Last night I was presented with a thought that got me to a thinking.............

If someone insulated their actic with say R60 but only had R12 in the walls, would the R60 act as such a good lid that it causes more of the heat to escape through the walls which are only R12? Yes I know heat rises, but after it has rose to the ceiling then what does it do, go outwards through the walls?

Now if this were to be true, what would be the perfect amount of insulation in the actic? Not what is code, but what is the right balance between enough but not to much? Oh, if you don't already know, I do live where winters are cold.

There is no such thing as too much. If you take the R value and divide one by it, you get the U-value, which is the number of BTU's per hour per square foot of surface that will escape through the assembly. For R-60, it is 1/60 or 0.0167 BTU/hour/sq. ft.

If you increase the insulation in the attic, the value of the insulation in the walls remains the same, therefore no more heat will escape through the walls than before. The heat will simply be retained in the space that much longer, since it is escaping through the attic at a slower rate.

The perfect amount of insulation is a balance between the building code requirements, the space available for insulation, the construction budget, and energy conservation, but basically is the most you can fit and the most you can afford. Be warm ).

Actually, there is defintitely a point of diminishing returns on insulation where more insulation does not produce a warmer or cooler home.

And energy loss can often be better measured by air infiltration than insulation and U and R values.

Types of insulation used can also affect the energy efficiency/inefficiency of a structure.

There is also diminishing returns on dollars invested where isnulation is concerned. You have to pay for the insulation first before it actually returns you any benefit on energy savings.

The government, model code agancies, insulation manufacturers and other have all concluded that more is not better, and which is why all these have adopted recommended amounts based on location, degree heating days, and other factors.

The codes offer a prescriptive method of energy compliance. This means a recommended so much R factor based on your location and degree heating days. This method is inefficent, however, and does not take into account all factors which account for energy loss such as location on a lot, exposure to wind, type of foundation, percentage of glass to wall ratio, etc...

The Codes therefore allow and sometimes demand a performance based approach that allows all these additional factors to be taken into account.

IRC 2003 energy section requires using the performance based International Energy Conservation Code {IECC) when a home has more than 15% glass-to-wall ratio and where a townhome has a 25% glass-to wall ratio. (See IRC 2003 N1101.2.1; N1102.2.2; N1101.3.2.1 and elsewhere...)

The US Department of Energy produces a similar tool with RESCheck for residential structures and COMcheck for commercial buildings.

Anyone can access this free REScheck and COMcheck software either by download or on-line at http://www.energycodes.com

REScheck takes into account just those things that you mention.

It allows for lower ceiling insulation values if more insulation is used in walls or floors, greater efficiency glass is used, or extremely high efficency heating equipment is used.

Where those states, like my Pennsylvania, have adopted the International Residentianl Codes with their energy provisions, REScheck is the choice for builders because it allows for greater flexibility in design when, for example, prescriptive insulation thicknesses like those of R-49 for ceilings or crawlspace floors are just not practical to achieve or require costly framing changes to accomodate such thick insulation amounts.

REScheck allows for lesser values in floors and walls to achieve the same or better energy compliance and efficiency in a 'trade off' approach by increasing the energy efficiency in other parts of the house.

Play around with the REScheck software and you will see that it works exactly as you propose:

http://www.energycodes.gov

Like I said...a BALANCE between many factors, including budget.

But more insulation in one spot will not INCREASE the heat loss in another spot, which is what the original question was.

You're right, Rich.

Adding insulation in one area does not increase heat loss in another.

But there are trade off approaches in balancing out the BTU loss or gain in a structure and more is not always better as far as controlling energy loss/gain goes.....and a structure needs to be dealt with as a whole for the best insulating methods and not as individual parts.

Increasing attic insulation to R-60 can have little effect on overall energy efficiency if one has leaky windows and a low efficiency furnace that no longer produces enough BTUs to adequately heat the structure for example...

Thanks guys and thanks for the link homebild. Now all I've got to do is figure out my numbers which shouldn't be hard. Thanks again.

First, and foremost, let me address the first mis-conception: Heat does NOT rise. Basic thermodynamics, a big word which describes the way heat behaves, which we all learned in high school, shows us that heat ALWAYS moves toward the cold. If you don't believe it, then try this: take a hot clothes iron, hold it over your head, and touch the sole plate with your cooler finger. Will the heat from the iron continue to move up, as was stated, or down, into the cooler finger? I think we all know the answer.
That having been disposed of, the technical definition of heat is: possessed of molecular motion. That is to say, all objects, solid, liquid, or gaseous, have a measurable latent heat within themselves, for as long as they exist above minus 452 degrees F., which, scientists tell us, is defined as absolute zero, the point at which all molecular motion ceases. If there is no internal friction of molecules rubbing against one another, then there is no latent heat being generated by the internal friction of those molecules.
Cold is defined as "lack of heat". There are no units of measurement for cold. It is a phenomenon, a state of being. On the other hand, there are plenty of ways to measure heat, among which are: degrees F, degrees C, degrees K, calories, kilo/mega calories, BTUs, therms, etc.
There are three modes of heat transfer: conduction, convection, and radiation. Conduction, going back to the hot iron/cold finger illustration, is the direct transfer of heat from the heat source to an abutting mass containing less heat, an attempt to establish equilibrium, or balance. It's also how the frying pan transfers heat from the flame of your stove to the cold (less heated) food within itself. Radiation is how the sun warms the earth, or why the front of you feels warm when you stand in front of a roaring fire in your fireplace. Convection is the reason we have ever-changing weather, or why the air near the ceiling of your house always feels warmer than that along the floor: warm air contains fewer molecules than cold air. Being less dense than cold air, it is pushed upward toward the ceiling by the denser cold air, which contains more air molecules per cubic foot of air than does its warmer counterpart.

Having established that heat always travels toward the cold(er), seeking equilibrium, the role of insulation is to retard heat transfer, regardless of direction of heat travel. In practical terms, that is why the biggest payback from an insulation project comes from doing the attic, or, more properly, from buffering the warm air along the second floor ceiling from the less warm (cold) winter attic air. Conversely, in the hot summer, when attic temperatures typically reach 130 degrees, or more, the heavier attic insulation will help retard the transfer of that heat into the cooler (less warm) rooms below. Now that you know all of this, review the other answers above. bmwjparker@hotmail.com

W.J.-
Soooo I see you are a bit of a insulation guru!
We are building a 2,400sq.ft. shop, and have
bought a "Radiant Bairrer" "Doubble Bubble" product. "They" say thats all the insulation we need! What do you think?
It will be installed over the purlins, under the roof deck.

The bubble-pak construction will provide a non-conductive buffer between the exterior and the conditioned interior air within your structure. The reflective mylar of the bubble pak will provide radient reflection, both of heat trying to escape in the winter, and of heat trying to enter the structure in the summer. Remembering that the function of any type of insulation is to retard the transfer of heat, not to totally stop it, the answer to your question really rests in the differential between interior and exterior temperatures at the most extreme conditions: winter and summer. Add to this the complexity of moisture within the conditioned structure, expressed as percent relative humidity at design temperature, and you can see that the complex calculations suggested by homebild, in a previous posting, are designed to take into account the real world in which we live.

There is no short answer to your question, since different structures fall under different Department of Energy regulations. A warehouse, for example, does not require the same level of insulation as does a residential dwelling, or the same number of air changes per hour as does an office. In a shop, with machinery operating and lights on, a certain amount of heat is being generated within the structure whenever it is in operation. Additionally, the people in the shop generate an average of 650 to 700 B.T.U./hour just by being there, and even more as they go about their respective tasks. At the same time, they are breathing, and, hopefully, for your bottom line, perspiring, which pumps moisture into the conditioned space, while depleting oxygen. If your shop incorporates open flame, such as a glass blower, or a metal working shop does, then those factors are also contributing to the heat and moisture load within the structure, as well as the pollutant level.

The answer to whether your bubble-pak will be enough comes from factoring into your energy calculations all of the above, by knowing the heat-loss or heat-gain of the building, and putting up enough insulation to help you stay at design temperature, with appropriate fresh air make-up, without creating a space that is so tight that you experience "sick building syndrome".
Hope this helps.

Happy to learn I shouldn't be insulating the rafters in my attic. But what would be your best recommendation for a 25 year old center-hall colonial in northeast NJ? Been trying to follow along, but the toddlers running around have won my attention. Is it recommended to tear out the original insulation that is in place? It no longer has (or may never have had) the paper covering and the pink is covered in black in areas from dirt (no apparent mold). This particular attic runs over the family room (built on a slab) and garage, yet I've recently noticed that there isn't any insulation over the garage portion. Would appreciate any recommendations as my husband grew up with a superintendant in the building, hence I'm the hardware store runner.

I would be surprised if a home built in c.1980 had NO paper at all. If properly installed, the paper, the vapor barrier, would be facing down, toward the top face of the ceiling underneath. As long as there is no moisture in the insulation, which pre-supposes adequate attic ventillation, and no damage to the vapor barrier, which is the asphaltic coated kraft paper, either foil-faced or brown with printing on the face, which should be facing the living space, then you can simply add additional UNFACED fiberglass insulation to that which you already have, or, if you prefer, can have either cellulose or loose-fill fiberglass insulation blown into the attic by professionals who specialize in the process. This is because insulation R-values are accumulative. In other words, by adding R-19 to an existing layer of R-19, you will achieve an accumulated insulation rating of R-38, as long as there are no breaches in the insulation layer.
The "R" value is the insulation's resistance to heat transfer through the product, which explains why the higher the R-value, the more resistance to heat transfer there is. The longer the expensive heat stays within the conditioned living space before escaping, the less your furnace will have to operate so as to try maintaining the desired comfort level, and the more money you save, while maintaining comfort.

A few words of caution are in order before you run out to Home Depot: If you have recessed lighting cans in the ceiling under the space you are planning to insulate, or augment the insulation of, then you must keep the insulation at least three inches away from touching the can of the fixture, which will be sticking up into the attic, in order to prevent overheating of the fixture, which could cause a fire, unless, of course the fixtures are "IC" rated, or rated for "insulation contact". Also, if you have soffit vents into the attic you will have to put vent baffles into each rafter bay so that the new, deeper insulation doesn't block the vents. Additionally, if you have an electric venting fan in your attic, then loose fill insulation is not a good idea, since the fan would operate in the exhaust mode, drawing excessive heat out of the attic in the summmer, and would wind up sucking some of the loose fill insulation out with the hot-air stream. Finally, if you intend to add fiberglass insulation batts or blankets to what you already have, be CERTAIN to add only unfaced, not faced insulation, so as not to create a condition which would create moisture condensation into the insulation.

Going back to Garret's original question: All other things being equal, the answer to your question is a "qualified" yes. This is because, as was mentioned, heat ALWAYS moves toward the cold (place of less heat), by the path(s) of least resistance. Since natural convection pushes the warmer air upward, toward the ceiling, if there is so much insulation there that the heat could not escape at all, then it would seek equilibrium by trying to get out through the walls.
At the same time, Richard's answer was also right, in that this scenario would not cause "more" heat to escape though the walls, but would simply allow the quantity of heat that is already within the conditioned space to seek equilibrium through a different, less resistive pathway, which could be the less-insulated walls, or, even, a poorly insulated floor.

WJ Parker
I realize that currently without code enforced air sealing, we rely on insulation thickness to provide our reduction in stack effect.

But if they did a phenomenal job of preventing air leakage in the ceiling plane, what R-Value would you need to get sufficient performance on reducing conductive heat transfer through that plane to a point where it makes no difference on our heating bills?