Insulation value of blinds

[redambrosia]

I live with my brother and his girlfriend right now. My brother has what seem to me, odd ideas about insulation and windows. He insists that we keep the blinds closed all the time to supposedly keep things warmer in here. But it seems to me that whatever teeny tiny amount is saved on energy for heating, we blow on lighting the place all day.

So, my question is, does anyone know the insulation value of those thin metal or plastic blinds? And would energy savings make it worth leaving the light on all day?

Cause seriously, it seems ridiculous to leave the lights on all day.

[Kathryn]

It seems like it'd be pretty minimal insulation to me, too, but now you don't just have to take my word for it--here's something approaching numbers!:

Double Pane – Uncovered Windows offer an R value of 1.9
1” Mini Blinds offer an R value of 2.3
http://tuckerfreelibrary.wordpress.com/

In addition to the money wasted on having the lights on during the daytime, if you've got south-facing windows you're probably *increasing* need to run the heat because the heat gain from passive solar is greater than the heat lost through the windows.

Now, if you want to get nitty-gritty, here's some calculators so you can present some cold, hard facts:

To calculate savings of keeping blinds drawn:
http://www.builditsolar.com/Referenc...sulUpgrade.htm
Using just typical numbers, you'd save about $3/year for each 3x5 window you keep covered.

And here you can calculate the cost of burning each extra light:
http://www.handymath.com/cgi-bin/electric.cgi
If the heating season is about 5 months, it may be costing you $9/60 watt bulb to keep the lights on during the day.

But that doesn't even take into account the solar heat gain you're losing out on.
A better option is to use either the shrink wrap window insulation kits (they will pay for themselves), which will insulate much more while still allowing the solar heat to get in during the daytime, or you could try the "bubble wrap" solution since your brother obviously doesn't care for the view. This boosts the r value a bit more than the film, and is also easier to install, reusable, and if you can find a free source of bubble wrap--free!

http://www.builditsolar.com/Projects...bubblewrap.htm

[lucille]

Blinds have minimal insulation value and your losing out on the solar gain during the day. You should try to leave the blinds open on windows that get intense sun during the day to gather the heat and close them at night to keep it in. We keep east windows without blinds in the morning and west blinds open in the afternoon. We have insulated drapes for these windows we close at night. We can keep our house heated this way down to about 30 degrees outside at night as long as the sun was shining. So we don't need to turn on the heat at night unless it dips below 30-20 degrees at night depending on the level of sunshine that day.

[gt0163c]

I have very lightweight curtains on my south facing windows in my bedroom and living room. I've gotten into the habit of opening the curtains during hot/light part of the day and closing them during the cooler/dark parts year round.
As I said, the curtains are very lightweight but this does make a big difference in the heating and cooling of my house.

The thing is, especially with something a bit more solid like blinds, it's not the fact that the material is thick or especially insulative, it's more than you're isolating the air that's right next to the windows. Insulation is really all about keeping air in small pockets (ideally less than 3/4ths of an inch in any direction as that's the amount of space needed for convection currents to set-up (that is for the air to move)) isolated and stationary. If you can do that, you have a greater chance of keeping the air the same temperature as it currently is.

By keeping the blinds closed at night and on days when it's especially cloudy, you're creating an isolating barrier of air right next to the windows that will cool but won't disperse a whole lot into the rest of the room. By keeping the blinds closed when the sun is shining in, you're creating that same isolating barrier or air next to the window, but now it's being heated up and that's heat that could be dissipated into your room and reducing your need for a heater (and lighting).

[Catana]

I doubt that it makes much difference whether you leave blinds open or closed at night. They leak air between the slats and around the edges, so cold air isn't going to be blocked. The only way to reduce the cold from windows is with something that can be sealed all the way around.

[starshard0]

That just seems silly. The savings would be minimal at best. I personally prefer to keep my blinds open during most of the day and even into the night, since I don't like the harshness of my flourescent light. For me it's not so much about heating as it is about light.

[JamboNeil]

In Winter I put white electricians tape along all the window frame joints. This cuts out the drafts totally and the room certainly feels warmer and seems easier to heat.
I wouldn't fancy spending the winter in a room with blanked out windows - I'd rather put on an extra sweater!

[frugileshopper]

You get an added R1 value for each layer over a window, mainly due to the dead air space between the layer(s) and the window. Curtains + blinds would be better. I don't think I'd keep blinds closed everyday, but I certainly might on windy, winter days if the windows have air leaks around them. Believe it or not, keeping blinds closed in such weather can keep a room 1-3 degrees warmer. (I'm in the far Northern Rockies, right below Canada, and we're to have blizzard conditions tomorrow and Sunday with daytime highs in single digits and night time lows dropping to -17 with winds 35-40 mph gusting to close to 100. We have two over sized windows in the great room that have storm windows but are still drafty and you can be sure the blinds will be kept closed during the storm--it's going to be a challenge to keep the house warm and the pipes from freezing.)

[purplefdu]

Living in ME (and just getting power back after a couple days without) we normally plastic wrap our windows with the blinds open and use curtains to let light in during the day. Generally for cold we have either blinds/insulated panels or inner sheer/light curtains and outer insulated ones to allow for both light and heat control.

I don't mind artificial light sometimes, but nothing makes you feel better than having sunshine on a beautiful day, even if there is 6ft of snow on the ground.