I have been reading up on the recommended insulation for houses in my climate and was wondering if anyone had any experience, did any tests, with how small single rooms effect this. Since body/appliance heat supply such a large percentage of the heating, and even halving your heating costs is relatively insignificant, it makes sense that less is needed.
Also surprisingly, the wall insulation recommendation is already extremely low. Can someone explain why a wall with 1/3 the insulation of the ceiling makes sense (I was expecting something most like 2/3s)? Is it just that low because it is pretty hard to get any better in the 3.5 inches a 2x4 frame gives you? The floor recommendation is even higher than the wall recommendation, by quite a lot, I am assuming that is because they assume that the floor is a concrete slab connected to the ground (a giant efficient heat sink)? And in other situations something significantly less than the wall is needed?
Usually the ceiling/roof gets a lot more because heat rises, so keeping your heat in is the most important. Depending on your wall construction so you have some depth of wall cavity AND what you insulate with, will affect your R value. Using something like a ceiling fan to send the heated air back down towards the floor will make for a warmer feeling space with less heating needed. Another trick is to use radiant floor heating. Warm floor will make the room feel warmer and the warmth will rise.
In hot climates the sun cooks the roof so insulating to keep the heat OUT is also important. Hence the ceiling often gets twice or more what the walls do.
If you are building a tiny structure, windbreak may be everything during the heating season. Outside using square bales stacked up against the side or sides that get the predominant winter winds... or some nearby bushes, shrubs, hedge, or the like of a suitable height. Or even a good tall hugel well planted, will do a lot for you.
Oops, it's not heat that rises, it's hot air (or liquid) that rises relative to cooler air (or liquid). Heat travels by radiation, conduction or convection, but only convection has this upward movement trend. Radiation and conduction go all directions without preference. If your heat source in the house is mostly hot air, it will mostly collect at the top of the room, which is why roof insulation is considered more important than wall insulation. The direct heat of the the high sun in summer is another reason, and that is to block the radiant heat coming (down) from the roof. Floor insulation is to protect against heat conducting (down) into the unlimited heat sink of the earth, and because if you don't wear slippers, your feet can lose heat quickly to a slab floor and reduce your comfort level.
Anyway I don't have a specific recommendation about insulation R values, but I would suggest trying to get some thermal mass into your living space too, because in my experience that really increases the comfort level of a space. Insulate as much as you can afford, I guess.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
You usually have much more room to add insulation to an attic than you do to walls.
Using 2x6 studs in a wall is a relatively cheap upgrade from 2x4, in many cases it can be done for almost no extra costs (assuming you're allowed to put 2x6 on 24" centers instead of 16" centers like 2x4)
However, going up to 2x8 or larger starts to get progressively more expensive for little additional gains.
Roughly speaking, to cut your energy loss in 1/2 you have to double the thickness of insulation. This is fairly cheap when going from 3" to 6", but get's more expensive when you go fro 6" to 12", or from 20" to 40". So every inch of insulation you add get's diminishing returns.
In addition to the 'hot air rises' issue mentioned above, more attic insulation also helps keep a house cooler in the summer. The roof is a major source of heat during the summer as it gets much hotter than the walls. My attic can get over 150° F with the sun beating down on the roof.
My opinions are barely worth the paper they are written on here, but hopefully they can spark some new ideas, or at least a different train of thought