I’m just about finished framing a new shop and am gearing up for the siding. I’ll be doing a rainscreen affair: WRB over the plywood sheathing, 1/2″ treated battens, then horizontal cedar cladding with open joints. The site is in the Pacific North west… plenty of rain here.
I have to decide on what material to use for the WRB. With the open joint detail UV damage is a distinct possibility. Vaproshield is very interesting. It is highly UV resistant and is spoken well of, but it is pricy. I’m wondering if I can simply use 15# felt in multiple layers. The outer layer would serve to protect the inner one by blocking the light. The cost differences between the two products are $2000 for Vaproshield and $200 for 15# felt. I’d like to save the money but if it means having to redo the job within 30 years then no thanks.
Any thoughts? Are there any other products I can look at? Thanks.
Replies
A few Qs
>> I'll be doing a rainscreen affair: WRB over the plywood sheathing, 1/2" treated battens, << sounds like thus far, you are really doing it right....
>> then horizontal cedar cladding with open joints. << What the advantage to that type of siding? Is this building to be more of a shed, or a structure that could, at least at some point have the interior air tempered?
Re the 15# felt, it is not clear to me that "felt" has much of any UV resistance - judging by how durable it is (not) on new constructions roofs when left exposed even for only a month. What would make that a good combination with the "air-conditioned" exterior cladding other than price?
Re your actual question, I've used a number of different house wraps and felts but know of none that are mfg approved to be left exposed for more than maybe 9 months..
UV resistant WRB
Check out Cosella-Dorken's UV Resistant WRB - DELTA-FASSADE S
UV resistant for 50 years - 74 perms (vapor permeable and waterproof). Unlike vaproshield, does not require a sacrificial layer (2 layers). #15 building paper is not a good idea as each layer will deteriorate when exposed to UV.
http://www.cosella-dorken.com/bvf-ca-en/products/wall_ext/wrb_open-joint/products/fassade-s.php
UV resistant WRB
Check out Cosella-Dorken's UV Resistant WRB - DELTA-FASSADE S
UV resistant for 50 years - 74 perms (vapor permeable and waterproof). Unlike vaproshield, does not require a sacrificial layer (2 layers). #15 building paper is not a good idea as each layer will deteriorate when exposed to UV.
http://www.cosella-dorken.com/bvf-ca-en/products/wall_ext/wrb_open-joint/products/fassade-s.php