I'm looking for suggestions about how to upgrade a vented cathedral ceiling covered with very nicely finished (albeit leaky) tongue and groove pine. Some specifics:


About 1/2 the assembly is vented from eave to ridge. The other 1/2 is tied into an accessible attic flat. Presumably, the 14" TJI's have poorly installed styrofoam proper vents. I don't believe they go all the way to the ridge and are not air sealed at all.


The 14" TJI is insulated with faced FGB (12"). The facing is installed to the warm side of the home.


There is a metal roof and the customer has no intention (or budget) to remove it and install rigid on the roof.


The tongue and groove is finished nicely with several coats of clear coat. It's a high end home and this assembly needs to be put back together perfectly.


The ceiling is peppered with recessed lights.


Each slope is 14' long and the room is 26' long.


I've noodled around with a few options based on the customer's budget and what we're hoping to achieve. They run the gamut from removing the T&G and FGB, installing sheetrock as an air barrier, dense packing the cavity, and re-installing the T&G. The ridge and eaves would be blocked and we'd have a hot roof. Moisture load in the home in low and managed.


Another option was to access the eave and ridge and 2 other area but removing strips of T&G. We'd then remove the FGB, block eaves and ridge, install 1" of CCF on the back side of the T&G (as an air barrier) and dense pack the cavity with cell. Might trap moisture, though?


How about removing sections of the T&G, removing FGB, and adding 3" of CCF to the underside of the roof then dense packing and re-installing T&G? Not a perfect air barrier but the likelihood of condensation is reduced from the foam.


Straight up dense pack the assembly? Just block the soffits/ ridge and keep the FGB?


I think creating a hot roof makes sense as it would be challenging to install a continuous vent from eave to ridge.


Like all T&G, the corners are leakiest although in this assembly, it was all leaky during my BD test.
Tongue and groove cathedrals without a proper air barrier (and poorly/ incorrectly vented) are a bugger! If anyone has any ideas on a reasonable way to make this assembly perform better, I'm open to suggestions.
Thanks!
Matt

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Replies to This Discussion

I hate to say this but budget wise & for looks, it would be easier, cleaner & cheaper to attack it from above. If you do remove the T&G look into a tool called the extractor as it is great at pulling the nails from the back

I don't know what the codes or exactly which climate zone where you are at in Maine but you need at least R20 air impermeable insulation added to either the underside or on top of the roof sheathing. If you come at it from below I would spray foam whereas from above I would lean more towards foam sheathing - 2 layers with offset seams For more: http://bit.ly/HotRoof 

Hi Matt,

Always super tough to fix these after they have been done so very wrong.  Tom Nichols just had a long thread on Linkedin on this very subject.  I didn't keep up with all of the posts but it might offer some advice.  I will read it later and re-post.

http://www.linkedin.com/groupItem?view=&srchtype=discussedNews&...

Can lights, no air barrier, and fiberglass insulation open to the flow of ventilation, not good.  R&R that T&G is going to be a bear, especially after it has been "finished nicely with several coats of clear coat".  Also, if that TJI is spaced 16" or 24" oc, then normal batt insulation does a poor job of filling the space between.  They make wider batts, but even with those it doesn't conform well around the bottom chord. 

I would avoid just dense packing what is there, moisture will still pass through the cellulose.  Any form of a hot roof, as Sean said, needs a substantial layer of spray or rigid foam to keep the inside surface above the dew point.  I'm assuming this is a year round home, not seasonal.

Back later.

Bud

The topic has been discussed ad infinitum at the linkedin group Bud shared.  I see this a lot; "High end home, but low budget."  Ironic to me.  If they want it fixed they need to pay the freight.  Do it right, or don't do it at all (or you'll buy it.)  My take; remove the t&g, throw the can lights away, remove the venting, install code-required insulation at a minimum, install drywall with finished joints/edges (durable air barrier), make provision for surface-mount light fixtures, reinstall the t&g, or find another nifty looking high-end finish product, and they'll likely go for it in a minute.

Hi Matt,

If you checked out Bud's link I'm sure you saw all of the ideas folks have on this.  Definitely no clear cut answers.  I would vote for the least intrusive method of opening the soffit, removing as much FGB you can and dense packing the rest to slow/stop air movement.  Reassemble and seal vent. 

For the lights, replace with sealed LED retrofits and caulk them in.

It's a tough situation no doubt.  Good luck

 Hi Matt,

The code in Maine does require a minimum of R20 impermeable insulation but it is important to note that this is based on a total insulation value of R49. If you can't get a total of R49 into the rafter space this R20 value isn't relevant.

Hi Thomas,  Ignoring the code for the moment we still need to follow best practices, like being sure the cold surface of that impermeable layer remains above the dew point.  Since local code officials have the final word, there is the place to start.  Once you know the total r-value required, then you can determine how much of that must be the outside impermeable insulation.

The unfortunate aspect here is air sealing is very important, but those beautiful T&G ceilings make that near impossible.

Bud

My thought is if the cold sheathing hasn't been a problem with the t&g and fiber why would it become one with sheetrock and dense packed cell, or even just adding dense packed cell.    We dense pack slopes on capes all the time and have yet to see an issue.  We make a real effort to control interior moisture as well.

The Op hasn't replied since his initial post so no idea as to where this stands.  But as posted, sheetrock was an option, but involved removing and reinstalling a very nice T&G ceiling.  That's no easy task.

But converting to a code compliant hot roof is also no easy task.  Improvements have to last longer than most of us will be around so science tends to error on the cautious side.  Dense packing an existing ceiling to the quality level necessary to ensure no moisture problems in the future would be a challenge.  The jobs I have seen where they tried to compress the fg with dense pack were far below the quality required.

One way or another this will end up being a major project if it is to be done correctly.

Bud

Thanks for all the comments. The customer did decide to move forward with the project and it went well. We carefully removed strips of the T&G at the eaves, in the middle of the ceiling, at the recessed lights, and near the ridge. We used ice and water shield to seal all the seams and then covered that with a thin layer of 2 part foam. In retrospect I would have used something like Siga tape but our method was effective. We blocked the soffit and ridge vents and then dense packed the cavities. The recessed lights were capped with Tenmats and air sealed. We ended up reducing air leakage in the home by a little over 70% which everyone was happy with. This project was featured as a case study by the Natural Resources Council of Maine both because the results were impressive (and the customers are extremely happy) but also because they financed it using an Efficiency Maine loan and also qualified for some rebates. 

Certainly, not all folks can finance a $25,000 loan but I feel like we could bring the price point down using Siga tape and refining our methods. Their T&G was pristine so it could be easier and cheaper in another home. All in all, the project went smoothly, the customers are happy, and we truly made a difference in how the home feels and performs.

Here is the link to the case study   CASE STUDY

Below are a few photos of the beginning stages of the project.

Hi Matt, thanks for the follow up.  It sure looks like it was a good project and great that they were able to do so much.  Many home owners are forced to do a little now and a little later but that would not have made these improvements tough.  Also read the Case Study, nice.

Bud

Very cool! Nice going!!!

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