OK, so it's better to have heating registers under windows (where they'll
hopefully combat the cold air coming off the glass) in a home and return
vents more central - that makes sense.

What about large picture windows, though? Is it better to have one central
register below the middle of the window, or two smaller ones to either
side?

I was just thinking that if the curtains are shut, most of the cold
air is going to be coming around them at the edges rather than in the
middle (and if the curtains are open, two side vents should still
hopefully help at least a little)

cheers

Jules

Jules wrote:


OK, so it's better to have heating registers under windows (where they'll
hopefully combat the cold air coming off the glass) in a home and return
vents more central - that makes sense.

What about large picture windows, though? Is it better to have one central
register below the middle of the window, or two smaller ones to either
side?

I've been waiting for a real engineer to answer. I guess I'll take a
shot and see if they'd rather correct me than answer you.g

I'm picturing a window about 8feet wide. And I think I remember
you're in Canada. Much smaller and I'd go with one. South of the
snowbelt and I'd probably say one, too.

My preference would be for 2 registers, splitting the ductwork with a
wye several feet back from the window.. My rationale is that you
have a giant cold spot there- but also a spot that the decorator would
like to place a table or some obstruction in the center.


I was just thinking that if the curtains are shut, most of the cold
air is going to be coming around them at the edges rather than in the
middle (and if the curtains are open, two side vents should still
hopefully help at least a little)

Better to have deflectors on those registers- or plan them to 'wash'
the wall/window from in front of the curtain line.

And as much as it is good to have registers placed properly, when I
bought this old house [near Albany, NY] it had 3 registers down the
center of the house- and a cold air return 2 feet from one of them. In
spite of that the fuel usage was pretty good- and the house only felt
cold on below zero days. I must say the insulation & windows
made the most difference- but relocating the registers helped some in
both comfort and economy.

Jim

cheers

Jules

On Tue, 15 Dec 2009 06:39:36 -0500, Jim Elbrecht wrote:
Jules wrote:

OK, so it's better to have heating registers under windows (where they'll
hopefully combat the cold air coming off the glass) in a home and return
vents more central - that makes sense.

What about large picture windows, though? Is it better to have one central
register below the middle of the window, or two smaller ones to either
side?

I've been waiting for a real engineer to answer. I guess I'll take a
shot and see if they'd rather correct me than answer you.g

:-)

I'm picturing a window about 8feet wide. And I think I remember you're
in Canada. Much smaller and I'd go with one. South of the snowbelt and
I'd probably say one, too.

Nearly Canada - northern MN. I can almost sneeze on 'em from here :-)
We've got a couple of big windows of about 8' wide (7' high) in the
downstairs of the house.

My preference would be for 2 registers, splitting the ductwork with a
wye several feet back from the window.. My rationale is that you have
a giant cold spot there- but also a spot that the decorator would like
to place a table or some obstruction in the center.

True. The way ductwork naturally falls in the basement would mean I can
easily have a duct running parallel to both big windows. Very quick
drawing of the front wall of the house and potential layout:
http://www.patooie.com/temp/registers.jpg

.... furnace in red, registers in green, windows in light blue. That leaves
the furnace reasonably central to the house, where it can service a couple
more windows (not shown) along the back wall of the house. I could set the
ductwork further back, but it makes it more likely to get in the way down
in the basement (I'm insulating all that and turning into habitable space)

I suspect some tuning would be needed to get a nice balanced flow to all
vents, of course. Ductwork sizing? No idea yet - not got that far :-)

I was just thinking that if the curtains are shut, most of the cold air
is going to be coming around them at the edges rather than in the middle
(and if the curtains are open, two side vents should still hopefully
help at least a little)

Better to have deflectors on those registers- or plan them to 'wash' the
wall/window from in front of the curtain line.

Yeah, I was thinking setting them maybe 7 or 8" back; the big windows
extend right to the floor, which means the curtains do too.

And as much as it is good to have registers placed properly, when I
bought this old house [near Albany, NY] it had 3 registers down the
center of the house- and a cold air return 2 feet from one of them.

OK, that sounds a bit familiar When we moved in we had three big
registers (about 10"x10") in the middle of the house. No return at all -
the furnace just sucks in nice cold basement air... (for giggles the
previous owners put a vent in the basement door in the kitchen, so the
furnace eats return air that way - which means it's running right through
the basement, and also getting cold air from the back porch opposite the
kitchen door).

It's an "interesting" setup :-)

Our furnace is more or less in a sensible place in the basement, although
to add proper ducted return-air I really need to move* the return air feed
to the other side of the furnace (or turn it through 180 degrees) - it
looks possible, although it's a bit of a pain in the butt.

* the furnace design allows the return air on either side at installation,
but I'm not certain yet that it can be easily moved after install/setup.
Still looking into that one.

There are no ducts at all upstairs - just electric baseboard. Adding any
up there would be really hard, too; I'm thinking of going water-filled
radiators up there as I can get plastic pipe in reasonably easily. The
baseboards are cheap (they're load controlled so work out cheaper than
propane) but I don't like 'em in the kids' rooms just in case they decide
to leave toys too close to them.

In
spite of that the fuel usage was pretty good- and the house only felt
cold on below zero days. I must say the insulation & windows made the
most difference- but relocating the registers helped some in both
comfort and economy.

Yeah, we have a problem with windows; they're all 60 year old wood-framed
French-style with lots of little 8x10" panes, and they leak air something
rotten. They've all got to go, but it's major $$$ to get the same sort of
style in modern materials (and we'd rather do the lot at once just so we
don't run into the problem where we change a few and then find the
manufacturer discontinues the model). Good, heavy curtains help a lot...

cheers

Jules

Jules wrote:
OK, so it's better to have heating registers under windows (where they'll
hopefully combat the cold air coming off the glass) in a home and return
vents more central - that makes sense.

What about large picture windows, though? Is it better to have one central
register below the middle of the window, or two smaller ones to either
side?

I was just thinking that if the curtains are shut, most of the cold
air is going to be coming around them at the edges rather than in the
middle (and if the curtains are open, two side vents should still
hopefully help at least a little)

With the curtains closed there will a reverse convection current between
the curtains and the window with cold air coming out of the bottom. Not
a good place for feet! Two smaller registers sound like a good idea for
the large window.

Not that you mentioned it, but many people still think that "heavy" or
"insulated" draperies hold in heat and save money. That is a long lived
old wives tale. They may make a tiny difference, maybe .5%. The only
way for insulated drapes to really save in heating demand is if they are
sealed to the wall all the way around all sides (and middle).

On Tue, 15 Dec 2009 23:37:59 -0500, Tony wrote:
With the curtains closed there will a reverse convection current between
the curtains and the window with cold air coming out of the bottom. Not
a good place for feet! Two smaller registers sound like a good idea for
the large window.

OK, two votes for smaller... I need to do some reading to figure
out exact sizes (and for ductwork too) I suppose :-)

Not that you mentioned it, but many people still think that "heavy" or
"insulated" draperies hold in heat and save money. That is a long lived
old wives tale. They may make a tiny difference, maybe .5%.

A lot of it comes from Victorian days and open fireplaces, I think -
those would suck combustion air in through whatever gap they could find,
so having big curtains acting as screens would divert the cold air
away from the room's occupants.

Part psychological too, no doubt - a heavy curtain 'feels' like it should
be warmer than one you can see daylight through...

The only
way for insulated drapes to really save in heating demand is if they are
sealed to the wall all the way around all sides (and middle).

Yeah, that makes sense. For the ones on our big windows I made sure there
was a nice overlap (the tracks overlap by a few inches at the top), and I
put tie-backs at the sides which are handy as when the curtains are closed
I can tuck the sides 'behind' the tie-backs so they're flush with the
wall. There are still little gaps at the sides toward the top, of course,
and behind the rail, but it's better than a gap down the middle and a 3"
wide gap all the way down either side.

cheers

Jules