The following photos and text show some examples of how dedicated we are to building durable, resilient homes and also shows how the small details that are Fiddlehead innovations add up to unexcelled performance and durability.
Detail 1:
Foundation
The foundation is a critical component in any home. On this particular build, the EPS insulation is exterior to the concrete. The thickened-edge monolithic slab is placed over 3-3/4" high density foam under the footers, and 7-1/2" EPS foam (R-30) under the slab. After the walls are waterproofed, there will be 7-1/2" EPS foam on the exterior of the walls. While we sometimes advocate for crawlspaces and frost-protected shallow foundations (slab-on-grade), when there is a walkout or extra storage space needed, a basement becomes a very cost-effective approach for lower cost square footage. The basement of a high performance home should be both dry and warm. The photos above show the process we use to achieve this. The first photo shows a typical poured concrete foundation after the forms are removed. The form ties leave voids, the joints between panels often have a ridge of concrete, and the joint between footer and wall is a weak spot for potential water migration. We grind the ridges smooth, fill the holes with mortar, and install a cant of mortar at the wall/footer intersection as a best practice procedure for that detail. At this point, we have a clean, smooth surface on which to install waterproofing (Tremco Tuff-n-Dri warranteed waterproofing- a superior product to standard dampproofing emulsions).
Detail 2:
Sill plate seal
The junction between foundation and a framed wall is a critical joint that needs thought and planning. Much the same as the foundation walls, the top of the foundation wall after the concrete subcontractor leaves is often not perfectly flat or level. This is not a fault of the concrete sub, but just the nature of standard concrete work. To create a permanent tight seal between the foundation and sill plate, we first grind the top of the concrete foundation with a diamond cup wheel to create a smooth surface for our plates to seal to. Instead of using pressure-treated plates, we choose to use standard SPF framing lumber and protect the sill with a waterproof membrane. Pressure-treated wood comes from the lumberyard with a very high moisture content and the result is that it shrinks and cups significantly when it dries. This is not ideal for creating a long-term airtight seal. The seal itself is made with two generous beads of acoustical sealant which is permanantly flexible. Our air barrier then gets tied directly to the sill plate to continue the wall air barrier to the wall/roof junction.
Detail 3:
Artic wall Assembly
Our insulation of choice for walls is mineral wool batts- in this case Roxul. We have found that it is the lowest-cost high-performing insulation. It has a higher r-value per inch than dense pack cellulose and has a lower installed cost than dense pack. It is also not nearly as dependent on installer skill as dense pack and is also easily visually inspected for quality installation after it is in place. Spray foam insulation is also more expensive and is also very sensitive to the skill level of the installer, along with sensitivity to installation temperature and humidity. Consequently, we have designed our wall assembly to accept these batts. The other design factor for these walls has to do with long-term moisture management. To have a margin of safety that we are comfortable with, we choose to build our walls as an Arctic Wall assembly. This is constructed by having an insulated service cavity/structural wall to the interior, sheathed with structural sheathing that also serves as an air barrier and vapor retarder. This is followed with a second insulation cavity to the exterior which is then sheathed with a WRB osb panel (green Zipwall). The difference between this wall and a double-stud dense pack cellulose wall is that there is a layer of sheathing in the middle of the wall to act as a throttle to retard winter migration of water vapor through the wall. Because this layer of sheathing is in the middle of the wall, the surface is warm enough to prohibit the vapor from condensing into liquid.
Detail 4:
Cathedral roof
This gallery shows the details for a robust-performing cathedral roof assembly. This R-60 roof is both airtight and also ventilated above. It has drying potential in both directions. Cathedral ceilings are notorious for having moisture issues, and this assembly is doubly-protected by an airtight, breathable membrane with battens and cross-members to vent even the difficult-to-vent valleys.
Detail 5:
ceiling service cavity
Our standard and lowest-cost roof assembly is a gable-truss attic that is filled with loose-blown cellulose, the most cost-effective insulation for attics. We make sure to design the truss with a 19" energy heel where the truss sits over the exterior top plate to have full R-60 value to the outside of the exterior wall. The other component is to use a service cavity in the ceiling. The left photo shows this service cavity framing, which is then sheathed with Ziproof OSB sheathing and taped to make up the ceiling air barrier. The service cavity in the ceiling allows mechanical ductwork and electrical to be run inside both the thermal envelope and inside the air barrier, further ensuring an airtight building envelope. The ductwork path is anticipated ahead of time in the framing to facilitate efficient and easy duct runs in the ceiling. As an additional bonus, the flat sheathing plane makes setting trusses a fast and safe operation.
Detail 6:
windows
Window and door openings are the most vulnerable components with respect to maintenance and bulk water intrusion, so we take extra steps to ensure the longevity of this detail. We start with shop-made window bucks (the rough opening of the window or door). Making them in a shop allows us to build a buck with tight dimensional tolerances. When we cut the opening, the bucks can be installed perfectly plumb and square making window installation and interior and exterior trim packages a quick and precise task. The window bucks are sealed to the air-barrier sheathing making them a component of the air barrier. When the window is installed, it is taped to the buck to complete the seal. Building the bucks in the shop also allows us to create a specialized sill profile that directs water back out to the WRB plane. The canted sill of the buck, plus the backdam, is coated with a liquid- applied waterproofing membrane that is also breathable (PolyWall). This seamless membrane eliminates the hazards of sill tapes. Lastly, a custom-fabricated sill pan that has the sides and back turned up with welded corners is integrated with the bottom edge of the window profile for durable, long-term protection against the elements.
The windows themselves are European tilt-turns with triple glazing. The whole window R-values are around R-7 compared to an energy star rated window of R-3.3. What's more is that with a high solar heat gain coefficient glass, these windows generally gain more heat through solar gain than they lose (net positive heat gain).
The windows are also installed in the center of the wall for both energy-efficiency and aethetics. The interior frame and trim is flared to allow a wider swing on the sash, and for greater daylighting and sight lines.
Detail 7:
air tightness/
ventilation
If there is one number or metric that gives a clear indication of a builder's commitment to building better homes and attention to design and details, we feel that it is the blower door number, a measure of air tightness of the home. We owe a lot to the building scientists and the Passive House community for developing a high standard and better science to inform the local building process. Meeting the Passive House standard comes down to 3 numbers; two energy usage metrics plus an airtightness number. Passive house has set the maximum infiltration rate at 0.6 Air Changes per Hour at 50 pascales (pressure). This has proven to be a hard target to achieve for those who are inexperienced with high performance homes, but in reality if the air barrier is planned during the design phase and executed by an experienced crew, meeting the Efficiency Vt HPH target of 1.0 ACH50 should not be an obstacle. Fiddlehead Construction consistently achieves an average of 0.2 ACH50, which is 3 times better than the more stringent Passive House number.
In an airtight home (and any home for that matter), mechanical ventilation is a must for healthy indoor air quality. We choose to use CERV balanced ventilation (Conditioning Energy Recovery Ventilation) for several reasons. The primary reason is that it is a balanced ventilation system that adds heating or cooling to the ventilation air. Balanced means that it is taking fresh air from the outside (heating or cooling it depending on season via a heat pump), and then distributing that fresh air throughout the house while simultaneously exhausting stale air. The heat pump makes this an extremely efficient process. This is in contrast to most other systems, which are distributing cooler than ambient temperature air (in winter). The other benefit of the CERV is that it is continuously monitoring the air quality for VOC's and CO2, and only runs when it is needed, in contrast to other systems that either run constantly or are on a timer.
Misc. Details
Rainscreen wall assembly.
A rainscreen wall simply means that there is an air gap between the siding and the wall sheathing. This allows any moisture that penetrates the siding to quickly dry and not saturate the siding. It is a safer wall assembly with regard to moisture management, and also has the benefit of having the paint film on the siding last much longer. Fiddlehead construction uses 3/4" battens, with Cor-a-vent screened intake and exhaust vents at top and bottom to prevent insects from entering the vent space. A 3/8" vent space is considered a minimum, so we do not consider the dimpled housewraps or mesh a rainscreen assembly.
Advanced Energy Framing.
The process of designing the structural frame for a home can have a surprising large effect on the thermal performance and daylighting potential for the finished structure. Advanced energy framing analysis sizes every structural component to meet the structural requirements without unnecessary or redundant framing. Window and door headers are sized for their load, and when possible, these headers double as rim joists to eliminate extra framing to allow for more insulation. Jack studs can even be eliminated with this method. When possible, the home's width is designed to have a single clear span to reduce costs and to provide windows on two or three sides of a room. Clear spans and structural rim joists also have the benefit of reducing the number of structural components which facilitates easier changes or modifications to the home later down the road (i.e. interior non-structural walls can be moved or eliminated during remodeling). Unless you live in a high wind area, old-school traditional framing has no place in a high performance home.
Waste Diversion
You will not see a dumpster or roll-off container at our job sites. We estimate that we are able to divert a minimum of 80% of the material that is taken to the dump at an average job site. Accurate takeoffs, efficient planning and use of materials, recycling metal, cardboard, bottles, etc, and repurposing offcuts for nailers, baffles, etc. are the first steps we take to reduce material going to the landfill. When the clean wood offcuts get too small to use, they are bundled and given away for kindling. Asphalt shingles and drywall can be recycled locally, too.