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Micro heaters cut 87% off my electric heat bill

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Re: Micro heaters cut 87% off my electric heat bill

#181

Post by scythe »

snicker wrote: post #124
jwmerrill wrote: post #114

Earlier quoted context omitted.

Your theoretical analysis misses an important physical fact: houses are able to exchange air with the outside world, not just heat. As you heat a normal room, it will expel air in order to maintain constant pressure, and similarly, as you allow a room to cool, outside air will enter again to keep the pressure constant. There was an article about this in the American Journal of Physics [1, 2] a couple years back, and…

...but the ideal structure is not supposed to exchange air with the outside particularly because of this. That is why windows and doors have seals on them. I'm no mechanical engineer, but I've worked with enough of them in my career to understand that their goal is usually keeping a structure tightly sealed when ingress/egress paths are closed (of course opening windows/doors is a choice of the occupant, which if you…

>...but the ideal structure is not supposed to exchange air with the outside particularly because of this.

With regard to letting a house cool down at night, that's impossible. If you heat a quantity of air from 273 K to 300 K at constant volume, the pressure increases from 1 atm to 1.1 atm. That may not sound like much, but it's better expressed as a pressure differential of 10 kilonewtons per square meter, and the surface area of your house is such that it could severely damage the walls and blow the door open -- popping it like a balloon.

(The fundamental mathematical error made by those who minimize this effect is ignoring the surface area of the building)

Re: Micro heaters cut 87% off my electric heat bill

#182

Post by stinos »

fulafel wrote: post #152
roel_v wrote: post #115

Earlier quoted context omitted.

Sure, if you have shitty insulation. The proper strategy is to have good insulation, and then to have the heat on constantly using a CV system at low temperatures, because heating constantly with water of 30 degrees (C, that is) is much more energy efficient than heating in peaks with much warmer water (60, 70, 90 even 20 years ago). So yes, in houses with crap insulation warming constantly is less efficient. However…

Most houses have poor in insulation. Also, adding good insulation without degrading indoor air quality and causing moisture/mildew problems is tricky. So improving energy efficiency of heating for existing houses with lesser insulation is very useful.

tricky

Well, it is mainly a matter of installing a proper ventilation system.

So improving energy efficiency of heating for existing houses with lesser insulation is very useful.

it is, but it can never reach the levels of energy savings coming form decent insulation (where decent means: German standards for instance)

Re: Micro heaters cut 87% off my electric heat bill

#183

Post by DanBC »

thaumasiotes wrote: post #178
roel_v wrote: post #119

Earlier quoted context omitted.

" 1) learn how to properly clean mold problems" That was one of the parts that made me go %O most - when you live in a house where the internal climate is such that it will let mold grow, it's downright unhealthy to live there . It's like saying 'yeah driving while drunk is dangerous, you'd better have a box of band aid laying around in your car for when you get into an accident'. Uh no, don't drive while drunk, eh?

> when you live in a house where the internal climate is such that it will let mold grow, it's downright unhealthy to live there Why do you believe this?

http://www.cdc.gov/mold/dampness_facts.htm

> In addition, in 2004 the IOM found sufficient evidence to link exposure to damp indoor environments in general to upper respiratory tract symptoms, cough, and wheeze in otherwise healthy people and with asthma symptoms in people with asthma. The IOM also found limited or suggestive evidence linking exposure to damp indoor environments in general to shortness of breath, to respiratory illness in otherwise healthy children and to potential development of asthma in susceptible individuals. In 2009, the World Health Organization issued additional guidance, the WHO Guidelines for Indoor Air Quality: Dampness and Mould. Other recent studies have suggested a potential link of early mold exposure to development of asthma in some children, particularly among children who may be genetically susceptible to asthma development, and that selected interventions that improve housing conditions can reduce morbidity from asthma and respiratory allergies, but more research is needed in this regard.

Whether that counts as "downright unhealthy" is up to you.

http://www.euro.who.int/__data/assets/pdf_file/0003/78636/Da...

Re: Micro heaters cut 87% off my electric heat bill

#184

Post by mhandley »

jwmerrill wrote: post #114
dredmorbius wrote: post #67

OK, Paul Wheaton simply doesn't know what he's talking about: "I think that this does produce some savings, but not as much as you might think. If you set your thermostat to a constant 70, the heater works a little at a time throughout the day. If you drop it to 50 at night or in the middle of the day, the heater stops working, but then when the time comes to warm the house again, the heater has to work at full power…

Your theoretical analysis misses an important physical fact: houses are able to exchange air with the outside world, not just heat. As you heat a normal room, it will expel air in order to maintain constant pressure, and similarly, as you allow a room to cool, outside air will enter again to keep the pressure constant. There was an article about this in the American Journal of Physics [1, 2] a couple years back, and…

This effect isn't going to be very significant. A constant exchange of air will have a significant effect, but a one-off exchange of 10% of the air will be negligible. The reason for this is that the air has a very small thermal mass compared to the building structure.

I've got mote sensors in every room in my house, including the hall. When my kids leave the front door open in winter for a few minutes, as kids tend to do, I can see the temperature in the hall dive on the graphs. But close the door again, and the temperature is right back up very close to where it started in just a few minutes - even when the heating is off.

Re: Micro heaters cut 87% off my electric heat bill

#185

Post by [deleted] »

jwmerrill wrote: post #126
snicker wrote: post #124

Earlier quoted context omitted.

...but the ideal structure is not supposed to exchange air with the outside particularly because of this. That is why windows and doors have seals on them. I'm no mechanical engineer, but I've worked with enough of them in my career to understand that their goal is usually keeping a structure tightly sealed when ingress/egress paths are closed (of course opening windows/doors is a choice of the occupant, which if you…

An ideal structure should minimize convection, but rooms for people really can't be allowed to undergo large changes in temperature without exchanging air with the outside environment, because that would imply a large change in pressure. A 10 percent increase over atmospheric pressure might not seem like that much, but it's enough to notice, and would probably be uncomfortable. It's like being under 1 meter of water.…

[deleted]

Re: Micro heaters cut 87% off my electric heat bill

#186

Post by carlob »

nkozyra wrote: post #45

I live in Florida. This entire discussion is bizarro world for me. It costs nearly $400 a month to keep my house at 74deg in the summer.

A few ideas:

1. Keep it at 80 for a couple of weeks, you'll get habituated quickly enough and will suffer less outside as a byproduct.

2. Use the AC only in the room you are actually in and close the door.

3. Unless it's very very very warm outside, and once you got used to higher temperatures a couple open windows or a simple fan will do wonders.

Source: I live in Rome, I have AC but I only turn it on when it's over 95 outside, because I have thick walls and good circulation.

Re: Micro heaters cut 87% off my electric heat bill

#187

Post by leni536 »

roel_v wrote: post #115
dredmorbius wrote: post #67

OK, Paul Wheaton simply doesn't know what he's talking about: "I think that this does produce some savings, but not as much as you might think. If you set your thermostat to a constant 70, the heater works a little at a time throughout the day. If you drop it to 50 at night or in the middle of the day, the heater stops working, but then when the time comes to warm the house again, the heater has to work at full power…

Sure, if you have shitty insulation. The proper strategy is to have good insulation, and then to have the heat on constantly using a CV system at low temperatures, because heating constantly with water of 30 degrees (C, that is) is much more energy efficient than heating in peaks with much warmer water (60, 70, 90 even 20 years ago). So yes, in houses with crap insulation warming constantly is less efficient. However…

How can heating be any less efficient than 100%? I get that engines can be less efficient than 100% since the remaining energy is dissipated as heat and heat is the not desired energy in that case.

What happens with the remaining energy if you heat with less than 100% efficiency? Does it start to rotate things?

Re: Micro heaters cut 87% off my electric heat bill

#188

Post by carlob »

peeters wrote: post #155
Swizec wrote: post #6

This is where I really prefer the European model[1] - you heat the whole house with hot water. You make hot water with cheap natural gas. If you're lucky enough, you can even use geothermal. Then you use insulation. This especially is something that feels nobody in the US has heard of. At least in California. As a result, your radiators are turned down to 2 out of 10 all day (heating turns off automatically overnight…

> you heat the whole house with hot water As others have said, try cooling a house with rads. It's not like North America is oblivious to radiators; they were very much a standard way of heating houses before the popularity of AC made forced air a much more logical choice. > Then you use insulation. This especially is something that feels nobody in the US has heard of. At least in California. If you only know about t…

> As others have said, try cooling a house with rads. It's not like North America is oblivious to radiators; they were very much a standard way of heating houses before the popularity of AC made forced air a much more logical choice.

I've always found the popularity of AC in the US bizarre, every single European who've traveled to the US in the summer and had to spend extensive time inside complained about the cold and quickly switched to long sleeves and trousers.

Re: Micro heaters cut 87% off my electric heat bill

#189

Post by DanBC »

leni536 wrote: post #187
roel_v wrote: post #115

Earlier quoted context omitted.

Sure, if you have shitty insulation. The proper strategy is to have good insulation, and then to have the heat on constantly using a CV system at low temperatures, because heating constantly with water of 30 degrees (C, that is) is much more energy efficient than heating in peaks with much warmer water (60, 70, 90 even 20 years ago). So yes, in houses with crap insulation warming constantly is less efficient. However…

How can heating be any less efficient than 100%? I get that engines can be less efficient than 100% since the remaining energy is dissipated as heat and heat is the not desired energy in that case. What happens with the remaining energy if you heat with less than 100% efficiency? Does it start to rotate things?

Energy is used to heat something, which is then used to heat a room.

Some devices will use more energy to get a room to X Celsius.

Those devices are less energy efficient than the other devices.

Re: Micro heaters cut 87% off my electric heat bill

#190

Post by JetSetWilly »

dredmorbius wrote: post #62
chaostheory wrote: post #25

Earlier quoted context omitted.

Yes mold is very annoying, but maybe he can experiment with dehumidifiers in key areas to mitigate it. Of course it would probably kill a lot of his energy savings.

Dehumidifiers are reasonably efficient, and in a cold-weather climate, the waste heat is actually a bonus as it contributes to interior heating.

They are only very efficient in warm temperatures. The colder it gets the harder the dehumidifier has to work and the less efficient it gets - as it operates based on a temperature differential. So I suppose, if you are running a dehumidifier in a cold room, you need to particularly consider how well it operates in cold, some dehumidifiers are particularly bad in that environment.
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