a structural engineers role in passive house · •know and understand the different ways...
TRANSCRIPT
A STRUCTURAL ENGINEERS ROLE IN PASSIVE HOUSE
Mark Benjamin, PE, CPHC, SECB
7777thththth Annual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceSeptember 27September 27September 27September 27----30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO
Session Learning Objectives:• Describe the role of structural engineers in Passive House, through
definition and examples. This will help in understanding and choosing a structural engineer.
• Describe the structural issues unique to Passive House, again through definition and examples. Being knowledgeable about these issues will help in discussions with structural engineers.
• Know and understand the different ways structural engineers have to approaching a problem, through explanation of the choices available. Knowing why your structural engineer would provide a particular solution despite or in agreement with your requirements will aid you in design and construction of a successful Passive House project.
• Know what questions to ask while interviewing a structural engineer, from a list of the questions provided. Structural engineering is not a black box full of mysterious potions, but rather an open science, open to those who know what to see.
7777thththth Annual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceSeptember 27September 27September 27September 27----30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO
Mark Benjamin, PE, CPHC, SECB
•BSCE in 1994 after a lifetime in construction of new homes and remodels• Including insulation, solar, sunrooms
• Residential, commercial
•PE in 2004 – 10 years due to good construction job after graduation
•MSCE in 2010, went back to school just for fun!
•Owner: Crown Jade Design and Engineering LLCBellvue, Colorado
Isn’t Passive House exciting?•DOE Challenge Home Partnership
•General Services Administration is embracing the Passive House standard
•RESNET has aligned with Passive House for an official HERS rating
Early Involvement: Integrated Design• Collaborative method for designing buildings which emphasizes the
development of a holistic design.
• Involves a “whole building design”
approach.
• As opposed to Hand-off approach currently used.
www.wikipedia.org
Integrated Design Teamwww.wbdg.org/design/engage_process.php
•Owner or owner’s representative: Decision maker
•Passive House consultant
•Architect: Lead designer
•Mechanical Engineer: HVAC systems
•Electrical Engineer: power, signal, illumination
•Civil Engineer: land, soil and regulations
•Landscape architect: affect of natural systems
•Construction Manager: GC, CM, or Architect
•…and Not the Least:
Structural Engineerwww.wbdg.org/design/engage_process.php
• Provides valuable input, addressing:
• Type of construction
• Column locations
• Floor to floor heights
• Bracing or shear wall locations
• Penetrations design
• Exterior cladding
• Equipment and utility locations and arrangements
• Modifications to existing buildings
• Especially Passive House criteria…
Some examples:
PASSIVISTA – On tour in Broomfield COHOT Soils! In the front range of Colorado and other areas of
the country, this refers to expansive clay soils.
The house has to set on concrete piers cast 25’ into firm bedrock.
PASSIVISTA – Expansive soilsThere is a deep expansion area beneath the basement floor.
PASSIVISTA – Suspended basement floorHow to insulate/isolate that space?
PASSIVISTA – Expand on what we learnedInstall a basement floor without concrete
8” x 12” concrete
thrust strips
2” to 6” foam in
intercrossed layers
Graded gravel bed¾” sheathing in
single or
intercrossed layers
Post bearing pads
at intersections
PASSIVISTA – Soil lateral loadAny kind of soil wants to tip the foundation wall over!
Extreme amount of
thermal bridges!
PASSIVISTASolution: use the floor framing as a horizontal beam (diaphragm)
MARTaK – Extended family Passive Housein Masonville, at 6400’ elevation
The owner has opted for a non-plastic envelope.
We saw this project last night during the poster presentations.
MARTaK – Site built sustainable insulation cavityModern Larsen trusses, site built from local Beetle Kill lumber, helping to stimulate local economy
2x3 for sheathing and
siding attachment 2x3 fastened to wall
sheathing at 24” o.c.
1x4 cross pieces at 24” o.c.
Felt paper cavity
separation material
1x4 support brace
All lumber and
connections have been
engineered to withstand
maximum loading;
however this is non-
structural so non-graded
and recycled lumber
can be utilized.
MARTaK – Imagine visiting this for a weekend
The experience will be available for short term rental, to see for yourself, or your clients, just what Passive House is, in a beautiful mountain setting.
MARTaK rest/work
cradle to cradle Passive House
View from the project
STRUCTURAL ENGINEER – Don’t have one who is sympathetic?
As much as I’d like to stay busy, I can’t serve all of you!
What to do?
Let’s ask everybody!
A survey would work.
Survey request sent to Alliance members in PHAUS Newsletter, Week 1, September, email dated 9-3-12
Some questions:
• What type of projects do you work on?
• Are you accredited in other rating systems?
• What percentage of your work is Passive House?
• What percentage requires a Structural Engineer?
• Does your building department require a PE/SE stamp?
• Do you work with a particular Structural Engineer?
Further drilling down:
• Is the Structural Engineer sensitive to Passive House?
• How does your Structural Engineer view PH issues?
• Thermal bridging in walls – double studs, columns, steel posts
• Thick walls – two layer, staggered studs, I-joists
• Air sealing, especially through structural connections
• Soil pressure – counterforts, floor connection, external wall
• Footing thermal bridge bearing on soil – foam, Foamglas, isolation
Educating Structural Engineers?
• Would it be helpful if the Structural Engineer had more knowledge of Passive House?
• Would you engage a familiar or PH experienced Structural Engineer?
• Who should train Structural Engineers in Passive House requirements?
• What areas from previous questions does your Structural Engineer need help with?
Results
1. What types of PH projects 100% residential, some others
2. What percentage is PH 25% to 50%
3. What percentage requires SE 25% to 50%
4. Does your building dept. require SE 67% yes
5. Do you engage a particular SE 67% yes
6. Are they sensitive to PH needs 50% yes, 50% need education
Results
7. What kind of SE do you prefer 75% practice the Art of Engineering
8. SE have problems with thermal bridging 50% yes
9. SE have problems with thick walls 100% no
10. SE have problems with air sealing 67% do not disturb connection
11. SE deal with soil pressure at top of wall 75% rigid floor connection
12. SE deal with footing bridge on soil 75% isolate
Results
1. Would it help for SE to know PH better 75% yes
2. Would you engage familiar or trained SE 75% experienced or trained
3. Who should train SE’s 50% architect, 50% PHIUS
4. What PH issues do SE need help with 75% bridging & fdn, rest airsealing
5. Final thoughts• So far, this has been a not very much thought about question, but will only become a bigger issue in
larger more complex buildings (and retrofits). As [someone] who has seen hundreds of projects, most problems presented here can be overcome (for instance no foam under the footing), but it would be quite excellent if details were designed for T[hermal] B[ridging] and adequate structure (particularly in seismic zones, which we have been rather ignorant of as well).
Choosing a Structural Engineer
Have you found and (Passive) house broken your Structural Engineer?
The fabled Art of Engineering is rare, except for firm with that name is Colorado Springs:“We all benefit from the wisdom and skill applied to building science by craftsman and others who long preceded us. Applying modern engineering to old world methods and materials is a lot of fun. Helping others to consume less resources gives us a great deal of satisfaction.”1
1 http://www.artofengineering.com/History.htm
Choosing a Structural EngineerInterview and choose one with the same science used in choosing a wall system or…
Philosophy of the Structural Engineer:
1. Are you creative? Ask for examples (SE’s love to talk about geeky solutions too)
2. What analysis programs do you use?
• It doesn’t matter if you know them, if a long list is given, beware of a non-creative thinker.
3. What groups do you belong to?
• ASCE only shows large projects and rote thinking;
• Structural groups shows knowledge gaining;
• Philanthropic groups shows empathy.
4. What credentials do you hold?
• SE is Structural Engineer who has taken extensive test;
• NCEES is a records program for easier multiple state licensing;
• SECB is Structural Engineers Certification Board, voluntary;
• Anything with F is a Fellow, one of the big guys.
Choosing a Structural Engineer
Experience of the Structural Engineer:
1. What type of projects do you engineer?
• Anything high rise shows computer and rote engineer
2. Have you worked with alternative construction?
• If you need to explain, they haven’t and may not be open to.
3. Have you worked with SIPs or ICF?
• Experience here represents energy efficient thinking;
• To drill down: how would they treat point loads in a SIPs wall;
4. Are you familiar with the thermal bridging issue in architecture?
• Typically the curtain wall installer designed the fasteners to the frame;
• The Structural Engineer reviewed the connections for strength;
• The Architect reviewed the connections for location;
• Who checks for a solid steel thermal bridge?
• Experience with composite connection details shows forward thinking.
Choosing a Structural Engineer
Receptivity of the Structural Engineer:
1. Are you willing to bear a foundation on foam?
• Understanding 1% vs 5% deformation rates is important
2. Are you willing to bear a foundation on glass?
• This is a trick question, but if they know the answer, hire them!
3. Are you willing to use a perlite-concrete structural slab?
• This is fairly new even to Passive House, but viable
4. Would you use mineral wool batts below grade?
• Has advantages, with constraints;
5. Would you attach siding over 4” – 6” of foam?
• Fastenmaster Headlok screws have testing and installation guidelines
• Familiarity with this takes research
6. How would you design a double stud wall?
• Floor bearing – will the SE allow the rim joist to be covered with the thermal layer?
• Shear layer location – will the SE allow for proper air sealing?
(Passive) House breaking a Structural Engineer
In the survey, remember 50% of the respondents answered PHIUS
The other 50% said the architect/consultant should
Respond to the survey:
https://www.surveymonkey.com/s/StructuralEngineersRoleinPassiveHouse
We’ll design a teaching program together!
Successful Passive House depends on knowledgeable team members
Remember the lessons taught in this book about the importance of a sympathetic Structural Engineer…and the problems that arise without one.
Let’s continue to learn…and teach…everyone involved
To make Passive House 100% successful!
Earthscape from Apollo 17,
December 7, 1972
THIS IS THE ONLY
“HOME” WE HAVE!
SIMPLY PUT:
GREEN BUILDING [AND
PASSIVE HOUSE] IS
THINKING ABOUT THIS >>
AND THE CONSEQUENCES
OF OUR ACTIONS!
Condensed from Green Definition Article by
Mark Benjamin, August 27, 2008
ANY QUESTIONS?• Contact info:
Mark Benjamin, PE, CPHC, SECB
970-472-2394
www.rm-ph.com
www.crownjade.com
www.roundfoothomes.com
with special thanks to Lisa Farmer
of Rocky Mountain Passive Associates