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Re: Plastic Dome Doghouse -- Leaky - Page 3

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Posted by nicksanspam on February 16, 2008, 10:33 pm
 


Chapter 9 (Environmental Control for Animals and Plants) of the ASHRAE
Handbook of Fundamentals says the basal heat of a W pound animal is
6.6W^0.75 Btu/h... 35% is latent, for a normally active dog.


Nice... Maybe R14, with foil.


Ohoh. Direct gain, aka "direct loss" :-)


You might make a U-shaped strawbale platform with the entrance door into
the opening of the U, inside an icosahedron made with 15 5.5' equilateral
triangles cut from 5 4'x8' sheets of foil foamboard with some foam in a can
for glue at the seams and white paint over it all.  That would have
a 5.5/tan(36) = 7.6' inner diameter and a 4' stemwall height and a peak
0.526x5.5 = 2.9' above that. Pretty big.

You could make a smaller version with more cutting and piecing. Maybe
divide each large triangle into 4 smaller triangles, conceptually, and
divide the foamboard into thirds lengthwise to make 5 big triangles
and 1 3/4 triangle and 4 small triangles and 6 half-small triangles,
like this, cut from 2 4x8 sheets, viewed in a fixed font:

 -----------------------------    The big triangles would have 3.7'
|1/ \         / \         / |   edges, and the dome would have
|/ 1 \       /   \       / 2 \|   a 5.05' ID and a 2.7' stemwall
|-----\  1  /  2  \  3  /-----|   height and a peak 1.9' above.
|\ 3 / \   /       \   / \ 4 /|
|3\ /   \ /         \ /   \ /4|
|--/     \-----------/     \--|
|5/   4   \    1    /   5   |
|/         \       /         \|
 -----------------------------


Sounds nice, on a sunny day.


An overhang might be more practical.


How about some mostly-shiny mass under the ceiling, with a insulated wall
between the glazing and the living space to make a sunspace and a vertical
duct on the living space side of the wall to allow hot ceiling air to return
to the sunspace without overheating the room? Maybe the dog can learn to
move around in the living space to stir up the air and bring down warm air
from the hot mass as needed. Alternatively, he might partially crawl under
a radiation shield to avoid overheating from the mass.


The dog could have a small well-insulated sleeping enclosure inside
the living space, a bedchamber, as in Jefferson's Monticello.


The dog might need 5 cfm of fresh air for breathing, which is enough to
avoid condensation on indoor wall surfaces, but the living space will be
warmer if outgoing indoor air heats incoming outdoor air on the way out.


More insulation will raise the indoor surface temp and allow higher
indoor humidity with less ventilation... 5 cfm adds about 5 Btu/h-F
to the doghouse conductance to outdoor air, or less, with the condensing
chimney, which acts like a normal air-air heat exchanger until outgoing
air begins to condense as it travels upwards. Above that point, the heat
transfer rate roughly doubles, with condensation happening on one side
of the common wall, and the outgoing air temp drops less than it would
without condensation, for the same heat energy removal.

Nick


Posted by gary on February 17, 2008, 6:41 pm
 
On Feb 16, 3:33 pm, nicksans...@ece.villanova.edu wrote:

Thanks.

This is the Atlas RBoard with the fiberglass(?) faces.  You lose the
foil R, but it makes for a nicer and tougher finish where its exposed.


In addition to that problem, the vet and my wife don't like the dog
lying on brick.  And, as soon as you put a pad on the brick you lose
the direct sun coupling.
And, as Jeff points out, its not a lot of mass anyway.


I'll think about that.

The thing I'm for the next few days is to insulate over the south
window on the inside with R12 and see how this does with just
simulated dog heat.  I think it might do pretty well.



Actually, I really like the idea of just rotating the house around
seasonally.   It does not suffer from the cold spring, warm fall thing
that overhangs do.
Wish I could do the same with my house.


Gary

Posted by nicksanspam on February 17, 2008, 8:37 pm
 

Oops. The big triangles would be 3/cos(30) = 3.46' on a side, and the dome
would have a 4.77' ID and a 3' stemwall and a peak 1.82' above that, with
64 ft^2 of surface, vs 80 ft^2 for a 4' cube, not counting the floor.


A 4' R12 cube with G = 6x4'x4'/R12 = 8 Btu/h-F and a 40 watt bulb and
no air leaks might be 40x3.412/8 = 17.1 F warmer than the outdoors...
5 cfm of fresh air would make it roughly 40x3.412/13 = 10.5 F warmer.

With indirect gain, if 1020 Btu/ft^2 falls on a south wall on an average
22.8 January day with a 31.8 max in Billings, a 4' R12 cube with 16 ft^2
of R2 sunspace glazing with 80% solar transmission over an air gap over
an R12 insulated south wall with lots of shiny ceiling mass and surface
and a 65 F average living space temp would have 0.8x16x1020+40x3.412x24h
= 16332 Btu = 6h(T-27.3)16/2 [for the south wall during the day]
+18h(65-22.8)16/18 [for the south wall at night] +24h(T-22.8)16/12 [for
the ceiling] +24h(65-22.8)4x16/12 [for the other 3 walls and the floor]
Btu/day, with ceiling mass temp T = 154 F, if I did that right.

If the average ceiling mass temp is (154+65)/2 = 109.5 over 5 cloudy days
while the cube loses 5x24((65-22.8)5x16/12+(109.5-22.8)16/12-40x3.412)
= 31254 Btu = (154-65)C, ceiling mass C = 351 Btu/F, eg a 4.2" x 16 ft^2
layer of water. Another layer of R12 ceiling insulation would help.

Nick


Posted by Steve Ackman on February 22, 2008, 5:53 pm
 ["Followup-To:" header set to alt.energy.renewable.]
on Sat, 16 Feb 2008 10:44:20 -0800 (PST), gary@builditsolar.com,
gary@builditsolar.com wrote:


  Think Trombe Wall.
http://en.wikipedia.org/wiki/Trombe_wall


Posted by Ally's Mom on December 5, 2016, 12:14 am
 replying to nicksanspam, Ally's  Mom wrote:
All that math does not keep my dog dry.  I put igloo on a pallet because I
thought water was running in the vents at bottom (very low on ground).   I buy
old coverlets at thrift stores and after a rain they are soaking wet.  He is
smart as he pulls quilt out onto ground so it can dry LOL.  Could water be
getting in at the vent on top.  I have bought my last igloo,  all have leaked
and first one got cracked over the base; put it on a big board  upon landscape
timbers.  

--
for full context, visit http://www.homeownershub.com/maintenance/plastic-dome-doghouse-leaky-288413-.htm  
 



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