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I am going have a finished basement of 1000 sq/ft which includes a theater room of 12X16. Currently I am in process of planning in stalling duct work to my basement.

I am thinking of not putting duct work in the theater room because in the winter we will only go to the basement for just watching movies. I don't want to turn up the thermostat upstairs to heat the whole basement and over heat the main living area, so instead I'm thinking of just using aspace heater in the theater room.

What are the pros & cons of using a space heater in the room instead of installing central heat, particularly in terms of electric bills ?

I don't have multiple zone in house.

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  • "Which is best?" is usually a very subjective question that generates opinions an is often closed as off-topic, so I reworded your question to ask for pros & cons, instead. Please make sure that my rewording still has the full essence of your question and that I haven't left anything critical out.
    – FreeMan
    Apr 8, 2021 at 16:29
  • What is the source of your central heat? What are your costs for that energy source, and for electricity to power resistive space heaters? In most cases, the math is firmly in favor of the central solution, and you can even set up the central heat with zones (not having them now is not a thing that can't be fixed) and automatic dampers and a thermostat in the room of concern to eliminate "overheating the whole house" as being a problem, automatically - or you can do it manually as suggested in answers.
    – Ecnerwal
    Apr 8, 2021 at 17:19
  • What kind of heat do you now have? This is really an opinion type question so it might get closed, if you ask about the efficiencies of , gas, electric, heat pump, or mini split. With the different types of room heaters it may be ok.
    – Ed Beal
    Apr 8, 2021 at 17:36
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    An electrical resistance space heater can be very practical in a space that is seldom used. You don't want to heat it all the time and other's here suggestions involve too much manual intervention. With that, you are essentially creating a zone, Apr 8, 2021 at 17:43
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    @FreeMan - I think this is a good question that I think a lot of people mull around in their head before finishing a basement. What is funny is that they probably don't understand that in their town there probably isn't a choice of whether to do this or not.
    – DMoore
    Apr 8, 2021 at 17:53

3 Answers 3

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TL;DR Space heating doesn't make sense in a typical US house that already has duct work in place.

There are, broadly speaking, 3 types of home heating in general use in the US:

  • Fossil fuels - Natural gas (generally most cost effective) or oil. If you have this, it would definitely be forced air, as that matches "duct work".

  • Electric resistance heating ("toaster") - Basically a giant metal wire that heats up, air is pushed past it and heats up and is distributed throughout your house. (There are also baseboard heaters, but again "duct work".)

  • Electric heat pump - This is basically an air conditioner in reverse. It heats in the winter and cools in the summer, and only goes to electric resistance heating on the very coldest days (in most areas, with modern equipment).

Electric space heaters (you can't, realistically, use a gas space heater inside a normal house) are the same as electric resistance heating, but for a room rather than an entire house. If you have resistance heating for your house then electric space heaters for individual rooms are essentially the same in terms of usage cost.

If, however, you have either natural gas or heat pump heating, those are almost always far more cost-effective than electric space heaters. To the extent that if you have electric resistance heating for your entire house then it may be cost-effective to replace the entire system due to energy savings over several years.

As far as heating rooms you don't need very often, it is easy enough to install adjustable covers over the registers in the rooms you don't use very often. Close them most of the time. Open them up an hour or two before you are going to watch a movie, close them when done.

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Summary... 100% add the duct work. It will be cheaper in long run, look better, and will increase resale value of the home.

Few things here:

  1. Once you add those walls/ceilings (given it is not a drop ceiling) adding duct work will be very costly and messy. This is sort of like running ethernet cable throughout the house, but air ducts probably have little chance of being under spec in your lifetime. Adding a damper with access to manually turn it off and on is common. (forgive the price here... usually about $15, just an example)

  2. Most inspectors will not allow a place to be label "finished" without it being conditioned in all rooms. This depends on where you live. So what I am saying is... before you ask this question on here and research options - Have you asked your inspector? I can't think of one place that would allow me to "finish" a basement (that's something I have done more than any project) and not require each room to be conditioned. I have had some inspectors require that I condition (add ducts) to the unfinished areas if any of the basement is considered finished. Yes I said that right - I have had to put ducts in unfinished storage or laundry room because I was getting the rest of basement signed off on.

  3. It makes no sense to have 1000 sq feet done by space heaters. That's just too big. To do it right you would need a few faux fireplaces with their own safety and shutoff devices. These would probably require special electrical. Running ducts in an unfinished space is cheap. Doing "nothing" sounds cheaper until it isn't.

  4. Even if you ignore all of the above just do it for the resale value of the home. If I were scoping out a home to buy I would notice the lack of duct work in a basement that size, would assume I would rip apart a lot to fix it and would adjust the price in my head. Worse though is that I would assume other things weren't done right. And even worse to the non-handyman is that the "fireplaces" or "heaters" probably make the finished area look a bit tacky.

Note: If someone were only finishing a small part of their basement - two small rooms (workout room + whatever) I could see the justification of not adding ducts as the bleeding of the heat would be costly and not efficient. This probably gets into what % of the basement is being finished. I think once you get over 60% or 500 sq ft the answer is probably yes you should.

Note to the note: In the case above if you don't condition those two rooms, likely the city will not consider that finished space when you are selling the home, no matter how nice it looks. (this also could be actual home square footage in a walk out basement)

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  • So manual damper will be accessible from unfinished area ? because all duct work will be covered by dry wall.
    – PowerTech
    Apr 8, 2021 at 19:29
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    Yes. If you cannot do this one line at a time (optimal) you will need an HVAC company to create a sub branch for the basement and put the damper there. This isn't costly either way - adding the duct work for the sub branch or doing it one at a time. If you have pictures of the unfinished area including the furnace area I could advise better. The HVAC work may seem "useless" or an area to save... but $800 might save you thousands in long run.
    – DMoore
    Apr 8, 2021 at 19:32
  • I like the idea of sub branch. But i don't have space for that. I have one stem for supply running in middle of basement ceiling and there are branches/ legs coming out to heat main floor. It seems I am ending up with adding few more legs/branches to heat basements area and, will have to manually control heat/cooling register vent in basement whenever needed. that sounds common, right ?
    – PowerTech
    Apr 9, 2021 at 12:56
  • @vickyP - there isn't really "lack of space" for a sub branch or "lack of space in general". This has to be part of the design of a finished basement. If you have pictures I can let you know more but this really isn't an option. Well it is if you want to sneak it in, not get to call the basement finished when you sell the house, have possible fire hazards, and want greater overall costs.
    – DMoore
    Apr 9, 2021 at 20:54
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One thing you could consider would be to install dampers in the duct work to close off various legs of duct. This would allow you to have heat available anywhere in the house you want, but to close off areas from heating when you don't want them to be heated. This would, effectively, give you multiple zones, though they'd be manually controlled.

Also, adding a vent (or multiple vents) should not cause your upstairs to overheat, just because you're now pumping some heat into the basement. Some heat will rise up the stairs, but that shouldn't significantly overheat the main floor.

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  • hrm... one random down vote for saying the same thing as the other two answers without down votes. I guess I shoulda put a title in bold. :(
    – FreeMan
    Apr 9, 2021 at 15:40

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