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Old_school (Old_school)
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Username: Old_school

Post Number: 24
Registered: 01-2009
Posted on Wednesday, January 14, 2009 - 10:25 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

It depends on the "size" of the attic space. Think of the roof as an "umbrella" over the house. You can insulate the "house" as much as you want, but make sure that the Roof and attic can stay as close a possible to the outside temprature. Soffit vents with gable vents work quite well. Also, a soffit vent with a power vent in the gable blowing air out will draw the air in the soffits and keep the humidity and temprature in control.

If the attic is living space and the bottoms of the rafters are the ceiling joists, then what Joe says makes perfect sense.
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Shrllc (Shrllc)
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Username: Shrllc

Post Number: 30
Registered: 12-2008
Posted on Wednesday, January 14, 2009 - 04:24 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

As the need for insulation to minimize heating costs has increased, the use of insulation in old buildings has become very desirable. I like Joe's ideas.
Although ventilation may not have been the motive, the old traditional high back gutter in conjunction with a slate roof proves to this day, a great means for ventilation. As we all know, a slate roof installed over barn board, ventilates very well all on its own. The detail I have noticed was the exclusion of a fascia board in the construction of the soffit. The high back gutter rides right over the rafter tails and returns up the roof an additional 4 inches. “Fire stops” were loosely fitted which allowed for increased ventilation. The incorporation of metal step flashings on dormer sidewalls, skylights, ridges and hips also helps to increase the flow.
Additionally, in later buildings or where the high back gutter was eliminated I have noted that often venting of the soffit was not taken into account. Did the original craftsmen intend, when excluding the fascia, to allow for increased ventilation or was it simply an added bonus?
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Joe (Joe)
Senior Member
Username: Joe

Post Number: 353
Registered: 07-2006
Posted on Tuesday, January 13, 2009 - 05:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I have built all my buildings "old style," with 1" rough-sawn roof sheathing, 30 lb. felt, and roofing slates, and fully insulated them, with no problems at all, and no ventilation. However, I always use an interior vapor barrier (plastic) to prevent interior moisture from entering the roof space. If you don't, you will get condensation on the roof sheathing right away (in cold weather), insulation or not, to the extent that it will drip water like a leaking roof.

I should add that I do not enclose the eaves (no soffit). If I did, I would add ventilation inlets to the soffit.

You can also insulate old, slate-roofed buildings without adding ventilation to the roofs. I have only used fiberglass and rigid styrofoam between the rafters (not blown in foam or anything else). Again, an interior vapor barrier is imperative (in cold climates) and it's a good idea to keep an air space underneath the roof sheathing. You can create an air space by using a syrofoam baffle against the sheathing, or just by using less insulation than the space will allow.
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Slate_man (Slate_man)
Senior Member
Username: Slate_man

Post Number: 342
Registered: 01-2007
Posted on Tuesday, January 13, 2009 - 06:36 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Can you post a picture.
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Kwhord (Kwhord)
Senior Member
Username: Kwhord

Post Number: 135
Registered: 10-2006
Posted on Monday, January 12, 2009 - 09:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Drafty is a good thing. Keeps the walls dry.
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Old_school (Old_school)
Junior Member
Username: Old_school

Post Number: 19
Registered: 01-2009
Posted on Monday, January 12, 2009 - 09:39 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Most of the "older homes" had very little insulation and were drafty too. They were "venting" all by themselves. If and when you retro-fit them with a bunch of insulation, your problems will start unless you also vent them at the same time.
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Shrllc (Shrllc)
Member
Username: Shrllc

Post Number: 28
Registered: 12-2008
Posted on Monday, January 12, 2009 - 06:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I see that we all have many ideas for venting our slate roofs. In my 10 years of experience dealing with restoration, rather than new installations, we rarely rip a whole roof to replace flashings. I have witnessed most all of the 100+ yo roofs with a similar detail, which combines the copper/galvanized high back gutter and return with a slate roof. I am curious, have others seen that same detail which aids in the ventilation? I have the answer, curious what other restoration specialists have noticed that make the ventilation of old roofs unique

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