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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

#191

Post by maccard »

mkesper wrote: post #175
XorNot wrote: post #93

Earlier quoted context omitted.

On hot water bottles: the energy spent boiling that water is likely comparable to the energy an electric blanket on low power would use.

Electric blankets can burn you and the whole house down and do not use the same form of heat transfer https://en.wikipedia.org/wiki/Heat_transfer . They just should not be used.

> Electric blankets can burn you and the whole house down and do not use the same form of heat transfer

Source on that? I had a quick search, and it seems to be one of those rumours... The only reference I could find was old (pre 2001) and faulty models.

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

#192

Post by mmikeff »

XorNot wrote: post #93
dredmorbius wrote: post #46

Spot-heating, especially within a leaky building envelope utilizing expensive heat sources (electric resistance) is one option. But it's hardly the only one, or the best. For northern climates, taking a whole-system approach to home/structure design gets you a tremendously greater payoff in terms of energy savings. Among the most powerful demonstrations of this I've seen are Thorsten Chlupp / Reina LLC's experiences…

On hot water bottles: the energy spent boiling that water is likely comparable to the energy an electric blanket on low power would use.

There are gel filled alternatives that can be heated in the microwave. No idea if they retain their heat as long.

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

#193

Post by abelsson »

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?

Heating can be more than 100% efficient. Before you go "what, lol, no" - let me clarify. Obviously it can't be even 100% thermodynamically efficient, but a heat pump for example can generate 3-4 kW of heat from 1 kW of power. The rest of the energy comes from the environment obviously, but naively assuming that the 100% efficient power-into-heat is the best you can do is not true.

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

#194

Post by anon4 »

mhandley wrote: post #184
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…

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…

That's not true of all houses and especially not true of cheap apartments, whose residents would benefit the most from saving on heating.

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

#195

Post by netnichols »

stinos wrote: post #182
fulafel wrote: post #152

Earlier quoted context omitted.

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)

My German apartment has drafty, unsealed wooden window frames, and the window in the kitchen is a single large sheet of glass. We have to hang a rug over that window in the winter, as it feels like you've left a freezer door open if you get within 3 feet of it.

But the walls are indeed very thick!

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

#196

Post by pjc50 »

vacri wrote: post #18
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…

Crappy insulation is the norm here in Australia as well, which is more of a problem down south where it gets cold in winter. I used to work with a Scot who highlighted the issue, saying that in a Scottish house, the insulation was good enough that you could basically heat a room with a candle. I once asked him if there were any wooden houses in Scotland, he replied "Yes, we keep our lawnmowers in them".

There's another historical difference between Scotland and the US here: the US has a near-unlimited supply of wood, while Scotland was mostly bare of trees by the 18th century.

Much cheaper to build walls from local stone and save the imported wood for the floors and roofs.

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

#197

Post by dirkf »

alricb wrote: post #86
dredmorbius wrote: post #46

Spot-heating, especially within a leaky building envelope utilizing expensive heat sources (electric resistance) is one option. But it's hardly the only one, or the best. For northern climates, taking a whole-system approach to home/structure design gets you a tremendously greater payoff in terms of energy savings. Among the most powerful demonstrations of this I've seen are Thorsten Chlupp / Reina LLC's experiences…

Not to mention: In a well-insulated, well-designed house, you won't have any worries about frozen pipes, even with a low thermostat temperature, since all pipes will be inside the insulated enclosure. There's a whole community of people trying to build better buildings out there. The Passivhaus people, the PERSIST (Saskatchewan) and REMOTE (Alaska) approaches ( http://www.greenbuildingadvisor.com/blogs/dept/musings/g…

I'm currently living in a passive house (in Belgium, Europe). We've only moved in two months ago so we haven't experienced a winter yet but even in the current summer climate it has already been an order of magnitude more comfortable than any of the other places I've lived in. When the temperature hit 30 degrees Celsius for a couple of days last week the house was at a comfortable 23 degrees. Everywhere.

Key design points:

- Insulation, insulation, insulation. We have 30cm cellulose in the walls and 36cm in the roof plus some 5cm fiberglass in the space between the walls and drywall.

- Airtightness, in combination with a ventilation system (with heat recovery).

- Large windows (triple glazing) on east, south and west sides to get free heat from the sun in the winter but have some screens to keep the sun out in the summer.

- We use a geothermal heat pump to prepare hot water and to be able to heat the house a little bit in the winter when needed, using underfloor heating pipes. Extra bonus that has turned out to be essential: we can use this system to passively cool the house by simply pumping the water through the pipes and into the ground. This can lower the temperature in the house by several degrees in an energy efficient way.

Based on our energy consumption for the two months we've lived here we'll end up at around 3500-4000kWh per year. And that includes everything: heat pump, ventilation, all electrical appliances, ...

Building such a house isn't rocket science. The materials and techniques are well known and readily available (at least here); it's mostly a matter of good planning upfront and paying attention to the details when executing. Not all construction companies are up to speed but they're slowly getting there (or they'll disappear).

As a matter of fact: the EU has mandated that by 2020 every newly built house must be more or less equivalent to a passive house.

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

#198

Post by anon4 »

jrockway wrote: post #106
staunch wrote: post #96

Kotatsu tables really are great. Some pictures here if you haven't seen them: http://en.wikipedia.org/wiki/Kotatsu Unfortunately even a cheap table in the U.S. is more expensive than it should be. There's an opportunity for someone to create kotatsu tables and things like them for the American market.

I think the problem is Americans don't want to sit on the floor. Which is strange, because carpet is more comfortable than tatami.

Probably because of their habit of wearing outside shoes inside the house, making the floor too dirty to sit on.

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

#199

Post by leni536 »

DanBC wrote: post #189
leni536 wrote: post #187

Earlier quoted context omitted.

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.

Electric heating has near 100% efficiency regardless how you use it[0]. Heating with furnace is less efficient since some of the heat escapes through the chimney directly and efficiency is typically disproportional to the heating power so it's better to heat constantly[1].

[0] https://en.wikipedia.org/wiki/Electric_heating#Environmental... [1] experience

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

#200

Post by Nursie »

raverbashing wrote: post #5

Yes Most people want "summer inside the house" which is absurdly wasteful Of course, it sucks when changing clothes or taking a shower, but there are ways of heating locally.

I want summer inside the house.

It may be wasteful, but that's what I want. I don't ever want to step out of the shower in the morning and shiver again, I find this deeply unpleasant. I also don't want to have to wear thick woollen clothes around the house. In pursuit of this I actually moved to Australia for a while, but it turns out I missed the temperate climate and UK culture (also my family, I guess...)

So when I own my own home in a few weeks it will be getting insulated to hell and back. Eliminating drafts, insulating attic space, replacing some of the old windows with double or triple glazed ones, checking the state of the wall insulation... etc etc.

But when it comes down to it, I'll pay the heating costs and swan around in my t-shirt all year. I like being warm.

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