Windows

I have learned more about windows than I ever thought.

I wish the experts who built our "extreme green" home had considered that it was passive solar in the purchase of windows for the south side of our house. I have learned too late to not have to replace windows about the "You - program won't let me use the letter" factor and the Solar Heat Gain Coefficient. Our "low e" windows have a "you" factor of .30 and a Solar Heat Gain Coefficient of .26 (when Solar Heat Gain Coefficient it needs to be close to .7). I have also learned that we are all told to replace single pane windows with dual pane windows when it would be more cost effective and better r value to make window quilts and add storm windows in the winter. I have also learned that standard curtains that are open at the top and bottom are more of a detriment to the heating and cooling of the room when we close them instead of saving energy like we thought. Due to heat rising and cold air sinking, this actually helps to circulate the temperature of the glass into the room. I have also run across research that says that even glass filters our too much of the UV rays to keep us healthy if we rarely go outside, and the more panes, air or argon we put in, the worse it gets. Turns out that is only good to keep the furniture and carpet from fading.

Please learn from my mistakes.

Yeah, I agree about the single panes. It's a long running point of disagreement between my husband and me, but he's more of the active designer and involved with building and maintenance. He's big on making double panes here, locally, or in his latest building, getting pre-made double panes from Delhi. Me, I like the single panes better, with a good thick curtain. The best double panes we can make still get cloudy inside eventually and can't be cleaned, and in the worst cases, bugs get in and can't get out -- in our office, one window used to have a good half inch of dried hornets in the bottom of one corner. Yuck! Somebody had to get up on a ladder to remove the outer pane, clean it and replace it, and it's a 5 foot tall pane.

I have heard that normal simple old curtains are supposed to be bad for heat retention but honestly I have not found it to be true. Our houses are solar heated with no active parts except us opening and closing windows and curtains at the right times of day. So curtaining off the windows is essential to keeping the rooms warm at night and until morning. I find that a simple curtain (made of blanket cloth) hanging from fairly close along the top of the window, and tucked to sit on the sill at the bottom, does indeed keep the room much warmer than no curtain or a thin curtain. It's not airtight at all but I can really feel the difference from one night to the next, whether I close that curtain or not. I'm sure a better curtain would be that much warmer, but this simple one does a good job.

Rebecca:

It sounds like you are hanging it inside the window opening so the top and bottom of the opening may stop the air flow?

This chimes in with an issue I have in the new house as the LL wants to put radiators under the windows. I thought of asking did he want us to heat the garden or the house. So I intend to extend the windowsill to force the warm air further from the window , and have curtains flush with the windowsill and build a pelmet at the top to further seal things up .
Do you guys think this worth the effort?

David

David Livingston wrote:This chimes in with an issue I have in the new house as the LL wants to put radiators under the windows. I thought of asking did he want us to heat the garden or the house. So I intend to extend the windowsill to force the warm air further from the window , and have curtains flush with the windowsill and build a pelmet at the top to further seal things up .
Do you guys think this worth the effort?

David

I used to live in a house with single pane windows, and radiators underneath them. It helped to prevent the build-up of frost on the windows in Winter. Of course, that was Chicago, IL, not France, so it might not be as much of an issue (I'm not sure what elevation you are. If in mountains, it might be as bad as Chicago.)

I like good shutters and good curtains as a solution here. When the sun is shining, open wide. When it isn't, button up. I like single-pane casement windows that can either tilt or swing open, with insulated rolling shutters that can be opened or closed from inside. These can also be locked, providing additional security, if that's a concern. But if that's too expensive, I would think that good, old-fashioned storm shutters would be useful.

KE

There are wooden shutters of quite an age on the building too but as for helping with keeping the heat it forget it

David

David Livingston wrote:This chimes in with an issue I have in the new house as the LL wants to put radiators under the windows. I thought of asking did he want us to heat the garden or the house. So I intend to extend the windowsill to force the warm air further from the window , and have curtains flush with the windowsill and build a pelmet at the top to further seal things up .
Do you guys think this worth the effort?

David

DEFINITELY! and add velcro, magnets, pins, etc. to stick the sides down and it will really seal up.

Another trick is to add bubblewrap to the windows (stick it on with a little spray of water). Lets light through and is as effective as an extra pane for practically free.

David Livingston wrote:There are wooden shutters of quite an age on the building too but as for helping with keeping the heat it forget it

David

I was thinking more of a modern version of the old-fashioned shutters. Not old, fashioned shutters!

Here's an idea:

http://lifehacker.com/5949581/diy-insulating-door-or-window-shutters

My plan is to make window quilts using cheap blinds where you take the slats off and use the mechanism in place. They will hang inside the window using the window frame itself to stop the air flow. I had planned to use a space blanket on the window side as a moisture barrier but worry about this making the window quilts unwashable.

You are absolutely correct to be concerned about convection around/behind curtains. This can be designed for though.

We will be installing rolling blinds in our new place. They run in a concealed groove and when down fit snuggly into a little niche thingy. If well made there should be no direct path for air from the room to get to the cold glass.

In front of those we'll be hanging traditional curtains for added layering and a better finsihed look.

R Scott wrote:

David Livingston wrote:This chimes in with an issue I have in the new house as the LL wants to put radiators under the windows. I thought of asking did he want us to heat the garden or the house. So I intend to extend the windowsill to force the warm air further from the window , and have curtains flush with the windowsill and build a pelmet at the top to further seal things up .
Do you guys think this worth the effort?

David

DEFINITELY! and add velcro, magnets, pins, etc. to stick the sides down and it will really seal up.

Another trick is to add bubblewrap to the windows (stick it on with a little spray of water). Lets light through and is as effective as an extra pane for practically free.

The bubblewrap trick is one of the best/easiest ways we've ever insulated for winter - I just took ours down yesterday, since it's finally warming up outside. And since we're renters, it's one of the best ways to do temporary insulation that we can take with us when we move elsewhere.

Ooh, that bubblewrap idea is great! I'll try it next winter, just for the coldest middle of winter.

Yes, our curtain is hung on short hooks sticking out barely from the lintel above the window, and then we tuck it on the sill so it sort of blocks the flow. It works well.

To the person concerned about the radiators being put under all the windows: That is standard practice and supposedly keeps the room warmer than the opposite that you would expect. If the radiators are on a different wall other than under windows, then a big convection gets set up where the air in front of the windows cools, falls, travels across the floor chilling your feet, and then rises over the radiator and the hot air travels across the ceiling where you don't feel it. That's why they put radiators under windows.

Hi, ya'll. Been reading the forum for a while, but haven't posted 'til now.

Bummer, Lynn, about the Low E windows. We have a passive solar house that works incredibly well, and it was just before the Low E windows were required. But all is not lost with double panes. We do have double-paned windows, floor, wall, and ceiling insulation, and it's really the Very Small Eaves coming off the roof that allows the sun to hit the big bank of our south-facing and east-facing 5-foot-tall windows (northern hemisphere). As soon as the sun is on the windows in the AM I can feel the heat coming in. The interior quickly gets up above 70 F by late morning on sunny days, and stays that way well into the night.

I use blackout pull-down window shades next to the glass (very inexpensive) plus thermal, blackout curtains that help in the summer to block heat, as well as keeping in the heat in winter. We have mild winters, but the house is tied into the 50 F ground, and it rarely goes below 50 F inside. If it goes just below freezing outside the inside will go down to 45 F with no heat on. I am always surprised when I walk out in the mornings and feel how much more chilly it is outside. Plus it keeps the interior from feeling clammy and moist along with the cold, we have no mold problems at all.

One problem with the single-pane windows is that moisture condenses on the inside and can cause problems that way, including causing black mold to form on non-sunny sides of the house (or windows under big trees). We had that happen in a past house of ours, in a very mild climate. So double-panes do have their advantages, and also help in the winter with some heat loss.

Great points I agree with mostly. Its unfortunate the builder screwed up such a major thing to get right but some of the fault has to lie with whoever helped select your project team. Hiring a builder thats proficient in "extreme green" and doesnt know about basic passive solar design? Seems there could have been a better choice. Was an architect or designer involved? Any good set of passive solar building plans Ive seen has SHGC notes spelled out very clearly.

Usually, designers choose SHGC based on whole window values. Never heard of a double pane window with a .7 SHGC. I think .5 is sufficient and might even settle for .4 with a good Uvalue to back it up.

As for choosing single pane instead of double pane and using window quilts and/or storm windows, thats certainly a more permaculturey approach, especially if the windows are salvaged although finding ones with good SHGC levels is a challenge. That approach is not without its problems though. It think it would work best with a very small home, easy to access windows and full time residents that are very hands on. Brian's right about window condensation, interior blinds/quilts can block solar gain, and it can be a challenge to get them in contact with the window enough to perform as well as a double pane. Many designers are choosing triple pane windows for very cold climates. Imagine the performance one could get with proper window quilt management and triple pane.

You also lose resiliency in the ability to better resist frozen plumbing when occupants are away. Personally, I would go through great lengths to no have to mess with operating window quilts at the beginning and end of every day. Double and triple pane windows are pretty simple. Set it and forget it.

I am in a high and dry climate. Really hot summers, and really cold winters, with this years cold snap lasting about a week or 2 longer than normal. I have double paned windows. And the greatest surface area are south and southwest facing. Our challenge is that we have only a wood stove for heat with a couple of ceiling fans to move the air around. I feel the home was designed poorly in this respect as the room with the wood stove has 30 foot ceiling. The windows are also set out from the house. If I used a curtain there would be a 3 foot gap between window and curtain. I plan on adding a rmh, but not for a while. I am starting small before I dig up my living room.