I thought I would share some blower door results for the current house Im building. I own a blower door so I keep one installed after I insulate to screw around with. The house is 4700 square feet and 42,000 cubic feet. Construction is typical 16" on center, OSB sheathing, I joist floor system and a trussed roof. I seal certain joints/junctures as we frame and then picture frame every stud bay with 1 part foam, seal the double top plate. Rim joists are spray foamed and wall insulation was dense pack fiberglass. Attic is cellulose. The extra sealing measures during framing took maybe 3 hours total and around 3 cases of sealant, stud bays for the whole house will take maybe 6 gun cans of foam and 4-6 hours.
The first reading I took was 1350 cfm50, this was with the house very leaky as far as penetrations. 8 of 17 windows completely installed, 1 window missing entirely just 1" foam board wedged in place, 3 door frames tacked in with a partial bead of sealant, temp natural draft furnace, cull doors with no sweeps, drywall hung over poly on attic ceilings with 3-6" of cellulose installed, 3 scuttle holes blocked but not sealed. From here I will detail what was done and the result as best I can. Numbers are rounded to the closest 25 cfm result because of magnehelic gauges.
Test #2 1300 cfm50: Installed approx. 117 LF of sealant along the bottom plate (when we stand walls we lay down a bead of sealant, this is the second pass on the inside of the bottom plate)
Test #3 1250 cfm50: 42 LF (complete) garage side drywall hung only.
Test #4 1175 cfm50: air sealed attic side 3 light boxes, 2 recessed, 1 fan, 3 wires, 2 - 2" and 1 - 3" pipe, 9 wire penetrations (those were sealed from below previously) and 3 couple square inch gaps in our ceiling poly.
Test #5 1150 cfm50: installed 84 LF of btm plate sealant.
Test #6 1150 cfm50: installed 2nd floor btm plate sealant (approx. 128 LF)
Test #7 1075 cfm50: air sealed 80% 2nd floor ceiling.
Test #8 975 cfm50: spray foamed 2nd floor rim joist; finished 2nd floor ceiling air seal, fully insulated attic from 3-6" cellulose to 15". Today I quick ran a test and came in at 725 cfm50. This was the result of fully installing 5 windows that were previously tacked in with a quick bead of window foam. Also installed 2 door sweeps on my cull doors and installed most of the poly. The temporary furnace that was vented out a basement window came out and the new furnace was installed. 725 cfm50 is .99 ACH50 and 38" ELA according to my iTEC app and I could easily get this lower if I wanted to fairly easily based on my infrared scan while the blower door is running. I'm happy to answer any questions as I can, I know there are a lot of details I have left out but hope it gives a glimpse into the effect of some air sealing measures. I also installed a few stud bays with dense pack cellulose and a few with fiberglass batt to compare thermal images to scare away anyone looking at batting a house.

If someone tells me how to edit in paragraphs Ill take care of it, it didn't post like I typed it.

I believe someone mentioned in the past (I think) that you have to have a space between the paragraphs. Normally, you would hit 'enter' once to start a new para. but I believe you need to hit 'enter' 2x to leave a space between them.

greentree,

Which internet browser are you using to post entries?

I do have spaces typed out. Safari on iPad.

That might actually be a real bug in the apple code.
Try the double carriage return.
Sometimes, putting < br>in works, but without the space before the "br".

greentree - this forum is not apple friendly. As Hybrid suggests manually insert breaks. Or if you are quoting, you will see the break and double break codes in the quoted text. Just copy one set and then paste every time you want to return.
Interestingly, when you type in the quick reply area, returns work.

I use IE11. Sometimes I get spaces if I hit RETURN, sometimes I don't. It is completely random. So now if I want paragraphs I put in two BRs as ICFHybrid wrote two posts earlier (you can also put two Ps each between the <> symbols). It is annoying. I wish it was better (and you can upload pics as well).

I also installed a few stud bays with dense pack cellulose and a few with fiberglass batt to compare thermal images to scare away anyone looking at batting a house.

can you please explain more about this? I am interested.

I am also interested to know what a good/bad blower door reading actually is. The numbers don't mean much to me having zero experience with a blowerdoor test. Is 750cfm good? What is the typical range...?

Found this from a greenbuildingadvisor article:

Is my house tight?

Here are some comparison points to help interpret an ach50 reading:
•A 2002 study of 24 new Wisconsin homes showed a median air leakage of 3.9 ach50.
•New home builders in Minnesota routinely achieve 2.5 ach50.
•The Canadian R-2000 program has an airtightness standard of 1.5 ach50.
•The Passivhaus airtightness standard — a tough standard to achieve — is 0.6 ach50.

David Keefe, the manager of training services for Vermont Energy Investment Corporation, recently wrote an article on blower-door testing. “Houses with less than 5 or 6 ach50 are considered tight, and those over 20 are quite leaky, though these numbers can be misleading without considering other variables such as climate, house size, and old versus new construction,” Keefe wrote. “Tight houses tend to measure less than 1,200 cfm50, and moderately leaky homes measure between 1,500 and 2,500 cfm50. Homes that measure over 3,000 cfm50 are considered leaky.”

According to The Homeowner’s Guide to Renewable Energy by Dan Chiras, “A really good measurement is around 500 to 1,500 cfm50. The older houses we work on typically fall in the 6,500 to 8,500 cfm50 range.”

Surfsup,
I will attempt to post a thermal image of a fiberglass stud cavity and a dense pack cavity side by side with a blower door running, you can see every little crease and defect in the installation, and it's reasonable to say it is not possible to perfectly install batts in a normal framing situation, let alone survive through poly if installed and drywallers.
You are correct a cfm50 number alone doesn't mean much for discussion unless compared to volume or some other comparable factor, I posted cfm50 numbers to show reduction in a blower door reading as related to certain steps in the construction process.
I do put a bead of foam everywhere wall sheathing meets framing, it doesn't take as long as it sounds and it is very cost effective. For 1 part foam I usually use Touch N Seal All Weather Formula, I use Touch N Seal 600 bd ft kits for rim joists, narrow wall cavities, or other hard to reach areas.
Long term durability of this could be debatable, however if you were to tear a bead of cured foam off you would notice foam remains in the joint that has been "injected" by the gun and cannot be easily removed. I had some 7 year old foam (great stuff gun foam) exposed in my shop which was exposed to freeze/thaw and it maintained its seal. After experimenting with sealant, I believe the 1 part foam is way more durable, not to mention cheaper and faster.

When I say foaming stud bays I mean airsealing only, not foam for any insulation value. I'm trying to stop air from getting into my stud cavities and reducing my effective R value. The fiberglass batts I put in were the high density fiberglass R21 batts.

I did not use exterior foam, this is a spec house and unfortunately my target market doesn't give two sharts about exterior foam or any of the other insulation/airsealing measures I did for that matter, I had to draw the line somewhere.

Posted By Surfsup on 22 Jan 2014 08:29 AM
I seal certain joints/junctures as we frame and then picture frame every stud bay with 1 part foam, seal the double top plate.

Are you saying you put a bead of foam around the inside edge of each stud cavity? What foam are you using for this? This home is large and your readings are low for the blowerdoor. Nice work. I am building a 3200SF home and want to implement some of these techniques. I have a framing crew and will ask them to caulk the exterior base plate, etc but I fear they will cut corners.

I plan to place a layer of 1.5in rigid foam on the exterior so that 4x8 sheet will effectively "foam" the stud bays. I will just need to seal the 4x8 sheet joints where one panel butts into another with tape and/or foam. I was considering HD batts for the walls to save money (since I am already doing the rigid foam) and would appreciate more detail on your comments about the batt comparison. Did you have exterior foam as well?

You can use foam, or acoustic sealant to seal each stud bay to the sheathing. There are specialty  low rise foams/caulks being hawked by the insulation vendors expressly for that purposes as well.  (Owens Corning Pro-Pink, Knauf Eco-Seal, etc.)  Be sure to foam-seal the stud penetrations of lateral wiring runs too, not just the plate penetrations. 

Air moves in all directions- sealing the seams and edges of both the structural sheathing and insulating sheathing is of course necessary, but not sufficient, not by a long shot.  Taped/sealed rigid foam on the exterior is not even remotely comparable to foam-sealing the stud bays.

I took a quick test with the poly completely installed (over windows as well) and it was right around 700 cfm50.

The drywall hangers finished yesterday and as a result the window poly has been cut out. I did not seal the poly to the studs around windows so I was expecting the cfm50 number to creep up a bit, but it did the opposite and is now at 625 cfm50 with no taping or mudding done to the drywall.

The ProPink looks more suitable for me. The Knauf looks like too much setup. I assume if I blow in 5" of ocSPF I don't need to do any of this manual sealing...?

5" of open cell doesn't seal under plates, between plates, multiple plies of studs, leakage under studs at exterior sheathing seams, floor sheathing joints, window opening corners, wall plate joints, ect. Bottom line is there is no cure all other than putting in some time.

All you're really getting with spray foam is stud bay sealing and wall bay penetration sealing although their is big perceived value by Joe Public.

^^^ what HE said^^^

Well then maybe for Zone5 here in Chicago, I will use the 1.5in exterior rigid sealed with tape and seal the wall bays/plates, etc with caulk/foam really well, and use batts instead of ocSPF to same some money...this will depend on my budget.

I was also going to go with the smart vapor barrier (MemBrain or IntelloPlus) on the inside of the wall to let it breathe to the inside should condensation occur (we've had two weeks of -5F to -20F here in Chicago lately, so even with 1.5in rigid exterior there will likely be condensation on the wall sheathing at some point that will need to dry)

and use batts instead of ocSPF

Where have you seen that batts are a good alternative?

so even with 1.5in rigid exterior there will likely be condensation on the wall sheathing

An extra half inch might be worth it to avoid the condensation in the first place.

Batts are really a second-rate solution, but if you go that route, spring for rock wool or high density "cathedral ceiling" fiberglass.

Caulking well and damp-spraying cellulose would likely be cheaper, and have far fewer fit & compression defects. Cellulose is also protective of the structural wood since it "shares" the moisture load with the structural wood due to it's ability to adsorb moisture into it's hollow fiber structures without damage or loss of insulating function.

The extra half-inch of foam might even be cheaper than a smart vapor retarder, (especially) if you apply any value to your time.

BTW: Not that it really matters, but a bit of building-science 101: Technically you never get condensation ON unpainted wood the way you do with non-porous materials. What happens is that the wood takes up moisture as adsorbed moisture in inside the fibers. Adsorb behaves differently from liquid or frozen water- it's almost like alloying the water with the adsorb-host material. Leave a piece of dry (not green or pond-soaked) 2x4 on the porch overnight, and bring it in some morning when it's 0F, and notice how you never see liquid water or frost on the wood, though it might feel vaguely damp to the touch after it's been indoors awhile. The temperature of that wood is WELL below the indoor dew point. If you run the same experiment with something non porous you'll see some frost on formation in the first few minutes.

During cold weather the sheathing adsorbs and releases moisture from/to the entrained cavity air daily as the temperatures vary, and the dew point of the entrained air inside the wall cavity is the temperature of the sheathing, not the dew point of the conditioned space air. When the temperature of the sheathing is colder than the dew point of the conditioned space air there's a vapor-pressure difference between the cavity air and conditioned air, which drives moisture to diffuse through the paint. It's the net accumulation moisture in the cavity (and by extension, the sheathing, which is what's buffering the moisture) over time that matters. As long as the moisture content of the sheathing doesn't persist at a level that produces mold/rot as the weather warms, the assembly is fine. The colder the average temp of the sheathing, the greater the vapor-pressure difference between cavity air & conditioned air, and the greater the moisture quantity that gets pulled into the cavity over the winter.