Opinions on Wall Insulation???

D107

Eric L._2

Opinions on Wall Insulation???

What have you guys found to be good/great/adequate insulation for wall cavities? I mean something that really made a difference to the comfort level/energy usage in your homes. I will be reframing all of my exterior walls (ughh..) with 2x4 and was curious with the results some of you out there might have had with a similiar project. Thanks in advance.

Eric L.

Brad White_9

Insulation

Best bang for the buck I have seen recently is Dense-Pack Cellulose (Nu-Wool is one brand but it really is the process more than the material.) When confined in a cavity under pressure the density is such that it all but stops air movement and with it the gross moisture that may be carried with it, if the literature pans out. (They say "no vapor barrier needed" but I am skeptical of any such claims.)

These have to be blown in, a skrim reinforced plastic is stapled over the studs and the stuff is blown in. Fills cavities in amazing ways.

Fiberglass loses R at lower temperatures, blown or batt. Hard to predict.

Icynene and other foams have about the same R value as fiberglass or cellulose (3.3 or so per inch) but the INTEGRITY is key. Closed cell inert foam. Costs double what the fiber types do I am told but you control infiltration much better with these foams.

Rigid boards are a nice compromise. On my own home I had short fiber fiberglass blown in in the 1980's. Full 4-inch studs. In 1999 I gut renovated my second floor and the insulation was intact like a felt blanket. I kept that and went over all studs with 1.5" polyisocyanurate (gesundheit!) and finished with plywood, blueboard and plaster for an R-27 wall. Spans the studs so you have at minimum a good layer of quality over any gaps. Foil faced boards were taped with aluminum foil and screwed to the studs though the plywood with barn screws. Snug!

Continuous insulation as a concept is a great one.

Brad.

Weezbo

optima....

it has a new cousin with "stickyness called something like spider mesh. 2X8 advanced framing methods vynil,tyveck,osb,insulation vaporbarrier W/Tremco,sheet rock taped primed textured and painted...R-30.

Cold climate building practises.

Billy March

closed cell insulation

I was reading an article recently about this insulation product called Corbond. It is a closed cell spray foam insulation that has an R-value of over 7 per inch of product. So if you were spraying this into a stud wall that was 2 x 4 framing, you would wind up with total R-value of about 22. Pretty impressive to me.You can go a website called Corbond.com and get more information on it.

GMcD

Insulation vs Thermal bridging

It's the thermal bridging at the studs, top and bottom plates that get you. Even if you pack in the most high performance insulation in the world, the overall thermal resistance of the wall can be reduced by up to 25% by the amount of thermal bridging present. The Canadian Wood Council has some good narratives and details (especially for us cold climate folks) and you can surf through here:

http://www.cwc.ca/design/building_science/thermal_insulation/

To find more information.

D107

very helpful stuff; so before dense packing cellulose bottom and

top plates should be sealed. I guess that's not only to reduce heat loss, but reduce loose cellulose from flying through openings at the attic and basement floors during the installation.

The other difficulty is making sure the contractor figures out where the horizontal fire stops are that will block cellulose input so he can drill additional holes above or below the stop so you won't end up with blank areas. (Those infrared cameras can detect the blank areas but very few contractors have them and it costs alot to have a test done.) I guess if you know your total cubic feet of the area to be insulated you can keep count of how many bags of cellulose are being used.

S Ebels

Best bang for the buck

Forget fiberglass batts. They do nohtign for air infiltration. Obsolete product except for sound deadening in interior walls. Many folks don't realize that r-value is only half the heatloss equation. Air infiltration is at least as significant as how thick and dense your insulation is. Remember they make air filters out of fiberglass!

Nearly all the builders here in Northern Michigan use Nu-Wool sprayed in cellulose be it 2x4, 2x6 or even 2x8 construction. The best ones will go overtop the exterior of the house with 1/2" to 1" blueboard to help eliminate the thermal migration through the studs. 2x6 or 8 on 24" centers instead of 16" help with this too.

We wrapped my son in law's new place with Low-E house wrap last year and it seems to perform well. The house heats better than expected with just the 6" blown in walls.

If I were using 2x4 construction I would try to get at least an inch of foam on the outside if not more. Then seal it, seal it, seal it!

Constantin

Almost agree...

... but not quite, so please allow me to quibble. While Icynene and other low-density foams are indeed around R3.7 per inch, Corbond and heavier foams make it up to 6.5 or so after outgassing. Each has their place, I used both types of foam in our house, more can be read over at buildingscience.com about the pros and cons of each.

I happen to like Mooney walls because they address the thermal bridging issues rather well - start with one load-bearing set of studs, then nail another set at a 90° angle (i.e. horizontal) on top. Then blow that cavity full of dense-pack cellulose and you have a very, very tight wall with almost no bridging. SIPs and ICF homes are another variation on that theme of very little bridging losses.

However, Brad and I remain in violent agreement that fiberglass is pretty much useless and that cellulose is a cost-effective and efficient way to add a lot of insulation to a home. If I had had thicker walls to play with (and no historic considerations in the way) then cellulose and Mooney walls could have been in our cards also.

Another thing to consider is what to do about the windows and other penetrations. There isn't much point to making the walls super-thermally efficient if the windows leak heat like sieves. Our windows are considered pretty good, and they only make it to R3. Some windows make it to R8, but they're triple-pane monsters...

Brad White_9

Thanks, Constantin

Corbond is a product I am not familiar with, but that it gets to the R6 range is exciting. Happy to be corrected and I never had a violent agreeement before. This is a first!

There are other foams that are Icynene competitive in R value and cost to which I was referring. The Mooney Walls I have to see. Mooney has a cultish ring to it..

I have to get over to see your project some time. Fascinating stuff!

Weezbo

We use a similar method...

Frame insulate blue foam 2X's horizontal tremco and foam edge ,tape and vaporbarrier with wind barrier on exterior.

right now my buddy and i are thinking going with a slightly different "Bridge" after the visquine is in place staple& Tape 1/2" foam to the interior then rock it...we considered another idea or two last night, tape foam (foam tape) to the stud face vapor barrier that then install the rock....we are always Thinking ...just how Good er:) that's another topic:)

on another note i have him exploring the IQ Glass windows and the availability of them in triple pane...

condensation is a biggie in the whole scheme of things so one pretty much needs to design for their area. conduction losses are huge numbers as Geoff pointed out....

Ventilation is a Key deal also ,may as well chirp that up a bit... where the plates meet the roof trusses or rafters there needs to be something done at that point to insulate properly and to allow air movement across the top of that for ventilation.... once again there is lots of minor defugalties that will result should that aspect of the building envelope be overlooked....

Constantin

... All true...

... to a point. IIRC, Corbond is only at R7/inch when its fresh. Let it outgas and the R value will drop. Also, keep in mind that while Corbond has a very high R-value, the studs in your walls most likely do not.

Thus, doing away with "thermal bridging" is very important as the wall thickness increases... there is little to no benefit of increasing the wall thickness beyond a certain point if the heat transfer can telegraph past the insulation inside. Hence the Mooney wall and other ways of offsetting the studs such that the inner and the outer walls are not connected by anythign but insulation - like a SIP, really.

And, windows will always rear their heads and cause a lot of pain when it comes to heat gain and loss.

JB_8

Try tiger foam.com. Use 1" of foam then put fiberglass on top of the foam and you have moved the vapor barrier outside the house. Foam cost more than fiberglass so its the best of both things.

Mark Hunt

Also


attention must be paid regarding ACH when using any of the insulation methods mentioned here especially foam. A home that tight will almost certainly need mechanical ventilation. "Build it tight, vent it right."

Not many foam applicators in this part of NY and I have been told that it is quite expensive to tool up for it.

We recommend dense packed cellulose to our customers.

FG, btw, has not been tested for R value since the 1970's. The material being made now is a heck of a lot different than it was back then. Factor in wind wash and the effective r value can drop by 40%. So R-11 is really R-6.6.

Waste of money to use FG IMHO.

Mark H

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Ted Robinson

Where is the vapor barrier?

For cold weather construction you want the vapor barrier on the warm side - the inside edge- otherwise you will have condensation within the insulation!
My 2 cents worth

Kniggit

Installation

I have seen several insulation contractors in this area install a great product but not well, with voids, and large gaps, it goes without saying look as some of their previous jobs without sheetrock up if you can. Just remember the same thing goes for all trades, the product that gets installed will only work as well as the people that installed it.

Kniggit

jeff_51

since you are reframing

I would go with closed cell. By far the best in my opinion if you have full access. Then you can glue and screw the drywall, cause no vapor barrier needed, at that is a fact, not theory.

Eric L._2

Wall insulation??

Thanks everyone for all of your input, I will try and put it to good use..
Eric l.

nick_7

I am just an HO in northeast, but have owned a few homes and seen a few things. Fiberglass is a poor insulater, but it allows air (and moisture) movement. The NE is very humid. If you have an older wood home with a porous basement you will have substantial moisture wicking up into the house. If you retrofit dense insulation that blocks air you may have unintended moisture build-up in spots throughout the house that can lead to mold and/or rot. Plus, air must enter your home in order to have enough oxygen to breath. With that air will come lots of moisture. That moisture must leave the house somehow. A very tight home can prevent that. In my experience, unless your home was built carefully as a new home with many design features to prevent ground moisture from accumulating inside plus well-planned and executed ventilation, you need the house to breath properly to avoid moisture problems, so the house will need to have some level of planned air infiltration and exit.