dense pack cellulose specification
MadisonRenovations
| Posted in Energy, Heating & Insulation on
Does anyone have a specification for a dense pack cellulose retrofit installation handy that I could steal and pass to my insulation guy?
Things like >3.5 pcf (or is >3.0 pcf enough), bays will be examined for obstructions, alll gaps identified by thermal scan will be filled, etc.
Is a thermal scan worth the $250? I’m thinking it is, because I won’t have sealed around the window frames, which should leak like crazy, making a blower test ineffective at determining leaks. I figure I should get one so that I don’t have areas that can cause condensation against the sheathing, now the there will be fewer areas for air to go.
thoughts anyone?
thanks,
—mike…
Cambridge, MA
Replies
Beyond a PCF and done in a workmanlike manner ... and all cavities filled ... I think it is a bit over the top to do a thermal scan to check up on him. Ask him how he fills awkward areas ... that would be your guide to a spec that would deal with those issues. But, with all do respect to your wishes, sure you could require a thermal scan and a corrrection of weak areas. As for things like gaps around windows, etc. Is he responsible for foaming or otherwise sealing these small areas?
IMO you can tell if he did a reasonable job w/ a physical inspection. No need to prove he did it REALLY well ... kind of like xray a solder joint to make sure he got 1/16" minimum solder on the pipe. Does even the most stringent construction require this? I don't think so. Focus on more important aspect of energy that can result in a bigger impact ... e.g. the installation of the weathersripping around a door (especially the garage door). I respect the point of view, but think the priorities can/should be elsewhere ... after you are reasonably certain he is going to install in a reasonable workmanlike manner standard in the industry.
Clewless1 responded:
I think it is a bit over the top to do a thermal scan to check up on him.
He doesn't have a problem with the scan, other than it might be getting too warm to do it. The scan isn't that I think they will intentionally miss anyplace, but it's a 1925 house, and things aren't all smooth and slick in the (closed) cavities. Plaster and lath, plank sheathing with gaps, all kinds of places to get stuck. A few of the corners have angled 2x bracing going from about 2/3 up the corner stud down to the floor at the 2nd stud away, with the middle stud cut and not all that well secured.
After they're done, I'm having the siding and window casings replaced, and will seal around the windows then, and wrap the whole shebang.
The new construction was all high density PU foamed - all rafter bays and opened walls, so I'm really trying to tighten up this old beast, at least from air, but leaving as much vapor permeability as possible since there's not interior vapor barrier except the paint.
---mike...
There is always a time and place for everything. BTW ... you can use vapor retarder paint that gives you a perm rating under 1.0 (the code standard). It's not really too special. Can't recall how to determine the perm rating. Flat finish doesn't do it, but can't recall what does. It was routinely used in lieu of a vapor retarder in lots of new construction in the PacNW. Food for thought.
If you are redoing the whole exterior of the house, the insulation contractor should be able to get at nearly every crevice that is exposed to the elements. Three or four holes per bay and he should be able to pack in the cells.
Bruce
>If you are redoing the whole exterior of the house
Strip and re-side two walls; the other two sides have good siding
Other thing is coordination. I could have the insulation done, then call for siding and paint, or else I'd strip, get insulation, then finish, but then the sheathing would be unprotected in wet-in-spring New England, plus the power would be off for the whole time to move the service conduit away from the wall.
I guess I extended the assumptions too far. Best of luck
Bruce
Bruce,Thanks. Anyone have suggestions about how dense for a 1925 plaster and lath interior? I read >3.6 pcf makes a good air barrier, but somewhere else 3.0-3.5 is good enough. The insulator says they usually do 2.5 to keep the interior walls from blowing out.BTW, he said he'd do the IR scan for free as long as he didn't need to do a write-up, just to check for and note if there were any missed spots. And that was after I said I was willing to pay.---mike...
At 2.5 there could be settling over time.
At 2.5 there could be settling over time.
Right, that was the other part - settling. Is 3.0 sufficient, or higher? They said they could dial-in whatever I wanted, but were concerned about wall blow-out.
---mike...
3.0 is sufficient if that is all that the can handle. Anything that you put in there is going to be better.
If there is knob and tube in the walls and H.O. won't upgrade electrical we don't do those bays. Bottom line -do what you can.
Moe
Well.. if you search around you will read a lot of things saying 3.5 lb./cf. The manufacturer I used (Regal) says 3 pcf is good. I've also read 2 pcf somewhere (Mike Smith's Mooney Wall thread I think). Theoretically... anything denser than it's natural settled density should be fine.. in my case the cellulose I used had a natural settled density of 1.3 pcf. I have only done dense pack one time.. behind insulmesh. 3 pcf seems pretty easy to get.. I really packed in one bay (the first one I did, wasn't sure what i was doing).. a whole bag in one 9' bay which comes to like 4.75 pcf or so ... that was tight and could probably blow out old walls... but 3 pcf seems like it should be fine.
In retro fit applications with lath and plaster 3+pcf is a good job any no need to go any higher, just adds more risk of a blowout.
If the contractor is set up to do a thermal scan $250 is a good price for the piece of mind that comes with it. He will probably scan the job anyway just to see how well the crew did on the instillation. His added cost is just in printing out the scans and reporting the results back to you. If he doesn't own an IR camera $250 is a steal, it will cost him that much to get it done.
The scans can be helpful at resale time if that is a possibility at all.
Any deal that works for both of you is a "good" deal.
What are your plans for the windows? Not much use in insulating the walls and then cutting into them to replace the windows later.
I'm glad to see homeowners being "green".
Good luck on the project,
Garett
So the insulation is done. The installation guys complained about clogging after I made them dial it up to 3 pcf (vs. 2.0 where they started) and use an insertion tube vs. just holding the large hose against the hole in the siding. The next day, a scan was done from the inside (about 75 deg for a couple hours) rather than outside (prev night in the 30's, in the 40's during the test, no wind).The scans showed warm bays and cooler studs in general. But... there were a few bays that registered cooler than others. Today I checked two bays in particular from the inside with a bent copper ground wire (from 12/2 romex) that extended about 4 or 5 inches sideways from the hole. I could insert the wire fully until it scraped the sheathing. Going sideways, it could spin freely - nothing in the bay.I tested another bay and the wire didn't spin, but it inserted without noticeable resistance in any direction and I could jiggle it a bit.I had specified dense pack verbally, but since I wanted a thermal scan and the temperatures were rising, I had to rush the installation and the proposal that came a couple days before the install didn't specify density, only R-value. Guess I should have had him redo the proposal.I wanted dense pack because I'm neither replacing siding nor gutting the interior on the north wall, so I wanted the cells to act as an air barrier. Now that it's in (except where it isn't :-/ ), I think I'm stuck.As a note, it's a long haul out this way for them (they're in the far suburbs), but they do have business in the city from time to time, so it's not like they're just around the corner to come back.I just got their invoice; any suggestions on what to do?thanks,
---mike...Madison Renovations
Cambridge, Mass.
I'd start by doing some math. By knowing the wall area (or volume) they insulated you can figure how many bags it should have taken to get to 3.0 pcf. The insulation I used had coverage charts on the side of the bag for wall area (2x4 or 2x6) dense packed at 3.0 pcf.