alt.energy.renewable

On Feb 16, 4:31 am, nicksans...@ece.villanova.edu wrote:
> Calab wrote:
> >"Davej" wrote in message
>
> >>> > Has anyone ever figured out how these dome doghouses leak? Maybe
> >>> > condensation? They are worthless.
>
> >>> Condensation is not a leak.
>
> >> Well, all I know is I'm tired of finding damp, moldy straw inside.
>
> >Put a wooden skid, or something else that will let moisture drain
> >underneath, yet keep the bedding, etc up off the ground.
>
> Sounds like it needs a vapor barrier on the ground, eg plastic film under
> Astroturf, and enough ventilation to keep the indoor air dew point below
> the temperature of the indoor surfaces...
>
> An ASHRAE-standard 50-pound dog makes 124.1 Btu/h of basal heat
> (vs 354.9 when normally active.) If 35% is latent, that's 0.043 pounds
> of water vapor per hour, with 1 pint of condensation every 3 nights. In
> a 2'x4'x4' tall R8 doghouse with a 56ft^2/R8 = 7 Btu/h-F conductance
> and 5 cfm of fresh air, he'd raise the indoor temp 124.1/(7+5) = 10.3 F,
> eg from 30 to 40.3 (brrr) on a 30 F day. We could make 5 cfm flow
> through the 4'-tall 40.3 F doghouse with a 5/(16.6sqrt(4'x(40.3-30)) =
> 0.047 ft^2 hole at the top, ie 6.75 in^2, eg 2.6"x2.6".
>
> An outdoor humidity ratio wo = 0.0025 pounds of water per pound of
> dry air (Phila in January), and 0.043 = 60m/hx5cfmx0.075lb/ft^3(wi-wo)
> make wi = 0.0044 indoors, with vapor pressure Pi = 29.921/
> (1+0.62198/wi) = 0.211 "Hg and dew point Td = 9621/(17.863-ln(Pa))-
> 460 = 35.4 (a Clausius-Clapeyron approximation.). With (40.3-30)/
> 1ft^2/R8 = 1.3 Btu/h-ft^2 of heatflow and an R2/3 indoor airfilm
> resistance, the wall temp would be 40.3-2/3x1.3 = 39.4 F indoors,
> with no condensation.
>
> A fancier doghouse might have more insulation and passive solar
> heat and a condensing double-wall thermal chimney (a passive
> thermosyphoning ERV) and 2 strawbales to make a sleeping platform
> above the top of the entrance door, so warm air is trapped upstairs.
>
> Nick

Wow, nice dog-math. These plastic domes have no insulation, and with a
curving surface it wouldn't be easy to add any. I doubt they are
particularly warm. In fact I see nothing redeeming about them.