Do not confuse the attic issue with an open ceiling in a metal building.
Insulation and vapor barrier underneath an unheated attic area has been
discussed before.
What you have is a standard metal building insulation package consisting
of fiberglass insulation ranging from 2" to 6" thick, factory laminated
to a white vinyl facing in a varying range of mil thicknesses and
strengths. Laminated in widths of 2' to 8', full length rolls eave to
peak or eave to eave, stapled and taped seams. Because it is pressed
tightly under the roof, there is no air space and consequently no
condensation between the insulation and the roof.
Ridge vents are supposed to relieve heat buildup under the roof in the
summer. Available operable (closable) or fixed (always open). A poor
idea best case, and I make a lot of money removing these guranteed roof
leaks and replacing with roof sheets. If you want to keep them,
definitely seal them off for the winter and heat away.
I heat my shop with a used mobile home heater. Uses oil, cost me $125,
mounted on a platform about 8' in the air. I have 14" ceilings,
insulated the overhead doors, and it keeps the area any temperature I
want it.
GPD4
On Wed, 8 Nov 2000 22:32:08 -0600 "Phil Ethier" <pethier@isd.net> writes:
>
> From: Keith Kaplan <keithka@Exchange.Microsoft.com>
> To: shop-talk@autox.team.net <shop-talk@autox.team.net>
> Date: Wednesday, November 08, 2000 12:29 PM
> Subject: Attic vents
>
>
> >
> >What's the actual purpose of attic vents? What am I trying to
> vent?
>
> Moisture and heat. Moisture rots stuff. Not good. Here where we
> have
> snow, heat escaping through the roof heats the shingles. Melts the
> snow.
> Water runs down to the eave area where it freezes. Ice dam forms.
> More
> water gets dammed and freezes. Ice backs up under shingles and
> destroys
> roof.
>
> >I've always thought the purpose was to prevent condensation in the
> >semi-heated area above the insulation. Is that right?
>
> Yes. Your attic should be cold and dry.
>
> >My new shop is a metal pole building (well, actually the poles are
> wood)
> >which has some kind of (blown-in?) insulation held between the
> metal
> >roof and a layer of heavy white plastic tarp-like material. Looks
> like
> >the white plastic was attached to the roof joists before the metal
> roof
> >panels were attached. So the insulation is pretty much sealed.
> There
> >are two ridge vents, which don't seem to do anything to vent the
> >insulation, but it sure seems like they'd let heat out of the shop.
>
>
> Vents are meant to be above insulation, in the part of the building
> that
> supposed to be cold. The insulation is supposed to keep the shop
> warm and
> the attic cold.
>
> >I'm hoping to install a natural gas shop heater this winter, but I
> don't
> >want the gas bills to be outrageous. What will I harm by closing
> off
> >those vents? I'm near Seattle, where it's not _that_ cold (never
> cold
> >enough to worry about ice dams), but it sure is wet a lot of the
> time.
>
>
> What you need is ceiling with a serious vapor barrier and insulation
> above
> it. My shop ceiling is, from the bottom up: White-painted
> hardboard; 8-mil
> plastic; 6-inch fiberglass batts beteween the joists; open-air
> attic.
> Ventilation in my case is that the attic area over the shop is open
> to the
> unheated and unsealed garage. The 8-foot portion of
> new-construction over
> the shop has soffit vents with wide plastic channels separating the
> ends of
> the fiberglass from the roof. The other 20 feet of the parking
> garage of
> course has the soffit vents too. The big garage door gets opened
> every day
> for the Saturn to do it's daily-driver thing, too. The shop door
> stays
> closed. I didn't even notice a jump in the gas bill since I have
> been
> heating the shop to 50 degrees all winter. It gets a LOT colder
> here than
> in Seattle.
>
> If my entire building was heated shop, and the attic was completely
> cut off,
> I'd want vents in the gable ends in addition to the soffit vents. I
> know
> that ridge-pole vents and mid-roof vents are popular, but I just
> hate to put
> anything through the shingles. I don't have anything disturbing the
> straight-gable roof, and that's the way I like it.
>
> >keithka
> >125 shifter kart
> >Elva 300 FJr.
>
>
> Phil Ethier Saint Paul Minnesota USA
> 1970 Lotus Europa, 1992 Saturn SL2, 1986 Suburban, 1962 Triumph TR4
> CT2846L
> LOON, MAC pethier@isd.net http://www.mnautox.com/
> "It makes a nice noise when it goes faster"
> - 4-year-old Adam, upon seeing a bitmap of Grandma Susie's TR4.
________________________________________________________________
|