Energy Efficiency and Your Windows

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Farmfresh
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Energy Efficiency and Your Windows

Unread post by Farmfresh » Fri Dec 05, 2014 8:00 pm

Windows are a very important part of your home. Windows provide light and a means of getting that fresh air in and the stinky air out. Windows are also one of the weakest links when trying to make a house energy efficient.

A typical wall in a modern home is insulated to provide a R-value (which is a measure of thermal resistance) of around R-13. Compare that insulation value to a single pane of glass which rates at R-0.14! Heck even a sheet of cardboard rates higher at around an R-3! So think of all of those windows in your house that are allowing your heating and cooling dollars to just pour out!

But R value alone is not sufficient to rate the energy efficiency of your windows. It gets much more confusing than just that. Windows are typically rated on their U-factor.

According to Wikipedia ... "The U-factor or U-value, is the overall heat transfer coefficient that describes how well a building element conducts heat or the rate of transfer of heat (in watts) through one square metre of a structure divided by the difference in temperature across the structure."

R-value (resisting heat transfer) is the exact opposite of U-factor (ability to transfer heat). So you want a HIGH R-value and a LOW U-factor when shopping for windows. { To compare R-value and U-factor, divide 1 by the U-factor number, E.g.: a 0.25 U-factor equals a 1/0.25 = 4 R-value. That is the formula that I found. http://www.efficientwindows.org/ufactor.php}

U-factor takes in lots of things including, how the window is affected by the airflow (convection) around the window and the emissivity (radiated or reflected heat) of the glass. http://www.nfrc.org/windowratings/Energy-ratings.html

This stuff is all well and good, but most of us are NOT window shopping. We have to deal with the windows that we have, so what steps can we take to make them as energy efficient as possible? Well to accomplish that task we have to take a look at the same factors that affect the U-factor rating with the primary one being air flow.

When a factory new window is properly installed into a newly built home they are usually pretty tight. The window itself is straight and tight with good weather stripping and intact glazing. There is caulk all around the window where it is mounted to the house sheathing. There is step flashing and more caulking around the outside of the window, then usually a house wrap of some kind and finally the exterior siding. Inside the gaps are insulated, often with foam, and caulked again. Finally they are trimmed and more caulk is applied around the trim work after finish painting. Modern windows operate on a spring balance system that is built into the window. The springs allow the window parts, called the sash to be moved easily into the desired position. Guess what. Most of these new windows are pretty darned efficient just as they come.

Enter the old house and the old window. Old windows have been serving their purpose for many years. Weather stripping is tired. Glazing has dried up and separated from around the glass panes or fallen completely out. Wood has dried out and window sashes fit loosely in their frames. In many old homes part of the sashes (usually the upper ones) are forever fixed into position by the years and eons of paint. Old windows were made in a simpler day. Many of them operate using sash weights and ropes and pulleys to assist the window opening. Some no longer have their ropes, instead you jerk them open and prop them on a stick. When the winter wind howls the curtains sway in the breeze! So what to do?

Tighten them up!

Start outside by scraping and re-glazing the window glass. A little putty will stop a lot of leaks. Then scrape and paint the window as well and caulk any cracks that you see. Next spend a little money and install some storm windows. For a relatively small investment new storm windows make a HUGE difference. They provide an air gap between driving winds and the interior windows and really cut down on heat loss. On windows that take a lot of direct sun adding a solar reflective film to the storm windows makes a great difference on solar heat gain and is easy to do. Much easier than adding it to the main window.

Is the window sash loose within its frame? Adding a window jamb liner http://www.jrproductsinc.com/shop/pc/Wi ... s-c299.htm can make a huge difference for little money. Also add new weather stripping where it is needed.

What about insulating AROUND those windows? By removing the window trim you can access those gaps that are leaking air. Use a foam insulation made for windows to avoid warping the wood and fill those gaps. If you have a upper sash that will never move again, like we did, you can clip the sash weight and remove it and then fill that space with foam as well. Re cord the remaining weights and then reinstall the trim.
Image

When these jobs are done you will be amazed at the difference!
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

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Farmfresh
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Re: Energy Efficiency and Your Windows

Unread post by Farmfresh » Sat Dec 06, 2014 6:11 am

So now you have your windows tight as possible and in decent repair, what is next? The next step is to boost the efficiency with window treatments.

I have already discussed one type of window treatment that can make a difference ... reflective film. Adding a layer of reflective film to the surface of the window (storm windows are the easiest to do) provides a radiant barrier that can bounce off the direct rays of the sun reducing solar gain in the summer and making your home easier to heat. The layer can also bounce back some of the heat that a home might otherwise lose. http://www.homedepot.com/c/installing_w ... m_HT_BG_DC If you want to allow solar gain during the winter months and reduce it during the summer it would be easy and not too expensive to have two sets of glass for the storm windows on the south of your house. That way all you would need to do is change the window glass to the filmed glass in summer and the clear glass in the winter months.

Another thing that we did at our old house that made a crazy amount of difference is to build solar shades for the outside of the windows. They were relatively inexpensive and easy to build out of pvc molding and solar shading material. The went up every summer on the windows that got baked with direct sunlight on the house. You can choose from several degrees of protection as well. The shades I made were from 80% solar block fabric that I bought from a company called FarmTek as remnants. http://www.farmtek.com/farm/supplies/Sc ... Records=20

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Stopping the sun BEFORE it comes in the window reduces heat gain in the summer far better than pulling the shades inside of the house. Plus the solar shades still allow the breezes to come in and you to see out. Another advantage is that they shield the window from all but driving rain. This allows you to keep the windows open during a rain shower providing ventilation without fear of water damage in the house. The shades are easy to remove in the fall and winter, when you WANT the heat gain, and easy to store.

Once inside the house the window treatments you choose make a HUGE difference in the efficiency of your windows. Just like with your clothes layering makes an important difference. I like to start my layers with simple roll up shades, room darkening on those sunny windows or in my bedrooms where I might want to take a nap. The vinyl layer may not seem like much, but it does slow down any lingering drafts coming from the window. It also starts the insulation factor by providing a thermal break and a small air pocket between the shade itself and the window. There are several other window options that do a similar thing, although usually at a higher cost. Honey comb shades http://www.blinds.com/control/infopage? ... learn.html provide a nice look AND that thermal air barrier between the harsh world and your home. Adding plastic inside of the window in the winter also adds that thermal air pocket and reduces drafts even more.

Next come the draperies. Usually chosen for the eye appeal you can really help the efficiency of your windows by giving a bit of thought to the drapes or other window treatments that you choose. Choosing an insulated drape that can be pulled when needed under a pretty drape might be the best of both worlds. Also choosing quilted window treatments or even shutters will provide even more R-value to the window.

When we were first married we lived in a town home with aluminum framed windows. They were horrible. They would actually ice over and freeze shut each year! I learned a lot about insulating windows from those. We made winter window quilts for each window. I used pretty winter fabrics and layered it - outside to inside... dark fabric (to absorb solar heat), 6 mil plastic (vapor barrier), quilt batting, pretty fabric. Then I fitted it to the window and bound the edges. I hung them simply with rings at the top and extra rings placed strategically so that I could lift and hook those lower rings and raise the shades about half way to let in the daylight. They helped immensely in the winter. I also learned that a new packing blanket, like you can buy from U-haul, makes a great inner layer since it is already quilted. It also makes a cheap quick window quilt on it's own, but it is a bit ugly. I imagine even a non sewer could dress it up with some hot glue and a fabric remnant.

Then I went the extra mile. Last winter we moved into this drafty COLD place. My living room picture window is 54 x 56 inches of north facing heat losing glass. I found several pieces of foam insulation board at our local Habitat for Humanity ReStore for a bargain of a price, so I hauled them home and made a difference. I used some old fabric and literally threw together a quilty top cover and more old fabric and made a pieced together backing. Then I took two panels that were each half the size of the picture window and I "booked" them together with duck tape. They fold closed on top of each other and when open are fastened side by side. Then I covered them with the quilt covers and whip stitched it in place. Now I can open this foam "shutter" and put it in the window (held by four twist out wood strips mounted to the window frame) to keep the cold air at bay on those bad days. I can also pop it out of the window and it folds down to neatly store behind the sofa when not in use. I love it. This is my hubby demonstrating it.

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So... what are YOU doing to make your windows more efficient?
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

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Sunsaver
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Re: Energy Efficiency and Your Windows

Unread post by Sunsaver » Sat Dec 06, 2014 6:18 am

My windows are awful, very old, thin, wavy glass with bubbles. They are very drafty, but original to the house, so I've been reluctant to anything to them. They need some weather stripping and heavy drapes at least.

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Farmfresh
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Re: Energy Efficiency and Your Windows

Unread post by Farmfresh » Sat Dec 06, 2014 6:39 am

I didn't want new windows in my old house either. That is why I re-worked them. It was much cheaper and made a world of difference. Plus things like a window jamb liner or new glazing putty are invisible. Adding storm windows is also a low cost option with big results. Add them on the prevailing wind side first for the biggest difference.
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

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Farmfresh
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Re: Energy Efficiency and Your Windows

Unread post by Farmfresh » Sat Dec 27, 2014 8:35 am

So ... I added storm windows to my north facing bedroom windows and also to my two smaller (normal sized) windows on the north. A storm for the picture window is going to be too expensive since the thing is so big so we are using the quilty foam shutter for now.

I also got a thermal leak detector for Christmas, so now I can give you the results.

I tested on a moderate 50 degree day outside with no hard winds and a internal house temperature of 73 degrees was the baseline.

First window tested was a single pane window with an old storm on the west of my house. That window registered at 54 degrees.
With the shade pulled and the insulated curtain drawn it was right at 69 degrees.

The next window tested was the newer double pane vinyl picture window on the north of the house. That window registered at 63 degrees.
The shutter was off due to it being a mild day.

The next windows tested were the identical double pane vinyl windows located on each side of the picture window that were now sporting the new storms as well. Those windows registered 67.9 degrees.

The north facing bedroom windows with storms had a similar reading of 67.9 without insulated curtain and with the curtain were 73 degrees.

So adding those new storms keeps my windows 5 degrees warmer on a moderate day. That has to add up.

The double pane and tighter window alone makes a 9 degree difference over the old single pane windows. Double pane PLUS storm is nearly a 14 degree difference over the old single pane window.
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

dizzy
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Re: Energy Efficiency and Your Windows

Unread post by dizzy » Sat Dec 27, 2014 5:52 pm

It's amazing how much difference a little thing can make.

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Farmfresh
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Re: Energy Efficiency and Your Windows

Unread post by Farmfresh » Sat Dec 27, 2014 7:17 pm

The best part is that the storm windows are relatively cheap - under $90 each - and the results lasts a long long time.
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

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Farmfresh
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Re: Energy Efficiency and Your Windows

Unread post by Farmfresh » Mon Feb 16, 2015 10:09 am

More energy updating took place on my bedroom windows this week end.

I took off all of the trim molding and discovered, as I suspected, there was no insulation around the windows between the window casing and the framing. When they installed the replacement windows (on the north wall only) of the bedroom, the did a little caulk and that was it. To correct that problem I installed window and door insulation foam around the entire window for each window in the room.

I also discovered that one the old single pane west window the window glazing was missing in spots and cracked in others. Window glazing does several jobs on a window. First it holds the glass panes in place. It also provides an air seal between the glass pane and the wood trim of the window. Modern windows usually come with clear silicone glazing, but back in the day it was a kind of greasy putty that would eventually dry out and crack and then it would fail. I decided not to go the "full monty" |em30| :lol: by getting out the ladder and re-glazing a crappy old window that I will hopefully be replacing soon, so I did a quick fix and simply siliconed it from the inside. It was an easy fix, but it sealed the air cracks and gave the window pane a bit of additional support.

After the extra work the bedroom was noticeably quieter, which is good since we get highway noise on that side of the house, as well as much warmer and less drafty.

|em15|
Matthew 19:26 Jesus looked at them and said, "With man this is impossible, but with God all things are possible."
"Stop Dreaming About the Good Life and Start Living IT !"
Every little bit ... is a little bit.

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Dragonlaurel
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Re: Energy Efficiency and Your Windows

Unread post by Dragonlaurel » Fri Feb 17, 2017 6:32 pm

Farmfresh wrote:More energy updating took place on my bedroom windows this week end.

I took off all of the trim molding and discovered, as I suspected, there was no insulation around the windows between the window casing and the framing. When they installed the replacement windows (on the north wall only) of the bedroom, the did a little caulk and that was it. To correct that problem I installed window and door insulation foam around the entire window for each window in the room.

I also discovered that one the old single pane west window the window glazing was missing in spots and cracked in others. Window glazing does several jobs on a window. First it holds the glass panes in place. It also provides an air seal between the glass pane and the wood trim of the window. Modern windows usually come with clear silicone glazing, but back in the day it was a kind of greasy putty that would eventually dry out and crack and then it would fail. I decided not to go the "full monty" |em30| :lol: by getting out the ladder and re-glazing a crappy old window that I will hopefully be replacing soon, so I did a quick fix and simply siliconed it from the inside. It was an easy fix, but it sealed the air cracks and gave the window pane a bit of additional support.

After the extra work the bedroom was noticeably quieter, which is good since we get highway noise on that side of the house, as well as much warmer and less drafty.

|em15|
It's amazing how little things can make a huge difference.
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