vinyl siding fixtures

[Salty]

I just don't understand these things. If installed as shown here, what's to keep water from entereng behind the siding as it runs down and around the part that is installed under the siding? Or doesn't that matter? In my case I installed 1/4" fan-fold foamboard under the siding panels. This was done primarily to provide a smoother surface upon which to install the siding.
Now, as I reflect back on my progress thus far, I am thinking that the vinyl siding will never be like a protective paint job since there are so many lap joints where rain water can enter the area behind the vinyl.
I am comforted in knowing that I took the time to seal the seams of the foamboard with HVAC aluminum tape. At least if water gets behind the panels it will not get past the foamboard.
Your thoughts!

[mschrank]

If installed as shown here, what's to keep water from entering behind the siding as it runs down and around the part that is installed under the siding?

I recently installed several exterior light fixtures (not on vinyl siding), and all of the instructions said you must caulk around the perimeter after installation.

[bigsteel15]

I recently installed several exterior light fixtures (not on vinyl siding), and all of the instructions said you must caulk around the perimeter after installation.

There are soooo many bad jokes that could start here.
Plumbers help line?

[mschrank]

There are soooo many bad jokes that could start here.
Plumbers help line?

huh?

[bigsteel15]

huh?

There was a radio bit on a couple of years ago that had someone calling a plumbers helpline and getting a recorded message on how to install caulk.
Things about how hard/soft/squeezing, you get the idea.
Anyways it was funny and I thought everyone would have heard it at least once.

Tried to find it on the web with no luck

[spazlab]

I definitely see your point about vinyl siding. I too have had those exact thoughts. I've installed many of this style mounting block, vents, outlets. I always flash around the mounting block nail flanges (like windows) with a self sealing water/ice membrane.

From the Vinyl Siding Institute - Installation Manual

Vinyl siding has always been designed as an exterior cladding, not a weather resistant barrier. Vinyl siding is designed to allow the material underneath it to breathe; therefore, it is not a watertight covering. Because of its design and application, it provides a supplemental rain screen that enhances the weather resistant barrier system by reducing the amount of water that reaches the underlying weather resistant barrier. What Is a Weather Resistant Barrier System? It is a system that includes water shedding materials and water diversion materials. Weather resistant barrier systems commonly consist of a combination of exterior cladding, flashed wall openings and penetrations, weather resistant barrier material, and sheathing. Effective weather resistant barrier systems will shed the water initially, control moisture flow by capillary and diffusion action, and minimize absorption into the wall structure. The level of weather resistance required is determined by the applicable building code and structure.