style="font-size:12.8px">heat loss of 4000BTU </span><span
style="font-size:12.8px">per </span><span
style="font-size:12.8px">sqft at the</span><span
style="font-size:12.8px"> </span><span
style="font-size:12.8px">most. </span><span
style="font-size:12.8px">Now,</span></div>
<div><span style="font-size:12.8px">the thicker </span><span
style="font-size:12.8px">(another 7 1/2" of cellulose) </span><span
style="font-size:12.8px">wall would come in </span><span
style="font-size:12.8px">at</span></div>
<div><span style="font-size:12.8px">around another </span><span
style="font-size:12.8px">R26, so lets just say R27 to </span><span
style="font-size:12.8px">make the math simple.</span><span
style="font-size:12.8px">.</span></div>
<div><span style="font-size:12.8px">It means you </span><span
style="font-size:12.8px">might save, at the very most, </span><span
style="font-size:12.8px">half (2000BTU/sqft/yr)</span></div>
<div><span style="font-size:12.8px">for having to </span><span
style="font-size:12.8px">build those </span><span
style="font-size:12.8px">Larson thingies, </span><span
style="font-size:12.8px">and </span><span
style="font-size:12.8px">paying for them, </span><span
style="font-size:12.8px">the</span></div>
<div><span style="font-size:12.8px">cellulose, and probably </span><span
style="font-size:12.8px">an extra layer of sheathing. </span><span
style="font-size:12.8px">2000 BTUs is</span></div>
<div><span style="font-size:12.8px">0.586kWh. So, even if you </span><span
style="font-size:12.8px">used electric resistance </span><span
style="font-size:12.8px">heating to make</span></div>
<div><span style="font-size:12.8px">up for it, </span><span
style="font-size:12.8px">in your region</span><span
style="font-size:12.8px"> </span><span
style="font-size:12.8px">with your </span><span
style="font-size:12.8px">cheap hydro electric </span><span
style="font-size:12.8px">it might save</span></div>
<div><span style="font-size:12.8px">2 cents per year, at most </span><span
style="font-size:12.8px"> </span><span
style="font-size:12.8px">And, </span><span
style="font-size:12.8px">the cost would </span><span
style="font-size:12.8px">be at </span><span
style="font-size:12.8px">least a couple</span></div>
<div><span style="font-size:12.8px">of dollars in materials. </span><span
style="font-size:12.8px">However, </span><span
style="font-size:12.8px">I suspect you may </span><span
style="font-size:12.8px">have a wood</span></div>
<div><span style="font-size:12.8px">burner, and that you</span><span
style="font-size:12.8px"> already keep your interior </span><span
style="font-size:12.8px">tem</span><span
style="font-size:12.8px">peratures </span><span
style="font-size:12.8px">lower,</span></div>
<div><span style="font-size:12.8px">which </span><span
style="font-size:12.8px">in your </span><span
style="font-size:12.8px">climate radically reduces your
annual heating load,</span></div>
<div><span style="font-size:12.8px">So, </span><span
style="font-size:12.8px">instead </span><span
style="font-size:12.8px">of the minimum 100 year payback
(calculated above)</span></div>
<div><span style="font-size:12.8px">you c</span><span
style="font-size:12.8px">ould likely be </span><span
style="font-size:12.8px">looking at more like </span><span
style="font-size:12.8px">200+.years, to break even.</span></div>
<div><span style="font-size:12.8px">And, if you have a decent </span><span
style="font-size:12.8px">mini-split </span><span
style="font-size:12.8px">heat pump, multiple time that.</span></div>
<div><span style="font-size:12.8px">In other words, putting </span><span
style="font-size:12.8px">your </span><span
style="font-size:12.8px">money, time and effort into such</span></div>
<div><span style="font-size:12.8px">extreme </span><span
style="font-size:12.8px">insulation layers, </span><span
style="font-size:12.8px">over the top of </span><span
style="font-size:12.8px">what is already quite</span></div>
<div><span style="font-size:12.8px">good insulation for your
climate </span><span style="font-size:12.8px">would </span><span
style="font-size:12.8px">be </span><span
style="font-size:12.8px">simply wasteful,</span></div>
<div><span style="font-size:12.8px">therefore not economical,
and not green. </span><span style="font-size:12.8px">Put </span><span
style="font-size:12.8px">your </span><span
style="font-size:12.8px">efforts into</span></div>
<div><span style="font-size:12.8px">a part of your energy usage </span><span
style="font-size:12.8px">where there is a </span><span
style="font-size:12.8px">lot of </span><span
style="font-size:12.8px">cheap </span><span
style="font-size:12.8px">and</span></div>
<div><span style="font-size:12.8px">easy </span><span
style="font-size:12.8px">improvement to be made. For what
you </span><span style="font-size:12.8px">are </span><span
style="font-size:12.8px">talking about</span></div>
<div><span style="font-size:12.8px">putting into wrapping your
house with second </span><span style="font-size:12.8px">walls,
just to</span></div>
<div><span style="font-size:12.8px">save a</span><span
style="font-size:12.8px"> miniscule amount of heating, </span><span
style="font-size:12.8px">you could </span><span
style="font-size:12.8px">likely </span><span
style="font-size:12.8px">buy a</span></div>
<div><span style="font-size:12.8px">used </span><span
style="font-size:12.8px">Nissan Leaf, electric car, and move
most </span><span style="font-size:12.8px">of your driving</span></div>
<div><span style="font-size:12.8px">off your </span><span
style="font-size:12.8px">fossil fuel list, and save
yourself </span><span style="font-size:12.8px">enough money
to</span></div>
<div><span style="font-size:12.8px">fund </span><span
style="font-size:12.8px">other energy </span><span
style="font-size:12.8px">saving projects. </span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">> </span><span
style="font-size:12.8px">Seems like a quick and in this
instance cheap way to get a lot of </span><span
style="font-size:12.8px">'r'</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"> </span></div>
<div><span style="font-size:12.8px"> A g</span><span
style="font-size:12.8px">ood deal on foam definitely can be,
if everything else is right for </span><span
style="font-size:12.8px">it.</span></div>
<div><span style="font-size:12.8px">The question </span><span
style="font-size:12.8px">is, after the foam, isn't </span><span
style="font-size:12.8px">adding another layer of framing
going</span></div>
<div><span style="font-size:12.8px">to be </span><span
style="font-size:12.8px">a very bad</span><span
style="font-size:12.8px"> idea, </span><span
style="font-size:12.8px">because your walls </span><span
style="font-size:12.8px">would </span><span
style="font-size:12.8px">already be </span><span
style="font-size:12.8px">well </span><span
style="font-size:12.8px">insulated,</span></div>
<div><span style="font-size:12.8px">for your fairly mild
climate? </span><span style="font-size:12.8px">Think about
wrapping your house with </span><span
style="font-size:12.8px">the foam,</span></div>
<div><span style="font-size:12.8px">instead of, and </span><span
style="font-size:12.8px">without, </span><span
style="font-size:12.8px">the second</span><span
style="font-size:12.8px"> exterior </span><span
style="font-size:12.8px">walls. </span><span
style="font-size:12.8px"> It could save you a lot</span></div>
<div><span style="font-size:12.8px">of money and </span><span
style="font-size:12.8px">work, and still save nearly as much
energy. Put the money</span></div>
<div><span style="font-size:12.8px">and time that you save, </span><span
style="font-size:12.8px">into </span><span
style="font-size:12.8px">other, more effective, energy </span><span
style="font-size:12.8px">saving projects.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">> </span><span
style="font-size:12.8px">But I also don't want to do
anything stupid when it comes to moisture.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px"> You ask a lot of good </span><span
style="font-size:12.8px">questions. That is the best way to
avoid mistakes.</span></div>
<div><span style="font-size:12.8px">Remember, your house
envelope is not the only place you </span><span
style="font-size:12.8px">use energy,</span></div>
<div><span style="font-size:12.8px">and now </span><span
style="font-size:12.8px">there are good </span><span
style="font-size:12.8px">options </span><span
style="font-size:12.8px">to improve other areas of our
energy</span></div>
<div><span style="font-size:12.8px">lives.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">BTW......about a week ago,
we</span><span style="font-size:12.8px"> bought an 8ft
pallet (45 sheets) of 2.18"</span></div>
<div><span style="font-size:12.8px">XPS, to wrap our 1925 house
in a climate much colder than yours. We</span></div>
<div><span style="font-size:12.8px">got it (new) for
25cents/sqft, and won't need extensive wood </span><span
style="font-size:12.8px">framing,</span></div>
<div><span style="font-size:12.8px">outside of it. </span><span
style="font-size:12.8px">Against a mini</span><span
style="font-size:12.8px">-split heat pump, </span><span
style="font-size:12.8px">using 100% renewable</span></div>
<div><span style="font-size:12.8px">electricity, our </span><span
style="font-size:12.8px">payback (since we will be re-siding
anyway) will be </span><span style="font-size:12.8px">less</span></div>
<div><span style="font-size:12.8px">than five years. Our
pre-leased e</span><span style="font-size:12.8px">lectric
car, which did not cost more</span></div>
<div><span style="font-size:12.8px">than a </span><span
style="font-size:12.8px">comparable used </span><span
style="font-size:12.8px">gasoline car,</span><span
style="font-size:12.8px"> saved </span><span
style="font-size:12.8px">us more </span><span
style="font-size:12.8px">than </span><span
style="font-size:12.8px">the foam</span></div>
<div><span style="font-size:12.8px">cost, </span><span
style="font-size:12.8px">in just </span><span
style="font-size:12.8px">the first six months. Put your
money </span><span style="font-size:12.8px">where it will do
the</span></div>
<div><span style="font-size:12.8px">most </span><span
style="font-size:12.8px">good, </span><span
style="font-size:12.8px">for you, for humanity, </span><span
style="font-size:12.8px">and for </span><span
style="font-size:12.8px">the planet.</span></div>
<div><span style="font-size:12.8px"><br>
</span></div>
<div><span style="font-size:12.8px">-Laren Corie-</span></div>
<div><span style="font-size:12.8px">Designer of Energy Efficient
Homes, Since 1975</span></div>
</div>
<br>
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