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Thread: basement heating/cooling question

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  1. #1
    DIY Member idoc4u's Avatar
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    Question basement heating/cooling question

    I am in the process of finishing my basement.

    The area that I wish to heat is 500 sq ft.

    I have a two part question; if I wish to heat with an electric fireplace or electric baseboard heat, do you guys think that an electric fireplace that is supposed to cover a 400 ft sq area would be adequate for a 500 sq ft basement rec area? Not being an HVAC specialist, my gut is that this is not adequate.

    The second part of the question is, assuming this is inadequate, would adding two 6" runs overhead to the area to be heated from the plenum of my 2 ton HVAC unit be additional sufficient heating for a carpeted basement rec area about 500 sq ft?

    So I'd have the electric fireplace + 2 - 6" diffusers from above for this area.

    I appreciate your input and interest.

  2. #2
    Nuclear Engineer nukeman's Avatar
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    That electric fireplace (assuming it is the 400W one in your other thread) would not cut it. Are you sure it is 400W and not 1400W? Most small space heaters are usually in the 1500W range to give you an idea. Most of the electric fireplaces that I've seen are also about 1500W. The 1500W rating is common since it can go on a 15A circuit with a bit to spare.

    With electric, watts are watts. It doesn't matter how it is done (oil, ceramic, halogen, ect.). Any will heat the same space with the same number of watts. One exception is radiant style heaters that will make you feel warmer when standing in front of them. These are good for workshops and similar where you have a large space, but maybe only a couple areas where you primarily work. The radiant style will keep you warm without having to really heat up the whole shop.

    On most of the space heaters and baseboards, they seem to be rated for about 10W/sqft. This means that you would need 5000W for your space assuming those numbers. However, we need to know more about your setup to really know. Insulation levels, is the basement fully below ground?, your location/design temperature, size/location of exterior doors/windows, air infiltration rates (new home/old home), etc. 5kW of heat would almost certainly keep that space warm, but you may get by with quite a bit less. Although, with electric resistance heat, having a system that is too big is not a big deal. It will cost more upfront, but won't cost any more in operating costs. A larger system will also bring the temperature up quicker, which could be important if it is a space that isn't used much (setback heat most of the time and kick the temperature up during those times that you use the space).

    For running new ducts, that is also a possibility, but it depends on how your system is sized. Often, systems will be sized large enough to heat the basement (assuming the basement was unfinished when the system was installed). Again, we don't know enough about your system to know or whether 2 ducts will be enough to heat the basement space or whether adding those additional runs will steal too much heat from the rest of the house.

    Assuming your system was large enough, I would be inclined to heat/cool the space with your HVAC system. Then also add a small amount of baseboards or an electric fireplace incase you need things a little warmer. Since your t-stat is probably on the main level, your basement may be a little cooler than the rest of the house. Instead of cranking up the heat for the rest of the house, the electric fireplace/baseboards can help take the chill off.

  3. #3
    DIY Senior Member Hube's Avatar
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    If it were my home I would just install 2 -5" diameter supplys from the plenum,and run them down to approx 6" above the floor level . Terminate each supply pipe with a 5"- 4x10 register boot, c/w registers.Make sure you install butterfly type dampers at the plenum takeoffs.
    Also, it would be essential to install a properly sized RETURN air from this 500 sq ft room and route it back to the main return duct. Using your existing heating system is all you need, no need for any electrical heater at all.
    If you have more questions as to sizing, etc, just ask. Be glad to help.

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    DIY Member idoc4u's Avatar
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    Wink

    Hey guys,

    Thanks for taking the time to help! I appreciate the input.

    Nukeman, I miswrote. The electric fireplaces are 1500W and claim to cover 400 sq ft.

    The home was built in 2009. The basement has two window wells. I believe you'd call it a "look-out" basement.

    The basement was unfinished. I am in the process. I have the framing complete, plumbing run and much of the electric in place. I have placed a in-wall-type baseboard heater in the bathroom I created along with a 6" supply from the plenum.

    The main rec area is 500 ft sq and I am trying to determine the most efficient and effective heating system. I am located in NW Indiana. My concern was that I may steal from the main floor or second floor to heat the basment. That said, when I last spoke with the original HVAC installer, I know he told me that if he was going to install the supplies to the basement he would take off of the plenum.

    Hube, I considered what you recommend. The problem is size. In order to maximize room dimensions, I have 2x4 framing and a 5" down the wall will not fit inside the wall, unless I create a chase and put the piping down the chase with a boot. The other issue I have is accessing the plenum. There are only two viable areas to take off from. Logistically, the space to access the plenum is limited due to gas pipe, copper and conduit. That is why I would need to heat from above, although I realize that this is not the most efficient method. Knowing my efficiency limitations, I wanted to augment by using an electric source such an electric fireplace.

    Thanks again for your kind assistance and time!

  5. #5
    Nuclear Engineer nukeman's Avatar
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    For your runs between the studs (if you go the HVAC route), you can use either "oval" or "wallstack" for those runs. Either will fit between a 2x4 stud bay. Oval tends to be better than wallstack, but a little worse than round. If 5" rounds was good enough, you might go to 6" oval, for instance. As far as getting around everything else, you just have to try to figure out some possibilities and try some things until you find something that works.

    Here are some oval ducts/fittings:

    http://www.audubonsupply.com/browse.cfm/2,176.html

    One thing that I don't like about baseboards is they don't look too great and they take up a lot of good wall pace (shouldn't block with furniture). I'm looking for a better solution myself. I have four 6" ducts feeding the basement and there was also baseboards in all of the basement rooms. I have removed the baseboards for the reno, but I would like to replace with something. I added radiant in-floor heat to the bath, but it would be too expensive to cover the whole basement (~1100 sqft). I may not even need the supplement heat anyway as now the basement has better insulation than the rest of the house. I'll have to figure it out.

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    DIY Member Lightwave's Avatar
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    As in said in my post in your other thread, you need to do a load calculation. Heat loads can't be guessed.

    Your existing HVAC might have the capacity to support another 500 sq ft of living space, but then again it might not. You must do a load calculation and compare the heat requirements to your system's capacity to know one way or the other.

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    DIY Senior Member Hube's Avatar
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    You can put in a 3-1/4 x10 duct in the wall cavities if you have no room for a 5" pipe.Use a 3 1/4 x 10 to a 6 x 10 register elbow at the terminating point. Once above the wall simply transition back to a 5" round at the plenum .Use a plenum takeoff (5") and attach to plenum.
    In most cases a furnace is sized to consider the htg of a basement in general, and even if it did'nt if would not make any significant effect to the rest of the home.

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    DIY Member idoc4u's Avatar
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    Cool

    Thanks again for all of the replies and interest.

    Yesterday, I took a look at some ventless gas fireplaces/fireboxes.

    This method of heating seems pretty effective and efficient.

    Any experience or thoughts with this method?

    Have a safe and relaxing Independence Day!

  9. #9
    DIY Member Lightwave's Avatar
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    Quote Originally Posted by idoc4u View Post
    Yesterday, I took a look at some ventless gas fireplaces/fireboxes.

    This method of heating seems pretty effective and efficient.

    Any experience or thoughts with this method?
    You'd need to be nuts to use a ventless fireplace as a heat source. At the absolute best, they're nothing more than slightly safe conversation pieces.

    Do a heat loss calc and either get some baseboard heaters or tie into your existing heating system.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    A ventless fireplace is sort of like leaving your gas stove running all day. As noted, the hydrocarbons produced along with the carbon dioxide all go into the room. Neither water vapor (a lot of it is produced!) and CO2 are not toxic (well, either in excessive quantities can be a problem), but not great in your living space. Also, to make all that H2O and CO2, you are taking up oxygen from the house. There are also some trace impurities that will produce other things. You really don't want this in the house. Get something with a flue, and if you want efficiency with a burner, feed it outside air.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Engineer Furd's Avatar
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    I personally think that ventless gas heaters should be outlawed. Even under the best of conditions they release a huge amount of water vapor to the heated space and under the worst of conditions they are spewing carbon monoxide. I would never have one in my home or even garage.


    I agree with the other responses given concerning ductwork and first doing a heatloss calculation. There are several free "quick and dirty" heatloss calculators available on the Internet. Here's one: http://www.heatload.com/
    Last edited by Furd; 07-02-2010 at 03:22 PM.

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