You should check the building code requirement while you are at it.

Does this sound okay?

Not according to the US Department of Energy which gives a general cost effective range of R 13-15 for wall cavities and R-38-R60 for attics in your area.

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The US Department of Energy provides zip Code specific recommendations for retrofitshere.

Nice link. You been surfing the web instead of working again?

thanks! just what i was looking for:-)

okay, we are in the zone 3 area, so i guess we are okay. r13-15 and r30-60. we would be on the lower end of the attic...would you bump that up? also, our ceilings are 10'...does that matter?

Use the zip code calculator worthy posted. It recommended a higher level of insulation than the map states for us (North GA), but it happened to be what we did. We have r-21 in the walls and r-38 in the attic and r-30 in the garage ceiling (playroom above).

I'd bump the attic to 40.

That's interesting, I'm in zone 2, Houston, and it recommends floor insulation. I don't think I've ever seen a house here have anything beyond a straight slab. Am I misunderstanding it?

When I did it, it said floor insulation over unheated, uninsulated space. Our garage is insulated but we are still putting insulation in the ceiling (r-30) since there is a playroom above.

eoz......that probably means if you have a crawl space.

How were you planning to get R16 in the walls? Batts are usually R13 or R15 for 2x4 walls, R19 or R21 for 2x6 walls.

If you havent seen the threads on air sealing and blower door tests, you should. Its a more cost effective approach than fretting over cavity insulation.

what Spingtime said. If you have any care in the world about energy savings, you would perform air sealing prior to insulation. Air infiltration is the single most robber of interior conditioned air. However, maybe I am assuming far to much, but by your comments on keeping the r value as low as possible, energy savings certainly is not that high of a priority for you. (ironically it is the only area in your house that will give you a pay back on investment and save you money the life of your home).

I'll check on the blower test. If we have a house wrap with an r value would that be added to the r value for the walls?
The recommend r value for an energy-efficient build from our utility company is r-15. I would think there would be a diminishing effect for the insulation after a certain point, lzerarc. If i weren't concerned with energy savings, i would not have asked the question:-) trying to be cost effective without going overboard.

We are in that general area (North Mississippi) and did R-60 something in our attic (batts and blown cellulose) and R-20something in our walls. It's been so long since we did the shop addition that I can't remember the exact numbers now. But we used foil faced foam on top of all of the sheathing and high density fiberglass for the cavities with 2x6 construction. We also insulated the slab because we planned radiant heat into the build. It was the best decision of the build! We had planned on hooking up the radiant heat flooring at some point down the road when the boiler could be afforded, and in the meantime, we've used two small space heaters to heat the shop. (10' ceilings, not 8') Two small space heaters can keep 18,000 cubic feet of steel machinery and vehicles perfectly comfortable because of the insulation level. Our two giant garage doors are the chinks in the armor, and they are R-15 or so. They were the highest R value garage doors we could find when we built. We may not have received full payback on our choices, but the difference in comfort level between the house and the shop is immediately noticeable. It's also much much quieter.

Which is why this fall's project is to retrofit the insulation levels of the house itself. We're tired of folks suggesting that we just move into the shop because it's better than the house. :) It's time for the house to catch up!r

thanks live wire and everyone else! i guess i need to call them quick, i think the insulation is going in this week.

If you are doing 2x6 framing with batts and house wrap, do not waste your money on a blower door test. All that will tell you is your house is very leaky and not efficient, which we already know with any code minimum construction type. However if you plan on caulking and air sealing EVERYTHING (which is too late at this point for a lot of areas) then yes, proceed with a blower door test (will be required as per 2012 energy code anyway, depending what is or isn't enforced in your area).
r-15 is by no means efficient for your area. In fact new 2012 energy codes for zone 3 are increasing to r-20 min. (or r 13 + r5" exterior foam, which is a lot better then r19 batts!)
If you are sticking with simple cavity wall insulation with no regard to thermal bridge heat losses nor infiltration limitations, then I would, at min, recommend a blown insulation such as fiberglass or cellulose (fiberglass giving you a slightly higher r per inch). If the budget allows spring for an expanding open cell foam (closed cell would be better, but cost more). This would also greatly reduce your infiltration at your walls (but still does not address thermal bridging or infiltration at truss bearing and box sills, around windows, etc).

If we have a house wrap with an r value would that be added to the r value for the walls?
like tyvecks radiant barrier housewrap?

don't think there are many house wraps with insulating
values.

foam sheathing boards eliminate the need for housewraps they also provide air sealing when seams are taped.

best of luck.

What many of the above posters are discussing is the difference between nominal R Value and the effective R Value of a building component.

Just filling a cavity wall with R15 doesn't mean that the wall achieves R15. Oversights in installation, thermal bridging, convective loss in loose fill insulation, thermal drift in foam insulation, settling etc. can greatly reduce the effective R Value.

Unfortunately, a week before the insulation is scheduled is too late to attack all the details that could have been addressed earlier in the design process.

If we have a house wrap with an r value would that be added to the R value for the walls?

Housewrap has no R value. But properly applied it can reduce air and water infiltration that will rob the insulation of its energy savings benefits. However, since housewrap is more often than not applied incorrectly, and counterproductively, I avoid it. Indeed, if your builder is only now thinking of applying it, I would be curious how he plans to integrate it with interior air /vapour barriers. Furthermore, many brands of housewrap are absolutely useless in performing the basic function of repelling water.

Every day for the past year I drive by a custom house under construction wrapped in Typar that will eventually command $3.5-$4 million. Problem? Typar degrades from UV exposure after a maximum 6 months.

Here is a link that might be useful: Making Sense of Housewraps

tyvek has a radaint barrier housewrap
that they claim has a R-4
personally as there are so many problems
with installing regular housewrap
I can't see them getting the rb housewrap
correctly installed.
add in that it will
need a 3/4" air space between it and the cladding..
and you'd better have the tyvek rep on hand
to get it done right.

oh and the fact that rb are for cooling climates
and only benefit in summer months..

the sun only hits one side of the house at a time
so that lessens the effectiveness even more.

its not a product that I recommend.
but I do recommend foil/foam sheathing boards
on exterior of walls with housewrap under or not
used at all. (builder's like housewraps)

best of luck

Installed corrctly, R.B. can be very effective in controlling heat loss in a home. That's what we accomplished on our build in the sierras and are very happy with the results. It's popularity is for controlling heat gain and as mentioned, is often installed incorrectly on roof sheathings as well as exterior walls. Even with an air space on exterior wall systems, you have to have the air space vented. Each "space" by way of furring strips simulating a stud wall with the exception of no upper and lower horizontal plates. You screen vent the bottom of the air,"stud", spaces with the top of those spaces leading up into a vented soffirt system or full on vent eaves so the trapped air in those spaces can travel up and out. Just having air spacing without a venting system would be as useless as just running R.B. as a wrap with no air spaces. For attics, it's far more effective to run the R.B on the underside of the rafters creating independent "air channels" between the R.B and the underside of the sheathing with a continous run ridgeventing, continous run soffit venting to allow the trapped air in each rafter space to have an avenue of escape. Using sheathing that is foil faced on one side for roof sheathing isn't as effective as installing the R.B. on the underside of the rafters similar to using an R.B. wrap on the walls no air space or no air space without ventilation.

Iam not so sure about that because it could be installed with a vented air space above it on the roof deck as well. Community should beware of any performance claims of RB, most of their beneficial applications can be found below. For the most part, ignore RB in favor of air sealing and insulation that is uninterrupted by thermal bridging.

Here is a link that might be useful: Oak Ridge National Labs Radiant Barrier Info

R.B. worked out on our build as a result of a gamble. We had the material so I did some homework and ran across someone who worked with it extensively during his carrer at NASA. He laid it all out for us and it paid off for our build. The application for us is controlling heat loss. It's not a method I would recommend to anyone, I put my faith in this guy like some folks here put it solely on studies. It wouldn't have broke the bank if it didn't work out, but the bottom line is any means of efficiency gained is highly dependent on geographical location and the correct install and application that works in your area of your build. Vent vs ventless, deflection vs. gain, airtight vs "breathable", and on and on and on.

Tyvek has a radaint barrier housewrap
that they claim has a R-4

Though, here their claim is R2 behind a 3/4" air gap. I wonder if the R2 includes the R value of the air film, 0.17.

I think we're quibbling about a tiny gain that in practice is virtually unachievable.

The choice of insulating material, workmanship and detailed air-sealing/reduced thermal bridging is much more important in reaching a cost effective R Value.

Here is a link that might be useful: How Heat Moves Through Homes

R-value isn't what R.B. is all about. It's miniscule if anything at best though there are distributors/retailers that will try to convince folks otherwise.

This says it best: "The choice of insulating material, workmanship and detailed air-sealing/reduced thermal bridging is much more important in reaching a cost effective R Value".

Should be one of the biggest concerns for any build in any area. Though not a big statistic fan, the sad truth is that it's not the bigger concern on most builds.

R.B. has it's place in certain areas of the country, again, if properly installed for the purpose of it's intention.

The O.P. why their only consideration is fiberglass batts, At this point it's obviously too late for the exterior, but there are still ways to make the inside work if it's not to late; batts installed?

Okay, so I waited too late to research this and it has made me sorta sick. However, there are some things I cannot change at this point. So here is what I have. Without telling me I made a huge mistake, you can just tell me what would work best at this point:-)
We did 2X4 exterior walls (didn't really think to ask for the 2X6 except as an afterthought. The radiant barrier is as already installed (I know it has those vents, but I know nothing else about how well it was put in place) and our Hardi Plank is in place and awaiting the painter to come prepare for the paint. Now I am faced with r-13 batts or a foam spray on exterior walls with r-13 batts, which the insulation guy said would get me about r-16. I'm not going to ask any more questions, becaue I do not want to know what all I did wrong in my forever house!

"foam spray on exterior walls with r-13 batts"

That would be your better choice of the two.

Loucie - just remember that you are talking with people who live a lot further North than you do. I have simple 2x4 with fiberglass batts in about your climate and don't really have an issue. You are also getting info from people who are passionate about efficient building. That means sometimes they go a little overboard in their verbage.

I will tell you that I spend about $1000 a year to condition my space and that is roughly 1/2 the average new house in my size and area -4500-5000 sqft.

Generally foaming the exterior walls is not worth it in your climate but see what it costs.

sighhhh. thank you:-)
one quote was $1600 extra to foam. it is a 3100 sq ft house.

I love complicating the situation when Iam not directly involved... Have you priced dense pack cellulose or BIB(blown in fiberglass)??

Airseal Airseal Airseal!!! before insulation. Focus on your foundation and ceiling plane.

$1600 isn't bad. That is for a thin layer - so called flash and batt?

is your spray foam full 3.5" thick or 1" and then batts? If so, that does not work the greatest since your batts are now compressed to nearly 1/3 their thickness, further reducing the effectiveness. If anything, shoot an inch of spray foam and then net and spray fiberglass. However this will be a big increase most likely. I would honestly recommend talking to your contractor about caulking the plates and framing around the windows, and considering net and blown blanket (fiberglass). This will give you roughly r-14-15 with the fiberglass at a 2.2-2.8 lb/sqft pressure, and also reducing air convection currents within your wall cavity. Batt insulation does nothing for this. The only thing batts are good for IMO is to make your arms itchy and throat sore.

However the best option would be to do an open cell foam for the full 3.5" if your budget can work (cheapest of the foam options). See if your $1600 was for closed or open cell...I am assuming open cell. Big difference between the 2 in performance and price. By foaming you can eliminate the need for caulking/sealing. However you will still want to do that at the top and bottom plates where there is no foam. Worse case, you should foam your box sills where your foundation meets the floor framing.

david cary-yes, it was for a thin layer.
lzerarc-thanks. i'll read again later and then talk to the contractor next week. i have a headache from all this! oh well.

To achieve the US Dept. of Energy recommended nominal values for walls, the OP could use high density FG (R-15), BIBs with blown fg at R-14 but likely to be tighter than the batts or blown cellulose, nominally R-12, but perhaps more effective than batts.

Flash and batt sounds like a great but practically problematic idea. Spray foamers can't place the foam that accurately. Your 3/4" -1" of foam is just as likely to be nil inches, providing neither sealing nor thermal value.

Full foam will obviously work. But over what payback period?

I'll just ditto what was said about thin foam. I think it makes the most sense in an attic with blown fiberglass above.

Full cavity foam is probably a $4k upcharge with a $100 a year savings. People do it around here (Raleigh,NC) on very expensive homes in areas without NG. Then the savings could be much greater since they are probably using propane rather than a heat pump.

The other issue I have read about the flash and batt is that it can cause moisture problems if not thick enough in some areas - not sure if that applies to your area or not. I have also heard that there are often problems with application evenness. It would do a good job of airsealing if done right, which is the most important part of an insulation job.

it can cause moisture problems if not thick enough in some area

In a predominantly cooling climate where the OP is, the impermeable insulation (foam etc.) should help move the first condensing surface to the exterior of the cavity rather than the backside of the gypsum wallboard. This is a good thing.

But inadequate foam "flash" lowers the R Value, does nothing for air leaks, and doesn't help move the condensing surface to the exterior of the cavity.

In a wall that already has a cavity (brick veneer cavity wall , etc.) an airspace might achieve an "effective" R value of about 1 (if conditions were perfect which they never are).

The "effective" R value of the cavity might be increased to 2 with a radiant weather/vapor barrier like DuPont's ThermaWrap but if the cavity was created for that purpose it would save energy to fill the space with insulation instead.

The bottom line is that radiant barriers are not cost effective in a wall and most manufacturers of sheathing with radiant foil facings do not recommend that they be used for walls. In my opinion DuPont has created ThermaWrap to enable commercial building owners to increase their LEED score.