January 6, 2013

BLDGTYP interview 2/2 – Exterior WRB/airseal and rainscreen details

shiplapped SOLITEX MENTO 1000 membrane over sheathing – BLDGTYP project is at this point waterproof and exterior airtight

We pick up the conversation, (from Part 1 here), with Ed May of BLDGTYP and Floris Keverling Buisman of 475.

FKB:You made use a vented rain-screen and vented roof (asphalt singles) protected by SOLITEX MENTO membrane. How did that work out?

EM: The SOLITEX membrane was so much easier and faster than working with tar paper. Carrying a 20lbs roll up a ladder beats carrying an 80lbs roll. The fleece backing on the membrane allows you to put it down on a 12-12 pitched roof and the backing will hold it in place – it doesn’t slide down the steep pitch. Both of these elements made installation very easy. The 5′ width meant we only needed to unroll 4 strips, so we had to roof covered in no time.

Battens for vented roof and rainscreen over SOLITEX

What we also noticed, after we put the venting battens and sheathing for the asphalt roof on, is that the vented space we just created, helped tremendously to keep the house cool. This made a huge difference as this was in the middle of summer and we had been quite uncomfortable inside until then.

In the walls we used Securock – as an extra layer of fire protection requested by the client – this board also has a perm rating of 26 and therefore doesn’t restrict the outward drying potential of the wall. Hanging the membrane with staples that would be ship-lapped by the next row of WRB, worked well as well as temporary attachment. However the 3/4″ vertical battens were what really secured the membrane solidly in place.

Rainscreen with vertical siding with horizontal & vert battens over SOLITEX membrane

FKB: Your vented rainscreen and roofs required battens – can you share specifics?

EM: The overhang with exposed rafters was part of the barn look that the project was going for. This meant that we could have a rather generous venting space between the membrane and the OSB sheathing above (see BLDGTYP blogpost) to which the conventional asphalt roofing was attached. The untreated pine was notched to make the rafters appear deeper, which meant we could use conventional 2×4’s on the remainder of the roof.

asphalt roof vented above the sheathing

The vented rainscreen is made out of stained white pine, which will weather over time. The pine is attached to horizontal 1×3 battens that are mounted on vertical 1×3’s that create a drainage plane on top of the lapped and taped SOLITEX membrane. These battens are made from very affordable lumber (not treated) and this leads to an interesting lattice work before we applied the final rainscreen. The venting of the entire assembly on all 6 sides allows the structure if it were to ever get wet, to dry out very quickly, preventing any rot or mold – prolonging the life of the siding and allowing us to use very sustainable and affordable materials in this assembly.

Windows flashed with WRB and TESCON tape

FKB: How did you integrate the windows with this drainage plane.

EM: We ran the SOLITEX membrane over the window openings and then cut a rotated “H” to create the window opening. The sides were folded in and stapled in the spots were the TESCON Profil tape would cover it.

On the bottom and top, from the cut-out membrane, we then sliced strips of SOLITEX that were used as sill pan. These pieces were measured so they would fill in the top and bottom of the window opening.

Connection of the window with tape to the drainage plane of the rainscreen

These strips were then taped with TESCON Profil in the corners, draped over to the sloped sill and taped to the the WRB on the front of the exterior with TESCON VANA. As last step the flanges of the windows were taped to the WRB with TESCON Profil. Working with the both the VANA and Profil tape was a pleasure. The fabric feels almost like clothing and the adhesion and release papers work very well – with 475’s instructions regarding how to  pre-make corners with the split release tape makes creating a continuous waterproof seal around a recessed window a breeze (and no heaps of caulk to struggle with).

Energy, temp and RH monitoring with IOBridge

FKB: Other note worthy items you think our readers will enjoy?

EM: What I am very excited about is the energy, temp and RH monitoring we have set up. We can remotely monitor the house and see how it is functioning with the iobridge we installed. It will enable the home-owners to control the HRV and other crucial functions of the house when unoccupied.

So the monitoring has shown that superinsulation is working well and the temperature in the house is very stable and even when unoccupied will only drop very slowly in a cold spell.

Editor’s note: This is a condensed version of the conversation. Comments have been paraphrased and edited for clarity and continuity.

All Images by BLDGTYP, this  is part 2/2, see part 1 for interior airsealing and insulation at this WI cabin.

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