why do builders put radiators under windows?

[NeilBlanchard]

Hi,

Moving air cools us off, and it would be perceived as drafts. It will also cause a noticeable temperature stratification -- the cooler air will stay settled nearer the floor and the warmer air will stay up at the top. It would not be a comfortable room to be in.

[dichotomous]

remember this all changes when you use a forced hot air system, but nonetheless. I agree that keeping the coldest part of the room warmer is nice for living in, but it IS far less effective at keeping the rest of the room warm since a good chunk of the heat is escaping directly out of the window.
and the heat cycle sort of DOES die when this happens, the cold air falling on the radiator gets heated and flows up to the window where it cools and falls. SOME of the air gets into the rest of the room, what passes by this cycle that is. its not a good way to do things, its there to eliminate drafts as was said. I have some education in this (and an ABET-Ass. to show it).

Now basically, if you want to pay less to heat your house, it works well to have that window area drafty, fun part is if there is no furniture there, who cares if its a few degrees colder? plus we are too soft lately as a people, must have fully even temperature, must have cell phones, must not do work or have any inconvience at all. bah, bah I say!

that window is a hole in the wall thermally. I dont care if you have the new super awsome R-5 windows or even R-10 windows which I'd sure like to see! a 2x4 wall has an R value of 19, a 2x6 wall with layer of foamboard on the outside as well is better than R-30. the roof should be R-50 or more. so that 0-8 R rating on the window, is a thermal hole.

how to fix your existing window for better heat retention in the winter? easy, get the shrink film, put that on, now drape a blanket over the window when you want to keep heat out.

[SmartTrucker]

I skipped to the bottom but you know it must work because haven't you seen the way places like Costco put the great big top down heaters at there entry points

[The Atomic Ass]

Originally Posted by dichotomous

that window is a hole in the wall thermally. I dont care if you have the new super awsome R-5 windows or even R-10 windows which I'd sure like to see! a 2x4 wall has an R value of 19, a 2x6 wall with layer of foamboard on the outside as well is better than R-30. the roof should be R-50 or more. so that 0-8 R rating on the window, is a thermal hole.

This has gotten me into thinking. If one were to design a window, double or triple-paned, with a vacuum between the panes, would this result in a satisfactory increase in the R value?

[ChrstphrR]

Originally Posted by The Atomic Ass

This has gotten me into thinking. If one were to design a window, double or triple-paned, with a vacuum between the panes, would this result in a satisfactory increase in the R value?

It would increase the R-value over using the inert krypton or argon gases that are used in the fancier high-tech windows. How much, I don't know, myself. But even with those inert gases, the gap between the panes they fill is eventually breached over time.


Understanding Energy-Efficient Windows - Fine Homebuilding Article

Snippet from the site:

... Argon and krypton are safe, inert gases, and they will leak from the window over time. Studies suggest a 10% loss over the course of 20 years, but that will reduce the U-value of the unit by only a few percent. ...

Like the isolated gasses, a vacuum between window panes will eventually be compromised, too. That's just the result of thermal expansions and contractions over the months and years.

I'd make a semi-educated guess that a vaccuum over inert gas would be chasing diminishing returns.

[bucknmusky]

Not to get too far off the original question, but it has been answered well here already but here is a sugestion for "windows"...hang a flat panel LCD monitor on the inside of your wall and a video camera on the outside, leaving the wall in between intact. Build some Faux windows on the outside. yes it sounds crazy but here, a very good well insulated window in 36"x48" can cost upwards of $500 to nearly $1000 and be a giant "thermal hole" with an R-value of about 4 vs your wall at R-20 to 30. The energy lost through the window panes and weatherseal etc. is roughly equivilent to the power required to run the monitor, and the monitor is only on when you want it, as opposed to 24 hours a day 365. Lifetime costs ~20 years you are far better off with the monitors and you can change the "view" to your liking

[gascort]

The TV would be good in the wintertime, but in the summer you wouldn't want to run it - the worst insulated windows would be better than turning on a 100-200W LCD heater on the wall.