[GSBN] Fwd: Embodied energy comparisons: SB vs Stick-built

John Swearingen jswearingen at skillful-means.com
Mon Feb 16 11:48:33 CST 2009

I don't really have a quick way to calculate the increased lumber, other
than rule of (bruised) thumb (hit by hammer).

I would reckon it like this, though: the increase in emissions is probably
pretty close to the increase in materials, since it's reflecting the area of
exterior walls and openings rather than the volume of the space.  (It would
be the ratio of the lineal perimeter to the square footage). This ratio
would carry through fairly consistently for interior walls.

So I'd venture that a 50% increase in square footage/volume would carry with
it a 33% increase in material.  Someone who is able to do more than count on
their fingers could probably define this mathematically better than I can.

We recently designed a passive solar house for a pair of professors, who
moved in and filled it with books. They should get special energy credits!


On Mon, Feb 16, 2009 at 8:48 AM, Derek Roff <derek at unm.edu> wrote:

> This is great, John.  Would it be easy for you to run one more set of
> numbers on these two houses in two sizes?  Assuming conventional frame
> construction, how much more wood and other carbon sequestering materials are
> in the larger versions of these houses?
> You've just told us that making the houses 50% larger increases the
> emissions by 33%/28% annually.  I want to add to this sentence that
> "increasing the size uses X% more wood framing and other carbon storing
> materials."    Those numbers, plus knowing the amount of carbon in a piece
> of framing lumber, would let us do a quick calculations on the trade-offs
> between storing more carbon in a bigger house that consumes more energy.
> We could start a betting pool.  My bet is that it would take four years for
> the increased energy use/higher carbon emissions of the enlarged
> conventional house to equal and exceed the amount of carbon stored in the
> extra framing.
> Derek
> --On Monday, February 16, 2009 7:59 AM -0800 John Swearingen <
> jswearingen at skillful-means.com> wrote:
>  Hi,
>> I did a quick simulation of a conventional house in Boston, 2000SF in
>> size, vs. an energy efficient one that uses "off the shelf"
>> improvements (better windows, furnace, etc.), and got a difference of
>> 4.2 times the emission for the conventional house.  In quantity,
>> that's about 24,000 more pounds of CO2 emitted annually (31,292 vs
>> 7,352), which is a striking difference.
>> If both of those houses were 50% larger, or 3000SF,  the emissions
>> are increased by about 30% (33% for the conventional and 28% for the
>> efficient one). You can get up to about 15,000 SF before the
>> efficient house burns as much as the smaller conventional house (but
>> I wouldn't spread that around).  So size matters but  efficiency
>> matters more.
>>  I've no idea how that compares with the carbon burned/sequestered
>> during construction, the "net" numbers, and would certainly be
>> interested to know.
>> John
> Derek Roff
> Language Learning Center
> Ortega Hall 129, MSC03-2100
> University of New Mexico
> Albuquerque, NM 87131-0001
> 505/277-7368, fax 505/277-3885
> Internet: derek at unm.edu

John Swearingen

Skillful Means
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