Ok smartypantses:
Myth #1: Back in the day, my HVAC instructor insisted that turning down the thermostat at night and while at work (forced air furnace) was less efficient than keeping it steady; because in a forced air system, you heat the air, which in turn heats the masses -- all objects in the house and the house itself. Therefore the inertia to reheat the objects upon returning from work/waking up in the morning was much greater than thought, much greater than just heating the air. You would have to heat the air, which would transfer heat to the now colder objects, sucking energy from you furnace
My energy company thinks otherwise, proclaiming that I can save 20% on my heating bill this winter... My landlord pays for the heat, crank it up, what do I care anyways? Well, I do care.
(Feel free to post any other myths you need debunked.)
theoreitcally you should save by cyclical lowering vs always at the higher temp
think of the heated area and contents as a 'box'. the boundary surfaces will be of lower temp while heat is turned down. anything inside will not lose temps to anything external.
also AFAIK heat transfer cannot have 'inertia'. (although convective heat transfer could act as if having the inertia of teh fluid which is 'convecting'?)
we should also assume that the radiatiing and heat xfer qualities of the skin do not change at different temps.
this may not be absolutely true, because lower temps may accumulate water condensate, which may alter radiation and xfer qualities.
just for amusement, consider an extra complicatoin: frost ice melts fastest off of the weakly insulated roofs. however a dark roof will convert insolation to more heat than a pale roof converts.
but it seems empirical results (cyclical settings save btu joules etc) are reliable, unless the utility regulators and utitlies are conspiring against us all.. :-)
ah, other myths. is it true that ice cream didn't exist until after the Cenozoic era?
also, heat is the form of "energy loss". therefore those household objects absorbing and releasing heat are acting as "100% efficient" heat batteries. (AFAIK)
When turning on the heat in the winter I claim that while the building have been left to accumulate moisture during summer ,the first few months are spend vaporing out the water from the building masses --- this cost a lot of energy ,just try wet your hands and blow a bit air to them and you feel the cold produced when water are vapored out into the air using the energy this requier.
Leaving the heat on during summer at first would seem strange, but keeping the temperture so, that moisture do not enter the building masses also make sure that the building stay "dry" --- dry in the sense that as soon as warm air meet cold building walls ,the water from the air will enter the bricks the wood whatever to ballance the amount of moisture compared temperture.
I don't know any calculations about this but I know houses where heat had been left on --- just to warm up when it become a bit cold, and houses where heat been shut off during summer ,and the strange thing is, that the heat bill are lowest in the houses where the heat are left on to prevent moisture buildup. ---- Well during the few first months the house are dried out, vaporing that water ask a lot of energy ,energy that do not heat up your rooms but are uses making the water go into the air again.
Oct 30, 05 6:22 am ·
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Architectural myths debunked!
Ok smartypantses:
Myth #1: Back in the day, my HVAC instructor insisted that turning down the thermostat at night and while at work (forced air furnace) was less efficient than keeping it steady; because in a forced air system, you heat the air, which in turn heats the masses -- all objects in the house and the house itself. Therefore the inertia to reheat the objects upon returning from work/waking up in the morning was much greater than thought, much greater than just heating the air. You would have to heat the air, which would transfer heat to the now colder objects, sucking energy from you furnace
My energy company thinks otherwise, proclaiming that I can save 20% on my heating bill this winter... My landlord pays for the heat, crank it up, what do I care anyways? Well, I do care.
(Feel free to post any other myths you need debunked.)
theoreitcally you should save by cyclical lowering vs always at the higher temp
think of the heated area and contents as a 'box'. the boundary surfaces will be of lower temp while heat is turned down. anything inside will not lose temps to anything external.
also AFAIK heat transfer cannot have 'inertia'. (although convective heat transfer could act as if having the inertia of teh fluid which is 'convecting'?)
we should also assume that the radiatiing and heat xfer qualities of the skin do not change at different temps.
this may not be absolutely true, because lower temps may accumulate water condensate, which may alter radiation and xfer qualities.
just for amusement, consider an extra complicatoin: frost ice melts fastest off of the weakly insulated roofs. however a dark roof will convert insolation to more heat than a pale roof converts.
but it seems empirical results (cyclical settings save btu joules etc) are reliable, unless the utility regulators and utitlies are conspiring against us all.. :-)
ah, other myths. is it true that ice cream didn't exist until after the Cenozoic era?
also, heat is the form of "energy loss". therefore those household objects absorbing and releasing heat are acting as "100% efficient" heat batteries. (AFAIK)
oops, forgot to elaborate on more-or-less obvious significance of my: [i]the boundary surfaces will be of lower temp while heat is turned down. [/]
rate of heat xfer is proportional to temp difference. so cold house skin will lose less heat to cold air than hot house skin will lose to cold air.
When turning on the heat in the winter I claim that while the building have been left to accumulate moisture during summer ,the first few months are spend vaporing out the water from the building masses --- this cost a lot of energy ,just try wet your hands and blow a bit air to them and you feel the cold produced when water are vapored out into the air using the energy this requier.
Leaving the heat on during summer at first would seem strange, but keeping the temperture so, that moisture do not enter the building masses also make sure that the building stay "dry" --- dry in the sense that as soon as warm air meet cold building walls ,the water from the air will enter the bricks the wood whatever to ballance the amount of moisture compared temperture.
I don't know any calculations about this but I know houses where heat had been left on --- just to warm up when it become a bit cold, and houses where heat been shut off during summer ,and the strange thing is, that the heat bill are lowest in the houses where the heat are left on to prevent moisture buildup. ---- Well during the few first months the house are dried out, vaporing that water ask a lot of energy ,energy that do not heat up your rooms but are uses making the water go into the air again.
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