Home>Discussions>INSULATION & HVAC>Insulation, venting - how does all of this work?
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Insulation, venting - how does all of this work?

Dear folks,

The house is a 1942 cape cod, in Ohio. Roof hits external walls with no overhang. Currently, the attic has a bedroom carved out of it, leaving two triangular-shaped storage areas to it's left and right. There's also a triangle above the bedroom (under the peak of the roof), but I have no idea what's there. There are gable-end vents (they probably open into the "triangle" above the bedroom and below the peak).

The storage areas seem insulated ok, though the fiberglass is mixed with a lot of dust, random little crap, and a lot of mouse droppings (the flooring nailed over the fiberglass is rather sub-par) The fiberglass covers the roof side, the bedroom wall, and the floor. In most places they're continuous rolls (it starts being on the floor, moves up the inside of the roof and finishes on the bedroom wall.

The roof is about to be changed. The roofing company wants to install a ridgetop vent (I'm for that), and also install these funny metal dealies that will basically add a soffit vent above my gutters.

The roofing guy swears this will work.

Will that actually work?
Is there a problem with there not being a gap, as such, in the insulation at the joing between the roof and the exterior walls?
How would one optimally insulate these spaces?

Re: Insulation, venting - how does all of this work?

There are several article on-line that discuss this. Try searching on "attic insulation." Here is a pretty good discussion, if not a bit in depth, on how roofs and ventilation work: http://www.factsfacts.com/MyHomeRepair/ventilation.htm.

The big idea is that air should come up through the eaves and exhaust out a ridge vent. That keeps air circulating around the wood that the roofing materials (ie. shingles, slate, etc.) and is called a convection cell. This kind of air circulation extends the roofing material's life, prevents mold, etc. Insulation is placed against the interior walls so that the air circulating under your roof doesn't cool or cook your living area, depending on the season.

In my house, they finished an attic and put insulation right against the roofing, between the rafters. When they did it, they plugged the "jog" between the wall and the roof; which I've been unplugging as time permits.

Timothy Miller
Re: Insulation, venting - how does all of this work?

Howdy, the adding a continuous ridge cap vent will allow the hot air to rise out of the attic by having cooler air enter threw the gable end vents. You mention gable end vents. Can you tell if air can flow above the storage areas and over the rooms ceiling? If it can then the gabel vents and ridge cap vent will allow the air to circulate. Is the roof top vent a ridge cap vent? if mot there are these 1'by1' vents that you can have installed near the peak of the roof( they kind of look like darth vadars helmet). So you can add these vents across the roof in order to vent the different sections of attic space if there are areas that are blocked by the room...
The metal vents are the rectangles or little circular disks? Either works but when you say above your gutters this is odd unless your gutters are installed like the ones in Europe that actually hang below the fascia trim board. Without sofits or is it without enclosed sofits?

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