been looking to add some insulation and install soffit vent channel in the attic.

does the channel has to be installed in ** all ** the void between the rafters or just a few around where the vents are?

thanks
richard

wrote in message
...
been looking to add some insulation and install soffit vent channel in
the attic.

does the channel has to be installed in ** all ** the void between the
rafters or just a few around where the vents are?

thanks
richard

The baffles are so the insulation won't cover the intake (vent). They are
installed for blown in insulation. The bay created by the rafters will
direct the intake towards the peak.

Some will argue you absolutely need baffles, but think about it b/4 putting
them in. As long as you don't block the intake (vent), you will get the
same result without them.

On Tue, 27 Aug 2013 08:02:29 -0700 (PDT), wrote:

been looking to add some insulation and install soffit vent channel in the attic.

does the channel has to be installed in ** all ** the void between the rafters or just a few around where the vents are?

thanks
richard

Just at the vents along the soffit. I see no need for a baffle in
each cavity?

On Tue, 27 Aug 2013 09:35:05 -0700, Oren wrote:

On Tue, 27 Aug 2013 08:02:29 -0700 (PDT), wrote:

been looking to add some insulation and install soffit vent channel in the attic.

does the channel has to be installed in ** all ** the void between the rafters or just a few around where the vents are?

thanks
richard

Just at the vents along the soffit. I see no need for a baffle in
each cavity?
unless you use vented soffit - in which case you trough them all.

On Tue, 27 Aug 2013 16:19:55 -0400, wrote:

On Tue, 27 Aug 2013 09:35:05 -0700, Oren wrote:

On Tue, 27 Aug 2013 08:02:29 -0700 (PDT), wrote:

been looking to add some insulation and install soffit vent channel in the attic.

does the channel has to be installed in ** all ** the void between the rafters or just a few around where the vents are?

thanks
richard

Just at the vents along the soffit. I see no need for a baffle in
each cavity?
unless you use vented soffit - in which case you trough them all.

True, but the OP has not stated such. He stated "vents" - normally
not at every cavity with a perforated soffit material.

I lieu of buying baffles, the OP could staple cardboard, at each
cavity onto the trusses, to keep insulation away from the soffit
vents.

My read is he has vents in a specific distance along the soffit.

If I'm wrong, then I'm mistaken. g

On Tuesday, August 27, 2013 12:35:05 PM UTC-4, Oren wrote:
On Tue, 27 Aug 2013 08:02:29 -0700 (PDT), wrote:



been looking to add some insulation and install soffit vent channel in the attic.



does the channel has to be installed in ** all ** the void between the rafters or just a few around where the vents are?



thanks

richard



Just at the vents along the soffit. I see no need for a baffle in

each cavity?

If it's a traditional attic, ie not a cathedral ceiling, there aren't
even cavities. As Stormin said, IF you can keep the insulation away,
you don't even need them. But from a practical standpoint, using one
of those cheap baffles is the easiest way I know to keep the insulation
out of the way, especially on a retrofit. If the insulation extends a
couple inches over the vent, you just work the baffle in, moving the
insulation back a bit, and voila it's done/.

And I agree you only need them where there are vents.
If it's continuous soffit vents, then you need them everywhere. Separate
ones, you only need them where there are vents or if it's a cathedral
ceiling, in which case, each separate section needs to be ventilated, top
and bottom.

If by "soffit vent channels" you mean the styrofoam trays you fit between the rafters before covering with fiberglass insulation, vapour barrier and drywall, then...

Consider installing extruded polystyrene insulation instead. Not only does using polystyrene foam insulation eliminate the need for those styrofoam trays, but it gives you much better R value. Fiberglass will typically be R=3.5 per inch, whereas extruded polystyrene will be R=5 per inch of thickness as a stabilized R value. So, if you have 3 1/2 inch rafters, and you devote 1 inch to ventilation under the roof sheathing, then 2 1/2 inches of extruded polystyrene is going to give you R=12.5 versus R=8.75 for fiberglass. That's a 42 percent increase in insulation.

If you opt for a 1/2 inch air gap under the roof sheathing, the difference in R value is even greater; R15 versus R10.5.

But, be aware that in order to add ventilation to your roof, you will need to cut through the shingles at the ridge of the roof to install a ridge vent. If you don't have a ridge vent now, it'd be best to save this work until you need to replace the shingles on your roof, and add a ridge vent and ventilation at the same time.

Answer this question, tho: On the coldest F***ing day of the winter, if you go into your attic, do you see any frost or condensation forming on the underside of the roof sheathing. If the answer is no, then you really don't need to add ventilation to your roof. You've got as much attic ventilation as you need to prevent damage and adding more isn't going to do any good.

Contrary to popular belief, attic ventilation is used to prevent condensation occuring in the attic in winter. While attic ventilation can also cool the attic in the summer, a super hot attic in summer won't do any harm to your house, whereas condensation forming in your attic in the winter can cause serious and extensive damage to a house. So, regardless of what you may have been told, the reason for attic and roof ventilation is to prevent condensation forming on the roof sheathing in winter, not to cool the attic in summer.

On Wednesday, August 28, 2013 3:32:56 AM UTC-4, nestork wrote:
If by "soffit vent channels" you mean the styrofoam trays you fit

between the rafters before covering with fiberglass insulation, vapour

barrier and drywall, then...



Consider installing extruded polystyrene insulation instead. Not only

does using polystyrene foam insulation eliminate the need for those

styrofoam trays, but it gives you much better R value. Fiberglass will

typically be R=3.5 per inch, whereas extruded polystyrene will be R=5

per inch of thickness as a stabilized R value. So, if you have 3 1/2

inch rafters,

2 x 4's for roof rafters? Where is that allowed?




and you devote 1 inch to ventilation under the roof

sheathing, then 2 1/2 inches of extruded polystyrene is going to give

you R=12.5 versus R=8.75 for fiberglass. That's a 42 percent increase

in insulation.



Since he used the word "attic", I would think he isn't limited to 3.5"
of space and he also stated he was adding insulation, which implies
there is existing insulation. I don't know of anyone using rigid
board insulation for that application.




If you opt for a 1/2 inch air gap under the roof sheathing, the

difference in R value is even greater; R15 versus R10.5.



But, be aware that in order to add ventilation to your roof, you will

need to cut through the shingles at the ridge of the roof to install a

ridge vent. If you don't have a ridge vent now, it'd be best to save

this work until you need to replace the shingles on your roof, and add a

ridge vent and ventilation at the same time.



He has an attic. And even if he didn't, say it was a cathedral ceiling,
and it's not vented properly,
why should he wait 20 years until he replaces the roof? By then the
roof will fail. It's very easy
to add a ridge vent to an existing roof. Run circular saw down the
roof, nail in vent, cover with new cap shingles.





Answer this question, tho: On the coldest F***ing day of the winter, if

you go into your attic, do you see any frost or condensation forming on

the underside of the roof sheathing. If the answer is no, then you

really don't need to add ventilation to your roof. You've got as much

attic ventilation as you need to prevent damage and adding more isn't

going to do any good.



The insulation goes between the ceiling of the living space and
the attic. There isn't supposed to be insulation under the rafters
in an unfinished attic.




Contrary to popular belief, attic ventilation is used to prevent

condensation occuring in the attic in winter. While attic ventilation

can also cool the attic in the summer, a super hot attic in summer won't

do any harm to your house,

That's it's primary function when it's a cold climate.
In a hot climate, it's function is to remove hot air which
reduces the heat getting into the living space and helps
lower the temps seen by the roof decking, shingles, etc.
In most places, you have winter and summer, so it's both.



whereas condensation forming in your attic in

the winter can cause serious and extensive damage to a house. So,

regardless of what you may have been told, the reason for attic and roof

ventilation is to prevent condensation forming on the roof sheathing in

winter, not to cool the attic in summer.



Having 130F air trapped inside an attic until it cools slowly by radiating to the outside and in to the house doesn't sound like a smart idea to
me. With proper ventilation, not only is the temp lower during the
day, but once the sun goes down, it can cool off quickly via convection.