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Old 08-09-2009, 07:56 PM   #1
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Hi There. I was wondering if anyone could help me? I need some advice.

We have a big detached two-story garage that needs new shingles for the roof. There is not an attic, per se. The second floor is only a half-open loft-type studio, very rough, that we use mostly for storage. So far the ceiling is just open framing on the inside. There is insulation installed under the roof which is attached directly to the ceiling. There is no gap between ceiling and insulation to allow for any airflow. Then there is plastic sheeting over the insulation to provide, I assume, a vapor barrier (stapled to the ceiling beams) just as it was done on the walls. The ceiling was insulated exactly the same way as the walls and i have never seen ceilings done this way before now.

My questions are concerning the insulation and the need to vent when we reroof. We only use the garage to store vehicles, tools and lawn furniture. There is plenty of air circulation below but it does get awfully hot upstairs. (However, we aren't storing Monets, if you know what I mean so that is not a huge concern.)

These are my questions and concerns:

1. Is there any danger leaving the insulation the way it is? Assuming there is no danger, then, when I leave the insulation where it is do I not vent it?

Or when i leave the insulation where it is should I do some creative venting? (i.e. bring down/extend vent tubing below the insulation)? Without a gap, would that not defeat the purpose of an airvent? Might let out hot air but not help with moisture. I am not sure.

2. Or, if i should i move the insulation (yellow fiberglass kind), can I create a 4-6" airflow gap between it and the ceiling or does it need to be an attic-like set-up of three feet or whatever?

I am so confused. I know there is also some debate on whether to vent or not to vent but i was assuming that was for houses and structures with attics and attached garages. I know venting is said to extend the life of the roof/shingles and regulate heat and moisture inside the structure. i don't want to go through the time and expense reroofing only to have to do it over again in a short time. I also do not want to create extra expense if work not necessary.I have two conflicting points of views with two different handy men I'm considering contracting.


Last edited by debster; 08-09-2009 at 08:00 PM.
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Old 08-09-2009, 08:38 PM   #2
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You don't want the situation you have now.

You have poly, the insulation, then another vapor barrier persay (ie sheathing). This is not good. The moisture that makes it past your poly now forms on the bottom of the sheathing and probably turns to frost.

You have to have it completely sealed from the bottom plate all the way up (almost impossible) or vent the ceiling.

Take the insulation down, put in chutes from the top plate to the peak, reinstall insulation and poly. Then use a ridge vent. This will create your best situation.

Venting is a benefit in the winter and summer, as long as the insulating is done correctly.

Any more info would be helpful.

Is it heated? Cooled? garage doors? how many? loft separated by a wall from the rest of the lower area?

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Old 08-09-2009, 08:39 PM   #3
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Just to add...........this is not handyman type work.
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Old 08-10-2009, 03:26 PM   #4
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Thanks, MJ. I went to Home Depot and bought styrofoam sheathing (spacers). Will take down the insulation, install sheathing, put insulation back up and then the poly. I will have a contractor roof the outside and put in the vent and perhaps help finish the underside.

There is a half-wall separating the loft from the open rafters to the cars below. There are three garage doors for cars (one for an RV) and three people doors: one into workshop, one into an addition ground level office area (with a furnace) which allows outside access to yard. Finally, there is one door from office to car area (within the garage).

Upstairs in the loft, there are several windows with crank openers. The windows on the ground floor do not open. Oh, there is also a door in the loft that leads outside to a balcony which isn't sealed very well. Huge but a real fixer-upper. Lots of drafts and activity in and out daily.

The buildings are 30 years old and not much improvements done in those years, I think. We've been here a couple of years and spent most of the time fixing the house. But now the shingles are curling up severely on the garage and I want to fix that before the roof leaks.
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Old 08-10-2009, 03:29 PM   #5
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P.s. the office is a separated add-on to the rest of the garage. That is where the furnace is. The roof there is separate and not a concern .. it is a flat roof and we haven't had any trouble signs with that part of the garage.

also, yes, it is very hot up top in "loft" and rafters. Cool below where the cars are, tho. The shingles have curled on that half of the garage.

Last edited by debster; 08-10-2009 at 03:31 PM.
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Old 08-10-2009, 04:48 PM   #6
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Once you take it apart, you will see what needs to be done. Post some pics too.

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