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Community and Q&A

How to Efficiently Heat an Unoccupied Home

NH_Advisee | Posted in GBA Pro Help on

Addendum: 

 
Thanks to everyone who answered thus far.  So here are the specifics: how to most efficiently heat a home that is largely unoccupied in the winter (in Zone 6), and has both radiant heat (in the kitchen floor), and forced hot air in the rest of the house.  Kitchen is about 25% of heated space.  Currently the kitchen heat is turned off, and the forced hot air is on a web-enabled thermostat set to 50 degrees.  I have a Marcell sensor at the most vulnerable pipes that records temps hourly and notifies me if it goes below a set threshold.  This system has worked fine (heat from the main part of the house adequately heats the kitchen), but it occurred to me that perhaps I should be doing it the other way around: if radiant heat is more efficient than forced air, would it make more sense to turn on the kitchen heat and let that do more work toward heating the rest of the house?  The forced hot air could still do some work, say, by being set to a lower temp than the kitchen.  Or should I let the radiant heat do all the work, since it is more efficient? 

I welcome any and all thoughts — thanks in advance.

First-time user here.  I don’t know if Dana Dorsett still contributes to this site, but I’d like to ask him a complicated (at least to me) question.  The question has to do with how to most efficiently heat an unoccupied home (i.e., temp set to 50’s) in Zone 5 that has part radiant and part forced-hot air. I don’t mean to freeload; I’d be happy pay him for his time.  If that’s not an option, I’ll post my question publicly and provide some additional details.  Thanks.

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Replies

  1. matt2021 | | #1

    You will find this thread helpful; and if you post there, Dana might see a notification:

    https://www.greenbuildingadvisor.com/question/who-is-dana-dorsett

    Also, I think I found Dana on LinkedIn, in case you want to connect with him that way.

    In any event, you should post your question here; you will receive a lot of helpful feedback. I am not sure your question is so much about heating though, as the heating systems at your house are already in place, as about insulation (including perhaps what to do with the windows during the times when the house is not occupied).

    Good luck!

  2. DC_Contrarian | | #2

    Just post your question, we'll help you figure it out.

    1. NH_Advisee | | #7

      Thank you. I added an addendum to my post with the specifics. Is this the best way, or should I start a new post?

      1. DC_Contrarian | | #8

        You'll probably draw more attention with a fresh thread.

  3. nynick | | #3

    I currently heat one home that has radiant floor heat in one section and baseboard heat in the rest, all fired by oil. I have Nest thermostats so I can check it online. I set it all to 50 degrees with no problems while we're away.

    I also heat another home with oil fired hot air. I set this one to 55 degrees because it's old and drafty. I make sure to turn off the house water supply (but keep the water supply to the boiler on!) in case of burst pipes. It hasn't been a problem either. I have a programmable thermostat in this home as well I can check it online.

    I have 5 battery powered "smart thing" sensors spread around the house, including leak sensors. These are pretty cheap and easy to buy and set up and I can see the temperatures all over the house on my cell phone. Pretty cool setup.

    I think the most important thing to do is to be able to turn off your household water supply in case something goes wrong while you're away. Just make sure you don't starve your boiler of water if it needs it.

    1. DC_Contrarian | | #4

      In normal operation the boiler doesn't need water. If it regularly needs makeup water you have a leak somewhere. The leak is introducing oxygen into the system which will dramatically shorten the life of the boiler. I prefer to leave the fill valve closed so that a leak won't go undetected.

      I also like to use a glycol mixture in the radiators so they won't burst if there is a power outage. If you're relying on glycol it's doubly important that there not be undetected leaks because they will cause your glycol to get diluted and reduce the protection.

  4. walta100 | | #5

    I have to ask why not fix leaks in the drafty house it seems likely you could recover the costs in a few months in fuel savings.

    Better yet rent the house our and collect rent and they pay for the fuel.

    Walta

    1. DC_Contrarian | | #6

      Or drain the pipes and turn the heat off.

  5. matt2021 | | #9

    My two cents (as a non-expert) regarding the OP's question:

    - Assuming that the Nest thermostat is for the forced air system, and that the radiant heat system in the kitchen has its own thermostat (it's an assumption because you did not explain that), it seems that you could (a) add a remote Nest sensor (https://www.homedepot.com/p/Google-Nest-Temperature-Sensor-Smart-Home-Thermostat-Sensor-T5000SF/304830932) AWAY from the kitchen, and in the area that risks being the coldest, and (b) turn the radiant heat on, and (c) set the furnace, via the Nest (set to follow the remote's temperature), to 50 degrees. The furnace would turn on only when the temperature in the area away from the kitchen falls below 50 degrees. (On your phone, you'd be able to also see the temperature at the main Nest thermostat; that will help you get an idea of whether the temperature is uniform around the house; and, if the Nest's history shows no furnace activity, you will know that the radiant heat is sufficient.) All of this assumes that the radiant heat system has a thermostat in the kitchen; otherwise, you risk having too high a temperature in the kitchen any time the furnace were to go on.

    - Again, in the spirit of a "two-cent" contribution, I am skeptical that switching from one system to another will mean much in terms of energy savings; yet, I don't know how (in)efficient is your furnace. Much greater savings would come from air sealing the house, most significantly the attic, and add insulation if need be, to bring it to the contemporary best standards (which in Zone 5 I am pretty sure are R-49). You could do the air sealing and insulation upgrade through some state program (I am not sure what the recent federal bill includes); that would give you discounts and rebates; and it would come with the requirement, for the contractor doing the job, of doing a blower test for the house prior and after the air sealing. I am in Zone 5 (Central New Jersey), and did that a couple of years ago; I have seen a significant different in how often the furnace goes on. As many folks on this blog will tell you, energy winter saving is much more about not losing heat, and letting cold come in, than about equipment efficiency.

    PS: In one place, you say you are in Zone 5, in another place you say Zone 6.

    (If we happen to be in the same area, I would have an excellent reference for the air sealing -- and I have no personal interest in the matter, or relation with the contractor; I just had an excellent experience, and have had independent HVAC contractors saying to me that those folks really seal your house very well.)

    I hope at least some of this helps!

    (Speaking of getting attention for one's questions by the way... folks, I have a couple that I think have for now fallen below the radar LOL I'd love to hear some input on them.)

    1. NH_Advisee | | #10

      Thanks for this. Yes, the kitchen has its own thermostat. As to my confusion re: heating zones, I looked at a USDA Plant Hardiness Zone Map before I realized this is not the same as the DOE Climate Zone Map (which shows me to be in Zone 6).

      1. matt2021 | | #11

        I understand.

        You're probably already acquainted with the chart included in this article:

        https://thehtrc.com/2020/insulation-requirements-2021-iecc

        It looks like, for Zone 6, the attic insulation recommendation is R60. If you find out how much insulation you currently have, that will give you a sense of how distant you are from that target. In any event, my understanding is that air sealing is the first thing to address; then you can install more insulation if need be. There can be some substantial energy savings, and the home will be more comfortable year round.

        1. NH_Advisee | | #12

          Thanks again. For the present, my query is how best to use the furnace to heat the house that I have. I understand that better insulation is the real solution, and I'll work on sealing air leaks and increasing R-value for future seasons.

  6. DC_Contrarian | | #13

    How long is the house unoccupied? Have you thought about draining the pipes and turning the heat off? That's the green thing to do.

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