Author Topic: What is the least silly way to reduce thermal transfer through windows  (Read 4489 times)

LadyMaWhiskers

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People who live in glass houses...

I live in a warm and sunny locale. How can I cost effectively reduce the extent to which that star that heats the planet heats up the inside of my house? I've been pitched on low-e replacement windows, but I have reasonably serviceable windows, so that would be facepunch territory.

Film?
Blinds?
Shades?

What else?

Thanks mustachians!

worms

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Curtains?

Shutters?

SailorGirl

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Plant trees?

SwordGuy

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When we were dirt poor (and for some decades afterwards) we used to get clear plastic sheeting and staple it to the outside of the window frames in wintertime.  It created a couple inch deep air pocket and helped keep the house or apartment much warmer inside. 

Can't help you with the heat, other than to say if you can keep the sun from hitting the glass at all, it's bound to help.

Abe

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Awnings that stick out enough to block the sun from hitting the window in summer close to noon-time, but not in winter, would help a lot. You can make these out of fabric, some wooden poles and some brackets.

MsPeacock

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I find that cellular blinds make a huge difference. The blackout ones or the ones w/ thermal stuff on the inside of the cell work even better than the regular blinds, but both help a lot. They are also relatively inexpensive. A combination of shade from outside (plants, awnings), window tinting, and blinds, would all likely make more impact than replacing the windows (unless your windows are particularly old and single pane). If you have a large dark-colored surface outside your windows (e.g. a deck, blacktop drive way, dark mulch) it also helps to get that area shaded.

Villanelle

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I've had good success with curtains (the thicker, darker, and heavier, the better) as well as shade outside. We put an umbrella outside on a deck and angled it such that it blocked as much of the mid-day sun as possible, and it made a significant difference. 

thingamabobs

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Blackout curtains

Astatine

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I live in Australia in a city which can get pretty hot in summer. What we have is:
- awnings (which stop a lot of the sun/heat reaching the windows in the first place)
- vertical blinds (the cheap and nasty ones - they were already installed when I bought this place and left them in place for an extra layer of reflection/insulation)
- thick curtains

The combination of the three helps quite a bit. I used to have a deciduous tree on the north facing side of the house (equivalent to the south side in the northern hemisphere) but had to have it removed for safety reasons. The shade from that tree was awesome. I've replanted with another deciduous tree but it will take quite a few years for it to grow high enough to make much of a difference.

Shinplaster

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What do you have on the windows now?  If you don't want to obstruct a view, etc., that would affect your decision as to the window treatments.  Planting trees strategically is a great solution if you can wait for them to get big enough.  In the meantime, perhaps retractable awnings would help.

We have windows that face both west and south on the entire back side of our house.  Our family room felt like an oven with all the solar gain in the summer, even with blinds.  I purchased window film from Home Depot, and installed it on all the windows.  It made a huge difference - of course it doesn't stop all heat transfer, but it made the room much more comfortable.  It was easy to install, and completely invisible.  The film also stops fabrics and floors from fading.

zolotiyeruki

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #10 on: March 20, 2016, 08:12:12 PM »
Another vote for window film here.  It also gives you the benefit of improved privacy--the windows look more mirror-ish from the outside

AZDude

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #11 on: March 21, 2016, 09:08:36 AM »
Arizonan here, I think I have tried or know people who have tried everything conceivable to stop this from happening.

Best solution: shade trees and living in a home without many windows on the western/southwestern part of the home. Ceiling fans or just a plug-ing fan also help to circulate the air so you don't get those unbearable hotspots near the windows.

After that, blackout curtains, aluminum foil/window film on the inside of the windows, and even crazier stuff like tacking up thick blankets to cover the window or putting styrofoam in the window sill.


HipGnosis

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #12 on: March 21, 2016, 11:59:36 AM »
Another vote for window film here.  It also gives you the benefit of improved privacy--the windows look more mirror-ish from the outside
+ 1
Just make sure that you get film that is made to block / reflect heat.  It may or may not be mirror-ish (I work in the plastic film industry).

But a multi-angle attack is best.  Shade from awnings, trees or pergola with thermal curtains and the right film.
Also, ensure your attic is sufficiently ventilated.

Dezrah

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #13 on: March 21, 2016, 06:15:18 PM »
I work in the commercial windows industry.  My background is in Structural more than Thermal, but the principles are pretty straightforward.

There are two primary forces at work when people talk about thermal efficiency of windows: conduction/convection and radiation.

Conduction/convection is the transfer of heat through the materials of the window framing and the glass from direct contact with air and/or materials of a different temperature.  This is much more critical in colder climates where your differential temperature between the inside and outside is more extreme than in warmer climates (70 degF inside – 20 degF outside > 100 degF outside – 70 degF inside).  This is combatted by using multiple panels of glass with a layer of air between them (air is very good insulator) and using strips of non-conductive materials in the frame itself (just Google “thermal struts”).  This strategy will probably not get you much bang for your buck in a dry heat climate.

Radiation is exactly what it sounds like.  The sun bombards us with radiation all day long and there's a lot more of it the closer you get to the equator.  When struck by radiation, all materials will absorb some, reflect some, and transmit some percentage along each radiation frequency range.  “Heat” is a frequency just below the visible spectrum while ultraviolet is just above it. 

In a perfect world, we could make futuristic glass materials that only transmit visible light and reflect back all the energy that makes us too hot and/or ruins the furniture, but we’re not there yet.  Most “low transmitting/high absorbing” windows end up being very dark while “high reflectivity” windows make everyone around them miserable from the glare.  If you change the glass (again, this is probably more expensive than it’s worth) try to strike a balance in these figures.

Blackout curtains on the inside of your house will absorb most of the radiation but then dump it back into the air inside your house.  This is why all the good solutions already suggested involve blocking the radiation before it hits your house/windows (using trees for shade, awnings, etc).


Funny side note, in some northern climates, we’ve gotten so good at thermal efficiency that it’s not that uncommon for buildings to ice over in sections and then threaten to fall off in dangerous levels.  This used to happen occasionally in old buildings but it’s a whole new level with modern buildings.  It’s completely changing the way we have to architecturally design our buildings.

tonysemail

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #14 on: March 21, 2016, 06:19:51 PM »
I've been pretty happy with window films.
But I'm in CA which has mild climate.

GuitarStv

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #15 on: March 21, 2016, 06:30:45 PM »
If you cut a piece of plywood to size, then cover the other side with fluffy insulation and plug the window opening shut it will insulate just as well as a wall.  (Maybe better if your walls aren't well insulated.)  The disadvantage is that you can't look out the window.

Gimesalot

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #16 on: March 21, 2016, 06:49:43 PM »
We made solar screens our selves and they have saved us int he summer.  We bought the solar netting and the screen kits at home depot.  We then spent about 2 hours measuring, cutting, and assembling 10 of them.  The bathroom window does not have a screen and you can notice a HUGE difference.  We spent about $250, but it was totally worth it.  FYI, we take them down in the winter to let the sun heat our house.

stashing_it

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #17 on: March 22, 2016, 07:11:09 AM »
Get a roll of white paper, or a bunch of 8.5x11 sheets, and tape them to the windows.

It will reflect a lot of light back through the window, but still let a decent amount in the house

Mega

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Re: What is the least silly way to reduce thermal transfer through windows
« Reply #18 on: March 22, 2016, 10:53:32 AM »
Best solution, and one that has been in use for thousands of years, plant tall trees on the southern facing of your home. Look at old farm houses. The trees along the side of the house and along the driveway were not for show.

This blocks your entire house from heating up (walls, roof, light through windows).

If you are able to plant tree, make sure to prepare the soil first, as the standard subdivision 'topsoil' is garbage. This will allow rapid and healthy growth of your trees (my cherry trees are growing around 1 meter a year, in Southern Ontario).

If you do not have space for southern trees, then use films / blinds / curtains as suggested above. But you should already have those, unless you are a really free spirit!