Question on cold room


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Old 12-01-09, 11:23 AM
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Question on cold room

I have one bedroom in my house which is always colder than the rest of the house by at least 2-3 degrees. The room is 13 x 16, and has 9 feet worth of window area (46 inches tall).

There is only one baseboard in the room which is 6 feet long and is directly under the 6 foot window.

I have suspected that this room lacks insulation, but the rest of the house doesn't have anything remotely close to this problem. There are NO drafts from outside (even checked on a windy day with a smoke machine....how's that for being creative).

So, to make a long story short, I think the issue is the baseboard is too short for the room. I've tried to find some rule of thumb for this but have come up empty.

The heat loss stuff will throw me for a loop, since the problem is confined to this one room.

Any ideas / suggestions ?. Should I just increase the baseboard run by 50%...100% ?.

Thanks
 
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Old 12-01-09, 12:44 PM
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Do the room x room heat loss. Determine how much over the other rooms are and make this room over by the same amount. The other option is to add radiation and zone that room separately so the heat stays on until the thermostat satisfies.
 
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Old 12-01-09, 02:29 PM
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Hi fx, there are two ways to approach making that room warmer, add more heat (at a cost) or reduce the heat loss (at a savings). Your information does not give enough detail to be specific, but if you suspect "NO INSULATION" you need to check. Pull off an electrical cover and see if you can see anything beside the box. Don't probe inside the box, but a plastic hook inserted between the box and the sheetrock might come back with some insulation on it. If truly nothing, that needs to be addressed.

You also didn't mention the type of windows and glass, single pane, double, or how they open. That is a lot of glass and if single pane, storms would be in order.

What is overhead, attic, and what is there for insulation? What is underneath, basement, or first floor?

The 6' of baseboard sounds small, but there may be other reasons this room is cold. Your smoke test, even on a windy day, would not show the normal slow leakage that all homes have.

More info, more help.

Bud
 
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Old 12-01-09, 03:08 PM
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Some of the guys here don't care for 'rules of thumb', but they can be helpful for quick estimates...

Let's say that your room requires ohhhhh, 25 BTU/SqFt to heat properly. That would put the heat loss of that room at about 5200 BTU. (25 is probably a reasonable estimate for an average home... older, leakier homes will likely be higher... maybe as high as 40 BTU/SqFt)

Next, let's say that your baseboard puts out about 550 BTU/FT with 180 water. That's about 3300 BTU of radiation.

It would appear that the room is under-radiated, but before we decide for certain, do the same estimates for the other rooms that heat properly. Use the same 25 BTU/SqFt and 550 BTU/FT for all the rooms/baseboards and see if PROPORTIONALLY they are roughly the same.

Another thing to keep in mind... most baseboards are SERIES LOOP systems, where the water from the boiler hits the first BB, comes out the other end A BIT COOLER, and then hits the next BB, comes out a bit cooler... etc etc... so that the further down the line you go, the cooler the water that enters the BB, and the less BTU it is able to radiate. Rooms at the ENDs of the heating loops should have proportionally more BB installed to compensate for this effect.

I'm not downplaying insulation at all! If you have none, you should think about upgrading... my friend Xiphias likes to say that "Insulation is fuel that you pay for only once".
 
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Old 12-01-09, 03:14 PM
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Originally Posted by fxcarden View Post
The room is 13 x 16, and has 9 feet worth of window area (46 inches tall).

There is only one baseboard in the room which is 6 feet long and is directly under the 6 foot window.
It seems like, at least in the old days, it was common to install hot-water baseboards almost continuously along the outside walls. I think that's how installers in our area did it. Look at your other rooms for comparison.

If this is a monoflo system, you might try putting monoflo tees on both the supply and return to the room. The return tee will be installed backwards.

If the room is over a basement, adding additional baseboards might be relatively easy. If all else fails, you can consider installaing an electric baseboard with its own thermostat
 
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Old 12-01-09, 04:36 PM
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More details.....

I forgot to mention the room is at the corner of the house so there are windows on two sides....and yes, they are double pane (and it looks like one panel has leaked out the gas or whatever because I can see a little condensation between the two panes, but we are talking about 1 sq foot's worth of area).

There is an insulated attic above half the bedroom, and the other part is under the second floor of the house with another bedroom above......below the problem room, there is a finished and heated basement.

The baseboard in question is the last one in the run, but it gets just as hot as the others (there may be a difference, but you can't tell by feel). Of course, being the last radiator in the chain, it takes about 1-2 minutes for it get to hot once the boiler fires, but once the line fills with hot water, it's good to go (at least with my untrained obswrvations).

The other rooms, comparable in size, have longer baseboards, almost wall to wall. I can easily add another 4 feet to this which would match the BTUs based on NJTROOPERs explanation....(thanks, dude).....one question though........

is 550 BTU/sqft more or less the norm for a standard baseboard ?

Thanks.
 
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Old 12-01-09, 05:31 PM
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Yes, 550 is something of a standard value.

As rbeck said, the right way to do this is a room by room heat loss and comparison of amount of baseboard relative to heat loss. Then duplicate the same proportion in this room.

And as others have said, the best way to improve things is to insulate more, if possible.

But... if you want to take a much less rigorous approach, here's some thoughts.

If the other comparably sized and exposed rooms have nearly wall-to-wall baseboard, it sounds like you just need to get a whole lot more baseboard in this room.

What you've got.... 6 ft of standard baseboard has a nominal output around 3300 BTU/hr.

That's probably about half of what you really need. But even doubling it sounds like you will not meet the proportion of baseboard in the other rooms.

If you can get 12 ft in there, that might do it. Nominal output of 6600 BTU/hr would be about 30 BTU/hr/sq.ft., which is a reasonable value for post-1970s moderately good and somewhat improved construction.

Alternatively, you could put in 9 ft or more of high-output baseboard, like Slantfin MP-80, which does about 730 BTU/hr/ft as opposed to the standard 550. This would get you headed toward the output proportionality that rbeck and Trooper suggest (and with which I agree, hence the repetition of some of their advice).
 
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Old 12-01-09, 06:15 PM
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A few other points about baseboard, often overlooked...

There needs to be full design airflow through the unit in order to achieve the rated output. Very often wall to wall carpet is added to rooms. The mistake that is sometimes made is to run the carpeting right up to the baseboard, and at least partially (if not in some cases FULLY) blocking the lower air intake. This will GREATLY reduce the output of the unit.

Another point is that even a small coating of dust or pet hair will do the same. This will generally collect on the BOTTOM of the fins as the air flows through. Most people don't think about this when doing their 'spring cleaning'. The covers of the BB should be removed and the fins brushed and vacuumed thoroughly. It's not easy or fun work, but worth the effort.
 
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Old 12-02-09, 08:25 AM
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Thanks !

I think I will pursue the extra feet of baseboard. Probably the cheapest and least destructive of all the options. I can do that myself, as opposed to having insulation blown in $$$$, etc.

We've been using one of those oil filled portable heaters, at close to the lowest setting (around 2500 btu), and it seems to do the job, but I'm not comfortable with the electrical setup, plus the way I see it, if the boiler is already supplying heat, why not get all the heat available from the line ?.

So, I will attempt to increase the length of the BB by 6 feet, and hopefully that should do it.

Thanks again.
 
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Old 12-07-09, 05:13 PM
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An experiment would be to put the thermostat in the cold room and then close the dampers on the baseboards in the other rooms as they got warmer than desired. It would ultimately be an inefficient way to achieve the desired result but it may be better than guessing and installing more baseboard heat in that room without knowing that it is correct. If it is a loop system, you could also reverse the flow and see if that helps. Just throwing ideas around.

Ken
 
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Old 12-07-09, 08:13 PM
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Like Ken said, you could try closing some of the other baseboards. Maybe you can find happy setting where all the rooms are a temperature where you like it? You could leave the thermostat where it is though, just close the dampers in that room, and it will take longer to get up to temp and give the cold room a chance to get the same temp as the rest of the rooms.

I remember we had to do that in our house growing up. In some of the rooms the baseboards were closed, others open. All rooms ended up the same temperature.
 
 

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