Langley Passive House – Part 5 – Door Install

Doors are installed similarly to windows. A 2×4 ripped is offset at jamb and head. The door frame rests on plywood spacers and is glued/sealed with adhesive foam. The frame is over a self-adhered flashing at sill which itself sits above rigid EPS at concrete foundation. The EPS is painted with compatible damp-proofing. 2 layers of rigid roxul provide a thermal bridge free installation at the wall. On the interior the door is taped to the concrete topping at floor and to the studs at jamb & head.

The door install shares the non-conventional details as the wall detail (see Part 4). The exterior insulated strategy shown here is considered the most robust (http://buildingscience.com/documents/insights/bsi-001-the-perfect-wall) is endorsed by the Home Protection Office (https://hpo.bc.ca/r22-effective-walls-wood-frame-in-BC) the same people who insure your home.

Langley Passive House Part 3 – Wall Detail

As mentioned in part 1 of the series this wall detail takes a high vapour permeance or breathable approach in contrast with a more vapour closed system such as traditional 6 mil poly, spray foam insulation, or SIPS panel. In an everyday example it is similar to choosing a breathable Gore-tex or Tyvek jacket over a fully waterproof rubber or latex one.

The sequence of assembley allows for easy access for sealing of the air barrier membrane and the vapour barrier is solid (plywood) avoiding the difficulties in sealing and movement of the traditional 6 mil poly. 1) a 2×4 stud wall is framed on conc. foundation 2) plywood is attached to the stud wall without gaps 3) air barrier membrane is draped over the plywood and sealed at edges with specialized tape 4) two layers of roxul insulation are installed with 5) 2×4 vertical strapping holding the insulation in place 6) fibre cement siding forms the finished cladding 7) Drywall is installed on the inside face of studs

1) 2×4 Stud Wall. The 2×4 stud wall is framed traditionally providing for a common and cost effective installation. 2x4s utilize less wood than the code standard 2×6 while providing adequate strength.

2) Plywood is installed over the 2×4 stud wall and form the vapour barrier and sheathing in a single step. The plywood is sealed at seams with vapour barrier tape. This vapour barrier is much more breathable than the traditional poly and more so than the code requirement. This allows for the wall to dry to the outside and inside should any moisture enter. As a solid sheet product this vapour barrier avoids the difficulties in 6 mil poly construction where care must be taken to ensure proper sealing with sealants, lapping at edges, solid backing at electrical boxes and other penetrations, and post construction movement during pressurization and depressurization due to wind pressure. An inherent property of plywood is its natural tendency to increase its vapour permeance when wetted. This allows it to dry itself out more rapidy if it ever gets wetted through condensation or rain penetration at window openings or other gaps.

3) Siga Majvest (http://www.siga.ch/en/product-overview/majvest-detail.html) is the air barrier membrane which is more vapour open that the code requirement in the BCBC allowing for greater drying capacity. As the air barrier is applied to the outside over plywood the installation is no different that the traditional installation of tar paper or Tyvek. Siga is taped at edges and seams to form a strong air barrier.

4) Roxul exterior semi-rigid insulation is used in two layers. These layers are lapped at edges so there is a lesser chance of gaps between insulation and avenues for water penetration. Roxul is made from rock and slag absorbs less than 1% of water and does not harbour mould according to their website http://www.roxul.com/products/commercial/products/roxul+comfortboard+cis. Partial assembley of the 2×4 strapping allow for install of the Roxul (see construction sequence image).

5) 2×4 borate treated vertical strapping is installed over the rigid Roxul. Long screws penetrate the strapping, plywood, and 1.5″ into the studs. The screws are installed traditionally with a common drill & bit and according to the installation crews are easy to install since the majority of the intervening material is Roxul which takes very little effort to penetrate. The only trick is the inability to pull out screws that miss their studs for fear of introducing penetrations to the air and vapour barrier. These screws are left in place.

6) Fibre cement cladding is to be added over top the 2×4 strapping. Nails penetrate the strapping only so no holes to the air & vapour barrier are introduced and reducing any small thermal bridging.

7) Drywall is installed on the inside face of studs as per typical residential construction.

This and similar exterior insulation systems for passive house are considered one of the most durable due to the solid plywood. It has seen application in Alaska as part of the REMOTE wall (http://cchrc.org/docs/best_practices/REMOTE_Manual.pdf) although this system utilizes an exterior 6 mil poly vapour barrier over the plywood and rigid EPS or XPS insulation (vapour closed).

Double wall is another system used for passive house. Typically this system utilizes a double 2×4 wall with a intervening space between the stud walls. This space is filled with insulation (typically blown cellulose) providing the additional insulation value without thermal bridging in the wall. A 6 mil poly vapour is typically used on the inside face of the inside stud wall with plywood or osb backer at electrical boxes and other penetrations. This is a good wall which utilizes conventional skills the trades already have and has a good track record for high performance with proper workmanship. Because the wall cavity is also used for plumbing and electrical runs the poly vapour barrier must be penetrated many times so the key in achieving the air tighness required here is proper sealing at penetrations. There have been questions on durability of the vapour barrier due to post construction use (picture hanging) and pressure differentials dislodging the poly vapour barrier. Nonetheless, this method is tried and true and has achieve net zero designations. The strongest advocate I’m aware of for this technique is Peter Amerongen (http://habitat-studio.com/?page_id=2).

SIPS panels consist of rigid insulation typically EPS/XPS sandwiched by OSB. These form a prefabricated panel which is often delivered onsite and assembled with a crane within a few days. This system is vapour closed due to the rigid insulation and the OSB. It is considered very durable and has a long history especially with Timberframe builders who have used the panels as infill between posts and beams and more currently outside the timbers as a continuous wall. Services can be run within pre-drilled holes in the insulation or within a backup stud service wall. To my knowledge this system works well but is considered more expensive than other systems. This is a good, durable, vapour closed system that has seen a long history use.

Vapour open exterior insulated wall as in the Langley home is described in the Building Enclosure Design Guide (HPO 2011) and Guide for Designing Energy Efficiency Building Enclosures (FPInnovations 2013) both by RDH. The wall design borrows from the North Shore Passive House in construction by the Econ Group (http://www.econgroup.ca/north-shore-passive-house/) and progress photos of the North Shore home are available at http://www.econgroup.ca/north-shore-passive-house/. This system borrows the durability of the REMOTE wall and other exterior insulation wall types common to commercial and multi-family construction. Its’ durability comes from the ease of installation on a solid vapour barrier and requires little additional skill from typical construction. It introduces an increased vapour permeance that allows the wall to breathe and dry out while maintaining a very tight envelope. The increased vapour permeance is not represented in the Building Code and results in greater reliance on consultants and their expertise.

Each of the wall types discussed above have a long history in construction in various forms each with their advantages and disadvantages. With the increased need for more energy efficient construction the budding popularity of high-efficiency wall types is certainly a good thing. Time will tell if the single family home will latch onto one of these systems to the exclusion of the others as has generally happened in the past or if it will embrace multiple wall types.

Langley Passive House Part 2 – Sunshade

The South facing sunshades on the Langley Passive House are permanent, sized to reject the overheating summer sun while allowing passage of the winter sun through the windows to heat the home, and fit the architectural style of the home. There are two levels of sunshade one at the roof level as an extension of the eaves and the other shades the main level windows and doors as a continuous wall mounted canopy.

The upper eaves are extensions of the top chord of the roof trusses and form an angled soffit with continuous venting. This overhang shades the upper level windows from the steep angle of the summer sun. The lower angle winter sun is not obsured by the length of the overhang allowing the warming rays to play a key role in heating the interior of the home.

The main level canopy is shown in the detailed close-up image and is attached such that it does not penetrate the insulation and create a thermal bridge. The trusses are hung off 2×4 ledgers which are in turn attached to the 2×4 vertical strapping without penetrating the insulation.

Passive House Detail

Langley Passive House Part 1 – In Progress

The Langley Passive house is a ‘split-insulated’ wall assembley pioneered by RDH Building Engineering for the BC climate. This strategy is described in the Building Enclosure Design Guide (HPO 2011) and Guide for Designing Energy Efficiency Building Enclosures (FPInnovations 2013) both by RDH. The wall design borrows from the North Shore Passive House in construction by the Econ Group (http://www.econgroup.ca/north-shore-passive-house/) and progress photos of the North Shore home are available at http://www.econgroup.ca/north-shore-passive-house/.

Passive House Detail
Passive house Wall, Roof, and Foundation design detail

The schematic roof – wall – foundation diagram shows the component parts for the Langley Passive house. The wall assembley consists of a 2×4 structural and service wall with a plywood vapour barrier at the exterior. An air barrier is taped to the rigid plywood backing. Two layers of rigid roxul provide exterior and continuous exterior insulation which in turn is held in place by 2×4 strapping on flat anchored with long screws.

The roof assembley consists of a truss roof with OSB vapour barrier attached to the underside and a 2×4 drop ceiling for services. Blown in insulation blanket the attic space.

A raft slab concrete foundation sits on 2 layers of rigid insulation which abut the rigid roxul of the wall assembley ensuring continuous insulation without thermal breaks.

The Langley Passive house is currently largely framed with roof membranes in, rigid roxul and wall strapping mostly present, and raft slab foundation installed and backfilled. The image shows the blue roofing membrane on the lower granny suite, staging is shown, double layer of rigid roxul at wall, 2×4 strapping, and south facing sunshades at the right-side of image.

The chosen assembley is a relatively vapour open system allowing any moisture that finds its way into the wall from condensation or through gaps in the assembley a way to dry out. The plywood vapour barrier has a permeance range of 115 – 252 ng/Pa*s*m2 above the prescriptive requirement of 60 ng/Pa*s*m2 (BCBC). This in addition to the vapour open air barrier and roxul insulation allows for drying to the outside. Similary the roxul in the stud wall cavity allows for drying to the inside. This contrasts with the relatively vapour closed passive house systems such as structurally insulated panels (SIPS), closed cell spray foam, EPS or XPS exterior wall insulation, and to a lesser extent systems using a traditional poly vapour barrier. The team including the passive house consultant Dale Mueller have chosen this strategy to best contend with British Columbia’s temperate rainforest climate.

Subsequent posts will go into more detail regarding the roof – wall- foundation assembley, exterior window and door installation and their construction sequencing.  There are some nonconventional methods used in the all these areas which may be of special interest

Langley Passive House -Part 4

Window Detail

Triple pane window is installed over sill flashing & weather resistant membrane and then taped.

Then there is a 2×4 ripped to the thickness of 1 layer of rigid roxul around the window offset about 3″. This holds a layer of rigid roxul tight against the window frame and provides a nailing & flashing surface. The second layer of rigid roxul covers up the 2×4 resulting in a thermal bridge free detail. Borate treated 2×4 strapping on flat hold the 2 layers of rigid roxul in place. Also shown here is the wall connection to the foundation. You can see the dimple board drainage layer with a self adhered flashing at the top and the rigid roxul over top. On the left of the lower picture (above) you can see how the rigid roxul is held in place with temporary bracing via leaning 2x4s before the install of permanent strapping and long screws.

You can see the head flashing at the top of window. This is nailed into the 2×4 ripped strip offset above the window. Wood trim is installed at jambs and sill flashing with end dams. What is left is the siding nailed into the strapping (not shown).

On the inside headers are installed at the floor joist level. Air barrier wrap can be seen surrounding the window head and jamb.

The windows are installed through the interior side of the window frame rather than with the common flange. Sill self adhered flashing can be seen with the air barrier membrane properly lapped. Tape from the window frame to the structure and rod & caulk will be provided in future (not shown).

The head and jamb are shown here.

Compared to a typical window installation there are some differences here. The membrane wraps are similar but the air barrier membrane needs to be taped at all seams. The window is flangeless and is mounted with side-mounted screws. There is a 2×4 nailing strip offset at head and jamb and the 2 layers of exterior rigid roxul is a new addition to the conventional sequence of installation. The 2×4 strapping on flat is larger than the standard and the required extra long screws must penetrate the 2×4 strapping, 2 layers of rigid roxul, plywood sheathing, and at least 1.5″ into the stud. This takes some skill as the studs can’t be seen and must be hit. Also, the screws should be angled upward slightly. This is due to the nature of long screws which tend to sag from the weight of the siding if installed horizontally. The angled installation slightly up mimics the final resting ‘sag’ of the screw such that there is no movement of the siding after install. Any screws that miss their mark are to be left in place. This avoids penetrations of the air barrier if these screws were removed.