How to create a well performing rainscreen wall system?
I am in the process of building a house for a client in NE Washington DC. The architect has specified a rainscreen wall system with open (exposed) joints in the exterior cladding. Typical system would include 1/2″ plywood sheathing, WRB, then batten strips, then exterior cladding (in this case it will be Hardie fiber cement siding panels 10ft x 8 inches) with 1/2inch thick batten strips.
In a previous home, we had a similar system where we used Vapro (black) mechanically fastened sheet membrane with 16 gage galvanized batten strips. It was expensive, time-consuming, and I was not a big fan of the Vapro system. Even with extensive rolling of the Vapro tape, it was difficult to get the tape to stick well without bubbles and pockets.
Anyone have suggestions of what to use for battens? How about an alternative to the Vapro? I would like to use a self-adhered product if available.
Thanks,
Tim
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Replies
Tim,
Hardie has a couple of PDF installation instruction on their website. One for rain screen and one without. You should also consider using at least 1"-2" of rigid insulation on the outside of the wall, between the WRB & the battens for better thermal performance and mitigation of thermal bridging and possible condensation on the wall. Same on your roof assembly.
Tim,
Most builders use 1x4s to create a rainscreen gap. Is there any reason you don't want to use 1x4s? I wouldn't trust a "self-adhered" furring strip.
Tim,
You might try DELTA-FASSADE S. It's a WRB developed specifically for open joint claddings.
http://www.doerken.de/bvf-ca-en/products/wall_ext/wrb_open-joint/products/fassade-s.php
i've been wanting to do a similar system; off the top of my head...
[note i don't see where any of the vapro products are UV stable unless you use the UV black tape behind all the joints which would only be feasible for large open joint panels]
the questions are:
1. what type of WRB is available that is black and UV stable
- Delta - Fassade S is an option, availability and cost are issues.
- i thought about using dark brown/grey rock wool covering, with a WRB underneath it. the rock wool is UV stable and protects the WRB from sun and damage. there are installation questions. this seems to be the most cost effective solution if you want outsulation and offers a number of options
roxul use a similar technique on their euro office, but covered it with a glass facade
- use durable sheet board like fiber cement that can be painted; hardi sheet panels coudl also be an option
- you could use foam or densglass and then stucco over it or use some other type of similar finish
- there are durable coatings that are made to go over XPS board that is placed over the foundation wall to simulate a dark block wall, basically a synthetic stucco. one could use this over the whole structure and then batten over it.
- only the foil faced and and a few white(for roofs) peel and stick membranes seem to offer UV protection - would be one heck of a unique look
-there are other commercial or european wraps and panels i've seen, generally they go behind a glass facade, but i'm not sure if available for residential use or in residental quantities
2. what type of batten to use
- knight systems just released a metal batten that could look sharp, although it is not meant for open joint screens so you have to space the siding to cover the holes
- there are plasticvinyl batten products but they can't go over foam and come in only light colors
- one window manufacturer makes a fiberglass based batten; probably costs a fortune
- metal Z type flashing, but it brings thermal bridging issues when use with insulation
- and thent he tried and true wood or get real fancy with the new composite or possibly pvc plank products