What are your thoughts here?
This does not really matter ultimately but its an interesting thought exercise.
Last winter my furnace stopped running (old age and a squirrel built a nest in the chimney), i have since replaced the furnace with high efficiency so the chimney is not an issue, but being a meticulous pragmatist (and a little measurement crazy) i noticed the water ended up colder then an empty tub. When the gas person was red tagging the gas lines he suggested filling the tub with hot water for some heat till the chimney was cleared, so i measured the temperature of the tub with my IR temperature gun before doing anything, after the water was filled and the next day. The tub was a bit below room temperature, it was nice and hot with the hot water and was cooler then the empty tub 24 hours later.
I can’t explain this so i recently repeated this (with a working furnace and hot water tank).
Before filling the tub was 17.5ºC, i half filled it with hot water (40G tank) which was something like 65ºC, and the next day it had cooled to 12ºC. The water again ended up cooler then the empty tub. The outdoor temp was about the same during the 24 hours (which i can’t remember). The IR reader is not able to be calibrated but makes very repeatable measurements, i have tested this.
This is the setup, the washroom is 6 feet deep (from the door) and 5 ft wide (as wide as the tub) The tub is on the only exterior wall in front of you when you walk in. When you walk in the toilet is on the immediate left, sink is beside the toilet (both on the left wall) and the tub is in front of you. The taps for the tub are on the right hand side. I hope this description makes sense with no picture.
I am pretty sure the wall is drywall, 2×4 with fiberglass, wood siding, very thin blanket and vinyl siding. The other 3 walls are interior walls at room temp.
Starting underground there is crawlspace, washroom, attic (being on the exterior wall there is very little attic left as it slopes this way, above the tub there may only be 6 inches of attic left, over the washroom sliding door there may be 2ft of attic height). Attic insulation is fiberglass in the studs, 2×4 or 2×6 at best. The washroom door is always open unless someone is using it.
Starting inside you have hallway, washroom, slab on grade outside the washroom at the same level as the washroom floor give or take a couple inches, its a covered porch area facing north. I don’t know deep the slab is.
So i can’t figure out why the water does not end up at the same temp as an empty tub, is the slab more conductive to heat then air or dirt would be? Is there another possibility?
The house has 14.85ACH50, with a high percentage of the leakage coming from the crawlspace, and more information that might be helpful is on another question i just posted
But keep in mind the lower tub water temp is happening at about the same temperature over the 24 hour test period. I am also hesitant to repeat this test a third time because of the high cost of water here.
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