Removing Insulation off of soffit..

paige2

We visited both Home Depot and Lowes today...priced out blown in insulation..and bought some baffles...They suggested that we install the baffles so every roof joist has one instead of the every other that is already there...then take the pink batts of insulation that were stuffed down that i removed at the base of the blown in and just insert them back in place against the baffles so we dont get the wind washing effect...I took some of the insulation rulers from the store and i am going to measure the height of the insulation throughout the attic and then we will rent the machine and blow in were it is needed...it looks to be only 6" deep as you get into the middle of the attic and towards the front and the highest point is near the back...I wish we had known that this was an issue before our home warranty for the interior ran out becasue i would be chasing the builders to come back and do the job correctly...live and learn i gues...ughhh lol

cschwehr

That is convenient since Lowes hasn't seen your roof and is more than happy to sell you twice the product even if it's not required.

Only put the channel where you have soffits, if you have continuous soffit venting, then yes - go ahead. If you had no fan and no exterior hole, but ran the piping for either, it's not effective and a waste of money.

In the case of venting, I would fill the void below the vent channel with a flat piece of EPS, cut to size with 1/2" 45 deg notches on the back side, then spray foamed (notches allow more sealing surface) to seal to prevent air from circumventing the channel and going through your batting or blown in... but that is not required and beyond what most people here recommend definitely.

HomeSealed

I think you mean XPS, but that's a good suggestion.

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cschwehr

You're entirely right, thanks for the correction.

HomeSealed

I appreciate the citing of your sources, but I have to question the "explain that stuff" numbers. The only way that energy loss through walls will approach 30% is if it includes the ceiling (which incidentally attic insulation/air-sealing addresses). A simple google search on energy loss will show 9 out of 10 sources put walls at that number when it includes the ceiling. The only way to see any type of bang for the buck improvement from sidewall insulation is 1) dense-packing an empty wall cavity, or 2) adding XPS to the exterior during siding installation. Spray foam is great, but cost prohibitive, and dense-packing a wall that already has r-11 or r-13 will result in little added benefit for the cost, especially in comparison to the attic. If you are unsure why the attic is so crucial, look up "stack effect".

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paige2

Actually Lowes didnt sell us anything we prices out both Lowes and Home Depot and HD was cheaper priced so we purchased the baffles from them and good thing we did..When i pulled back the batt insulation that was stuffed between the baffle and bottom of the roof joist that the builder had put in a noticed that the bottom of the baffles were butted right up against the wood (near the edge of the soffit overhang) so no air was getting up the baffle..I installed the new baffles about 2 inches away from the bottom of the roof. I stuck my hand down the ones the builder installed and there was no air flow..I could feel air flow coming up the ones I installed..I placed the batts of insulation back against the baffles not squashing them and pushed the blown in back in place...So hopefully we get more air flow and then we will be looking into adding more blow in insulation..Now we just have to remove the piece of styrofoam and base built around the hatch due to some mould growth there..I dont think the styrofoam was deep enough and was a snug fit so warm air must have leaked around it causing the mould...there is no wet spots or mould anywhere else in the attic..How deep should the styrofoam be? Anyone know how much it would cost to have closed cell spray foam insulation installed in a 1300 sq ft bungalow attic...I live in Innisfil Ontario..thanks for all of your input!!

Gary in WA

" A simple google search on energy loss will show 9 out of 10 sources put walls at that number when it includes the ceiling. The only way to see any type of bang for the buck improvement from sidewall insulation is 1) dense-packing an empty wall cavity, or 2) adding XPS to the exterior during siding installation. Spray foam is great, but cost prohibitive, and dense-packing a wall that already has r-11 or r-13 will result in little added benefit for the cost, especially in comparison to the attic. If you are unsure why the attic is so crucial, look up "stack effect"." ----- you kind of missed my point. With the reqired minimum R-value in the attic for the OP's location- as I said Building Department check, it would be wise to check if any insulation is in the walls. R-11 will give you convective loops inside the batts that move heat from the room to the top plate and out because of the thinner insulation there. Adding any amount over the required (R-49) attic insulation wouldn't be as good a payback for the money as adding wall insulation, if needed. After R-20, you are fighting for 1-3% as the articles explained. I am familiar with the stack effect and have been answering on that here for over a year.

If you push the f.g. up against the roof sheathing to stop wind-washing, you will create a thermal bridge from the top plate to the roof, wicking the heat right up.

Gary

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cschwehr

wha? Isn't f.g. naturally an insulator?

How can that be?

What about the mention I had about putting the foam below the vents?

Just curious.

HomeSealed

Come on now Gary, let's not change up what we are suggesting. You stated "You may want to upgrade the low density wall insulation with higher density material rather than putting all your money in the roof, a place for diminishing returns on the money"... That is not assuming that the ho has no insulation in the walls, unless by your definition, air is "low density wall insulation". Furthermore, it is quite evident that home does NOT have r-49 existing in the attic (based on the description), nor did I recommend adding insulation if it did. As for your comment on r-11 and the top-plate, that is why I am such a huge proponent of air-sealing-- top plates are covered.(and this addresses the thermal bridge concern as well).

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cschwehr

My antidotal experience suggests that if I wall is closed up with 2x6 in a newer home with fiberglass it would be of little benefit to install different insulation before other upgrades are done in the attic. I know a couple who installed new drywall, insulation and vapor on 2x4 studs with plaster that used to have very old fiberglass (they were told it would be better). Their bill is within a dollar this year for heating costs as before. This is also with new renovator windows on a 1960's house.

I heard it and first thing I thought was, wow - there was some good salesmanship on the contractors part.

I always look at attic sealing, insulation levels in attic, sill plates and any simple air leaks/vent sealing in the home. I'm not a contractor in that area - but it's always seemed like the fastest payoff for the labor (personally - not contracted out).

paige2

My house is only 8 yrs old as stated way above in my original post and full brick..i really dont want to start ripping out drywall in my house and adding insulation...lol but what i do want to do is add blown in insulation to the areas that are lacking like the 6" areas!!!! that obviously is the problem here....There is no way that was done to code especially here in Southern Ontario...Either the installer was an idiot or just decided to race through the job...Nobody commented on the foam baffles being butted up against the wood on the overhang by the builder..where the soffit is installed (not sure what you would call that right where the eaves trough would be installed) I was told to install the baffles about 2 inches from the bottom of the roof. Is that correct? Maybe I should get Mike Holmes to come to my house lol!! I would love to spray foam but can't afford it right now!!

nickelshine

Can we get a little more information on the "thermal wick". I think I understand the concept... contact between insulation and the sheathing, but... how about if the top plate was completely air sealed with foam?

Here's my situation as it stands: new continuous soffit venting, top plate seams foam sealed ( a struggle), air baffles in every bay, with R-49 batts at eaves. That's R-19 between joists plus R-30 (15" x 15") piece stuffed between vent baffles and bottom layer.

So the insulation is technically not in contact with the roof, but snug to the stapled baffle vent. Do you think this will still be a problem for ice dams or whatever?

billyh

I have a similar situation to Paige.

I just bought a house that is 60 years old and I looked at the soffits from inside the attic and insulation has been placed on top of them everywhere. The attic is end vented with whirly birds.

This winter, there was frost on the underside of the sheathing in the attic. I have sealed all of the air holes that I can find (there were quite a few) but I am also wondering if it would be a good idea to switch my venting to soffit and ridge before blowing insulation in?

The soffits are currently solid and not vented at all, but have the perforated covering. I was going to put in the rafter vents (moore?) and make a makeshift wind screen out of fiberglass insulation (the windscreens mentioned above are not available here).

One big catch is that I have run out of time to finish this before the end of the month and get an eco grant (I've been working my butt off on the house). Is it possible to put in the vents, the makeshift windscreen, then blow insulation in.... then at the end of March (in 10 days), cut the 4" slot in the soffit and take out any insulation that may still be blocking the vent? Basically, I am trying to put off removing the soffit covering from the exterior and cutting the vent because this will take a few days.

Thanks for any tips on this project.
I want to make sure I get it right before I blow in the insulation!

Gary in WA

Builders usually insulate to the minimum required by local Code. The least expensive insulation is low density. Some low density blow-in was tested and found a 30-50% reduction in R-value at 60-70* when 20*F. outside. Check out the density used in the test. Check out the similar low density insulation installed by builders today. R-19 f.g. batt used in walls is compressed to the 5-1/2” from 6-1/4” for a reduction to R-17. This R-19 is a low density insulation with inherent convective loops used in 2x6 walls, and R-11 was used in 2x4 walls. With the new energy codes, R-11 (low density) is no longer produced with R-13 (medium density) taking its place. This is all sited in my stated article on “The biggest loser” I already posted on #4. http://www.buildingscience.com/docum...archterm=insul

Cschwehr, you are correct using foam board on edge. Sorry I missed that! With R-5 per inch, 4” would give you R-20 or 96% heat flow reduction. As in my post #15 and a similar one here; http://www.buildings.com/ArticleDeta...1/Default.aspx So if your wall top plates happen to be heated, from the drywall ceiling/wall corner joint or the wall cavity convective loops depositing heat there, to 70*, the foam would stop 96% plus a little more due to conductive loss through the plates (5-1/2” wood is R-6.88 minus ? due to contact with the colder sheathing and siding). Rolled up, compressed fiberglass has the fibers in direct contact with others for good heat flow, no air space to slow the heat transfer; http://www.greenbuildingadvisor.com/...ort/html/12484 At a soffit, because of being exposed to the outside moisture, the f.g. will transfer heat even faster when wet; http://www.nrc-cnrc.gc.ca/eng/ibp/ir...ling-heat.html 200 times more effective, though I lost that reference……. I don’t have any heat loss figures on the top plate heat transfer to the roof sheathing, I don’t know of any testing yet. I would be curious though….. Perhaps its minimal, but why take that chance when you’re installing then?
Dense pack cellulose would solve the cold walls especially if a low density f.g. batt is existing, and help with the stack effect; http://www.wag-aic.org/1999/WAG_99_baker.pdf Just a hole in each stud bay through the drywall.

Install the continuous venting close to the fascia board for optimum air flow away from the house wall pressure, pp.616; http://books.google.com/books?id=Z8a...0vents&f=false

Gary

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