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OT: Home Insulation Help Needed

JohnMartin

Hot Rolled
Joined
Jul 8, 2006
Location
Cumberland, Maine
One of my sons recently purchased his first home, a Lincoln Logs kit cabin built in about 2005. It was built by the owner’s son, and a lot of what I’ve seen is pretty questionable. Interior is cathedral ceiling, mostly T&G V match pine boards. Rafters are 2x12, on 24” centers. Roof is asphalt shingles, with ridge vent.

Here’s the insulation situation. The only place I can see the roof insulation is in the crawl spaces behind the knee walls in the loft. Rather than use 23” insulation - which would have been correct for the 24” on center joists - they instead used the 15” batts (R38, faced) designed for 16” on center joists, with a cut 8” piece alongside. There was no attempt to tape or otherwise join the pieces. There is one batt from about the top of the crawl space down to about two feet from the floor, and another 4’ piece from there down - which means that about 2’ of it is stuffed into the soffit. No vents or baffles are present. They did, for some reason, staple cardboard to the underside of the roof sheathing. Squirrels have gotten in and made a terrible mess of things, and the insulation has been pulled down in many places. Our plan is to pull out the ripped insulation that we can get to in the crawl space and replace it with the correct 23” faced R38 batts. Roof insulation that we cannot get to from the crawl space will stay as is.

Here are my questions:

1. How far - if at all - should the new batts be stuffed down into the soffits? The soffits are properly vented at the bottom.

2. Should we be using baffles or vent panels under the new insulation? Given that there are no vents the rest of the way up from the top of the crawl spaces to the ridge vent, I can’t see that they would do much good. Perhaps one of the J-shaped baffle vents part way down into the soffit?

I realize that proper installation would have had rafter vents going all the way to the ridge, but that area is inaccessible now.

Thanks,

John
 

deltap

Cast Iron
Joined
Sep 3, 2004
Location
Wisconsin, USA
Depends on where you live. Maine has extreme winter weather. Ventilated roof is the least troublesome system in harsh climates. Insulation where roof meets outer wall need only extend to outer wall line. Vapor resistant facing should only be used on the warm side of a panel. If you don't leave an area for air to circulate upward at the eave line, you will get heat transfer to the shingles causing ice damming on the shingles. When the snow melts, water ponds behind the ice dam causing the roof to leak. Higher insulation levels require more careful moisture control. Mold and rot are the result of not controlling moisture. This man from your part of the country has been the authority on this subject for a long time.
Joseph Lstiburek
Engineer
You can get his books or find him on youtube.
 

SteveF

Titanium
Joined
Jul 4, 2004
Location
central NC
I would suggest your son sign up for an online subscription to Journal of Light Construction. Then he can look up large number of articles written by and for the construction trades on how to correctly do things. The other good magazine is Fine Home Building.



Lstiburek also has published some excellent work and you can find his organization here:



Steve
 

gustafson

Diamond
Joined
Sep 4, 2002
Location
People's Republic
I would suggest your son sign up for an online subscription to Journal of Light Construction. Then he can look up large number of articles written by and for the construction trades on how to correctly do things. The other good magazine is Fine Home Building.



Lstiburek also has published some excellent work and you can find his organization here:



Steve
Greenbuildingadvisor.com is connected with the above, and a great resource.
You pretty much know the correct answer is to rip it out and do over. With the price of energy, it might be worth pondering that pain, as you will not have to do it twice.
Airtightness is as important as insulation and is really tough in log homes, but it is worth trying to chase that. Holes in the bottom of the house create a 'stack effect' with holes in the top of the house and lose more heat than you would think
 

JohnMartin

Hot Rolled
Joined
Jul 8, 2006
Location
Cumberland, Maine
Thanks very much for all the good replies.

The only part of the roof insulation that is accessible now is that which is behind the knee walls. The cathedral roof is finished with V match T&G pine, and there is no way that we want to remove that to get at the insulation underneath. It’s our guess that they used the same insulation there as is visible in the knee wall crawl spaces - 15” and 8” R38 faced batts side by side. But it’s not a problem, as the ceiling keeps it in place.

It’s in the knee walls that there is a problem. Squirrels have gotten in and torn up the insulation. (He trapped and released about 25 of them last winter - almost all flying squirrels. And they were released far enough away that none would have come back.). With the side by side batts, not joined, most are hanging down. So our plan is just to replace those that are hanging and torn with the correct size 23” batts.

But the two main questions are:

1. Given that there are no rafter vents up above the knee wall area, does it make any sense to install them in the knee wall sections?

2. The original batts were stuffed right down into the soffits. I would plan to stuff the new batts only a short distance into the soffits, leaving the bottom of the soffits open. Make sense?

John
down to 11 here on the mountain in New Hampshire last night, and eager to get to work
 

APD

Stainless
Joined
Nov 5, 2005
Location
Hudson Valley, NY
Is there venting at the ridge?
The purpose of venting is to provide air on the underside of the roof sheathing, this helps reduce condensation, Ice damming, and allow the wood to dry out when condensation occurs.
In houses where the roof is spray foamed, it is essentially air tight, and condensation will not occur on the interior side of the roof sheathing. Fully spray foamed houses usually are so tight they require HRV or ERV to allow fresh air exchanges.
Fiberglass batting is the worst type of insulation, it leaks a lot, especially when installed poorly...as yours was. Venting of a fiberglass insulated roof is good practice. When built, they should have created a continuous air path from eave to ridge, with baffles behind the insulation. Hottest air at the ridge will draw in cooler air from the soffit vents.

However, if your ridge is not vented, the soffit vents are nearly worthless. If it is vented, and they didn't leave space behind the insulation, its better, but not ideal, as there will be much less air movement on the roof sheathing.
If there is no ridge vent, then you can block off the soffits, but also expect moisture to be trapped.
If there is a ridge a vent, put baffles behind the insulation, to leave an air gap, even if it is blocked further up the roof, at least you know you've done the what's appropriate even though the others before you didn't.
You want something like this:
When I bought my house it had FG insulation in the rafters with no ridge vent, eave vents, or air space . Condensation would form on the recessed can lights and drip sometimes.....until I cut in a roof vent . Condensation stopped, and then In 2019 I ripped the roof off for an addition and got rid of the shit FG insulation.
 
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guythatbrews

Hot Rolled
Joined
Dec 14, 2017
Location
MO, USA
I have a similar situation. 625 sq ft lake cabin added onto up to 2500 sq ft 25 years ago by others. Amateur others with amateur buddies with lots of beer involved according to my old neighbor. And back the about zero inspection and code enforcement. Sounds like your place may be the same situation.

Lots of cathedral ceilings. I'd never have a house with cathedral ceilings again. The ceiling/roof insulation stopped short of the walls by 0 ft to 2 ft when I bought the place 15 years ago. Perforated vinyl soffits. The wind blew through the ceiling at gale force, that is between the ceiling and under the insulation. And like you it was impossible to vent properly.

This is Missouri so it does get below zero from time to time. I decided to stuff the voids with batt insulation and block the rafter tails just outside the walls with 2" styrofoam board, caulked in place. I have not detected any moisture problems. Of course it is hard to tell up in the ceiling. And the house is pretty dry, humidity-wise. The bath ceilings are vented more or less correctly so that helps.

In your situation i would not extend the insulation down into the eaves, but i would try to ensure wind would not be able to blow through the soffit vents under the insulation. Sounds like the work was shoddy initially and that might help due to lots af air leakage making for ad hoc ventilation.

I also had damage from a big coon looking for shelter from my dog. The house is built on a hill at the lake and at the back one spot the eave comes within a few feet of the ground. The coon tore the soffit loose and crawled up in the rafter space along with my little dog. It's a long story but 4 or 5 holes in the ceiling, a coon bite, and rabies shots later, I nailed OSB under the vinyl soffit so that wouldn't happen again. My little bitch dog came out unscathed, happy as could be.
 

guythatbrews

Hot Rolled
Joined
Dec 14, 2017
Location
MO, USA
As APD says, be sure you do what you can with ridge venting. My place has a flat ceiling for a bit under the vented ridge so maybe that helps a little. When the roof get replaced next year I'll have new better ridge vents installed and gable vents installed, too.
 








 
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