Off Topic, insulation

Jay_17

I am working on tightening up the envelope on my 1910 house. So during the residing job I am going to have the wall cavities filled with blown in insulation, most likely cellulose. I have no experience with this stuff, so what should I be aware of when hiring someone to install it? Any particular questions to ask or things to check out? How do I know they filled the right amount etc?
Along those lines, if anyone has a recommended installer in Northeast Connecticut, that would be a help too!
Between the fill and 3/4 inch of foam outside, I think the difference will be pretty noticable!
Jay

Brad White_98

Certification

as to density, coverage and final R-Value.

For cellulose, what is known as "Dense-Pack" is becoming the norm. Nu-Wool is one system. The material is blown in under about twice the pressure of older blown-in applications and the material is more granular so it flows better around obstructions. Less likely to clump and hang up.

It is claimed by the manufacturer that when applied to density it does not need a vapor barrier. The theory being that the density essentially stops airflow through the wall cavities and hence the moisture borne by it.

My take is that moisture is driven by vapor pressure and it takes a lot of air through the fabric of a wall to carry any appreciable amount of moisture through it compared to diffusion (normal molecules passing from moist indoors to dry outdoors).

Still, they stand by their system so get it in writing and what they expect to do if it fails or if they miss some spots as determined by thermograph or infra-red scanning. Ask if they do these also.

The notion of using rigid board on the outside troubles me for it may constitute a vapor barrier on the cold side of the wall. Moisture can stop there and being only R-3.8 or so compared with R-14 or so behind it in the cavity, that surface of the insulation board would be below the dewpoint.

I like continuous insulation systems for wall thermal integrity but only on the inside. Outside would be fine so long as it exceeds the interior insulation by at least 200% in general terms.

My $0.02

Brad

D107

have the same situation

I had blown-in cellulose installed. Though it was done in late winter so I don't yet have a full test of a winter, I'd say it's helped with heating and cooling. What you want to watch out for:

1-Make sure you spend time to identify and seal any holes on the inside of your envelope before the job is done. Radiator pipe entry points, holes in wall plaster, attic periphery. The stuff is blown in at high pressure and some will seep in anyway and leave a bit of fine dust around, but do the sealing. I also sealed my electrical outlets and switches with cheap styrofoam gaskets to contain the dust and for insulation well. got them at efi.org.

2-you might want to watch them do the job. Usually to do this they remove one clapboard near bottom and one higher up and drill holes in a row between the studs and pump both up and down. Sometimes due to wood firestops or other blockages they have to remove a third clapboard in between to be able to pump into that space. There were times, where, let's say above a roofed portico that blocked part of a clapboard or between the top of a window and an attic where I convinced them to drill another hole to reach another stud bay or remove another clapboard. I was also able to get them to fill the mini-roof of the attached porch by pumping from within a bedroom closet. The peak of the portico they also reached from inside.

3-They can sometimes forget to caulk all the seams of wherever they've made the clapboard cuts near the corner pieces or window frames.

4- As for verification, you can figure out your cubic footage of cellulose required and then keep track of the bags they use. I chose not to do this but I could see from their work that they were pumping to the point where it started piling out of the holes. You can get a guy with an infra-red camera afterwards--as I did--and check it that way. Turned out OK; just keep in mind that they usually can't get into the corners--not enough room--and the headers above windows and the studs will show up as conducting cold, but you can't do much about that.

As for the 3/4" rigid insulation. I am proposing to install
same size extruded polystyrene insulation over the clapboards and vinyl over that. I got some concerns from the Wall about moisture in winter not being able to pass through the insulation and causing rot on the clapboard surface.

I had a consult with an insulation specialist. He feels that having constructed a model similar to page 144 of Bulding Science's book 'cold climates', (see attached) that the perm factor of the 3/4" insulation--which is 1.2, is semi-permeable enough to allow moisture to leave. He said something that I don't quite understand, that the perm rate is not exactly cumulative like the R-factor. (Below a perm rate of 1 would be a problem, he advised.) He felt the overall permeability of the plaster, lathing, cellulose, sheathing, black paper, clapboards, rigid insulation and vinyl would be Ok.

Brad's comment about preferring that outside insulation be 200% of the inside is interesting, and mirrors a comment by another wallie Constantin who suggested that such a setup would be good because then the dewpoint would occur inside the external insulation and not cause rot. In the Building Science assembly, the dewpoint occurs on the cavity side of the sheathing, at least at the given outside temperature, which I gather is based on an average. "This assemblly has some exterior vapor resistance, but since this resistance is provided by insulating sheathing that also sufficiently warms the condensing surface--the cavity side of the sheathing--this assembly does not require a specific vapor resistance on the interior."

Seems like a complex issue to me; I hope Brad might see this post. This area (NY, CT) is a tough climate both cold and hot/humid. The specialist I used recommends a 'flow-through' design. That the moisture will dry to the dry side where the humidity is less at that time. In winter dry side would be outer, summer (with AC) the inside wall.

Good luck,

David

Harold

If you strip the siding you can do a closed cell urethane foam spray. This seals all the penetrations/cracks, has the highest R value of any blown insulation, is not premeable to moisture, and if done right for the climate, moves the location of the condensation point into the foam (hence, no condensation inside the walls).

Down side - expensive. Hard to get into some of the nooks and crannies. But other blowing has this problem as well. Look at the walls and talk to the applier. Stuff something into areas they can't fill but can still seal over the material you have stuffed.

David Zierke

Did you look into Air Krete, I like the stuff and in your area you should be able to find an installer

www.airkrete.com


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