Plastic Dome Doghouse -- Leaky

[Davej]

Has anyone ever figured out how these dome doghouses leak? Maybe condensation? They are worthless.

[Calab]

Condensation is not a leak.

[Davej]

Well, all I know is I'm tired of finding damp, moldy straw inside.

[SteveB]

BE GOOD, CLEAN UP YOUR ACT, and maybe SWMBO will allow you to sleep in the extra bedroom!

Steve

[Calab]

Put a wooden skid, or something else that will let moisture drain underneath, yet keep the bedding, etc up off the ground.

[mike_0_007]

never had that problem in 10 years of using one. Do you have the vent open at the top? you need to, to let the dog's breath vent out...

[nicksanspam]

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

[Davej]

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.

[Calab]

Not sure how much they cost, but if cheap enough, you could buy two and use a layer of spray foam between them.

[Jeff]

What's the point in insulating something that has a big hole to the outside in it?

Jeff

[gary]

Hi Nick, Helpful calcs on the dog house -- thanks. Where does the ASHRAE dog data come from? The fundamentals volume? or?

I've been working on a solar dog house -- some results to date:

Control Igloo House: My control for the new doghouse is an igloo style, uninsulated dog house with an improvised heavy cloth door. It has a 40 watt bulb inside to simulate dog heat. It is worthless. The only time the temperature in the igloo goes above ambient is for an hour or two a day when the sun is shining directly on the door, otherwise it tracks with a couple degrees of ambient even when the 40 watt dog is on. I suppose it provides some wind protection, but thats about it.

New Solar Dog House Prototype Description: The prototype solar dog house is wood construction. Insulated to an average of about R12 on all sides, ceiling and floor

-- mostly 2 inch polyiso. Floor is single layer brick for thermal mass (insulation below this).

Entrance is a tunnel arrangement with commercial heavy poly dog flapper doors that seal fairly well -- one on each end of the tunnel. First entrance is part way below 2nd for some, but not enough for full thermal trap.

Inside space is just large enough for dog to stand in, turn around, and lay down to minimize heat loss. Roof is flat to minimize volume and provide a place to dog to lay around on roof.

"South" wall is about 80% glazed (a high fraction of floor area). The glazing is homemade double Acrylic that seals well. The house is on ball casters so that the "south" window can be turned to the north in the summer to prevent overheating.

I'm planning on adding solar chimney in summer.

Performance: As mentioned, the Igloo is near to worthless, and just tracks ambient.

The protoype solar behaves better, but well short of perfect. On a sunny day, temp inside the dog house can go up to as high as 110F even when ambient is 20F. Too much glazing for the mass. This day overtemp may not be a serious problem in that dogs spend day mostly outside.

At night, the prototype maintains about 15 to 20F over ambient. The effect of the dog simulating 40 watt bulb can clearly be seen on the temperature plots -- there is a distinct reduction in temperature drop rate when the light goes on -- so insulation and sealing are good enough to make a small heat source useful in heating the space. I would call the current night performance marginal in a cold climate, but much better than the Igloo.

Yesterday, I tried adding 10 gallons of water in black painted pails to the house. Positioned so they got sun through the window. This resulted in a big change for the good. Peak day temp was down to 90F where it would have been easily been over 110F. Night time temperature drop rate was less than half the previous rate. Morning temp was nearly 30F over ambient and a comfortable 55F. I guess (not surprisingly) that mass helps.

Problems/Questions: Brick floor is undesirable, but putting a pad over the brick means the brick mass does not get direct sun. How to get good solar transfer to the mass and still have a good sleeping surface?

How to add more thermal mass without taking up too much space?

Would I be better off with less (maybe much less) glazing, and just rely on dog heat + good insulation + thermal mass to even out the temperature and keep it enough above ambient for dog comfort? This seems like it might have some benefit on strings of cold, cloudy days as well?

I'd like to hear more about the "condensing double wall thermal chimney"

Not sure if when I add dog produced moisture if I can stand the ventilation rate that will be required to control condensation?

Any ideas anyone has on making the design better?

Gary

[hallerb]

R8

dogs should live indoors with their family. not outdoors espically in too hot cold wet or snowey weather. we have 3 furry friends they have dog doors, and a fenced in yard for their protection.

dogs forced to live outdoors, thats just plain cruel!!!!!!!!!

[Jeff]

I don't think the brick is doing much. The specific heat of brick is fairly low. Add another 5 gallons of water.

Jeff

How to get good solar transfer to

[nicksanspam]

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/ \\ / \\ / \\2| 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 \\6| |/ \\ / \\| -----------------------------

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

[nicksanspam]

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

[Steve Ackman]

Think Trombe Wall.

[Ally's Mom]

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.

[ItsJoanNotJoAnn]

replying to Ally's Mom, ItsJoanNotJoAnn wrote: Good grief, you are replying to an *EIGHT YEAR OLD THREAD* but that is to be expected from people who use HomeMoanersHub to post replies. But if you want to keep your dog dry while using an igloo doghouse that leaks either use a tarp or a plastic garbage bag that has been split open to cover the dome. Use some duck tape to tape it down so it won't blow away.

Shaking my head in disbelief.

[Robert Green]

"ItsJoanNotJoAnn"

Some newsreaders don't display the age of a these reposts from HOH so scolding respondents isn't likely to change anything. I don't see any indication it's 8 years old when using Outlook Express.

The larger question is does is really hurt to discuss on topic material even if the OP is long gone?

I suspect some troll is having fun getting people to keep complaining about old threads because someone always feeds them . . .

[ItsJoanNotJoann]

On Monday, December 5, 2016 at 7:46:29 AM UTC-6, Robert Green whined:

I got news for you ace, HomeMoanersHub DOES display the date.

You got a leaky dog house or are you IN the dog house?

No Bubby, it's the same twits that post to old, sometimes 20 year old threads.