When we bought new drapes we went with insulated linings. (Northeast
Ohio). I doubt it saves much on heat or cooling, but it does make a
noticable improvement in comfort. My favorite chair is right next to
a double patio door. It's a good Pella door, not drafty and has
double panes, but when it's really cold out you can feel the heat
being sucked right out of your body. Closing the drapes helps quite a
bit. The old drapes helped a bit, but the lined ones are noticeably
One thing we learned...the insulated linings add a lot of weight. We
had to upgrade to premium traverse rods to handle them. The standard
home center white jobs weren't up to the task of opening and closing
all the weight. So add the cost of that to the equation.
Do you need drapes anyhow?
My drapes are white on the window side, to cut down absorption of heat
in the summer and radiation of heat in the winter.
I suppose the same people who don't bellieve light colored shingles are
better than dark shinges, or that light colored convertible tops are
better than dark ones, won't believe this works either, but it does.
One thing to watch out for is condensation in winter.
A curtain won't help if it doesn't let the window
surface get colder. You might end up with puddles
of water everywhere...and mildew to go with it.
The improvement of curtains is critically dependent
on limiting air flow.
They need to touch the floor, wrap to the wall on the sides
and have the top space covered to the wall.
All of those increase the condensation problem.
Pop over to engineeringtoolbox.com
and download a psychrometric chart.
If your internal temperature is 70F and 50% humidity,
your windows will be dripping water if the surface
temperature goes below about 50F. That includes
the surface temperature of the frames due to conduction
or air leakage.
You can find an interesting mildew calculator at
Measure the temperature and humidity in your attic
and crawl space. Put the numbers into dpcalc.
You don't have these problems with curtains in summer.
The climate where you live matters a lot.
Back in the day, I did some experiments.
Everything I tried inside resulted in condensation.
I put 1" rigid pink insulation foam over the windows
on the OUTSIDE and painted it to match the house.
No, I'm not married ;-)
That made a significant improvement.
When I replaced the single-pane windows with double-pane
and removed the pink foam, heating costs were similar.
I didn't have any use for the pink foam, so I put it back
on the windows on the backside of the house.
There are lots of computer modeling programs to predict
the effectiveness of insulation upgrades.
I used "resfen", but there are likely newer ones now.
The more you open the curtains, the less effective they'll be.
But that's not the whole story.
If you open the curtains in the middle, the middle of the window
will get warmer, but the edges might not. You're concentrating
the mildew in the areas still covered and getting colder. Any part
of ANYTHING in the house that gets colder than the dewpoint will get wet.
The thing right next to it may still be above the dewpoint and stay dry.
Certainly depends on the construction of your windows, but the edges
of the frame will likely be the coldest part. In order to keep the
coldest part above the dewpoint, you may have to get the rest of the area
much hotter than you'd like.
You really want your insulation on the coldest side of the window.
In winter, that's outside.
Infiltration matters. In winter, the dewpoint outside is likely lower
than the dewpoint inside. Air leaking in will balance air going out and the
dewpoint will be lowered inside.
If you turn on the bathroom vent and crack a window on the other end of the
house, the dewpoint will likely be lowered, but it sends energy you paid
for right out the fan.
I got my house so tight that it flunked the blower door test.
I put a small homebrew heat recovery ventilator in one bedroom
to keep the air from going stale inside. Since I control the
location of the air "leakage", I can get back over half of the heat.
When it gets much below freezing outside, the thing becomes a solid
block of ice. And that's not condensing on my windows.
Sure, but that's where compromise comes in. I hope Congress hasn't made
compromise a dirty word everywhere!
Most people aren't going to do that. For one thing, it's too hard to
adjust when one wants light or the sun's winter heat on sunny days.
Sure it's nice if there is no condensation, but I've had condensation on
my aluminum frames and it's never led to mold or mildew. Over a
decade it's cause in some places damage to the paint on the wood window
sills, but they can be easily repainted if it's a problem. I think the
OP should try curtains and pay attention to what happens, especially
mold. (I've also had black-colored mold elsewhere which caused no
problems either. When I had time I killed it with bleach and painted it
A lot might depend on how tightly the drapes fit to the window and wall. If
there are large gaps top and bottom then you'd just be creating a
convection tunnel and would have a torrent of cold air pouring out the
bottom (winter) or heat out the top (summer). I went to heavy blackout
cellular shades which fit inside the window frame with very little
clearance -- these seem to help with drafts in the rooms that have them. I
can't really tell if they help with the utilities since I burn up so much
power running five computers 24 X 7.
In Alaska I had a spare bedroom fitted out for my aquaria and made a
'blind' from 1.5" closed-cell foam insulation covered with black plastic
and fitted it into the oversized window opening to provide darkness and
insulation. Very effective in both although, had I been married at the
time, it might not have been permissible.
Anything will help. A thin paper pull down creates another air pocket. It
also reflects infra red. It also slows down convection currents. A thicker
material will add even more. I'm talking windows. Don't know what other
insulation problems you might have.
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