What thermostat temp setting - empty house in Jan-Mar

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Slowgowing

Dryer sheet wannabe
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My home is located in mid-Maryland and am planning to be away from January through March. I've done some reading/research and the typical recommendation I've seen is to set the thermostat at 55 degrees.

Is there any particular reason I couldn't safely set the thermostat to a lower temperature - perhaps 45 degrees for energy savings?

What might you recommend?


I am not a winterizing expert by any means, and have more research to do, but planning on at least the following:

Main water valve inside the home will be turned off and inside/outside faucets left open a bit to drain.

P-traps filled with RV antifreeze to prevent evaporation, possible freezing, etc.

Bleach added to toilets and covered tightly with plastic wrap.
 
We set at 55F. Since we are heating to 55F I don't bother with RV antifreeze, etc. I do turn off the water supply and open a valve for a few seconds to relieve the pressure.

While I don't do it I could open all the faucets so the we had no heat and the house froze that the freezing water could expand some. Our house is all pex whh in theory could freeze without any damage.

Important to have some way to monitor temperature in the house. I have Blink security cameras on each floor and can monitor the temperature through those.

We have had no heat situations that I picked up through the security cameras and then called to have a friend check on it. In one case the thermostat batteries needed to be replaced and in another a part failed and my plumber had to come and replace the part. I also have internet thermostats to monitor the temperature as well.
 
I'm bad. We go with no heat in Oregon, where it does freeze. I shut off water at the meter, blow out the lines, including some head space on the water heater, anti freeze the traps, and put a bleach/antifreeze mix in the toilets with saran wrap over the bowls. Interior sucks up ambient moisture to some balancing point, then dries in spring/summer.

In OMG hot La Quinta Ca we cover the toilet bowls and I leave the AC off. The interior hits 115 easy and elastic (swim suit waistbands and such) and candles are pretty much dead after a summer without us. Without concern for the water table we drain the pool and leave it dry.

In both the freezing and baking climates we've had very few problems and have saved a considerable amount not heating or cooling (or pool maintaining). Works for us, but not what is commonly recommended.
 
The risk of 45 is that this will be the low at your thermostat, but could get a lot colder elsewhere. If it gets below freezing where your pipes are they could freeze and burst. Shutting off the water and draining the lines might make it safe. I've done that and gone to 50 degrees. I only had one problem with radiant heat pipes bursting because the furnace room had an outside air intake so it got really cold. I read up and found that my room size was right on the border, and didn't need the intake if I left the inside door open. I've blocked up the intake, and monitor with a co2 detector.
 
The 55°F recommendation comes from wanting to keep the coldest parts of the house, such as basement pipes next to an exterior wall above freezing. If you put your hand on the inside of an exterior wall in the depth of winter you'll find it is quite a bit cooler than whatever the interior temperature is. That 55° gives you a "margin" of safety but without running up a huge heating bill.

Of course everyone's house is different so there is no "one size fits all".
 
As others have said, never set the thermostat lower than 55°F. We lived in Alaska for a while, and that was standard procedure... But I'd tell people the same even if your area rarely gets below freezing. Remember that "55°F" according you your thermostat is going to be 40-45°F along the exterior walls/windows and any cabinets on the home's exterior (like under your kitchen sink). That is the case even more if you have 2+ levels in the home... then you might need to keep the thermostat set even higher (58-60°F), unless you have dual-zone heating for upstairs/downstairs.

If you set your thermostat to 45°F, I can almost guarantee that at least some of your pipes will freeze, especially if your home is in an area that regularly spends days/weeks at/below freezing. If you drain the water system completely (possible, but challenging), your pipes will still be frozen when you return home & go to re-open the pipes. So either you live without water for a couple days while the pipes re-warm, or you risk opening the valves & having the water freeze on contact with your pipes (creating a bad situation).
 
Yes, we use 55 degrees F. Fortunately, we at least theoretically have someone looking in on the place - especially in very cold weather. YMMV
 
At my high-country boondocks home (7000 ft elevation), I set the thermostat at 45F year round. The temperature can get down below -5F (-15C). So far so good, after 17 years.

I do shut down the water at the meter, which is 3 ft deep in the ground. I drained the line every time I left the home.

Yet, I have had the meter froze and also the shut-off valve busted by freezing twice in the 17 years. They are 100 ft from the house.

Yes, I had a pipe heater tape for the meter and the shut-off valve, but they froze when the power line to the heater tape failed. I will have to remember to check the heater tape operation in Nov/Dec.

PS. Each time, the water company shut off the water with an upstream backup valve (buried even deeper), then called me to warn of the busted valve. They replaced the meter free-of-charge. I had to replace the downstream shut-off valve at my cost.

PPS. Apparently, the water company sends personnel out for freeze damage inspection after every cold spell. Usually, the low is only about 20F, but a cold spell may drop it down to -10F or below. When a house is vacant and nobody uses the water, the underground pipe gets cold-soaked, and freezes.
 
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I have to wonder whether the savings of 55F vs 45F would be very significant. I'm not sure how you could estimate it.
 
pb4uski said:
I have to wonder whether the savings of 55F vs 45F would be very significant. I'm not sure how you could estimate it.
Click to expand...

My Thermodynamics training is rusty - having taken place 55 years ago - and I never really used it:blush:. But I can tell you this: Every degree colder you set your thermostat, the less you save. So lowering from 65 to 55 saves more than when you lower from 55 to 45. YMMV
 
pb4uski said:
I have to wonder whether the savings of 55F vs 45F would be very significant. I'm not sure how you could estimate it.
Click to expand...
I'm not sure how to estimate it (short of experimentation) ... but the answer depends on the thermal gradient compared to the outside. On cold Alaska days, we often had a delta of 70-80°F between inside & outside. Whereas in NC, you'd probably only have a difference of 30°F on the coldest of nights.

It's not exactly an exponential relationship, but it's definitely not linear either. The larger that temperature gradient, an "extra-larger" amount of energy will be required to heat it.

Perhaps easiest to demonstrate with running time (I'm using guesstimates to demonstrate the point) -- keeping a 30°F temperature gradient at bay might only require furnace run-time of 15 minutes per hour. A 70°F gradient might require a furnace run-time of 45 minutes per hour. There were some nights (-30°F or lower is ZERO fun) that our furnace literally never shut off, and we woke up to a house colder than when we went to bed. Space heaters & the fireplace became our friend. Yes, we probably needed a new furnace.
 
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Kork13 said:
I'm not sure how to estimate it (short of experimentation) ... but the answer depends on the thermal gradient compared to the outside. On cold Alaska days, we often had a delta of 70-80°F between inside & outside. Whereas in NC, you'd probably only have a difference of 30°F on the coldest of nights.

It's not exactly an exponential relationship, but it's definitely not linear either. The larger that temperature gradient, an "extra-larger" amount of energy will be required to heat it.
Click to expand...

Actually it is a linear relationship based on R-value, or at least a chain of linear relationships. But I agree with your main point that the important thing is to be confident your pipes don't freeze.

Our heater died just before a cold spell in Arizona a few years ago. We camped around the fireplace in the living room for several days while it was low 20s/mid teens outside before a contractor could inslall a new heater.

I can't tell you how cold the house got because thermostats don't go that low. But I can tell you the attic got cold enough that the pipes froze and ruptured in a few locations. There was no real damage because I anticipated this but a friend of ours had her entire house flooded from a similar incident a few years before.

My suggestion would be to cut off your water if leaving for a week or more even in the summer and stick with a temperature that keeps the house warm enough that temperature gradients do not cause problems. It gets pretty cold in Maryland so I would stick with 55 but that's just me.

Your insurance company, which may cover some potantial damage may also have advice.
 
Koolau said:
My Thermodynamics training is rusty - having taken place 55 years ago - and I never really used it:blush:. But I can tell you this: Every degree colder you set your thermostat, the less you save. So lowering from 65 to 55 saves more than when you lower from 55 to 45. YMMV
Click to expand...

Thats because your cost is based on average R-value. (R=resistance) If the R-value from the inside of your house to the outside is 50 the watts you feed to the outside and therefore waste on vacation is ((Tinside)-(Toutside))/R

If Tinside is 55 and Toutside is 0 with R=50 the heat flow is (55-0)/50 = 1.1 watt/m2

If Tinside is 45 and Toutside is 0 with R=50 the heat flow is (45-0)/50 = 0.9 watt/m2

So a 30 ft x 30 ft x 10 ft (10x10x30 m) house would have a loss area of 220 m2 and lose 242 w at 55 and 198 at 45.

If you pay 10c /kwh then 55 deg costs you (198 w)(/1000)(10c/kwh)(30days)(24hrs)= $14.25

If you pay 10c /kwh then 45 deg costs you (242 w)(/1000)(10c/kwh)(30days)(24hrs)= $17.42

So you will pay $3.17 per month to keep your house 10 degrees colder. Does not seem like a good risk to me but you'll nee to correct for your actual energy costs.
 
Southern Md here. Shut water Main off, drain all faucets, open all cabinet doors to give some heat to pipe. I set mine to 57, using nest thermostat and cameras to monitor home. Then as we start north I’ll slowly increase house temp.
 
calmloki said:
I'm bad. We go with no heat in Oregon, where it does freeze. I shut off water at the meter, blow out the lines, including some head space on the water heater, anti freeze the traps, and put a bleach/antifreeze mix in the toilets with saran wrap over the bowls. Interior sucks up ambient moisture to some balancing point, then dries in spring/summer.

In OMG hot La Quinta Ca we cover the toilet bowls and I leave the AC off. The interior hits 115 easy and elastic (swim suit waistbands and such) and candles are pretty much dead after a summer without us. Without concern for the water table we drain the pool and leave it dry.

In both the freezing and baking climates we've had very few problems and have saved a considerable amount not heating or cooling (or pool maintaining). Works for us, but not what is commonly recommended.
Click to expand...

I do the same for my Mom's summer home... blow out the water piping with air, open all the faucsts so when what little residual water that is in there freezes that it has room to expand, drain the water out of the toilet bowls and put RV antifreeze in the toilet bowls and p-traps. Works like a charm for the 60 years that we've owned the place.

Many people say that it is not good to leave a building unheated for the winter but we have had very few problems. We do heat our place to 55F so if there is some family emergency and we need to come back during the winter then we could use it rather than a hotel. I figure that between propane and electricity to heat and snowplowing so the propane truck can made winter deliveries (and we could access the place if needed) that the cost is only about $1,500-$2,000 annually but it is nice to know that if we need to use it that it is readily available rather than using a hotel or staying with family.

I would never think of not running the AC over the summer in Florida while we are gone... I'm afraid that I would have mold all over with the humidity.
 
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SecondAttempt said:
.... My suggestion would be to cut off your water if leaving for a week or more...
Click to expand...

Our condo association requires this of owners... not everyone does it but most do as it is very easy to do and just the right thing to do.

... For example, should a Unit Owner fail to shut off the main water valve to the Owner's Unit when the Unit is vacant, if water damage originating from the Owner's Unit occurs to the Common Elements, Association Property or other Units, the cost of any maintenance, repair, or replacement necessitated thereby may be assessed against the responsibie Unit Owner and Unit. ...
Click to expand...
 
All -

Many thanks for your comments and responses.

Although there would be some savings by setting the thermostat lower than 55, I would rather pay a bit extra than to have a more serious problem.

Rather than starting a new thread - one other question for the group:

Should I completely turn off the gas water heater, or, just use the "vacation" setting?
 
I am a retired HVAC engineer. No lower than 55 for sure. You risk condensation inside walls as well as freezing a pipe that’s in a spot not as well insulated or located as others. This happened to my FIL in Ohio who left it set at 55 during a very cold weather event with sub zero conditions at night. These are now more common.

I also recommend a Nest thermostat. You can view or change the thermostat entirely remotely on your iPhone.
 
I would caution those with hot water baseboard heat like us. I will not shut off water when leaving during freezing weather. IMO, a small leak that may occur in the heating system needs water to replace it, otherwise you will have NO heat. With an older boiler system, there may not be a low water shutoff. Another, worse situation could occur.

We are on a well. I have to admit, I am a bit hesitant about leaving an unchecked water supply free to supply as much water as it could. During Summer months we do shut off the water valve from the pressure tank, the power to the well pump as well as the water heater. We did have a pressure tank burst a couple of hours after returning from a long trip. The timing was very fortunate. 50 gallons of water plus a pump that would run forever.
 
Slowgowing said:
All -

Many thanks for your comments and responses.

Although there would be some savings by setting the thermostat lower than 55, I would rather pay a bit extra than to have a more serious problem.

Rather than starting a new thread - one other question for the group:

Should I completely turn off the gas water heater, or, just use the "vacation" setting?
Click to expand...
That one's more a question of convenience. How comfortable are you with getting the pilot light re-lit (if you have a gas water heater)? Is it easy & reliable? I know some older water heaters were/are a pain in the butt... But newer ones can be super easy.

Personally, I would probably go ahead & turn it off completely. While you're at it, could be a good opportunity to totally drain/flush the thing (people never do it often enough -- myself included), and draining it would again prevent freezing problems (being turned off), since your mech area probably sits colder than the rest of the house.
 
CRLLS said:
I would caution those with hot water baseboard heat like us. I will not shut off water when leaving during freezing weather. IMO, a small leak that may occur in the heating system needs water to replace it, otherwise you will have NO heat. With an older boiler system, there may not be a low water shutoff. Another, worse situation could occur.

We are on a well. I have to admit, I am a bit hesitant about leaving an unchecked water supply free to supply as much water as it could. During Summer months we do shut off the water valve from the pressure tank, the power to the well pump as well as the water heater. We did have a pressure tank burst a couple of hours after returning from a long trip. The timing was very fortunate. 50 gallons of water plus a pump that would run forever.
Click to expand...

There are power monitors (I think the upgraded Sense is one) that can be set to monitor usage and text you, for example, if your pump runs more than x minutes.

Regarding thermostats, there are relatively inexpensive WiFi ones now, around $100, that will let you monitor and adjust your setting. I'm not sure if the cheaper ones will notify you, but I imagine some will. We put Honeywell ones in the last house; this one has an Emerson Sensi. The Sensi app will show you how long your furnace or AC runs each day. Look on eBay for open-box ones.

No one has mentioned that the temperature setting might depend on whether you have basement, crawlspace, or slab construction, and where in those spaces the pipes are. It might make a difference. I put a remote thermometer probe a foot down into the crawlspace through a small hole, and discovered that the temperature there is just about the same as the home interior.
 
Thanks for starting this thread, OP, as I am starting to ponder it with plans to be away in January and February. I live in a townhouse in DC, and I drain the exterior spigots every winter anyway. But my house has a hard time getting too warm in winter (high ceilings with the vents right at the top of the walls). I use space heaters when I'm there, but that won't be an option if I'm not. I may have to do the full water shut off and learn about the antifreeze thing.

I am actually planning to be in Wyoming, so won't have to worry about what the cold does to my new place out here other than in November and December. But it looks like these places were built with extreme cold temperatures in mind. All of the water pipes with the exception of the exterior spigots are clustered in the interior of the house, and there is a three foot crawlspace with the furnace right in the middle, under the kitchen. And I see that there is a flow monitor on the main water pipe that can alert the water service (in this case, the development itself) in case of problems.

I have Nest thermostats and cameras in both places, and I'm very good at crossing my fingers. [emoji1696]
 
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