The Bungaloft project plods along,
The list grows.
The list occasionally shrinks.
We begin the preemptive siding project on the front of the house.
The purpose . . .
To figure out how the insulated rainscreen siding will go together
and . . .
to give us something more hopeful to look at towards the end of the day.
So . . .
We have HardiePlank 5 1/4″ lap siding stacked up in the house. Lisa applied the first coat of a delicious Benjamin Moore red paint to each plank. They’ll get finishing coats after installation in complete.
The extant walls in the front (the back half of the house will eventually be almost completely new) are 2 by 4 fir studs with 3/4″ t&g fir cladding on the outside. Among the other creative things the original builder of our house did was to choose a pleasingly random stud spacing. The standard practice for Hardie involves looking for studs at standard spacing to attach to. This was clearly not gonna happen intentionally on the Bungaloft. Dialogs with fiber cement siding engineers and a couple of obscure Hardie documents on rainscreen siding (Technical Bulletin 09152008B) and SIPs construction (Technical Bulletin 07102008) led to the alternative concept of firmly re-attaching the existing fir cladding and using it for the siding substrate.
The rainscreen system will consist of a layer of 15 lb felt serving as a secondary water resistive barrier over the original fir cladding , a layer of 1 ” extruded polystyrene insulation taped, sealed and flashed as the primary water resistive barrier, 1/2 inch pressure treated plywood furring strips and cor-a-vent strips to provide a ventilation space and finally the Hardie siding.
The view above shows the Hardie plank applied to the front of the Bungaloft and the preparatory work done on the adjacent side. the first strip of siding is applied with a thin starter strip over the cor-a-vent which is in turn applied at the intersection of the 1 inch Fomular insulation and the custom flashing I designed to manage water intrusion and keep bugs away from the bottom edge of the foam. That detail can be seen below.
I’ve consulted voluminous sources of information during the course of the Bungaloft project and on the rainscreen issue in particular I have found the extensive writings of modern building science researcher Joe Lstiburek of BuildingScience.com very informative. A lot of similar information is now routinely presented and discussed on the GreenBuildingAdvisor.com website. Some usefull information can also be found at the ToolBase Services Rainscreen article. But one thing is painfully clear – there is no one single one-size-fits-all solution for rainscreen design. You have to evaluate your particular case against climate issues, structural issues, budget issues, local practice and the building codes to find something that makes sense.