Replies

1. 
   Gabe_Martel | Jun 26, 1999 10:07pm | #1

   *
   You didn't mention what you were going to insulate or if you used or wanted to use the attic space. A little information about the rafter or truss construction would also help. Any reason why you can't put powered or wind driven roof vents or powered exhaust fans on the gable ends?

   Also, can you indicate the size of the attic and pitch of roof as well as roofing materials.

   The more relevant information you give the better informed the answers will be.

   Gabe

1. 
   Rich_Beckman | Jun 27, 1999 06:37am | #2

   *lprobert,You will probably get a lot of interesting responses, and you will find that they will not all agree. Some will say vent with this or that, others will say do not vent at all.BUT, everyone will agree on one thing. Before you put insulation on the attic floor, be sure to COMPLETELY seal the attic floor so NO air from the living area can get in. This includes sealing the cracks between the drywall and the top plate on all walls, and sealing around all penetrations: lights, ceiling fans, exhaust fans, etc.Just in case no one brings it up....On to the venting or lack thereof!Rich Beckman

1. 
   Gene_Leger_ | Jun 27, 1999 11:49pm | #3

   *lprobert. Rich gives good advice. however go firdst inot the cellar and seal all the opening in the basement ceiling.The chimney anmd the stack vent will have the largest openings. For chimney chase make a sheet metal collar out of aluminum sheeting. Do same forstack vent.Now go inot attic and seal all opening in attic floor. If you have a ceiling mounted bathroom exhaust fan, seal between the fan housing and the sheetrock.Gable-end louvered vents work only when the wind blow at them.When the wind is perpendicular to the ridge very little air gets inot the vent. What does get in goes in a very short distance and exits out of the same vent.The air flow pattern with these vents is over the attic floor where it doesn't belong. Power fans may drop the attic temperature 20-30 degrees, but it has little or no effect on the houses total air conditioning load. If you havbe a leaky ceiling the fans will cool off the house. but remember that these same fans will suck the heat out of the house in winter. Wind drive roof vents fail at the most crucial time: whe there is no wind. They can and do reverse bringing in snow and rain. Thousand of houses in Oklahoma have sand covered attic floor insulation brought in by wind driven--turbine -vents. Year and years of testing at Texax A&M prove they do not work. Theyu do not move air through an attic but only in the immediate vicinity of the vent. For a complete discussion of attic ventilation see my book, _Complete _Building_Construction_, 4th Edition published by Macmillan.Why do you want to ventilate the attic? Remember you cannot flush radiant heat out of an attic. If you insist on attic ventilation the only system that will work is a ridge vent with an external bsffle(Air Vent's Shingle Vent II) and in your case a so-called starter vent called ComboVent (800-298-7610.Stsay away from any other drip-edge vent. Do not attempt to use a ridge vent with the existing gable end vents. This defeats the reason for using a ridge vent Insulate you attic with cellulose insulation which is more effective at stopping radiant heat than is fiberglass insulation. GeneL..

1. 
   lprobert | Jun 28, 1999 07:42am | #4

   *Thanks for all the good responses, especially about sealing openings in the cielings. I hadn't thought about that. The openings around the DWV stack and chimney are well-sealed at the roof, but not necessarily below, and could still draw air up into the attic. The consensus seems to be: forget about the attic ventilation, seal the leaks, and insulate the attic.

1. 
   Matt_G. | Jun 29, 1999 07:17am | #5

   *Gene:Thanks for all the good info on my other post on attic ventilation.Gene et all:Re Gene's above comments, what materials/methods are most practical and effective for sealing the ceiling (attic floor) and crawl ceiling? Gene has already mentioned the metal collar, but what else do you suggest. My building jurisdiction requires all such sealing to be fire resistant, so I plan to get some fire proof caulk, but what about larger holes such as were the plumber "cut" the holes for the tub/shower drains? (Still don't understand why a 2 or 2.5" pipe needs a 8" hole!!) Plumber said use rock wool but that does not seem very impervious/permanent.I have read other posts in this forum about hanging the ceiling sheet rock before building the interior partitions, installing poly on the ceiling before the interior partitions, and not having any penetrations in the ceilings/floors, but none of this is practical for my situation.TIA

2. 
   Gene_Leger_ | Jun 30, 1999 12:36am | #6

   *MattG.You need an 8-inch hole when you use a chain saw.Ha. As a fire stop, or what is called safing insulation, rockwool is better(withstands higher tempertures) than fiberglass. Fiberglass does not stop air movement, if it did it wouldn't be used in furnace filters.The larger openings are too large to easily fill with caulk. Ask your building inspector what he'll allow. under the bathtub. GeneL

3. 
   andrew_d | Jul 08, 1999 04:41am | #7

   *On caulk: I found & bought a cylinder of the "intumescent" (sp?) caulk, which I believe is the true fireproof caulk. It expands when heated, sealing rather than disintegrating. They also make a putty or mastic-like substance, all fairly expensive. Are these necessary? (BTW, regular caulk burns.)Why not use sheet metal on the plumbing penetrations too? Or wood blocking even.

2. 
   lprobert | Jul 08, 1999 04:41am | #8

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   I have a small, 65 year-old, cottage-style house with a gable roof. The roof has the "snub cornice" type of construction, where the roof stops right at the outside edge of the walls, leaving no eaves. The attic, which is uninsulated, is currently ventilated by a small louver vent under each gable end. How can I improve the attic ventilation with this type of construction? I'd like to do this before I insulate.