Is there some new revolutionary venting concept

[gkdesigntech]

I should caution RTF and other users of Icynene - it's a great system, but make sure you ready the ICC ES report carefully. There are several applications that I've seen done in the field that are NOT approved methods. Some methods also require a thermal barrier be installed so the icynene isn't exposed. The biggest thing is the shingle warranty. I'm not aware of any shingles that are warrnated for use on an unvented attic or rafter space.

[gkdesigntech]

The probably could have gotten creative on the ResCheck Compliance Certificate and made up for the arched windows...I've rarely seen a situation where a trade off wouldn't work.

[MOM]

I want them to compensate us for the change. How much price difference would there be for 7 windows?

I also noticed that on the same model they're building down the street, that they went ahead and put 4 off-ridge vents on that house too.

[maj]

MOM, what you call off-ridge vents are called many things throughout the country. In my area, we call them cut-in vents or pods (as referred to by Bighammer). You CANNOT use soffit venting as cross-flow ventilation. Soffit vents are INTAKE only. The air must freely flow in from the soffit, through the unconditioned attic space, and out the highest available point of the roof. Whether it be ridge vent or off-ridge vents, the ratio of 1/150 is known countrywide as the acceptable ratio, with 1/300 being minimum.

Natural attic ventilation, IOW.... unassisted airflow (unlike powervents), works just like a chimney. The exhaust vents (ridge, pods, or whirlybirds) are located high on the roof and intake (soffit) is located at the lowest points. Thus creating a natural draw just like a chimney. In order for this to work properly, the amount of intake and exhaust must be balanced. If you restrict the amount of exhaust (roof vents), you may cause a "flooding" of intake air. This is bad for attic ventilation. It is always better to restrict the intake vs. the exhaust. At least with an unbalanced intake ratio, all the air infiltrating the attic will be expelled out the roof vents.

Another very important (at least in Northern areas) thing to consider...... NEVER install off-ridge (pod) vents on opposite sides of the ridge. In your case with the hip roof, the vents should only be placed on 2 sides(maximum) of the roof. I've seen this done on too many houses by inexperienced builders. They have a hip roof with not alot of ridge line, so they just put a pod vent on all 4 slopes at the peak. BAD idea..... what this does is allows the natural winds to blow in one vent and directly out the other, called cross air flow. This disrupts the natural "chimney" effect of soffit to ridge air flow.
What I've always done in applications like this is piggyback the roof vents, IOW..... stack the vents on top of each other up the slope of no more than 2 sides.


gkdesigntech...... Almost ALL shingle manufacturers that we deal with DO support and warranty spray foam applications on the underside of the roof deck. link

[MOM]

Thanks Maj. I don't know how they got it to pass code, but it did. I do have 4 pods on the back side of the house in two pairs, side-by-side. They did install baffles around the permiter. I don't know if this was done to prevent the blown-in insulation from blocking the soffit or to restrict the intake, or both, but my current house does not have these baffles (soffit with larger off-ridge vents, the style prior to storm-resistant type).

[rwanders]

Originally Posted by gkdesigntech

I should caution RTF and other users of Icynene - it's a great system, but make sure you ready the ICC ES report carefully. There are several applications that I've seen done in the field that are NOT approved methods. Some methods also require a thermal barrier be installed so the icynene isn't exposed. The biggest thing is the shingle warranty. I'm not aware of any shingles that are warrnated for use on an unvented attic or rafter space.

Gkdesigntech: Up here in the great white north (Alaska) unvented roof systems using spray foam against the roof sheathing is becoming more and more popular---I sprayed 11" of closed cell foam between the 2x12 rafters on my 12/12 metal roof----great system! Achieving R-48 or above while leaving ventilation space is almost impossible in a cathedral ceiling design. I only burnt 300 gallons of fuel oil last year to heat a 900 sqft cabin with abundant windows in an area that sees 35-40 below in the winter.

[RonaldKlondike]

rwanders, that is some serious roof efficiency.