Radiators under windows heat loss

GreenBo

So this past year I've been taking various steps to help me reduce the energy consumption of my home to great effect, including:

Installing a Smappee energy monitor, setting the Comfort Plugs to auto-switch everything off when we're asleep or are out of the house.

Getting solar installed on the garage roof.

Fitting additional insulation in the loft.

Draft excluders everywhere.

I'm halfway through fitting secondary glazing but something is really bothering me.

Why are radiators always fitted under windows? with the curtains closed at night surely all the radiator is heating is the air between the radiator and the window. In fact, what motivated me to post this is that I just walked into the bedroom which was freezing but when I felt behind the curtains to check if the radiators were on I felt a huge waft of warm air from behind the curtains. Are there any energy professionals or people in the know that can explain to me what good is a radiator when it's hidden behind a ceiling to floor thick curtain which seems to prevent it from heating the room.

Is it me or am I missing something

I'm thinking if something needs to change then now is the time, as I'm doing all this DIY around the windows to fit the secondary glazing.

Martyn1981

Firstly, don't put the curtain in front of the radiator, it needs to go behind. But here's an old theory:-

Going back to poor(er) quality windows, single glazing etc, the window area would be the coldest part of the room. (Probably still is, but double glazing, rubber seals on glazing units, and foam filled gaps around edges mean they are much better now, especially regarding drafts.)

However, radiators work by convection, the air is warmed and rises, travels up the wall, across the ceiling, down the opposite wall, then across the floor, and your feet.

If the rad was on the opposite wall to the window then it would be drawing the coldest air from the window area/wall and across the floor first.

Don't know if this is the reason for rads and windows, but suspect it's largely irrelevant these days with good DG ...... so long as curtains are behind the rad.

Mart.

comeandgo

I always thought radiators were under windows to leave the other walls free to put furniture against. Nothing worse than a huge radiator taking up the main wall meaning no furniture can be placed there.