About to begin a basement remodel with 3/4 bath (Massachusetts). Finished space will be approx. 500 sq. ft. Present temperature (winter season) of unfinished space is 58 degrees. Customer would like electric heat. Question is how many lineal feet of electric baseboard will be sufficient to made this space a comfortable (68 degrees) playroom / tv room.
Local supply house sells 6 foot sections (110 volt, 1500W). Electric panel has ample room for some 20A circuits.
Thanks
Replies
Best guest is that the space will require about 4500 watts to heat.
anywhere from 2 feet to 20 feet with the meager info given
How many watts per foot heaters envisioned.
wall heightt, material, insulations?
floor, ditto say
hiegth of walls above ground and insulation?
ceiling insulation and temp on other side of ceiling, (probably zero watts)
windows?
someone can make a better estmate with the above info, or you could calculate it yourself with a little web legwork, then you will have that knowledge forever.
Finally, why not consider a heat pump, 1/3 the elec bill.
Elec res. heat baseboard so cheap simply run ita ll the way along one wall if homeowner simply wnats elec. heat.
Local supply house sells 6 foot sections (110 volt, 1500W
I looked for these and was only able to find 220V. Do you mind sharing your source please, (I'm north of Boston).Thanks.
Thanks for the info. As for more details...
Present basement is not insultated but will be with roughly R15.
Present basement is walk out style. Rear wall (approx 25 feet finished space) is the walk out wall. Other 3 walls are below grade. The rear wall has 1 window (maybe 2'X3') and 1 exterior 32" door..
The finished ceiling (drop ceiling) height will be about 7 feet high.
Above the basement is finished (heated) living space.
Basically the customer wanted to get some "cheap" auxillay heat source. They will only be turning on the heat 1-2 days per week during the heating season.
As for the 1500W baseboards, check out the Cadet web sight, they have model number 6F15001A (1500W, 120V, 6 foot section). They also list companies that sell their product.
I will search the internet for some formulas but if anyone has any general rules of thumb, that would be appreciated
Thanks
The R15 wall help a lot. With the ceiling as a heat source, one 1500 W heater will likely be fine for SUSTAINING 68-70F, but would take hours to come up to heat after heat turned on the once or twice a week. As before, the baseboard is so cheap you might as well put in all that will fit without sacrificing space for what you can put against the walls.
Keep in mind that you don't heat SPACE, you heat AREA. If there were no heat loss through the walls and floor, a basement would not need to be heated. Basically, you need to calculate what the heat loss is through the walls and floor, and that will tell you how much heat you need.
As a rough first cut, you can assume that the earth outside floor and walls is at 50F, and calculate the heat transfer based on the R value of the concrete.
Dan,
Maybe I misunderstand what you are trying to say, but what you DID say is incorrect.
".... you don't heat SPACE, you heat AREA".
In reality you DO heat space, or more acurately, volume. With the exception being purely radiant heat, which heats objects, though no "pure" radiant heat exists. All radiators also heat by convection. Heat loss is determined on an area basis, but a competent designer has to take the volume (and associated air changes) into account.
My point is that heat loss is a function of exposed area, and the heat loss across that. Volume (partially) determines how much time it may take to bring an area up to the desired temp, and how much air volume one needs to move for ventillation, temperature equalization, etc, but has negligible effect on heat loss.In this case, where electric baseboard heaters are proposed (IIRC), if you could ignore the floor you'd need nnn watts of heat per foot of basement exterior wall, regardless of overall room size (with nnn being determined by the vertical heat loss profile of the wall). The ceiling, being a heated space, can be largely ignored from a heat loss standpoint (though some heat loss due to convection into the rooms above may be experienced if the ceiling is not well sealed, or there are open stairwells, etc).Unfortunately, you can't ignore the floor. If it's uninsulated then it can absorb a substantial amount of heat and is probably the largest single factor in the equation.
The fact is that the heat loss in a space like a basement takes place in any wall exposed to air, the first 3' below grade and air changes, which is directly related to the volume. The floor, if uninsulated, accounts for very little except during a heat-up from no heat to "normal". If there is any insulation under the slab or any type of floor covering, the floor is always ignored. The volume does not account for a lot of heat loss either, but in spaces that are not directly exposed to exterior wall, is still a large portion of the small losses that exist.
Say a poured concrete floor is 4" thick and sits on a base of 4" of pea gravel or sand. The R-value of such would be about 2. Inside temp is 70 and ground temp is 55. There will be heat transmission through the slab at 7.5 btu/sq.ft, and this would only occur when the ground was at 55, which below a heated space will warm up due to the heat transmission. Standard engineering practice would account for 25% of this to be conservative, and is usually ignored. An uninsulated, 8" foundation wall will have approximately the same R value but 5 times the temperature difference (assuming a design temp of -5) in most parts of the country. In a 10x10 room, 8' high the floor would acount for 250 btuh, the walls 4500 btuh (with no surface exposed to air) and at 1/4 air change per hour would also account for 250 btuh. If this space is heated continuously for more than a week, the ground heats up very gradually and stays warm for a long time, which practically eliminates that as a source of heat loss. The other heat losses (under design conditions) remain relatively constant.
That seems to cover it in pretty good detail. However, one detail I'd pick at is the assumption that the ground under the floor will warm. This is true in general, but not the case if significant groundwater is present (and flowing to any degree).Another point to consider is simply that one may not want to wait (several days minimum) for the ground under the floor to warm up before the space can maintain a comfortable temp, so in terms of calculating heater size one might want to assume no warming of the ground occurs. Cost/efficiency calculations would still assume the ground heats up, though.