# To Open or Not to open the Curtains **URL:** \ **Category:** Factual Questions\ **Created:** [November 13, 2014, 7:56pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557 "2014-11-13T19:56:13Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [November 13, 2014, 7:56pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/1 "2014-11-13T19:56:13Z")
As a result of the Arctic Blast, thank you Canada for that, the outside temperature over the past week has been in the teens during the day and below zero at night. Fortunately, the weather has been dry with mostly clear skies and not much wind to speak of. We keep our house at a toasty 65 degrees and since it’s sunny outside I keep the drapes, curtains and blinds open to let whatever sunlight we might get this time of year in. Other people I know, with similarly built houses, do the exact opposite and keep their drapes, curtains and blinds closed in order to retain heat. We all have well insulated houses with double pane windows. I haven’t done the experiment to see which approach is better, but all things being equal doesn’t letting the sun in during the day provide more net warmth than covering up the windows, or is it a wash? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 13, 2014, 8:01pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/2 "2014-11-13T20:01:17Z")
It depends on the window exposure. It’s probably a win for a south-facing window where the drapes are only opened during the direct-sun part of the day. East and west are less certain, and north is a guaranteed net loss. ETA: the sun must shine into the room- sky exposure isn’t good enough. ---
**Author:** ![sitchensis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sitchensis/32/4892_2.png) [@sitchensis](https://boards.straightdope.com/u/sitchensis)\ **Post date:** [November 13, 2014, 8:15pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/3 "2014-11-13T20:15:05Z")
My parents have a recently built south facing house. With high efficiency picture windows, their house hit 74 F on a 10 F day without the heater kicking on. They keep the drapes open when the sun is shining. It makes you want to lay out on the carpet in the sun spot and nap. ---
**Author:** ![HipGnosis](https://avatars.discourse-cdn.com/v4/letter/h/76d3ee/32.png) [@HipGnosis](https://boards.straightdope.com/u/HipGnosis)\ **Post date:** [November 13, 2014, 9:11pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/4 "2014-11-13T21:11:10Z")
> [@sitchensis](#): > > My parents have a recently built south facing house. With high efficiency picture windows, their house hit 74 F on a 10 F day without the heater kicking on. They keep the drapes open when the sun is shining. It makes you want to lay out on the carpet in the sun spot and nap. Does the house have any automated system to deal with the extra heat in the summer? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [November 13, 2014, 9:47pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/5 "2014-11-13T21:47:41Z")
a south facing window with full sun exposure will gain heat through the middle of the day. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [November 13, 2014, 10:48pm UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/6 "2014-11-13T22:48:50Z")
One simple way to decide this is to close the curtains for most of one day and then feel the temperature of the window, the curtain and an indoor object like a table. If the window feels very cold, that tells you heat is being lost through it. A good double-paned window shouldn’t be too much colder than the indoor object, but you’ll really feel the difference with single panes. If the window is cold, keeping the curtains closed will help to minimize airflow across and heat loss from the window. If the curtains feel much warmer than the indoor object, you know that sunlight has been heating them up. Letting that heat into the main part of the room (by opening the curtains) could be a net gain. This is especially true because most curtains have a white backing to minimize heat gain. (And on a tangent, this is why I planted a deciduous tree in my south-east-facing front yard. In the summer with full leaves, it blocks the morning sun that comes through my large windows, keeping us cool. In the winter, when bare, any sunshine comes right inside to warm us up.) ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [November 14, 2014, 5:06am UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/7 "2014-11-14T05:06:37Z")
A thin piece of glass is very poor insulator. Meanwhile the warming effect of the sunlight is only worth a few degrees about ambient. If its much colder outside than in, you surely must be better off to provide a better insulator, such as the sum of the curtain and the air layers trapped at and near the curtain… The curtain reduces convection and drafts - adjustments to the curtain to stop air flow past the glass can be a very cheap and quick way to make the curtain more effective. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 14, 2014, 5:14am UTC](https://boards.straightdope.com/t/to-open-or-not-to-open-the-curtains/704557/8 "2014-11-14T05:14:16Z")
> [@Isilder](#): > > A thin piece of glass is very poor insulator. > > Meanwhile the warming effect of the sunlight is only worth a few degrees about ambient. > > If its much colder outside than in, you surely must be better off to provide a better insulator, > such as the sum of the curtain and the air layers trapped at and near the curtain… The curtain reduces convection and drafts - adjustments to the curtain to stop air flow past the glass can be a very cheap and quick way to make the curtain more effective. The OP said: > [@](#): > > We all have well insulated houses with double pane windows.