Heating question

[Remi]

I have recently moved into a house with electric baseboard heaters. My living room has a very large window and an electric baseboard heater below it that runs the full length of the window. There are curtains on the window that we draw at night for privacy. The bottom of the curtains is about 6 inches above the baseboard heater. Last night we closed the curtains and for the first time turned the heat on. The room got warm, but we noticed that a lot of the heat was going behind the curtain and filling the space between the curtain and the window. Is this right? Thanks to all.

[Pete C.]

No, it's not really "right", but it's a common problem. Doesn't really matter whether it's electric baseboard, hydronic baseboard or floor vented forced hot air. If the window treatments (curtains, blinds, etc.) are further forward than the baseboard or vent, when they are closed they direct a sizable portion of the heat right out the window greatly reducing efficiency.

In a similar situation with hydronic baseboard and vertical blinds I installed a curtain rod bracket at each side, just above the bottom of the blinds. At night when the blinds were closed I simply placed a length of unobtrusive white PVC pipe across the brackets so it pushed the blinds back against the wall and behind the face of the baseboard. This allowed the heated air from the baseboard to go into the room instead of behind the blinds where much heat would be lost before it exited at the top of the blinds. This made a noticeable difference in both room comfort and fuel bills in the cold New England winter.

Pete C.

[Vietnam Vet.]

If I were you , I would convert these radiators to true radiators and not convection units as they are. If you have no small children, remove any tin that blocks the radiant energy from these units. and add deflectors over them to divert the rising heat from the curtains. good luck. g.

g adds. MONEY , what a concept

[yellowbirddog]

Don't be so quick to keep warm air away from windows. There are reasons houses are designed with heat sources under windows.

1. It prevents condensation and the accompanying mold, mildew and water damage.

1. It prevents a "drafty" feeling when you're next to windows by ensuring the windows are warmer and thus giving off almost as much radiant energy as interior walls.

Yes, it wastes some energy, but if you're that set on saving energy, look to newer windows.... although I won't guarantee you'll save money in the effort. :)

[flansp78]

Where do you get your information? Heat sources, as you call them, are NOT installed under windows for the reasons you mention. Radiators, either electric or hot water, are installed on OUTSIDE walls because of convection.......Cooler walls cause the warmer air to rise, which in turn, cause warm air to circulate.

Paul

[yellowbirddog]

If the air from a heat source is warmer than the ambient air, it rises because it is less dense and therefore buoyant. The walls don't cause the air to rise.

If you want to dismiss my advice, feel free. Just keep the rag handy to keep the condensation off your windows and stock up on mildew cleaner.

P.S. Next time you go to other people's houses, look where the heat souces are in relation to windows. Maybe your house is odd. (The original poster's example demonstrates what I'm talking about.)

[Pete C.]

The heat sources are located in proximity to the greatest heat loss areas i.e. windows so that the room heats more evenly, it has nothing to do with condensation or mold. Move the radiator to an interior wall and you're far more likely to have a steep temperature gradient from over hot by the radiator to bloody chilly by the window.

Pete C.

[yellowbirddog]

I agree with the first statement, but not the second. Condensation, mold, and mildew problems regularly appear in window areas when people try to block warm dry air from flowing over windows, and is especially a problem with single paned and aluminum pane windows.

[-zero]

Actually, it's neither. It is called perimeter heating. You are simply replacing the heat energy that is lost. If you had perfect insulation you would have no heat loss. you would need an A/C to cool you and your appliances. You can probably Google its progress through the 20th century. It was accepted around the turn of the century, (NOTE*bad memory=possible bullshit>check facts) then from somewhere around 1910-1920ish until the

1950's the opposite was believed to be true and hot air heating was all the rage. This is why the old gravity furnaces had the supply registers along the interior walls.

Then, we're back to perimeter heating.

Now, a few years later, incorporate cooling. Higher air velocities, fighting stratification zones.... so yes, now we have "air circulating". And to the other poster "windows are as warm as interior walls".... yes you've overcome the heat loss and are now feeling the additional heat. So you're both kinda right! 8-)

-zero

[Pete C.]

Yes, people do have those problems with non-thermal windows, but HVAC design is about heating the room evenly, not defogging windows.

As for the OPs issues, during the day when the blinds are open the windows will get plenty of ventilation and in the evening when the blinds are closed and moved back there will be an insulating pocket of air which will moderate the temperature differential and minimize condensation.

As I noted, I did this in cold New England and it made a noticeable comfort and fuel economy difference. It made no detectable difference in condensation or mold. I rarely had any condensation except for the kitchen and bathroom after high moisture activities and that quickly dissipated. I also use bleach containing cleaners which inhibit mold growth anyway.

Pete C.

[Goedjn]

Radiators are frequently put in cold spots to prevent a situation where you have the coldest air in the room falling in front of the window, and flowing across the floor to the radiator, and then rising, which creates strong drafts and a cold floor. Putting the radiator under the window results in weaker drafts, and a shallower thermal gradient in the room.

Forced air systems may behave differently.

[Goedjn]

There's a good reason for this, too. THe air that would normally be carrying heat to the windows is the same air that would be carrying water to them.