Foam Insulation Requires roof Ventilation

I didn’t read them both yet.

I’m going back and read them both and see what the differences are.

Let me what your thoughts are Dave.

Thanks, Pete

They say here very little difference to shingle temp or life span…

http://www.buildingscience.com/documents/digests/bsd-102-understanding-attic-ventilation/files/BSD-102_Understanding%20Attic%20Ventilation_rev.pdf

Mr.Cooke I see way I appreciate your thinking process.Again I am humbled by your keen observations,and simple explanation.That tell what is at hand throughly.
I truly hope to be that concise,one day.
Thanks again.I will give you a call in a couple of weeks for that hand you offered me.
If you are busy I will understand completely.

I inspected a new construction home a couple of weeks ago here in Austin. Over 100 degrees outside. Inside home 74 degrees…inside attic, at ridge no less, 76 degrees. Amazing for here in the south. I hear lots of pros and cons so I guess the jury is still out but I’m seeing several builders go this way.

Only way to go if you can afford the $1.00 PBF+ cost. :mrgreen:

Actually you can do basically the same exact thing with cellulose. Spray it wet then button it up with whatever. Close to 1/2 the cost.

Both of these applications scream for an ERV or HRV.

APS, one of our local power companies, is looking in to giving rebates on ERV systems here in AZ.

JJ

You are right Jason. SPF and Cellulose have a different price tag and also have pros and cons to both of them.
Basically it is up to the individual to decide what their pocket books can afford and what expectation of performace result is expected.

If you use a heating system more often than air conditioning, you need an HRV. If the opposite is the case, an ERV is recommended.

ERV

Models that exchange moisture between the two air streams are referred to as Energy Recovery Ventilators (ERVs). ERVs are especially recommended in climates where cooling loads place strong demands on HVAC systems. However, keep in mind that ERVs are not dehumidifiers. They transfer moisture from the humid air stream (incoming outdoor air in the summer) to the exhaust air stream. But, the desiccant wheels used in many ERVs become saturated fairly quickly and the moisture transfer mechanism becomes less effective with successive hot, humid periods. In some cases, ERVs may be suitable in climates with very cold winters. If indoor relative humidity tends to be too low, what available moisture there is in the indoor exhaust air stream is transferred to incoming outdoor air.

Since you are in Arizona, I guess there is no question as to what is required. :):wink:

Always eager to help . Send me Email I can call for free ( Magic Jack )

Why ERV’s? You’ve got almost no moisture to deal with there…that’s where better ERV’s can help reduce a cooling load a bit by moisture transfer…or are they thinking about saving winter moisture from being lost from the home??

ERVs do not remove moisture from the air. ERVs work way better in AZ than an HRV. You can seal a home down 100% and then bring the ducts in to the conditioned space with spray foam and have 0 moisture issues.

JJ