Topic: Heating on or off?

[rhos1355]

Ok, I've been on this forum for just over a couple of years and have come to the conclusion you are a smart/clever bunch of people. So I'd love for somebody to give me a valid reason why I should NOT leave my heating on minimum during the day whilst the house is empty.
My landlady at the place where I'm staying at the moment has asked me to switch off the heating when I'm at work. My argument is that it's been below zero degrees celsius for 2 weeks now, sometimes as much as -6°C and colder at night, and it takes about 3-4 hours of the boiler going on full blast for the interior temp to reach anything near comfortable after it's been switched off.
It's an old 19th century farm cottage with 2ft+ thick stone walls. Apart from the ceiling I doubt there's much insulation downstairs.
I've googled the question but all I get is peoples opinions as in "when I was little, my greatgrandma used to say..........blah blah blah"
What do you people reccomend?

[Bob Wessner]

What sort of heating system are we talking about? Are you saying there it no insulating material at all on the interior of the walls? Typically, here, a home will lose approx. 1 degree of heat per hour in the winter with no heat, not sure what impact bare, stone walls of that thickness will have on that, but I suspect the affects will not be good.

[pidaster]

I'd leave the heat on but you could turn it down some. That's what I do.

[Alan F.]

Heat off is not a good option, pipes will freeze and burst eventually. I'd turn it down some so that she's satisfied, but down just enough that the 'warming back up time' is not too long. What type of heating system is it? Maybe run some circulating fans to help speed the warm up?

[rhos1355]

It's a combination boiler (central heating/hot water combined) and runs on bottles of LPG (liquid petroleum gas) I think. There is no thermostat in the house, just a graded min to max scale on the boiler. The cottage is not that big; about 16ft by 12ft downstairs and the same upstairs. the good thing is that the cottage itself is one of three and nestles between the other two. Which means the other 2 cottages act as insulation.
Someone once told me there is a calculation you can work out, as in; price per thermal unit X amount of thermal units required to heat a certain volume one degree etc.
As regards the pipes bursting, I was told years ago that there's only a danger of that if the external temp goes below -10°C and stays that way for more that 12 hours.
Is that true??

[Stev-o]

Don't turn it off, it requires more energy to get back to a comfort level than if you just turn it down 8 degrees or so.
I recomend turning it down to 60-62 F.

How low does the temp go when you turn it off and what temp do you set it at when you are home?

[flybox1]

Don't turn it off, it requires more energy to get back to a comfort level than if you just turn it down 8 degrees or so.
I recomend turning it down to 60-62 F.

+1

[rhos1355]

I reckon the temp in the house is about 5°C /41°F (and that's being generous) when the heat is off.........and say the outside temp is 0°C/32°F or less.
When I get the internal temp to a comfortable level, I reckon it's about 20°-21°C.
There is no thermostat, just a min to max dial with graduations in between on the boiler.

[Bob Wessner]

Wow, 41F is pretty low. What is the recovery time to get it back to 20C/68F? Those stone walls are killers for sure, huge heat sinks. If not covered/insulated maybe your landlord should consider it. As for the pipes, the only thing that matters is if the temp of the water hits 32F. Another reason to not turn the heat off entirely. What if  you get stuck away while it is off and you can't get back. Frequently, plumbing is in cabinets and in kitchens, could be on an outer wall. I would just turn down the temp, but not off and you can leave the cabinet doors ajar some so some heated air gets in there.

[flybox1]

thats too cold, brutha!
your building is on the path to some serious frozen pipe/water damage.
Hope you get out of the freeze in your neck of the woods.

we dont get the extreme cold you are experiencing very often.  Prolonged freezes are pretty uncommon.  our average winter we see 25F-45F, maybe 50F, each day.
even with these temps, i never let the house get below 60F(night) and max 65F during the day.
Not a cheap bastard by any means.  just trying to train the kids to put on a sweatshirt and be aware of the energy useage...and protect my house from frozen pipes and expensive water damage.

[demon78]

It's not even the water damage from frozen pipes it's the damage from too cool temps and moisture, houses are not found of cold, that causes corrosion in electrical circuits, wood to start change composition, mold to form, it's like your bike, it does better if you run it regularly, rather than let it sit in the winter, also if it takes 3-4 hours to warm up from cold and an hour to warm up from cool you're saving energy from cool to warm. This is from observations of cottagers returning every year to reopen their cottages, another thought is if your fridge has a compressor they don't really like starting in the cold.
Bill the demon.

[mystic_1]

I'm not sure about the UK but here in the states there are laws that regulate provision of heat by landlords, minimum temperature that must be maintained during winter, etc.  You may want to look into what's on the books in your area.

mystic_1

[gmonkey]

If it's hot water radiators, don't turn it all the way off for sure.  I lived in an old house with what turned out to be nearly no insulation.  I used to turn the heat down to 45 downstairs and 55 upstairs for the night (2 floors, 2 thermostats).  One night the outside temps dropped a bit below 0F.  A section of the hot water pipe to the first floor radiators that ran through a corner of the house froze while the heat inside the house itself was above 45 so the heating wasn't active and water not flowing.  Once that froze, the pipe was effectively blocked and no more hot water could get to the radiators so the rest of the pipe proceeded to freeze all the way around the first floor of the house.  It burst at most of the joints.  That house was wood and in pretty bad shape but it demonstrates that it doesn't even have to be all that cold inside the house for a pipe to freeze and things go down hill from there.  Something to consider.

[Don R]

If I can afford fuel, then it's all about comfort.

[TwoTired]

It's going to pretty tough to do a heat gain/loss rate calculation without knowing the mass that is being heated, the heat conduction parameters for the materials and size of the space.

Can you estimate the R value of the walls/ceiling and floor?  Then the heat transfer rate can be calculated if you also now the temperature differential.

Stone has been used as a heat storage device.  Walls two feet thick will retain some storage, and buffer the change rate internal temps.  But, if "stone" has differing R values among types, as the density varies.

One way of doing an approximation is to monitor both the outside and inside temperatures, and note the change rate when the internal heat is off.  Using a known cu. feet of heated space and charting the temperature change curve you could arrive at a "defacto" containment R value.  Then compare it to the BTU's required to increase the temperature back to what's comfortable.  You will need to know the BTU output rating of the heating unit.   Remember, heat loss through a mass changes rate with the temperature differential.  So, you will be losing heat while the internal temp rises.  If the R value is low enough, and the temperature differential high enough, you will reach a point where maximum space heating occurs, as heat exit equals heat input.


One thing sure, you can't do calculations without numbers.  Without those, all you can make is estimates (and stories about great grandmas or being able to cut glass with parts of the local witch's pointy bits).  

Cheers,

[Damfino]

I have a house full of paint peeling off the walls as well as about 3 busted radiators. All the effects of the previous owners not leaving the heat up high enough and using portable heaters instead. I still need to use portable heaters*, but I leave the thermostat set at at least 60 degrees F. I think the previous owners never turned on the boiler except in extreme circumstances.


*The reason for not just turning up the thermostat, is that I live in a rather large brick & stucco house built in 1910. Somebody had the bright idea to install two high BTU boilers. (One for upstairs, one for down.) My Jan. 2010 heating bill with the thermostat set at 60 was $700.00!!

[demon78]

Jeez can I watch TT, and Schmithaus $700 sounds almost like you're on Ontario Hydro's special rebate for electrical heat do they send the armoured car to your door?
Bill the demon.

[Skunk Stripe]

I have heard the R value of 8" poured concrete used in foundations has the approximate rating of 2. Now I am assuming here but I would not figure that bare stone walls are much different. So you have 2 foot think walls about, and that would come to about R6 in concrete.
Again, just a guesstimate but I doubt it would be much greater for stone walls.

[Bob Wessner]

Must say, this has gotten me Googling.  From an architecture site;

"Stone isn't much of an insulator...at roughly 0.08 R per inch, a 2-foot wall has an R-value of about 1.92.
A stone wall makes for great thermal mass in passive solar applications; it's a conductor, not an insulator."

[paulages]

Must say, this has gotten me Googling.   From an architecture site;

"Stone isn't much of an insulator...at roughly 0.08 R per inch, a 2-foot wall has an R-value of about 1.92.
A stone wall makes for great thermal mass in passive solar applications; it's a conductor, not an insulator."

...but (without googling) stone also has a lot of thermal mass, meaning that heat absorbed by the stone will also be transferred back to the ambient air when it cools below the temp of the stone, much like water barrels used in greenhouses to help stabilize temperatures at night. The question is, "does the stone have too much thermal mass?", meaning that the temperature required to drive useful heat into the stone rather than it just being continually wicked away by the cold on the other side is unrealistic.

For example, my wood-fired oven has 5" thick refractory brick walls, and after an evening of pizza cooking at 900F the internal temp is still 200-300F the next morning with full ambient-air ventilation. The dome is insulated on the outside, but fresh air flows across the inside all night, and the bricks still retain that much heat overnight.

I asked this same question to a local energy savings NPO (they supply plastic wrap for windows, pipe insulation, etc), and they told me it was more energy-efficient to turn the heat down rather than off when asleep or away. Not sure if that counts with R2 walls though...

[Skunk Stripe]

I wonder though, for your brick, if it does not have something to do with all the air pockets, not that they are large of course. I could be way off. Though there is something to brick as kilns are usually brick. At least smaller ones I have seen.

[Bob Wessner]

I know what you mean, though not sure the small amount of heat in this application would make much use of this property. I've read, even considered it for my garage, a box of some sort with black back/sides and glass, and a transparent cover facing south to absorb the solar energy from the sun. A small fan circulates the hot air over rocks which store it, then give off the heat at night. Opted for an electric heater considering the limited use during the winter months... and a lot easier.   Besides, I'm not sure how much sunlight you have in merry England, let alone in the winter.

It think kilns use a different sort of brick, firebrick, which is lighter and more porous. We have it in the firebox of our fireplace. They at least got that right 70 years ago.

[paulages]

I wonder though, for your brick, if it does not have something to do with all the air pockets, not that they are large of course. I could be way off. Though there is something to brick as kilns are usually brick. At least smaller ones I have seen.

Red brick has lots of thermal mass, as does concrete. Refractory brick however, contains higher amounts of silica, designed to reflect the heat back inward for quicker and higher temps. Anyway, like TT said, the type of stone in the walls will likely matter, and I bet one could find general thermal values for different stone (basalt, limestone, etc) with a little google searching. Anyway, I'm no engineer, so I'm probably stating more than a few things wrong here.

[plug1]

This may make no sense at all but when a thermostat is set at a certain temp and left there, whether it be 85 or 65, that temp just has to be maintained. Turning the temp down may stall the unit for a while but it will eventually run and have to maintain that lower temp just the same. Then when the thermostat is set back to the higher temp the unit will have to run for a while to reach that temp only to maintain it once again. Therefor, wouldn't it make more sense to set it at a comfortable level and leave it there? Is it really more cost efficient to keep turning the stat up and down? It seems to me that the unit would run more when doing this. OK HVAC folks, have at it.

[Bob Wessner]

Plug, like everything else in the world, "it depends." We have gas, forced air heating. In the winter here, we can go days with temps below freezing with only a handful of nights with temps down to, or a little below zero. We have a programmable thermostat (didn't always) and we set the temp back to 60F overnight. We saw a significant savings doing this and it rarely cycles overnight unless we in a deep, long, very cold stretch. With the forced air, the temp recovers quite quickly in the morning. We set it to come back up 20 min. before we get up. Other forms of heating may take longer.