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Rigid foam question

GunsandHoses's picture

I have am considering putting up 1" foam on the interior side of rafters on a cathedral ceiling, very bad ice daming going on and very difficult access to attic. Ceiling has R30 and blown 10". The attic has been airsealed and I think the T&G is a leaking mess and currently nailed to the rafters with no backing of any kind. Any thoughts would be great. If you need more detail please ask thanks in advance for your input guys.

G&H (post #207310, reply #1 of 10)

I had a little hard time following the make up of your ceiling.

See if I have this right. 

You have T&G boards as a finished ceiling.  Above that, no drywall?

I'm assuming this might be scissor trusses, as you mention attic?

If so-

despite what you think you have as air sealing, all those T's & G's are a path for warm air to make it's way up into the "attic" space.

Can lights or other penetrations-ceiling boxes for tracks or surface mounted fixtures?  These also have the potential of leaking air and with the wiring above probably could provide paths for the warm air to make it above the insulation.

At the low end of the finished board ceiling, what seals that from air passage? 

After a light snow or even a frosty morning, can you see areas of melt appear on the shingles?  I've seen individual cans melt a nice circle on a frosted roof.

 

What's there in the way of venting of this space above?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Rigid foam question (post #207310, reply #2 of 10)

Hi Calvin thanks for the input I am aware that the t&G is sucking the heat right to the roof. The roof is rafters with collar ties 12' off floor  pitch is 10-12 front, 8-12 back there are proper vents and airsealing has been done in the attic space acoustical caulk and can foam I know this is not enough and really hope that I am on the right path with the rigid foam, spray foam is not in the budget so we think we can acomplish the same thing with rigid. No can lights only 2 ceiling fans. As far as where the t&g meets wall I plan to open it up and close up end of rafter bays with rigid foam. Hope this helps this is pretty hard to explain. Thanks again!

G&H (post #207310, reply #3 of 10)

Ok, I guess I read it right.

Tape the seams on that foam.

 

Any noticeable "hot" spots when frost or light snow on the roof?  It'd be a bi ch to miss some major air leak that might need more detailing.

Also, Is there any Ice and water shield along the eaves?

Any flashing problems (such as not high enough, counterflashed- or maybe gooped up with black tar in an attempt to "flash")?

I agree, there's a need to seal above tongue and groove paneling, but even with the ice damns, it'd be nice to know there's no water entry possible.

 

Here, while air leaks do cause ice daming, hot sun during the day on a roof will tend to melt snow...........that freezes in/at the gutter.  The colder nights freeze that up, and the process continues the following days.  Keeping water out is the real deal.

Best of luck in this.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


rigid foam question (post #207310, reply #4 of 10)

I know the hot spots, no leaks in 20yrs new roof summer 2013 I forgot to mention there are three dormers on the 10-12 side not vented!!

G&H (post #207310, reply #7 of 10)

"close up end of rafter bays with rigid foam"

 

Remember to still allow the soffit vents to work.  What's up at the ridge, continuous ridge vent?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Rigid foam question (post #207310, reply #8 of 10)

Yes continuous rigid vent, the plan is to use foam to close end of bays and can foam for caulk, In one of your posts you mentioned snowmelt from the sun which I understand, I think that this project will keep conditioned air where it belongs, and overall be of great benefit for the ice dams. As for hot spots the snow melts at the point where the collar ties meet the rafters on the roof. I read your posts often and from one old hippie to another thanks for your input I value your opinion. Marc, Central New York

Central NY? (post #207310, reply #10 of 10)

Born in Rome (NY), brought up the first few years between Eagle Bay and Inlet.

Old hippie....................thanks.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Warm air leaking into roof? (post #207310, reply #5 of 10)

Are you writing that, the warm air from your home is rising into the roof and melting the snow?

Yes Thats what I imply! (post #207310, reply #9 of 10)

Yes Thats what I imply!

Warm air leaking into roof? (post #207310, reply #6 of 10)

Are you writing that, the warm air from your home is rising into the roof and melting the snow?