Will Solar Panel Mounts Cause Roof Leaks?

Twice as Many Members Agree
by John Brooks

as of today ....67% agree that Compact Insulated Roof assemblies are more problematic and should probably be vented to avoid problems!
Do you realize that we are taliking about 2 out of every 3 members! ;-)

*voting members

Surge in Voting
by John Brooks

A recent surge in voting is swinging towards non-vented

OK, Sorry about the joking around
by John Brooks

Consider a hypothetical .....there is only a 2% chance that a penetration might leak.
If there are 54 fasteners.....what are the odds that at least one fastener/penetration leaks?

of course I am just making up the 2% number

apples and oranges
by Whetstone Green

I don't see what one has to do with the other. How does spraying the roof deck increase the likelihood of a leak? As mentioned by John, I would be more concerned about the difficulty (and higher cost) of future roof repairs.

The decision as to whether to encapsulate the attic comes down to cost vs. potential energy savings. Closing an existing vented roof can be expensive. The ceiling insulation must be removed and the roof vent system closed. And if the roof extends over a porch or garage, that portion should be blocked off, otherwise you'll have to seal off and insulate a larger area than necessary. It's important to align the air barrier with the thermal boundary.

In order to calculate potential savings, it's necessary to estimate how much energy that particular HVAC system (presumably there is more than one) contributes to the overall energy bill. It would be reasonable to expect encapsulation would save 10% to 15% of that system's operating costs. The percentage would be higher in mid winter and mid summer, and less in milder weather.

Finally, don't confuse conducted heat loss with duct leakage. The latter typically represents a bigger loss and is much less expensive to fix.

The likelihood of a leak
by Martin Holladay, GBA Advisor

Whetstone,
You're right — spraying foam against the roof sheathing does not increase the likelihood of a leak.

However, it complicates leak detection and leak location, leading many to worry that a small leak might cause sheathing rot before it is detected.

Insulated Roof deck with a few inches plenum to vent
by Harry Zhou

I thought an insulated roof deck can be vented by creating a suspended plenum on top of the roof deck - perhaps a little additional material for an extra layer sheathing and some 2X purlin. But you get both insulated attic and roof venting. Isn't that what the 1st PH in IL did?

Venting roof sheathing
by Martin Holladay, GBA Advisor

Harry,
You're right, or course. It's possible to build a ventilated insulated roof with the vent channel on top of the roof sheathing. Such a design usually requires a second layer of sheathing, unless you use metal roofing.

Replaceing shingles under solar panels
by Carl Mezoff

While it is true that it will be difficult to re-shingle under the solar panels, the need to do is also likely to be much less.

After 30 years, I had to re-shingle my house (built during the Carter administration) and was faced with this very question. Getting up close to my Revere Solar panels, I was able to see that the asphalt shingles (Timberline) under the panels were as good as new. So, we just re-shingled around them - for another thirty years of life (I hope). After 60 years, it may be time to replace the solar panels anyway.

The panels do a good job of protecting the underlying shingles from ultra violet insult and most other weathering influences, so the life of the shingles is likely to approach that of the panels above.