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The Best Way to Ventilate Siding

Daniel Morrison, Executive editor, Fine Homebuilding & Green Building Advisor

12 users recommend

Paint lasts longer when the siding is vented.
Vertical strapping lets water drain down and air flow up. This allows the back of the siding to dry as fast as the front, keeping the wood stable and extending the life of the paint, siding, and sheathing.

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In researching an article for the magazine, senior editor Justin Fink sent an email to the Green Building Advisor Help Desk. A couple of good replies came in from John Straube and Joe Lstiburek, which we thought the FHB readers would find useful, intertesting, or both.

The question:

Gentlemen,

I’m researching/writing an article about vented rainscreens for Fine Homebuilding. Though most building scientists/disciples seem to be in general agreement about 90% of the overarching concepts, I’m finding contradictory information on two areas:

1.) Should venting be continuous around inside and outside corners, or broken up so each face of the house is a separate unit?

2.) Is it a good idea to tie the “exhaust” end of the vented rainscreen to the roof venting setup, or safer/just as effective to vent it under the soffits (at the fascia board)?

John Straube, principle at Building Science Corporation and professor of engineering at University of Waterloo, answers:

I am somewhat passionate about this topic since I have spent years studying it in great depth. I may be the only person on this list who has comprehensively measured the pressures behind claddings in real buildings. I would like to see other data if my assumption is incorrect. Much of my PhD work focused on the topic of pressure equalization and ventilation drying and so I spent more than 3 years measuring pressures at 1 to 3 second intervals in 200 spots around a building. At the time, the quantity of data, measured in GigaBytes was a source of wonder to geeks.

Taunton's for Pros By Pros: Exterior Siding, Trim, and Finishes
From the editors of Fine Homebuilding Essential Design and Installation Information $17.95 more info...

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Comments (4)

civiletti writes: Properly detailed, vented siding will keep out creatures. I used stacked black corrugated sign plastic with fiberglass insect screen wrapped around it at the top and bottom of each bay. Cor-A-Vent or Cedar Breather also work, albeit at higher cost.

Rain infiltration is one of the most common causes of water damage in walls. Modern, highly insulated walls are less forgiving than older leaky systems.
Posted: 2:54 am on July 14th

GregW3 writes: I cant see much benifit in this. My 100 year old siding is on top of 30# tarpaper which is on top of T&G boarding. During my renovation I saw no, I mean absolutely no sign of water getting behind my siding anywhere. That picture looks like a great place for critters to live and water to condensate. No thanks.
Posted: 2:41 am on June 21st

DanMorrison writes: Drainage mat material, such as Cedar Breather,works. Also I've heard of people using ridge vent material (CoraVent).
Posted: 12:33 pm on April 23rd

jdh256 writes: What is the recommeded material used for insect screens at the top and bottom venting locations on this setup?
Posted: 12:51 pm on April 21st

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