what misty fies me is how houses are built today with 2 or even 4 windows per room. why is this? i guess it is for natural lighting.
Modern windows have awesome radiation barriers - which is how most of the heat will get in (assuming there's no air leaks) There's a cool display at home depot using two radiometer globes (radiant heat makes them spin), some glass and a halogen light bulb - one with old window glass, and the other that's filtered. The difference in amazing
If your windows aren't like this (like most people's), the insulation idea is a pretty good idea. Just make it removable in case of a fire. Adding an attic fan also helps out a whole lot
Time is the best teacher. Unfortunately it kills all its students.
window displays at the depot generally show best case scenario. theres no such thing as a window thats as good as a well insulated wall (as in not having a window). perhaps on the space shuttle or other extreme concept. but not in a house. its just not practical.
there may be modern windows that are well insulated compared to old single pane windows, i cannot argue that fact. but there isn't an actual "well insulated" window. the very nature of a window means it can't be well insulated.
there is generally 3 types of heat transfer. radiation is only 1 of the3 convection and conduction are the other 2. so a radiation display at the depot would only adress 1 of the 3 ways heat and cold gets through windows.
i cut my electric bill by a solid $75 a month just by covering the windows with 4 inch of styrofoam. and i have those double pane agron or whatever filled windows with DIY limo black solar tint on the outside. still i got a $75 a month savings.
besides windows, theres tonnes of things one can do to save electricity, power and gas. when you brush yer teeth or wash yer hands, the water that goes down the sink drain is wasted. its basically clean waste water. why not plumb that water into you're toilets charge tank? could also save the shower water for the same purpose. shower water and sink water is clean waste water and would work well for flushing a toilet. so would the waste water from a washing machine.
theres so many ways to save money but nobody does it. i can guarantee none of you will insulate you're windows with 4 inches of foam like i suggested. none of my friends or family have insulated their windows like mine except for my dad. but he liked it so much that he went a step farther and drywalled over 75% of the windows in his house. he also put new vinyl siding over the outside walls and covered up most of the windows.
down here in the summer there is a 30 degree temparture differential between indoors and outdoors. for you northern types the winter could see temps from 70-100 degree temparture differential from indoors to ourdoors. that means window insulation is even more important up north in the middle of winter than it is for me in the summer.
i can guarantee none of you will insulate you're windows with 4 inches of foam like i suggested.
The foam idea is actually pretty good for the SUMMER.
However, in the winter you actually want the "greenhouse effect" to warm the house. And you get that by having the sun come in through the (closed, and hopefully well insulated) windows into the room (where the sunlight bounces off things and some of that light gets converted into heat as a result). Effectively, this is a passive form of "solar heating", and it REQUIRES windows that will let light in (but stop drafts). And you prevent that from happening, when you put the foam up.
Of course, as already mentioned, the idea is great for keeping cool in summer (as you are using it for), because the foam will not only provide insulation, but also cut down on the greenhouse effect (and in summer the last thing you want is to heat things up more). But in winter, you want all the passive solar heating you can easily get. And that actually argues for having the shades (or anything else blocking the sunlight) open during daylight hours when the sun is shining (as that sunlight can be usefully turned into HEAT for the home, by use of the same principle that heats a glass greenhouse)!
BTW: I have actually used foam sheets as a makeshift shade (and heat barrier) on my windows in the past. However, I only do this in the summer (when I want to block the sun from heating the house), not in the winter (when you want the passive solar heat), and so far I haven't used as thick of foam as you have (I think my foam sheets are only an inch or two thick).
tomorrow I will be getting some caulk and going to town on all the small edges on my Anderson windows. the north side i use the shrink wrap plastic, i had a small hole last year and the cold air was pouring in fast through the dime sized hole. the 2 east windows i used bubble wrap on the inside of the glass, you can feel the difference in temp, and it lets light in while keeping the view private. the other window on the east is 1pain glass, the wife likes it so i used Plexiglas with foam tape, screwed it right to the window frame outside and inside I'll use shrink wrap plastic. west/south windows i keep them clean as possible and use the sun to heat during the day.
It is funny that up here (Wisconsin) they require you to have 16 sq feet of glass in a bedroom in new construction, that’s typically two 2 foot by 4 foot windows. On the flip side they require you to have a minimum of 6 inches of insulation or R-19. Guess what the BEST windows are, R-2.2 (with storm). A typical window is about R-.75 with some cheap ones at R-.25 and "good" ones about R-1. Anyway I just about fell over, a single 2x4 windows is what we had designed for energy reasons, but they made us add more, crazy.
Oh if you cover the inside of a window make sure it is sealed air tight or you will get a lot of condensation on the interior sill. It is far better to insulate the outside, but typically much more difficult if not impossible in some situations.
One of the neater things I saw were insulated awning that opened and closed with photo cells. So in the daylight they would open, then when the sun went down they closed an R-10 shutter to keep the solar gain in, pricey but neat.
The easiest thing and likely the cheapest is the clear heat shrink inside plastic.
styrofoam has an r value of 3.0 per half inch of thickness.
so a typical window of of r1 plus my suggested 4 inches of styrofoam would equal an r value of 25? holy **** thats alot.
can that be true? i always knew styrofoam was one of the best insulators for a house, but that much? look at a cup of hot coffee. the liquid is 180 degrees. 1/16th inch thick styrofoam keeps youre fingers barely warm. thats some good insulation.
wikipedia says per inch 3.6 to 4.7 for low-density, 5 to 5.4 for high-density.
for you northern types, i wonder is styrofoam in the windows could be more efficient than letting the sun in.
An option for those who live in temperate regions where either the night or day is in the desired temperature range is to duct a fan to pump air inside the house from directly outside (better than an exhaust fan because the air sucked in can get heated by walls etc). Often here in summer Australia the nights will be at a tolerable temperature but the days will be intolerably hot. If you have a reasonable amount of thermal mass (i.e. concrete or brick walls) inside, they will keep the inside air cool for several days. You just have to remember to turn the fan off during the day.