Local Lumber Yard

My local lumber yard has a building consultant on staff who is there to assist with just these types of questions, at no charge. If you are their customer, they will help you with the planning of your project and find answers to these kinds of questions. Check with them.

insulation recommendations

Information and help along these lines should also be available through your local utility companies.

Not sure there is one formula

I think it depends on several factors, like location, heating days fuel costs and your system efficiency.

A google search on cost benefit of home insulation turned up several calculators and a few good government sites.  Like this: http://energy.gov/sites/prod/files/guide_to_home_insulation.pdf.

I found a foam sprayed on the walls and ceiling before the other type insulation to be particularly good to prevent drafts, etc.  

Insulation is good for other things besides heat transfer.  Specifically, it absorbs noise.  There are other things that are better, but the labor costs drove me to use more or less standard insulation in the floors between the main and lower floors.  May not be perfect, but it works great, can't hear a loud TV on the other floor went your trying to sleep.

Heating and cooling info

Your local heat pump companies can provide information on what is best and how much you will save by adding. When I was building my home, the energy savings for exterior walls being 2x6 versus 2x4 paid for the materials difference within the first two years. Keep in mind its more than just walls. Your doors and windows are where you lose heat/cool. Ceilings, attics and crawl spaces all contribute.

Structure wise, a good contractor can give correct advice on wall requirements like basement wall thickness, ideas on floor beams and other framing items. I used the laminated floor I beams for floor joists. They provide good strength and after 12 years have had zero issues.

If your designing from the start, check on having 9 ft basement ceilings. This allows you to have a finished 8 ft ceiling with the ducts for heating/cooling above. I did 9 ft concrete walls and its been a fantastic investment! Left me headroom in the basement but still access to pipes if needed without tearing out layout.

Hope that helps some.

Heat Loss/Heat Gain Calc...

To determine the cost effectiveness of adding additional insulation a heat loss/heat gain calculation needs to be run on the addition. Like Larry said, "it depends on several factors". Size of the building, (sq. ft.), The amount of and sq. ft. of the exposed wall, which direction does the addition face, color of the roof, shading coefficient, number of windows and size of windows, roof overhang, doors, building materials, slab on grade, craw space or basement, is the basement/ craw space insulated, does the slab have perimeter insulation and on and on. If you're working with a good, and I repeat good, HVAC Contractor he will, should, run this calculation to determine the correct size of the heating and cooling equipment. From the heat loss/heat gain, which is the number of BTU's per hour that are lost in the winter and the number of BTU's per hour gained in the summer, and based on the heating and cooling degree days for the area you live in and the thermostat setting for each season, he will determine the proper size of the heating and cooling equipment. Quick note here, bigger is not better when it comes to the furnace and A/C. From those numbers and the fuel cost he can estimate the operating cost of the base building design.Once he has the base building run you can play with the numbers by changing the building components like windows and insulation amounts which will yield a different operating cost.

Couple more things, insulation has diminishing returns. The first 6" has a very short payback but the additional 6" will have a very long payback. BTW, you mentioned 12'' of insulation; were you kidding? Because that's not reasonable. Think about this...you fly in a passenger jet at 30,000 ft...does it have 12" of insulation in the wall? NO! Yet you stay warm! There are a couple of reasons, but one is NO AIR INFILTRATION. An inexpensive and effective way to reduce air infiltration in your new addition is to purchase a case of cheap caulk and spend the weekend, after it is all framed up and closed in, caulking all the gaps in framing members, top plate penetrations from wiring and plumbing and around windows. Caulk the bottom plate at the sub-floor and anywhere you see light from the outside.

One way to greatly reduce the btu loss and gain is to reduce the number of windows and doors. Think about this for a minute...You spend all that money to insulate and seal the outside walls to an R factor 19, then you cut big holes, windows, in the wall that have an R factor of 2 or less. Window efficiency is measured in U factor, the inverse of R factor. Lower the U, the better the insulating properties of the window.

Bob is correct. Many electric and gas utilities have someone on staff to assist or at the very least many of them maintain a list of HVAC contractors that can help. Most HVAC guys will give you a bid free of charge that would include(you need to demand it) the load calculation. It's your money your spending on the addition make sure it's built correctly and it's efficient to operate.

That's your heating and cooling lesson for today boys and girls...

John

Good things to know...

I should add, there will be no windows in this addition, as the first floor is a garage, and the second floor will be the railroad room.  As far as doors, there will be "air lock" rooms with two exterior doors, and I was thinking of using, at least for the winter season, one of those super blower heaters found at some stores that keeps the entrance where the double doors are very warm.  Just a thought.

And actually i wasn't joking about 12" of insulation IF it improves from any heat/cooling loss.  On the other hand, if the standard 6" of wall insulation PLUS taking the time when the roughing of the extension is done is caulked and sealed (with Tyvek paper for instance) and other sealing type products, then that will be the route I will go.  The BOTTOM LINE is I want to reduce heat/cooling loss to keep the utility cost as low as possible (not the cost of the equipment, the size of the space will determine that I would think) I am speaking of the monthly electrical and propane bills.  If however I'm spending $6000 more for insulation, and the savings on the utility bill is less than say $75 a month, then it isn't worth it.  The way I would justify the upfront cost is, the home equity loan is a 10 year loan, so the money spent up front must result in a savings greater than that cost in 10 years.( cost being the loan amount plus interest of course and the savings would actually need to be significantly greater)

Thanks again.  Please continue with the feedback, or pm me.

Ken L.

 "I need to determine how

I don't know about New York but here the County building department has all the info available, in fact they make one meet their insulation requirements before issuing a permit. If any new homes are being built in your area they'd probably be the  easiest  way to see what is most cost efficient and locally favored.......DaveB

Cost Benefit

You won't get a huge benefit going from 6" of batt insulation between the studs to 12" of insulation between the studs from an energy loss standpoint.  Keep in mind that you will not only have the added cost of the insulation, but you will need to consider the added cost of 2x12 construction vs. 2x6 construction.  You can't just shove 12" of insulation into the 6" deep cavity - you will get zero added benefit from that.  If you want to reduce the heat loss/gain problem, you will get better benefit from 2x6 studs with 6" (R-19) insulation between the studs and a continuous 2" layer of rigid (pink or blue) board insulation (an additional R-10) outside of the sheathing and behind the siding and building wrap.  The continuous insulation will help prevent loss from the stud itself.  It will be even better if you use 2 layers of 1" insulation and stagger the board joints about 6".  Don't forget the vapor barrier on the inside face of the studs behind your wallboard!

@Alan & DaveB

Alan, those are all good suggestions, but at what cost and what is the payback? You can't figure out the cost savings unless you know how much it will COST TO OPERATE the base design compared to the upgraded construction design. The only true way is a load calculation, loss and gain. How many BTU's will you reduce the heat loss or heat gain by building to your suggested method, I like your suggestion, again, cost vs, payback in energy saving or energy cost.

DaveB, Building codes and insulation standards will not tell him how much it will cost to heat and cool the building. I venture to say the code officials are not familiar with the load calculation or have the ability to run one. Look up Manual J Load calculation on the internet for a complete description, better than I can give.

Ken, building above the garage presents one additional problem. The floor is over an unheated space. Make sure your design plans include insulating the floor for the space above the garage. In the winter the garage door open...huge amount of cold air comes in( heat loss ) and in the summer same thing for hot air( heat gain ) except you add the additional heat from the automobile engine at 200 degrees, bad for summer, helps in the winter. Bonus rooms above garages need to be designed properly.

John

Insulation plans INCLUDE the floor

In addition to filling the floor joists with the appropriate insulation, I was going add foam board insulation to increase the R Value through the floor.

As for the walls, I was going to use 2 - 2x6" walls.  Though with the R Value of the insulation board, perhaps going with 2 sheets of 2" foam (R-20 total from that correct?) instead of R-19 from adding a second wall would work out better. At least in terms of labor time, it would be quicker to put up a 4x8 sheet of foam, versus building a second 2x6 wall and filling it with insulation. 

Perhaps I should started this thread by asking what is an optimal R-value for the ceiling, walls, and floors, with say 3 exterior doors (that are actual double doors, with the small entrance/exit rooms being independently super heated/cooled to reduce heat/cool loss from the main room and with no windows, to reduce the operating utility costs over 10 years.  In other words, what I need to find out, and ask someone, and I will pursue the leads given here as to who to speak too, how much is the potential savings from my utility bills with each increase in R-Value and is that savings for the next 10 years more or less than the additional cost.  That is what I would like to determine.  Thanks.

Ken L.

Oak Ridge National Laborator R_Value Calculator

You could start with the ORNL R-Value Calculator. There are two versions available the online Go To Simple Calculato and the downloadable version. Use the Click Here To Compare With Another Technology feature to compare different build configurations.

"Building codes and

    One doesn't need to know the actual cost to know the most cost effective solution. In this age of energy consciousness the free market has already done that by codifying the base requirements  and by those building homes that exceed them. No reason to re-calc the wheel when all these factors are already included in the new construction and permitting process.Lumber yards and building suppliers should be able to tell you what high end, high  efficiency homes are using in the area  which is probably the most direct answer.....DaveB

Building Insulation and Cost Benefit Analysis

I am a retired architect who practiced in Syracuse, NY, for almost 50 years. There is much good advice offered above, especially by John Winters. I did many an evaluation such as you seek and can tell you this, I believe confirming what John has offered. In my experience, provide the insulation and construction details mandated by the local building codes (almost certainly the NY State codes, including that related to energy). No more and no less. Anything beyond those requirements is highly unlikely to pay back within your 10 year horizon-simple as that. Save yourself a lot of time, effort and money.

Dante

Building Insulation and Cost Benefit Analysis

I am a retired architect who practiced in Syracuse, NY, for almost 50 years. There is much good advice offered above, especially by John Winters. I did many an evaluation such as you seek and can tell you this, confirming what John has offered, I believe. In my experience, provide the insulation and construction details mandated by the local building code (almost certainly the NY State codes, including that related to energy). Anything beyond those requirements is highly unlikely to pay back within your 10 year horizon-simple as that. Save yourself a lot of time, effort and money.

Dante

Another thing to consider is

Another thing to consider is the type of insulation. Some types are better than others and last longer. Fiberglass bats tend to settle over time or can be damaged by rodents rather easily. Spray in foam particularly the closed cell type might produce higher R values and last longer. They also tend to fill all the voids as they expand and are trimmed off flush with the openings in the cavity.

One also should consider the ability of moisture to exit the home or the space. If it will not get out it will tend to produce mildew and rot and can make a house or space unlivable.

One good series that you can watch on you tube for some information and general information is the this old house series as questions like this often come up on the show and the answers as well.

The other thing to keep in mind is heating and cooling costs are likely to continue to rise and if you are using todays costs you are looking at a worst case scenario as to payback. Consider how much this will save you after the payback as well because the savings will continue when the expense of materials have all been amortized.

ehh...not quite right

No disrespect John, but the analogy to an aircraft is not relevant. You are correct, there is not 12" of insulation in an aircraft, but the insulation that is in aircraft is also not affordable to civilians. And aircraft do bring in outside air for ventilation. But you are very correct on sealing all the gaps and cracks. Every year before heating season, I go around with my Fluke Thermal camera and find where the heat is leaking thru. You can also use a digital thermometer ( the kind with the laser dot ) to find warm, or cold, spots around the house to caulk. Cheap, simple and easy fix with big paybacks. There is a breaking point for insulation, I wish when I bought my house, that the new spray foam, specifically closed cell, was available. Very high R value, plus vapor barrier built in. In lieu of that I did fiberglass in the walls, and blow in cellulose in the ceiling. I blew in 24" in the ceiling ( only 10% more than doing 16" ) and have never regretted it. My heating and cooling bills have never gone over $100 per month here in St.Louis. Not much heating here, -10 at the coldest for a few days, but the summers are brutal. 100+ for weeks on end. 20 years later, gas and electric prices have gone up and up, and now my energy bills are considerably cheaper than my neighbors. Also, check into rebates from either your gas or electric company, right now we have some going on for insulation, as well as higher efficiency furnaces and A/C, and appliances. Any good HVAC contractor will do a heat loss / heat gain for your home, and should be aware of any rebates for equipment and insulation. I would contact them first, and get at least 3 estimates.

Michael