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stuffnsuch 04-09-2013 08:52 PM

Insulating 2 1/2 story attic room--with Dormers?
We have a 3rd floor living space that has a "multi-faceted" hip roof. The attic space is broken-up with dormer (rooms), and the peak above each dormer is 'dead space", cut-off from the rest of the attic.

Two of the dormers are small bedrooms, and the third is a bathroom.

There is a soffit vent (track) all the way around the perimeter of the roof, as we have about a 24" overhang. But, there are NO ridge vents, nor any kind of vent holes up near the peaks...anywhere!

These are kids rooms, and they become unbearable in the summer months. The attic side of the wall of these rooms does have fiberglass insulation.

We have some sheets of Styrofoam sheets (approx. 2' X 4' X 1"), and we have some rolls of silver radiant barrier.

If we used these Styrofoam sheets, do we put the radiant barrier against the fiberglass batting, and then the Styrofoam? Or, vice versa?

What should we do to the space above the ceiling of each dormer? (We would have to cut a small access hole, because it is closed.)

The roof rafters have no insulation.

How do we insulate this space so that it is livable...?

Thanks, ~

Mightygiving 04-09-2013 10:09 PM

Several things which you need to consider regarding this insulation project.

1. Proper roof ventilation so as to not prematurely destroy the exterior roofing materials
2. Existing access to the rafter area of the true roof in the areas which you describe as "dormer rooms and bathroom" and access to the rafter area in the non-dormer room and bathroom areas of the attic.

Roofs as I'm sure you are aware of per your discussion regarding the lack of draw vents near the, or ridge vents, at the peak areas of the house, need air flow from the soffit vent area to the draw vents at a point higher on the roof. Draft exhaust or Ridge vents need be installed.

So to allow flow of air at those tight (ceiling to rafter) installations one must use 22" x 4' Extruded Foam Rafter Vent in the space immediately below the true roof substrate (plywood) then fiberglass bat insullation below that then covered by the sheetrock. Any Dormer exterior walls or knee walls on the exterior side should be equally installed with fiberglass bat insulation to close off the living space from the attic dead space.

Additionally, placing a window treatment on all windows which allow heavy sunlight in would further decrease heat entry into the living areas.

stuffnsuch 04-11-2013 10:43 AM

Thanks MightyGiving!

The roof is steel that looks like slate tiles.

I can cut-in vents at the highest point in the open attic space, which would be at the top edge of the dormer allow draw.

But, what should I do about the peak above the dormer?

The peaks above the dormer rooms have Can lights, but it have no access hole. It seems that they (whoever renovated this house) did put insulation above the can lights, but probably not in the rafters--there is no insulation in the rafters anywhere.

If I do cut an access door, and add some kind of vent near the peak, (the way that the dormer room is built does not allow draw from the soffit around the perimeter of the base of the roof)...will convection make the heat rise and go out, or do I have to find some way (???) to add a lower vent hole?

Or, can I just pump that area full of that "blown" insulation?

The dormer rooms are about 8' wide on the floor, the flat part of the ceiling is about 2' wide. The angled part of the ceiling (the pitch) is about 30" wide, and I doubt there is any insulation...again, it is cut off from the rest of the attic.

As far as layering: Should I use that roll of mylar radiant barrier? Should I use the sheets of extruded polystyrene?

The walls (on the attic side of the dormers) do have fiberglass batting...but there are pipes and wires in the way, in many places.

I'm not sure about moisture barriers...if I use the styrofoam sheets, or the radiant barrier, do I stop short at the bottom and top?

Thanks in advance!

stuffnsuch 04-11-2013 11:13 AM


The flat part of the ceiling in one dormer is 15" and 11" in the other...not much of an access door could be cut.

The angled part of the ceiling that matches the pitch is about 40" all the dormer rooms.

nealtw 04-11-2013 03:30 PM

Just a couple questions. Do you know if the roof is hand framed or engineered trusses? Engineered trusses are built like a lot of triangle and every joint has metal plates across the joint of these triangles.
Do you think these rooms were part of the origanal build or finnished later?
How old is the house and do you have plaster or drywall?
Is the roof sheeting right against the rafters or are the 1x4s or 2x4s going the other way between the rafter and sheeting?

stuffnsuch 04-11-2013 04:11 PM

3 Attachment(s)
The house was built in 1923. Had a fire in the 70's...not sure how bad. The trusses are old, dark wood, 2 X 8 and some 2 X 10's. No metal plates.

The dormer rooms were added in the 80's..I think. There are many triangles that terminate at or just after the top of the dormer wall. The walls in the interior space of the dormer room is sheet rocked with thick fiberglass insulation behind it.

The sheeting or decking is against the 1 X 6's that go horizontally across the trusses...with a 1" -- 2" gap between. The 1 X 6's are attached to the top of the trusses (then the novaply, and then the metal roof). When we had it re-roofed 4 years ago...I was told that the 1 X 6 slats were breaking when they tried to put the metal roof on, so they had to re-sheet it (Not sure if that was correct, but I agreed, and paid for it).

Is there a way to attach a photo...? I'll check.



stuffnsuch 04-11-2013 04:15 PM

First photo shows all the hip joints
Second show the soffit at the bottom that goes all the way around the house
Third shows the top of the dormer room wall

I thought roofers did not put roofs on without vents anymore, I guess I should have reminded him!

nealtw 04-11-2013 04:54 PM

In todays houses built like this would have 2x10 rafters to allow for lots of insulation and areas like hip ends in finished spaces would be straped with 2x4 to allow air flow above.

There are few answers that you or may not like

1 Remove the drywall from the angled portioned of the ceiling and 3 1/2 inches to the rafters to allow for lots of insulation and air flow.

2 remove part of that drywall so you can attach air shoots to the decking and work in some batt insulation

3 Try to fish both in from below.

With all of the above you will need to open the flat part of the ceiling to insulate that and add a ridge vent for air movement and every closed cavity at the hips will need a vent.

4 Vent the area outside the room and do your best to fill all the spaces above with blown in insulation, no venting above.

5 same as 4 but insulate the whole roof and side walls, no venting, the whole attic is conditioned.

Mightygiving 04-13-2013 04:01 AM

1. All of the slate appearing steel roofing manufacturers today make a ridge vent system for their ridge caps courses. whether yours had one installed is something you would have to investigate and would look like a dark gap between the last course of the shingle course and have the steel ridge cap attached above it. From inside at the ridge you would see a plastic corregated plastic coated interwoven fiber looking materials at the peak of the roof, if looking from the attic up with the wood cut back approx. 2-1/2" each side of the peak. If you could see that, it would be ran at all ridges inclusive of the dormers ridges.

2. I agree with nealtw, that the only way to properly insulate the ceiling slopes and flats is to remove the sheetrock then do as I said in my previous post regarding Extruded Foam Rafter Venting to keep insulation off of the roof decking and insulate below it. Because trying to do a proper job without accessing the entire area would take you a lot of time and patching but not get the insulation properly set to condition the living spaces you are trying to cool off (summer) and warm up (winter).

3. window treatment - google 3M™ Sun Control Window Films the Ceramic or night vision series would drasticly reduce UV entry and allow for much cooler spaces.


GBR 04-14-2013 02:44 PM

With no insulation in the rafters (sloped ceilings), your rooms will be hot from the solar gain of the roofing. Demo the drywall and insulate, using either the vented system or unvented system (conditioned attic);

Location, location;


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