PATH 5 - Passive House: PATH 5 - Passive House: Principles into PracticePrinciples into Practice

A Case Study in A Case Study in Future FittingFuture Fitting

Thursday, April 22, 2010  -  10:30 AM - 12:00 PMThursday, April 22, 2010  -  10:30 AM - 12:00 PMTad Everhart presented by Graham S. WrightTad Everhart presented by Graham S. Wright

Overview

House “Futurefitting” 12-year old 2,150 square foot 2-story detached single family

Ventilated crawlspace Portland, OR PH standard

Project Summary

Superinsulated and air-sealed the envelope.Replaced our 80 kBtu/h (condensing) gas furnace & 25 kBtu/h direct vent gas fireplace.

Installed mechanical, balanced HRV with an in-duct 8.5 kBtu/h (2500W) electric resistance heater.

We gave the gas furnace to charity and the gas fireplace to a friend last September.

Note: In Portland, OR natural gas is a greater contributor to household GHG

Insulation Climate-appropriate Insulation (“Superinsulation”) Walls: Increase from R11 to R50. Superinsulation with 10”

deep exterior Larsen Trusses on 90% of exterior walls and XPS inside and outside of remaining walls.

Attic: Increase from an unknown R to R80. Superinsulation of attic by adding 6” of EPS under existing 10” of loose fiberglass and 10” cap of cellulose over the fiberglass.

Floor: Increase from R15 to R48. Superinsulation of ground floor by adding 9.5” tall blocks of EPS, 1” of Insulcap to bottom of joists, and 0.75” of EPS panels.

Insulation of foundation walls with Polyiso, XPS, and EPS.

Air-sealing

A. Improvements to exterior plywood sheathing.

B. Reduce wall penetrations to 6 dedicated, sleeved penetrations.

C. Eliminate plumbing vent pipe penetrations. D. Replace all windows and 3 of 6 doors. E. Remedial air-tightening to remaining doors.

Balanced Mechanical Ventilation

A. ZehnderAmerica ComfoAir 350, 84% thermal efficiency HRV.

B. ComfoTube duct system with air-tight registers and manifolds.

C. Seiho PK far-throwing diffusers. D. Bathroom switched ventilation boosting

system. E. Clothes drying closet integrated into return

air system.

Lighting and Daylighting Upgrades

Replace 6 CFLs and 2 fluorescent tubes in kitchen with 5 LED cans.

Install dimmer switches on LEDs. Install additional dedicated CFL light fixtures. Install motion sensors in 2nd floor bedrooms. Through-second floor light wells in kitchen

and back hallway.

Larsen Trusses

A. Raw Materials: LP “SolidStart” 1.5X3.5” Laminated-veneer lumber (LVL) (13 veneers), GRK RSS 0.25X3.5” structural screws, GRK 3.125” cabinet screws, 0.5” 5-ply exterior glue CDX plywood gussets, and 1.5” staples.

Larsen Trusses

B. Assembly: Rip LVL on table saw, lay LVL on jig; staple plywood gussets to LVL chords, staple on “Hanes” polyester fabric.

Larsen Trusses

C. Install with two structural screws through inner LVL chord at each gusset. Gussets at top and bottom plates, rim joist, and every 48” for total of 6 per 18.5’ tall Larsen Truss. Cabinets screws every 12” in field.

Larsen Trusses

D. Cover with Knight-Celotex 0.5” fiberboard for non-structural sheathing with asphalt water barrier facing out. Cover with Tyvek.

Larsen Trusses

E. Load-bearing Larsen Trusses below front and back decks have 2” deep LVL outer chord sitting on bottom plate and sheathed with 0.5” plywood.

Larsen Trusses

F. We blew in cellulose from the top of the cells working off scaffolding to achieve 2 to 3 pcf density.

Larsen Trusses

G. We drilled 2.5” diameter holes in existing bird blocks at eaves and exterior plywood sheathing at gables we can “top off” the cellulose from inside the attic if it settles.

Larsen Trusses

H. We held Larsen Trusses 6” back from window and door openings and plan to trim the openings around them with XPS covered with molded polyurethane trim.

Larsen Trusses

A. Raw Materials: LP “SolidStart” 1.5X3.5” Laminated-veneer lumber (LVL) (13 veneers), GRK RSS 0.25X3.5” structural screws, GRK 3.125” cabinet screws, 0.5” 5-ply exterior glue CDX plywood gussets, and 1.5” staples.

B. Assembly: Rip LVL on table saw, lay LVL on jig; staple plywood gussets to LVL chords, staple on “Hanes” polyester fabric.

C. Install with two structural screws through inner LVL chord at each gusset. Gussets at top and bottom plates, rim joist, and every 48” for total of 6 per 18.5’ tall Larsen Truss. Cabinets screws every 12” in field.

D. Cover with Knight-Celotex 0.5” fiberboard for non-structural sheathing with asphalt water barrier facing out. Cover with Tyvek.

Larsen Trusses

E. Load-bearing Larsen Trusses below front and back decks have 2” deep LVL outer chord sitting on bottom plate and sheathed with 0.5” plywood.

F. We blew in cellulose from the top of the cells working off scaffolding to achieve 2 to 3 psf density.

G. We drilled 2.5” diameter holes in existing bird blocks at eaves and exterior plywood sheathing at gables we can “top off” the cellulose from inside the attic if it settles.

H. We held Larsen Trusses 6” back from window and door openings and plan to trim the openings around them with XPS covered with molded polyurethane trim.

Lessons Learned on LTs:

Have a factory build them for you Consider LVL without wax coating so you can glue gussets to the LVL. There’s not enough room to drive screws straight in through the inner

chord. Solution: Predrill the screw holes, insert the screws prior to attaching the LT, and use an offset drill to drive the screws

Consider a continuous horizontal bottom chord to “suck-in” the sheathing to the bottom plate

Always net the top of the cells before you start the cellulose fill to avoid the mess from “blow-back” and to achieve higher density

Check and re-check for shiners

Air-Sealing Strategies

A. Eliminated Unnecessary Wall Penetrations by eliminating or consolidating electrical wiring and plumbing.

B. Route essential plumbing, air supply, air exhaust, electrical, and vacuum through 6 dedicated, fully-sealed, sleeved openings.

B. Eliminated Unnecessary Ceiling Plumbing Penetrations with Studor AAVs (for negative pressure) and 2-way vent (for positive pressure).

C. Minimized ceiling electrical penetrations by having electrician reroute and changing ceiling light fixtures to surface mount (after being convinced that eliminating all ceiling fixtures was not necessary).

D. Flexible flashings on the sheathing with and without painted-on adhesive but always using mechanical fastening (either LTs or battens). Would thin, self-adhesive foam tape worked better?

Air-Sealing Strategies

E. Using 2-sided adhesive foam tape plus flexible flashing on window and door. This creates adhesive-to-adhesive bonds plus adhesive onto flexible flashing bonds.

F. Remedial interior approaches (“caulking” sealants, backer rod, expanding foams, and 3M All Weather Flashing tape).

G. Top plate and GWB nailer sealing in the attic with all of the above plus gaskets.H. Plan to use sealant caulking on bottom side of floor seams with adhesive foam tape

over held in place by metal flashing in crawlspace for side seams of plywood floor sheathing. Devising strategy for butt joints above joists.

Windows and Doors

We made many hard choices to give up windows and doors with glazing. I spent 4 months considering window choices, consulted family members, and created multiple PHPP files to make my choices. It was time well spent. Until we have better windows, you must make every window count. Will the North, East, and West sides of our passive buildings look like pioneer houses where windows were small because glass was so expensive.

I made every door (except to the garage and attic) glazed so it will do double duty as a window. The R value of even the best door is not near to a wall, so make them do double-duty as windows.

I gave up cross flow ventilation in two rooms to eliminate operating windows on the South side since they significantly reduce the glazing fraction. We will experiment with through-wall inter-room ventilation across the house aligned with the prevailing summer wind from Northwest (with our operable windows and doors on West and East).

A picture window has a much higher glazing fraction than a casement, and a casement much higher than a single-hung. Another good reason besides air-tightness to abandon most windows that slide.

Casements are air scoops. I believe our new 2/6 by 4/0 casements will provide as much or more ventilation than our twin 3/0X5/0 SH windows did in the past because they are air scoops. And our 2/0X2/0 casement in our bathroom provides more ventilation than the 2/0X3/0 SH it replaces (in addition to sufficient daylight and more privacy).

It’s exciting to see condensation on the outside of the outside layer! And to feel the inner pane that doesn’t feel cold. Expensive, but worth it.

5. HRVs, Ducts, and Furnaces

It’s a wonderful feeling to get rid of loud kitchen and bathroom exhaust fans that discard your warmest air. My wife has a sensitive nose, and she says we have better air quality. I’m thrilled to recycle the heat from our warmest rooms. I’m also looking forward to our HRV’s automated night cooling flush setting so I don’t have to get up early in the morning and being able to cool incoming ventilation air in the 100-degree summer days.

I don’t have enough experience to know if our sheet metal work was good, bad, or average. It certainly wasn’t air-tight or smooth.

We should design ventilation ductwork for air-tightness just as we should for the envelope’s air-tightness layer. Applying mastic to seams and holes in sheet metal ducts is like remedial air-sealing of a leaky envelope. Why build something that is inherently so leaky that it immediately needs remedial sealing? Are you sure the mastic will hold for 50 years? 100 years?

I’m sold on Zehender’s ComfoTube system. With low flows, you need airtight connections even if all of the ducts are within the envelope. Air-tightness is designed in when you use continuous plastic ducts with tight-fitting rubber gaskets. We used to run water in building through metal pipes, and now we use PEX. What works for water works for air. In a low-energy system, you don’t want air leaks any more than water leaks.

I hate my new auxiliary heater, and I’m getting rid of it as soon as I can install a better system. Even if the 8.5 kbtu output is a 10th of our old 80 kbtu furnace, I wince every time I think about electric resistance heating. Even two hairdryers use a lot of electricity if they are on all of the time!

6. Real Life Lessons Learned

0.6 ACH @ 50 Pa is tough. Don’t cover any part of assembly until you’re sure it is air-tight. I wish we’d had windows & doors in time to do air-test before we started attaching Larsen Trusses.

Great components are fun —especially our ZehnderAmerica HRV and ComfoTube, Studor AAVs, Innotech Doors, Serious Windows, Apex polyurethane trim, and Insulcap aerogel.

Friends Can Help A Lot. Many of you have helped with advice. We all have a long way to go and a lot to do to change our built environment. We’ll go faster and farther together. Take time to help others! Our end (saving the Earth) should inspire our means (cooperation). We are in it together.

Don’t delay good enough waiting for perfection

I’m glad I started when I did even though I may have made some mistakes I’d have avoided if I waited---proceed if you are 80% sure (MOB).

I’d have preferred: White/alum metal roof instead of comp with

reflective paint Heat pump instead of electrical resistance aux.

heating Heat pump instead of gas water heater Remove and replace roof instead of Dutch Hip Installing a thermal break at the foundation

There will be mistakes! Here’s a few:

South gable overhang shades 2nd floor south-facing windows too much

HRV ducts to ambient should not run 10’ inside the envelope

Relying on oral/written instructions for carpenters and subs instead of constant supervision

Thinking I can change my carpenters’ and subs’ ways of thinking. If I constantly supervise them, I can ensure they produce the product I want, but no amount of encouragement/incentives will change some minds.

For more information

Email: tad.everhart@comcast.net

Website: everhartpassivehouse.net

Phone: 503 239-8961

Copyright © 2009-10 by Tad Everhart.

All rights reserved.