[GSBN] and No Crawlspace nor Earth-coupling either for Alberta house (was re: no Timber frame ...)

[RT]

On Sun, 18 Sep 2011 17:51:45 -0400, <GSBN-request at sustainablesources.com>  
wrote:

> From: Robert Riversong <housewright at ponds-edge.net>
[snip]
> Of course, this is the principle of a shallow, frost-protected  
> foundation: heat loss downward from the conditioned space warms the  
> ground sufficiently to prevent frost penetration below
[snip]

and the Alberquerky Derelict wrote:
[snip]
> I'd like to hear more from [Stronzo di Nord] how he would insulate under  
> the floor and address moisture questions in the stone plinth design that  
> he mentioned.  Also, please tell us more about the amount of excavation  
> required, if any, before beginning construction of the plinth.
[snip]
and on  Sept 19 Frank Tettemer wrote:

> I've used horticultural Perlite under a standard construction wooden 
> floor as insulation.

> The perlite was packed onto the ground under the joists before/asthey  
> were being installed, to a depth of 12"

> Can anyone else comment on [the R-value] ?

> One unsettling element of this type of construction is that there
> is no space to crawl in.


(for full text of above messages and related thread, see GSBN List  
archives beginning with Duck Foo'd's message:

         http://sustainablesources.com/pipermail/gsbn/2011q3/001525.html
)


First of all, I'd argue that an earth-coupled, main level floor of a  
building intended for human occupancy would not be advisable anywhere in  
Canada or in any climate colder than say, 6000 HDD/yr (degF).  I certainly  
wouldn't do it.

Second, I'd argue that if one is going to be using frost-protected shallow  
foundation (FPSF) design, one should be looking at the design  
specifications for unheated buildings rather than those for heated  
buildings, the latter, as
Robert Riversong mentions, relies upon heat loss from the building to warm  
the ground in the vicinity of the foundation.

In 2011, it is (in my weenie opinion) unconscionable to be designing a  
building that intentionally heats the infinite heat-sink that is the Earth  
as a means of preserving the building, if that building is one that  
aspires to be Green. Such a design dooms the building to requiring  
auxiliary heating for the rest of the service life of that building.

With FPSF design for unheated buildings, the foundation insulation helps  
to retain the heat that emanates from the Earth under the insulation  
umbrella and deflects it horizontally until it is out of the zone of  
influence (re: soil around the foundation) before allowing it to be lost  
to the uninsulated earth and the atmosphere above. For FPSF design for  
unheated buildings, unfortunately, one cannot use the Simplified Design  
Method.

                                      *

re: moisture and insulation questions re: stone plinth design

Moisture would not be an issue with a foundation/floor built on a stone  
plinth for the same reason that baleheads like the Skillful Meany (used to  
?) use crushed stone as a capillary break between their foundations and  
the base of their bale walls or between the bales and bale-wrapped  
shipping containers (a la bbbbBob Bolles and Preston of the Mojave) -- the  
stone rubble allows water to drain away and further, as with rubble trench  
foundations (RTF) the interstitial voids provide room for frost expansion  
of any residual moisture that may have accumulated.

With knowing anything about the site specifics of the proposed Alberta  
house, about all I can say is that I doubt that I'd look at anything less  
than R-30 for underfloor insulation. Typically I would sandwich the soil  
gas/moisture barrier between layers of rigid insulation to protect its  
integrity before, during and long after the installation of the floor.

As mentioned in my first post to this thread, I'd simply fill in the area  
inside of the grade beam (or stem wall) with compacted stone use that  
stone as the "structure" for the floor (ie concrete or stone or earthen)  
thereby eliminating the need for the piers, spot footings, beams, joists,  
decking, buck-toothed rodents, wood-destroying insects, mould, mildew,  
fetid goo brew etc that are associated with suspended wood floors over  
crawlspaces.

And as mentioned previously, I would create accessible service chases  
inside of the thermal envelope (by incorporating them integrally into the  
floor scheme as formed channels or by elevating the portions of the plan  
where there will be underfloor plumbing runs) to eliminate the concerns  
Frank mentioned.

				*

re: R-value of Perlite

It would of course depend upon the ultimate density to which the Perlite  
was compacted and the degree to which is is protected from getting wet but  
the R-values listed for expanded Perlite in the ASHRAE Handbook of  
Fundamentals are:

=====================================
(copied from ASHRAE HoF Table 3A "Thermal Properties...")

			Density			(Thermal) Resistance
			lbs/ft^3		per inch thickness
					(h*ft^2*degF)/Btu

Perlite, expanded	2.0-  4.1		3.7 - 3.3
			4.1 - 7.4		3.3 - 2.8
			7.4 - 11.0		2.8 - 2.4
============================================
You may want to check the above values in the original source using your  
own eyeballs since mine are becoming increasingly unreliable due to  
advancing Geezerdom (tiny print with numbers all clustered together. Eh ?).

						*
And before I forget, I'd venture that all the lovingly-applied/ well-cured  
plaster in the world won't make a lick of difference to out-of-plane wind  
loading (re: stiffness of plastered bale walls vs braced timber frame  
discussion)  if tensile reinforcement  (preferably mesh incorporated into  
the plaster and doing triple duty as secondary reinforcement (ie  
temperature and shrinkage (T&S) ) as well ... or Beel and Athena's bamboo  
exoskeleton approach (no T&S contribution) ) isn't pre-tensioned and  
systematically anchored to the foundation.

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  C A >
(manually winnow the chaff from my edress if you hit REPLY)