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Thread: Electric Baseboard Heat Calculation

  1. #11
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    the fact you have insulation in the ceiling helps, otherwise most heat loss will be to the floor above, and probably still will be the majority of the heat loss unless you have windows - especially poor windows. Otherwise general rule of thumb for general living spaces is 10 watts per square foot, but if you only want to keep it above freezing you can get by with a lot less then that. I have put 5 kW heaters in garages that are maybe near 10k square feet and they do just fine keeping it warm enough to thaw snow and ice off a car - and those have overhead doors that don't have the greatest R value and they do get opened to let vehicles in and out as well.

  2. #12
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    Most unfinished basements I have been in would never get below freezing with no heat in them at all. In this case, 3 feet of wall above grade is more than normal, so it may not be true here.

  3. #13
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    Quote Originally Posted by kwired View Post
    the fact you have insulation in the ceiling helps, otherwise most heat loss will be to the floor above, and probably still will be the majority of the heat loss unless you have windows - especially poor windows. Otherwise general rule of thumb for general living spaces is 10 watts per square foot, but if you only want to keep it above freezing you can get by with a lot less then that. I have put 5 kW heaters in garages that are maybe near 10k square feet and they do just fine keeping it warm enough to thaw snow and ice off a car - and those have overhead doors that don't have the greatest R value and they do get opened to let vehicles in and out as well.
    My uneducated gut was telling me that because the basement ceiling will be insulated it will make it harder to heat not easier. My thinking was that the heated first floor would cause heat to migrate into the basement. I realize heat rises but I assume it would mix with the colder air below. Not true?

  4. #14
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    Quote Originally Posted by mkgrady View Post
    My uneducated gut was telling me that because the basement ceiling will be insulated it will make it harder to heat not easier.
    That is correct if the living space is conditioned, which is my understanding. I believe kwired's comment was assuming the living space would be unconditioned.

    Quote Originally Posted by mkgrady View Post
    My thinking was that the heated first floor would cause heat to migrate into the basement. I realize heat rises but I assume it would mix with the colder air below. Not true?
    Hot air rises, but heat can also be transferred by conduction or radiation. The basement will gain some heat from the conditioned living space above it. Depending on how poorly the basement ceiling is insulated, and the location of the pipes involved, that could be enough to keep the pipes from freezing. If all of the pipes are in the basement ceiling, then relocating the basement ceiling insulation to be under the pipes should be sufficient to keep them from freezing.

    Cheers, Wayne

  5. #15
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    Quote Originally Posted by retirede View Post
    Most unfinished basements I have been in would never get below freezing with no heat in them at all. In this case, 3 feet of wall above grade is more than normal, so it may not be true here.
    That has been my experience too. Being partially below grade seems to keep the temps above freezing. I'm torn between thinking trying to heat the space to 40 is going to be very costly to being no big deal. Pretty confusing. I should probably tell the customer that installing the heat is only cost effective if he insulates the walls.

  6. #16
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    Most states have an energy code with a free spreadsheet to do the heat loss calculations.

    Here is the one for WA.
    http://www.energy.wsu.edu/Documents/...Worksheet.xlsx

    BTW, electric heat in MA???!! Sell them a mini-split, even just heating to 40F will pay for itself in a year or 2.

    Also, if an electric dryer, vent it thru a filter into the basement, no need to waste that heat. Have vented mine into basement for 45 years, no problems. But do hang clothes outside on a line all summer and when outside temp over 60F. Parents ventied into basement from their first electric dryer (cica 1960) and still doing so. Grandma hung out all year around in IL, sometimes took a week for the frozen clothes to sublimate or hang inside if < 0F

    Sealing and adding insulation to any un-insulated space is nearly always the best and most cost effective first approach!

  7. #17
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    Quote Originally Posted by mkgrady View Post
    My uneducated gut was telling me that because the basement ceiling will be insulated it will make it harder to heat not easier. My thinking was that the heated first floor would cause heat to migrate into the basement. I realize heat rises but I assume it would mix with the colder air below. Not true?
    Not quite. Heat doesn't rise. Heated fluids tend to rise and carry heat with them. Heat travels from a warmer place to a cooler place, regardless of which direction that might be.

    The basement ceiling insulation won't have much effect on the basement heat load. Insulated or not, there won't be much downward heat flow. The temperature difference isn't large enough for significant radiant heat transfer. Convective heat transfer won't be very effective because the air near the warm basement ceiling will be stagnant. And conductive heat transfer won't be very effective because air isn't a great conductor of heat.

    If the house is heated with something more economical than electricity, install a duct & fan or radiator & pump instead of resistance heaters. Residential heating plants almost always have excess capacity available.

  8. #18
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    Quote Originally Posted by junkhound View Post
    Most states have an energy code with a free spreadsheet to do the heat loss calculations.

    Here is the one for WA.
    http://www.energy.wsu.edu/Documents/...Worksheet.xlsx

    BTW, electric heat in MA???!! Sell them a mini-split, even just heating to 40F will pay for itself in a year or 2.

    Also, if an electric dryer, vent it thru a filter into the basement, no need to waste that heat. Have vented mine into basement for 45 years, no problems. But do hang clothes outside on a line all summer and when outside temp over 60F. Parents ventied into basement from their first electric dryer (cica 1960) and still doing so. Grandma hung out all year around in IL, sometimes took a week for the frozen clothes to sublimate or hang inside if < 0F

    Sealing and adding insulation to any un-insulated space is nearly always the best and most cost effective first approach!
    Mini split sounds interesting. I wire them often but have never installed one. Not sure how the line set install works. Seemspulling a vacuum is required. Is this something electricians typically get into? Not sure the thermostat, which is usually a remote would have a setting as low as 40 degrees.

  9. #19
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    Quote Originally Posted by mkgrady View Post
    Mini split sounds interesting. I wire them often but have never installed one. Not sure how the line set install works. Seemspulling a vacuum is required. Is this something electricians typically get into? Not sure the thermostat, which is usually a remote would have a setting as low as 40 degrees.
    A common technique for minisplit line sets is to ship the compressor unit fully charged with freon, the evaporator coil (inside unit) pumped down to a good vacuum, and the line set either pumped down to a vacuum or carrying an amount of Freon appropriate for the length of the set.
    Each component has a seal at its connectors which is automatically broken as the connector is mated and tightened.
    The result is an install without the need for either a vacuum pump or a bulk container of refrigerant.

  10. #20
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    Quote Originally Posted by mkgrady View Post
    Mini split sounds interesting. ...
    That would be the worst selection possible. This basement will need heat only on the coldest days of the year, during which a mini split (or any other heat pump) will switch over to resistance heat.

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