Attic Insulation Option - Top Wall Sealing?

[crybdr]

I have a quote from a reputable insulation contractor that I am ready to pull the trigger on. However, there is an option that I am unsure of...and I'm looking for input that anyone can provide.

At the bare minimum - I plan to have them put more insulation in the attic. Right now - I have the original (60's era) blown-in fire-retarded sawdust that is just barely covering the joists. It's pathetic, and I've been heating/cooling the outside world for quite some time - R20 at best, and that's generous. Their plan is to do the appropriate sealing, ducting, and blocking in order to blow in fiberglass to bring the level up to R50. This should make an immediately recognizable difference in heating and cooling my home from what I am told - and I believe them (am I wrong to believe them?). They will do some other specific things with regards to my house construction that made sense to me as both of us worked the flashlight around the attic, but I can't describe them sufficiently here. I trust the contractor - that's not the issue.

The additional option is to seal the interior and exterior 'top walls' with expanded urethane foam - prior to the attic insulation work. The estimator said it would improve efficiency - but admitted that it was probably only another 10% - and was hesitant to recommend it. Doing this would double the cost of the insulation work. One of my coworkers thinks I'm a fool for not doing the 'top wall' sealing....to be fair, he's completely 'gutting' and rebuilding his home - and he's planning on doing the 'top wall' sealing himself.

Does anyone here have any input regarding sealing the 'top walls'? I don't plan on being in my house more than 5 years and would rather spend the money on 'visible' improvements.

Thanks for any shared wisdom here,

coryb

[toolguy1000]

what, exactly, are "top walls"?

[conscience]

Pretty much that just means the tops of the walls where they terminate underneath the joists. Conditioned air can seep in behind the drywall and up through the wall cavities and release into the attic. Sealing them keeps that conditioned air out of the attic.

As far as is it worth it, for the price difference and the relatively little increase in performance you'd probably be better off investing that money in sealing your door and window openings which usually allow more air loss. Of course, you could always seal the top walls yourself with a couple of cans of expanding spray foam and save all that cash.

[parnelli]

I have a quote from a reputable insulation contractor that I am ready to pull the trigger on. However, there is an option that I am unsure of...and I'm looking for input that anyone can provide.

At the bare minimum - I plan to have them put more insulation in the attic. Right now - I have the original (60's era) blown-in fire-retarded sawdust that is just barely covering the joists. It's pathetic, and I've been heating/cooling the outside world for quite some time - R20 at best, and that's generous. Their plan is to do the appropriate sealing, ducting, and blocking in order to blow in fiberglass to bring the level up to R50. This should make an immediately recognizable difference in heating and cooling my home from what I am told - and I believe them (am I wrong to believe them?). They will do some other specific things with regards to my house construction that made sense to me as both of us worked the flashlight around the attic, but I can't describe them sufficiently here. I trust the contractor - that's not the issue.

The additional option is to seal the interior and exterior 'top walls' with expanded urethane foam - prior to the attic insulation work. The estimator said it would improve efficiency - but admitted that it was probably only another 10% - and was hesitant to recommend it. Doing this would double the cost of the insulation work. One of my coworkers thinks I'm a fool for not doing the 'top wall' sealing....to be fair, he's completely 'gutting' and rebuilding his home - and he's planning on doing the 'top wall' sealing himself.

Does anyone here have any input regarding sealing the 'top walls'? I don't plan on being in my house more than 5 years and would rather spend the money on 'visible' improvements.

Thanks for any shared wisdom here,

coryb

I don't have the time tonight to find the article, but you should be able to find something on the building science corporation website.

I just had a blower door/thermal imaging test done of my house a couple months ago. I've got R29 in the attic and while that's low for Chicago nowadays, it was not recommended to add to it- as it's not cost effective. Sealing the airleaks up there was recommended.

Basically the idea goes like: lots of open voids from basement up thru first,second and into attic. Plumbing, electrical etc. This creates a chimney effect and a)wastes energy and b)causes things like windows to be more drafty because the makeup air has to come from somewhere.

I've been told to go up there and seal and to seal the basement ceiling areas as well.

The other big thing from the attic was ceiling electrical boxes and insulation that had gotten 'moved' for conduit runs etc and then replaced. Where it wasn't replaced carefully (eg- in good contact with the drywall- the heat loss was pretty amazing. You could clearly see 15 degree temperature difference on the camera from where I had run conduit a year ago, and apparently didn't put the insulation back well enough- even though from up in the attic to the naked eye it looked fine

[crybdr]

Indeed....'top wall' or 'top plate' sealing is applying expanding foam to the tops of the walls as they terminate in the attic - clarified with the contractor.

I have a roof with a fairly shallow pitch. I've been in the attic before installing a bathroom fan, and trying to find a rodent that I heard scurrying around the soffit. I had an impossible time getting close enough to the edge to even see the top plates, let alone the soffit.

My walls are plaster lath, most or all of the fixture locations are original, and windows are brand new Andersons professionally installed.

The contractor reiterated that the sealing could pay itself off in about 20 years - which is too long for me. I like the idea of sealing doors and other 'holes' that I can get to. I'm frankly not small or flat enough to work expanding foam into the perimeter of the attic - which is probably why the quote is high for this service.

Thanks for the insight - I'll think more about this before I move ahead.

Best,

coryb

[toolguy1000]

is this process of sealiing the top wall going to prevent air from passing through the soffit vents up the underside of the sheathing in the attic and out the ridge/gable vents?

[pelligrini]

Sounds like it's just sealing the penetrations in the top plate (vent stacks, elec holes, etc.) and possibly sealing the edges of the sheetrock to the top plate. It should not affect the attic ventilation.

I would probably not spend the money on it, the return on the cost is marginal. For it to be really effective you also need to seal up all ceiling penetrations (can lights, J-boxes, etc.)

[crybdr]

Yes. 'Top plate' sealing wouldn't affect attic ventilation - just the amount of air 'leaking' through the 'top plates' of the walls into the attic. The flow of air through the soffits through the roof is unaffected.

The contractor will 'seal' the major accessible 'holes' into the attic (soil stacks, buttresses, vent fans, etc.) but 'top plates' at the walls are beyond the quote.

Thanks to everyone here for their input. I have made a decision.

Best,

coryb