The Forum
 

Dear Ken

I read your article on Protection from Precipitation Cladding Provisions in the Building Envelope Forum.

I am based in New Zealand and we have similar problems with leaky buildings as Canada does so the subject is of interest.

You refer to a Two Plane System for certain claddings. In New Zealand we have adopted a similar cavity drainage system for ventilation and draining. This is formed by timber battens between the outer cladding and building wrap on the timber framework.

My company has just developed and launched on the market a polypropylene batten that has holes through it to drain or ventilate when installed in a horizontal or vertical position. If you have a look on my web page you will get a better understanding of it. www.cavibat.co.nz  It has numerous advantages over timber which are listed in the brochure section.

The system has had independent testing at  BRANZ a division of NZ's department of Building and Housing  

I am looking at the feasibility of bringing the batten system to Canada. You have obviously had experience in the building arena and I would value your opinion as to the suitability of my system for your construction industry in Canada. 

Thanking you in anticipation, I look forward to your response

Kindest regards

Graeme Webster

Managing Director

Cavity Batten Systems

graeme@cavibat.co.nz

http://www.cavibat.co.nz

Dear Jacques Rousseau,

Contact Information
----------------------------
Mr. Bion D. Howard
Building Environmental Science and Technology
P. O. Box 23858
Hilton Head Island, SC 29925
  Web:  http://www.energybuilder.com

Dear Jacques Rousseau,

I really enjoy reading the various views of current construction techniques and the problems and solutions expressed in the forum.

My quest for something better over the last 20 years  led me to build an ICF (insulated concrete form) bungalow with a Can-am Hambro poured in place main floor.  Both the basement and the main floor have hot water radiant floor heat supplied with a New York Thermal  Infinity wall mount boiler.

The roof trusses have a raised heel to allow full depth insulation to the outside surface of the perimeter walls. There are no load bearing interior  walls. That made it easier to attach  Nudura ceiling technology to the under side of the trusses and completely drywall the ceiling before installing steel stud interior walls.

Nudura ceiling technology is 3.5” type 2 EPS foam with 1 X 3 wood molded into it on 16” centers. Each pot light in the ceiling had a box installed fabricated from 2 “ extruded foam insulation and 5/8” fire code drywall. All gaps, seams and service penetrations in the ceiling were filled with low rise expanding foam. See attached photo. The ceiling also has a 6 mil poly vapour barrier. If anyone has any questions or comments on these building processes I would be pleased to answer them.

Larry Ryan

Gormley, Ont

lryan@ican.net

Dear Jacques Rousseau,

Figure 1: Does your air barrier consistently look like this? It should ! I HOPE NOT!

Membrane laps/seams not staggered.

Continuity between columns and roof. Must be work in progress??

Wall preparation, mortar joints not cleaned.

Primer spilt onto exposed slab.

Polyethylene not removed on laps/seams

Dear Jacques Rousseau,

CMHC's New Best Practice Guide for ElFS:
 

I am an architect in the US and teach building technology to architecture students at Cornell University.  I noticed images of a pressure-equalized EIFS cladding system in a recent article in the

Construction Specifier (CSI, May 2006, p. 50), and some internet research turned up your name as CMHC Project Manager on a study of such

systems.

I have always wondered how introducing pressure-equalization channels behind, or cut into the back of, the insulation boards is compatible with their function as insulation.  Wouldn't exterior air introduced on the interior side of the insulation compromise its thermal performance?

I have asked industry representatives about this and have never received a cogent reply.  Do you have any insight into the question, or can you refer me to anyone who might?

Thanks in advance for your help.

Jonathan Ochshorn

Associate Professor, Architecture

phone:  607-255-1194

fax:       607-255-0291

email:   jo24@cornell.edu

address: 143 E. Sibley Hall

            Cornell University

            Ithaca, NY  14853

internet: http://www.people.cornell.edu/pages/jo24

Dear Jonathan ... very good question!

The channels or the cavity behind the cladding will not have a great influence on the thermal performance of the insulation.

For pressure equalization to occur it requires a very small amount of air (a few %).  The normal pressure in channels or the cavity behind the cladding is at atmospheric pressure 100 kilopascals, a very strong wind will generate an equivalent pressure of 1 kilopascal.  Therefore the amount of air required to increase the pressure behind the cladding is very small.

The effect of the additional air entering the cavity to pressure

equalize the compartment will be located at the vent hole and should not cause a convective flow.  The effect on the insulation will be localised near the vent hole.

I hope that my explanation is clear and answers your question.

... Jacques

Dear Jacques,

Thanks for your answer: I think I get it.  I had a mistaken vision of the channels being more like the continuous vent spaces above insulation in roof rafters which are designed such that cold air is encouraged to circulate through the channel.  Instead, these "channels" are more like "chambers" with a single opening that effectively traps the air, designed to equalize pressure only.  The trapped air basically stays warm (in winter) since only a small amount of cold "new" air enters to equalize the pressure inside.

As to your other request about posting on the"Building Envelope Forum" website, I originally intended to post the question but could not (and still cannot) figure out how to accomplish that task.  I can find no links or instructions on the site.  Feel free to forward this correspondence to someone who can post the conversation, or let me know how to do it myself.

Again, thanks for your help.

Jonathan

Dear Jacques Rousseau,

Do you know of any solution to keep woodpeckers from destroying our brand new EFS and acrylic stucco finish on a multi family building we have just completed?

Thanks,

Ken Webster

Kelowna, BC

Day, Kevin [mailto:KDay@halsall.com]

Dear Kevin,

I fake owl is not a bad trick, these shots are from North Vancouver where Wpeckers can be an issue...

Jacques

Dear Jacques,

Thanks for the e-mail. We've tried the fake owl in the past and the woodpeckers seem intelligent enough to figure it out after a while. However, maybe we'll try again.

Please fell free to post this on your "Forum". We're open to any advice at this point.

Thanks again,

Ken Webster

GENERAL

Great news source!  Many thanks for adding me to your mail list.

Arthur Walter, CSI, PSA
Webmaster, Palm Beach Chapter, CSI
Delray Beach, Florida

GENERAL

Dear Jacques Rousseau, 

Thank you for including me in this forum.  I am a licensed Architect in California working for a consulting group.  We have defended developers, general contractors and subcontractors against allegations with regard to the construction of large and small buildings.  One of our efforts now focuses on "Peer Review" of projects before they are built.  Obviously an open forum like this will provide useful discussion and ideas as to how we can improve the built environment. 

I look forward to discussions on issues.

Robert Stowell, AIA

Project Manager

Roel Consulting Group

Dear Jacques Rousseau, 

I have finally found time to read this forum and it reminds me of the round tables we used to have at the Alberta Building Envelope Council in the 80s and not at all surprising to me some of the names I am reading in the articles were there at the meetings. Keep up the good work!!

Regards:

Jim Jennings

Manager

Canadian Academy of Building Sciences

Dear Jacques Rousseau,

Your newsletter sounds great. I have one problem; I am in Texas, where the heat is usually on the outside Not the inside. Will your newsletter describe solutions for both cold climate and hot-humid climate situations or at least differentiate between the two conditions?

Thanks,

Amanda Tullos, Assoc. AIA, LEED AP
co-Chair
AIA COTE – Houston
American Institute of Architects
Committee on the Environment
http://www.aiahouston.org/cote

Heights Venture Architects, LLP
1111 North Loop West, Suite 800
Houston, Texas 77008
V 713-869-1103

Direct- 281-854-6111
F 713-869-5573
E amanda.tullos@hva.cc
www.heightsventure.com

Dear Jacques Rousseau, 

Congratulations on the Building Envelope Forum. It's awesome!!!

 If it's of value to you, I would be pleased to put a free ad/announcement for it in one of my future BCBuilding.info newsletter issues. My little ol' rag now goes to over 800 building industry subscribers, most of which are here in B.C.I think your site/newsletter would be an excellent resource for at least some of them. Let me know if this is of interest to you, and I'll do what I can to make it work.

Have a Top Drawer day.
Ken :o)
 
Ken Farrish
BCBuilding.info
E-mail: ken@bcbuilding.info
Phone: 604-943-9299
Web site: www.bcbuilding.info
A free e-mail newsletter on building technology.
Written for the British Columbia building industry.

Dear Jacques Rousseau,

Recently I received an email announcing your Building Envelope Forum newsletter.  Considering your position as publisher and profession as civil engineer, I find it surprising that the newsletter thus far ignores grading and drainage, site design and circulation, and landscape architecture.  As you know, these design components are integral to a comprehensive design package. 

You may have familiarity with the Whole Building Design Guide website (http://www.wbdg.org).  Again, a similar issue with primary consideration for the building alone.  The website publishers are currently working to include "whole site" aspects as part of their website articles and references.  I would urge you to consider the same action.

In my opinion, the inclusion of planning, landscape architecture and civil engineering into the various aspects of building function and siting, sustainability, and other site/building life-cycle considerations and costs would greatly benefit your newsletter subscribers. 

Respectfully,
Amy Baquial

Amy E. Baquial, RLA, ASLA, LEED AP
Sr. Landscape Architect
Naval Facilities Engineering Command
Southwest Division
1220 Pacific Hwy, Code CI5
San Diego, CA 92132
Phone: (619) 532-1523, Fax -1195 DSN 522-
Email: Amy.Baquial@navy.mil

Dear Jacques Rousseau, 

Colleagues at the Boundary Layer Wind Tunnel Laboratory at Western recently passed along your email about the first issue of the Building Envelope Forum. Congratulations, it is topical and does look very interesting.  How does one subscribe to it, please?

I don't know if you've heard about our "Three Little Pigs" project.  We are in the process of constructing a $7 M facility to be able to subject full-scale houses and light frame construction to time- and spatially varying loads that accurately simulate the turbulent wind.  Our facility will also offer the opportunity to do building science research -- moisture penetration through walls that may have been damaged by simulated extreme wind loads, for example. We will also be researching the development and growth of mould.

You can find out more about our facility and research objectives from our

website:  http://www.eng.uwo.ca/research/ttlpp/

You know...after 30 years in this business, I had a bit of an epiphany yesterday.

I was on site at CFB Borden with my old friend Gerry Gardiner of Defense Construction, and we were there for a "deficiency" inspection of one of our Projects.

For me, deficiencies have always been the bane of my existence...not because I have more than my share of them, but because here, at the end of a job, no matter how well the Project has gone, you actually spend time picking it apart to find out what is wrong or "deficient" in how it has been done. It is always so negative.

Even the word "deficiency" is negative in its connotation. Yesterday, Gerry decided to call it something else...he called it "Quality Control". For me, it was like the difference between saying..."that's a bad kid" and "that kid has bad habits" We are all in this game to produce something of lasting value. Instituting Quality Controls, rather than Deficiency Lists sure makes a lot of sense to me.

It's a little difference, but I think it is a positive one.

Regards,

Brian Shedden, BSSO

V.P. Client Services

 Office Tel: 416-431-7770 ext. 25

Office Fax: 416-431-4335

Cell:       416-991-1083

Dear Jacques Rousseau (and Luis),
I would really like to see an editorial discussion in your Forum on the issue of the Poly vapour barrier that we normally install in walls. This vapour barrier is seen in the multitude of CMHC Best Practice Guides on Wood Frame and Steel Stud Insulated construction, and is also still a code requirement.

I recently attended a presentation by Joe Lstiburek and my colleague John Straube, emphasizing to my students the prevailing laws of physics that would seem to indicate that we should not use poly vapour barriers as it traps the moisture inside the insulation and  is the root cause of mold and rot. It also presented quite a different wall section for frame construction, that relied much more on rigid cavity insulation, to the point of excluding batt insulation in some cavities since it would cause convection currents anyway due to poor installation practices, and end up wet in the long run.
http://www.buildingscience.com/resources/walls/Vapor_Barriers_Wall_Design.pdf

Where this construction type makes full sense for concrete block walls with brick veneer (type normally used in commercial and industrial types with lower insulation code requirements), it is difficult to implement in residential construction. The amount of rigid cavity placed insulation required to meet code, without the use of batt insulation in the wall is very high. You need much stronger brick ties to create the space and this also affects the foundation detail. Most residential foundations are simply not wide enough to hold the brick veneer, large gap for rigid and the sill plate.

As a professor of architecture and building construction and building science I am totally perplexed as to what I am to teach!

Firstly, I have mostly students in the 18 to 19 year old range, right from high school, in my class. I am not sure that they are up to understanding the fine points between the issues, nor prepared to take on the building inspector or building officials should they try to get a permit and build without installing a vapour barrier.

Secondly, as an accredited program that is supposed to be sending out students that know the rules and how to do things properly, this puts me in an awkward position.

Thirdly, I am not sure what the law says if an Architect decided not to install one, which is still required by code, and runs into trouble down the road. Mind you, I am sure that whatever you do, you are damned in this case.

Fourthly, is the code (and the full range of CMHC Best Practice Guides) ready to implement this change in vapour barrier use for frame construction?

Fifthly, sigh.

thanks

Terri Meyer Boake BES BArch MArch LEED AP
Associate Professor
School of Architecture
University of Waterloo

Dear Jacques Rousseau, 

I first wish to thank you for your excellent work and informative newsletters.  Next, I wish to pass along a Green tip to include in your next update of the publication entitled “Farewell to Cockroaches” 60948 or 61145.  My tip consists of a bait recipe that I have found to be cheap, very effective, easy to make, and long lasting.  To wit,

·         Buy a one pound container of Mr. Roach Killer, BoraDust, or Roach Proof (all 99%+ boric acid).

·         Buy a small can of Eagle sweetened, condensed milk or equivalent

·         Wear a simple dust mask

·         Mix the two ingredients in any bowl to a dough like consistency

·         Form dough balls or small flattened patties and leave to dry on a piece of foil or wax paper, they harden in a few hours

·         Carefully wash your hands and the bowl

·         Place them in roach, silverfish, ant territory like behind the freezer, lay them on top of the ducts in the basement, stand at the attic hatch and toss them around in the attic, slide one under the water heater, or pull out a bottom drawer in the kitchen and lob them over the back to lay on the floor under the cabinets, etc – the patties fit into thin places and the balls lend themselves to being rolled into hard to reach spots

·         The left over bait can then be placed in a clearly labeled zip lock bag and stored for years in the freezer

·         The bugs love the sugar and protein of the sweetened condensed milk and feed it to the colony

·         They never figure out its poison and never develop an immunity to the boric acid

Why pay the high cost for commercial bait when any bachelor can make this inexpensive recipe?

Yours,

Doug Garrett, CEM

President

Building Performance & Comfort, Inc.

PS – Hope to see you at Joe’s this summer and Happy Holidays to you and yours from warm Austin, Texas!

Dear Jacques Rousseau, 

Tin can by the sea. I like it.

You said:

'We would appreciate any suggestions for topics and speakers that you would recommend'

I would love to speak in Toronto on the frustrated market in Britain for high performance manufactured Canadian housing, and how despite a dilapidating and aged British building stock, a booming property market, household demand, and plenty of land, it is the planning system here that works against a steady order stream.

I'm a co-author of 'Why is construction so backward?' (Wiley 2004)

Regards

YRM

 Ian Abley

iabley@yrm.co.uk

http://www.yrm.co.uk

YRM ARCHITECTS

32 York Way London N1 9AB

t: 020 7014 4300  f: 020 7014 4301  yrm@yrm.co.uk  www.yrm.co.uk YRM Limited. Incorporated in England and Wales No 3335485.  Registered at the above address.

Building Air Barrier Testing and Verification Using Smoke Flow Testing and Infrared Thermography in the Canadian Arctic: A Case Study - 2002-2003

Bill,

 Am I right in assuming your the co-author of the Inuvik Hospital case study cited below?

 This email came "out of the blue" from Jacques Rousseau "Somewhere in Mexico".

 Do you know if this is all valid stuff?

Thanks,

Don Worrall

Executive Director

NWT Construction Association

Jacques Rousseau has been working with building physics and envelopes for over 35 years and is well-respected in construction circles.  He retired from CMHC last year and operates the building envelope website from either his Mexico part-year residence (winter) or from eastern Canada in summer.  I believe “tin-can-by-the sea” may refer to a type of dwelling, perhaps a metal skinned modular house, but I am not sure of that.

 The articles are submitted from various sources and I take them to be considered expert opinion from the authors, many of whose work I know. Jacques Rousseau runs quality control on the articles so they conform to currently accepted practice.

 Richard Ogle and I developed the Inuvik hospital report for presentation to the Canadian Civil Engineering Society two years ago in June.  I have e-mailed Jacques to get my name re-inserted along with Richard’s into the article posted on the web site, so Richard does not need to take any of the flack all by himself.

Regards,

Bill

-----Original Message-----

From: Maria.Spinu /unix [mailto:Maria.Spinu@usa.dupont.com]

Sent: January 13, 2006 8:47 AM

To: richard /unix; Bill Wyness /YK /PWS

Subject: Your case study article

To:  Richard Ogle and Bill Wyness

Dear Richard and Bill,

I work for DuPont Building Innovation in Wilmington, Delaware, and I am the Building Science Integration manager.  I have recently read your article on "Building Air Barrier Testing and Verification Using Smoke Flow Testing and Infrared Thermography in the Canadian Arctic: A Case Study - 2002-2003" which was published in the Building Envelope Forum.

I have a 2-part follow-up/question:

1.  Has it been any follow-up on the building energy performance after repair?  This would be extremely valuable for the industry, since there is no "before" and "after" documented performance to support the importance of building airtightness. You might be familiar with the

current effort led by Wagdy Anis, AIA, an architect with Shepley Bulfinch Richardson and Abbott in Boston, and ABAA (Air barrier association of America);  they have been trying to introduce a code requirement for airtight buildings in the US.  However, there is resistance from some building trades or building professionals, because there are no documented cases of improved energy performance by making buildings airtight;  extensive energy modeling done at NIST (in support of this proposal) clearly support improved energy performance of airtight buildings, but engineers want to see real data.  Your case study would be excellent to provide this type of documentation.  If there hasn't been a follow-up, would it be difficult to at least get some information on the energy bills before and after?  

2.  If you are doing a similar project in the future Tyvek(R) would like to get involved.  Using a continuous air barrier is an easier and more durable solution for the building airtightness, and we would love to get some documentation on specific case studies.

 Please do not hesitate to contact me either on the phone or email, if you have any information or are interested to work with us on future projects.

Regards,

Maria

Maria.Spinu@usa.dupont.com

(302) 999-2839 (W)

(302) 999-4763 (Fax)

(302) 545-0980 (cell)

Bill Wyness NWTAA

Sr. Technical Officer - Architectural/Structural

Technical Support Services - Asset Management Division

Public Works & Services - GNWT

5009 49 St.,  SMH 3,

Yellowknife NT X1A 2L9

867 873 7847  Fax 867 873 0226

mailto:Bill_Wyness@gov.nt.ca

To: Maria Spinu – Dupont Building Innovation

Maria - Thanks for your interest and note.

Comment 1)

The building in the case study was coming out of construction.  As such, it had no long-term documented operating cost history prior to the remedial work on the envelope; therefore we have no comparative base for before and after.

Additionally, we recognize that inexact operational parameters for ventilation in the high arctic can mask the benefits of a tight envelope, because of the high heating cost of bringing in normally very cold air, particularly with the air change rates mandated in a health care facility.  Consider Fairbanks as a climate equivalent for the winter operational model of the Inuvik hospital.

The primary envelope tightness benefit in this building is considered to be the stable interior airshed created by effective control of infiltration and exfiltration.  The summer environment in Inuvik can be dusty, encouraging tighter envelopes and better air filtration at the envelope perimeter and at outside air intakes.  We positively pressurize this class of building (15 Pa or so in this case) to offset infiltration, so leakage is a primary consideration, because it generates condensate and frost building up in the envelope air channels.

I am familiar with the NIST comparative theoretical models, and believe the benefits of a tight envelope are becoming more universally recognized as fuel costs increase.  The European Union has instigated building energy performance standards starting in 2006, and, in Canada, Natural Resources Canada has for many years sponsored energy conservation in buildings through the Commercial Building Inventive Program (CBIP) which subsidizes sensitivity analysis during design to maximize return on energy conserving components and systems in buildings.

A way to get comparative data from the IRHSSC study would be to estimate the envelope leakage rates of the building before and after remediation, based on calculated exfiltration volumes.  My personal sense is we reduced the exfiltration rate by about 65%, because we did not seal all the leakage paths found by the thermographic surveying. (Richard Ogle may have another view of this, so I speak only for my self).

With this in mind, it is possible to do energy models (Eg DOE 2, EE4) with the two exfiltration rates (envelope air ex/infiltration comparison) and with the degree heating days prevailing in Inuvik (about 11,000 Celsius degree heating days), holding other variables constant, and see the theoretical energy consumption variance.

Comment 2)

We recognize the air-barrier qualities of the various Dupont products and how they are effective in certain classes of construction.  The air barrier system in a structurally insulated panel system such as was used on the IRHSSC does not lend itself to using Tyvek, because in Canada the National Building Code requires air barrier components to be mechanically supported sufficiently to withstand structural loads (such as wind gusting) which may impinge upon them.  Tyvek is commonly used when construction configurations (wood frame, for instance) can provide the required structural support for the air-barrier component, but does not traditionally readily lend itself for application in non-combustible steel framed construction.

Our Section has examined the newer self-adhering and dimensionally flexible Tyvek variants; we have examined them here in the past 2-1/2 years and recognize they have application where they can be adhered to substrates and not de-bond over time. The adhesive bed of a peel and stick membrane creates a vapour barrier in the same plane, and that effect must be considered when positioning the air barrier in the thermal gradient of the building envelope. The majority of our communities have low annual mean temperatures and short construction season, making the application of self-adhering (peel and stick) air barrier materials problematic because of adhered frost, and low temperatures at construction sites. 

We recommend in GNWT buildings hot applied (torch bonded) air barriers for the building envelopes in the cold northern climate, and highly impermeable materials, so the air and vapour barrier are in the same plane and positioned within the warmer portion of the envelope, with thermal insulation outboard of this plane.  This is the building physics solution for a cold-climate building, and would not necessarily be appropriate for a warm climate or humid climate building.

Please feel free to review “Good Building Practice for Northern Facilities”, available at the GNWT Public Works and Services web page at http://www.pws.gov.nt.ca/pdf/GBP/GBP%20home.pdf.  That Year 2000 version is currently outdated in some areas, and is under revision, containing recommended best practices for building envelopes.

Your attention to Building Envelope Forum is much appreciated, and I hope you can provide any comments to Jacques Rousseau, who has been instrumental in establishing that forum for dialogue.

Please feel free to contact me if any additional information is needed.

Sincerely,

Bill Wyness NWTAA

Sr. Technical Officer - Architectural/Structural

Technical Support Services - Asset Management Division

Public Works & Services - GNWT

5009 49 St.,  SMH 3,

Yellowknife NT X1A 2L9

867 873 7847  Fax 867 873 0226

mailto:Bill_Wyness@gov.nt.ca

INTERIOR DAMPPROOFING OF BASEMENT WALLS

Ken,

Interesting article.   I have recently been asked to comment on a 50yr old house in Toronto with regards to insulating the basement walls.  I was hoping to get your thoughts on the matter.

The basement has never been finished (only paint) or  insulated.  The foundation walls consist of brick masonry. The lower few feet of the foundation wall are always damp and "look wet".  We cannot access the exterior of the walls to install a proper drainage layer and insulation.  The first floor wood joists frame into the solid masonry walls.  The existing basement floor (slab on grade) is being removed.  There is a thought of installing an interior weep tile below the new basement floor slab.  I believe that the foundation wall should not be insulated as this will reduce the drying potential of the wall and increase its moisture content.  I am suggesting that an interior drainage layer is installed against the full height of the foundation wall (that dimpled layer that is commonly used on the exterior of foundations).  This layer will serve to isolate the new interior finishes from moisture, and also function as a vapour barrier.  The bottom of the drainage layer can be made to connect to the new weep tile (should we be worried about gases?).

Your thoughts would be greatly appreciated.

Regards,

Paul Pasqualini

Hi Paul,

I’m going to pass on a copy of my reply to Jacques Rousseau, editor of the newsletter who can review my observations and perhaps refer you to someone with more background in solving these kinds of problems.

If the problem were mine, I think I’d consider doing the following (accepting that access to the exterior is not possible and that the floor slab is going to be removed in any case):

1.         Install a perimeter run of perforated pipe (protected by a geotextile ‘sock’) just inside the footing so that the top of the pipe is at or below the elevation of the base of the footing;

2.         Connect the perimeter run to the exterior side of the foundation at intervals with perforated pipe (tunnel beneath the footing). Protect the pipe including its open end with geotextile ‘sock’.

3.         Connect the perimeter run, with perforated pipe (in a ‘sock’) to a sump (or the storm sewer if it’s permitted);

4.         Spread 6 inches or so of coarse granular fill over the floor to the top of the footings (0.15 mm poly over the granular fill would be a good idea, but care in placing and finishing the new concrete slab will be required);

5.         Install the interior drainage layer as you suggest, but only from the top of the new floor slab to the elevation of the exterior grade;

6.         Place the new floor slab;

7.         Repair any obvious cracks or mortar gaps in the wall;

8.         Frame the walls and insulate to a couple of feet below grade—install 0.15 mm poly over the insulated portion.

And the usual:

9.         Make sure eavestroughs and downspouts are installed and lead water away from the foundation;

10.      Seal any cracks where paved driveway or walkways abut the foundation; and

11.      Slope grade away from the foundation.

I think that, even with the insulation, moisture will continue to wick to the upper portion of the wall and be able to leave toward the exterior. Hopefully the moisture load will be reduced by some of the sealing and drainage measures. Hopefully the exterior of the foundation will not be painted or otherwise face-sealed to inhibit escape of water vapour (not likely paint would stay in place anyway). Poly beneath the slab will inhibit soil gas entry—including water vapour. Good luck!

Ken Rauch

I will suggest a minor change in the title for the discussion of Code Issues:  Ice Hotel in need of sprinklers as desperate guests need warming - but are they legal?

Anne

Anne Lewison, AIA

Downtown Design Partnership

7 Hanover Square/ 18th Floor

New York, NY 10004

FLAT ROOF OR WALL IS THERE A DIFFERENCE 

Letter by George Torok, B.Tech.(Arch.Sci.), Project Manager / Technical Specialist, Gerald R. Genge   Building Consultants Inc., Newmarket, Ontario, Canada.

 In response to your question, “Flat roof or wall, is there a difference?” let me respond by saying that of    course, there is a difference.  The difference is set out in the second paragraph of your article:  flat roofs are “expected to be watertight, perhaps even to the point of allowing ponding water to stand for a short period of time…”  Certainly some components of walls need to be watertight (through-wall flashings, for example) but we don’t expect walls to resist “ponded” water over their entire surface (although in the wake of Hurricane Katrina, undoubtedly there are many people in New Orleans who wish otherwise).  This fundamental difference is well reflected in the requirements of the NBCC, including the article you cite.

NBCC Article 9.25.1.2 describes general principles of Heat Transfer, Air Leakage and Condensation Control (the title of Section 9.25).  Your paraphrasing of the requirements of 9.25.1.2 is incomplete and therefore, your interpretation is flawed.  There are three (3) requirements for the location of “sheet or panel type materials with an air leakage characteristic less than 0.1 L/(s·m²) at 75 Pa and water vapour permeance less than 60 ng/ (Pa·s·m²)”, as follows (paraphrased, to simplify the gobbledygook):

a)                          the material shall be installed on the warm side of the material;

b)                          the material may be installed within the thickness of the thermal insulation, in accordance with Table 9.25.1.2; or

c)                          the material shall be installed outboard of an air space that is vented to the outdoors, and for walls, drained.

Appendix A of the NBCC for this article describes the theoretical background for these requirements.  The intent is to “avoid moisture accumulation” within the assembly due to air leakage and water vapour diffusion from the warm, humid air from within the building to the exterior, through the assembly.  Provided that the vapour barrier in a “conventional” flat roof assembly does this (and it certainly can), the construction is not at variance with the requirements of Article 9.25.1.2.  In this context, the discussion from the NBCC User’s Guide quoted later in your article does not contradict the requirements of Article 9.25.1.2.

Conventional flat roofs, like other types of roof assembly or wall assembly, can work very well and provide many years of service, provided they are constructed in a manner appropriate for the service environment.  That’s the key.  Kirby Garden figured that out in 1969 (CBD 120).  Unfortunately, this is often forgotten and we do silly things like try to build face-sealed wall and roof assemblies (like the conventional flat roofs considered in your article) in the BC rainforest (where you practice) when other types of wall or roof may be more appropriate, such as the inverted or protected membrane roof systems and “rainscreen” wall assembly described in your article.  A face-sealed wall assembly, if built with care, can provide many years of good service in the Prairie Provinces and even here, in Ontario (where I practice).

I encourage you to download the public review draft of revisions to CSA-A440.4, Window, Door and Skylight Installation.  The committee, of which I was a part, struggled with the notion of the appropriateness of installation details in different climatic regions of Canada.  Early in our deliberations, there was a strong push to adopt “rainscreen” technology as the only way to prepare the rough opening space around a window product, but the threat of riot from our colleagues from the dry Prairies (John Ink of CWD Windows and Doors and Dennis Little of New Home Warranty Program Alberta in particular) and gentle prodding by Adaire Chown of NRCC (who reminded us that the NBCC does not mandate the “rainscreen” approach and therefore, a standard cited by the NBCC could not, either) swayed the committee that another, more flexible approach was necessary.  The solution came from committee member Brian Hubbs and his colleagues at RDH in Vancouver, using the “Moisture Index” system of classifying severity of wetting developed at IRC / NRCC and adding modifiers for exposure and protection.  A nomograph for selection of appropriate rough opening constructions to address Moisture index, exposure and protection was developed and has been included in Appendix A of the public review draft of CSA-A440.4 standard, together with descriptions of appropriate rough opening treatments and some amazing construction details (intended for guidance) developed by RDH.  The concept behind this – selection of construction appropriate for the service environment – is what you failed to consider in your argument that the universally most appropriate roof system is an inverted, or protected membrane, assembly, and that similarly, the universally most appropriate wall system is a “rainscreen” assembly.  Don’t get me wrong, these are good, systems, and they probably will work in any service environment, but other assemblies may provide reasonable service also.

“Reasonable service?” I hear you ask.  By that I mean that any roof or wall assembly, in addition to meeting the technical requirements of environmental separation, must also be economically feasible for the purchaser of it.  A face-sealed wall assembly in Vancouver with no roof overhang would be outright foolish technically, forcing a “rainscreen” approach; however, a face-sealed assembly in Toronto (or on the dry Prairies) with no roof overhang (most high-rise residential condos, for example) can work just fine.  A “rainscreen” approach in Toronto could be adopted in lieu of a face-sealed approach, but it would cost more; the question that must be asked is if the purchaser can afford it at the time.  I’ve heard the argument that a face-sealed assembly may require more frequent future maintenance, and if such costs are considered at the time of construction, the “true” capital cost of a face-sealed system may be higher than a “rainscreen” system.  However, if the purchaser cannot afford the technology at the time, a simpler face-sealed approach may be more appropriate provided that the future maintenance cost can also be afforded.  Again, in Vancouver this would be foolish but elsewhere where the climate is different, more flexibility may be possible.

George Torok is a Project Manager and Technical Specialist with Gerald R. Genge Building Consultants Inc. in Newmarket, Ontario.  He has 18 years experience in the diagnosis and repair of building envelope performance failures, with special emphasis on glazing systems including windows, skylights, curtain walls, and insulating glass units.  George may be reached at 1-800-838-8183 or at gtorok@grgbuilding.com.

REPLY BY GARY JOHNSON

It never fails to amaze me the extent that people will go to justify the old traditional methods of construction.  I sit on the Standing Committee for Part 5 and have had this argument many times and hear the same rational - it has worked in some areas under some conditions so why change.  (I'm sure one of the reasons the NRC is resistant to change is that they would be embarrassed to admit that their promotion of poly vapour barriers over the years has been a mistake.)

Mr.Torok makes this same point when he states " Conventional flat roofs . . . can provide many years of service, provided they are constructed in a manner appropriate for the service environment."  There have been a number of attempts at quantifying the service environment including the IRC/NRCC Moisture Index and Joe Lstiburek's map of North America which, I suggest, just muddies the water, if you will forgive the pun.  We seem to stand on our head trying to make the old systems work.  A good example of just how ridiculous this can get is found in the CMHC Technical e-Newsletter 2005-09-19 article on a test of a "Dynamic Buffer Zone" approach to a brick veneer/steel stud assembly.

Perhaps I was not sufficiently clear about the importance of the continuity of the air barrier in my article.  I contend that the air barrier defines the envelope (the argument will be presented in a future edition of the BE Forum I believe).  I was not promoting the use of a rain screen per say, it is just that a rain screen is a natural result of the argument.  Given this fact (contentious I'm sure) then the approach to envelope assemblies becomes very straight forward, applicable to all conditions and, last but not least, almost idiot proof.  Once we get accustomed to building in this manner cost (both initial and life cycle) will drop.

We could go back to building the way we did before 1975 - nice and leaky (drafty) with little insulation that ensured that assemblies dried out soon after they got wet.  Today's requirements for low energy consumption and high expectations for comfort demand a good air barrier and that requires that the air barrier be understood (it is not a vapour barrier).

To get back to the roof/wall discussion I find that many designers do not consider where the plane of the air barrier is in a roof assembly.  Is it the roof membrane on top of a conventional assembly or the "vapour barrier" on the bottom of the assembly?  To what and how does one connect the wall air barrier?  Mr. Torok seems to be of the opinion that the vapour barrier will perform this function.  Certainly it will, provided it is a material that will seal around penetrations and take air pressure differential, but then we are talking about a good membrane so why put another membrane over it?  Poly full of holes from mechanical fasteners for insulation is not the best of air barriers.  (I can hear the argument now - but air can't move it through it because of all the material on top.  If that is so then where is the air barrier, it certainly isn't the poly - which is my point - people don't seem to understand the concept of air barriers in roofs.)  (Another pet peeve of mine is why would someone put a vapour diffusion barrier over steel deck, if there is no air movement through the assembly (i.e. an air barrier) then the steel deck is just as good as poly when it comes to vapour diffusion.)

I would agree that we can build conventional assemblies that work but it takes a lot of care, knowledge and attention on the part of the designer, builder and maintenance personnel to do it right.  Why not use a simple assembly that will work in every environment and that everyone can understand - I might even be out of a job if that happened.

Gary F. Johnson
Building Envelope Specialist
Read Jones Christofferson Ltd.
220, 645 Tyee Road
Victoria, BC
V9A 6X5
Ph: (250) 386-7794
Fax: (250) 381-7900
gjohnson@rjc.ca

REPLY BY Bill Wyness

Hi George -

I read your letter to the Editor at Building Envelope Forum, and felt urged to advise that the service environment of “the prairies” is not always as dry as might be inferred. 

I used to sit in lectures at UBC when Gus, Kirby and others from the old DBR group came out to the B.C. coast in the '60's and promoted the building physics deployment in that province.  I still have the original CBD binder they handed out, and agree with you a lot of the building science determined in the '60's and the '70's was almost lost in the '80's and the '90's in Canada.

I grew up and trained in the “rainforest” of the B.C. lower mainland and the rainscreen back-vented pressure equalized style of cladding was a natural consequence of the construction technology on the west coast, where wood was cheap and a normal cladding of choice, and exterior stucco (the primordial face-sealed wood-frame construction cladding) only started appearing en-masse after WWII with the huge VLA tract housing developments.  And this all worked because the construction was air-leaky and heating was cheap in the mild coastal climate.

Then I moved to Alberta and practiced architecture in Edmonton for 12 years.  Having been told the prairies was “Dry”, I was amazed to see building after building with failed exterior cladding, no eaves protection, and failed face sealed construction joints. Apparently the industry did not believe the sideways rain that came without fail every

June through September in northern Alberta actually soaked cladding materials and crept into envelope crevices either through capillary action or through air pressure effects! Some dry service environment!

Now I live in the NWT, one of the most diverse and demanding building envelope performance environments in the world, and have learned some of the beliefs and generalizations about the performance environment north of 60 are naive at best, and outright dangerous at their worst.

I would suggest that broad categorizations of Canadian regions as having generically pre-defined “service environments” is a risky belief system. A few years back we ended up cutting off the 30” wide eaves during the renovation of a 1950's era wood frame two storey building in a MacKenzie valley community where, just by chance, the “dry” north of 60 service environment has a one day maximum rainfall of 70 mm, much of it coming sideways with the wind.  We tried to avoid cutting off the eaves, but the eaves were eventually cut off after all, to meet a design aesthetic, and operating under the belief we “don't get enough rain in the north to worry about eaves” - and now the inevitable wetting action on the wall is an ongoing maintenance concern.

Fortunately, there is renewed recognition of the need to incorporate the impact of microclimatic on building envelopes, but that can be jeopardized when large multi-provincial design agencies or national organizations use broad-brush approaches to envelope design. 

My experience tells me we will all make better envelopes if we recognize the benefits of knowing the building's microclimate, trends in the microclimate, and apply our proven building physics technology in that context.

Regards,

Bill Wyness NWTAA, MAIBC

Sr. Technical Officer - Architectural/Structural

Technical Support Services - Asset Management Division

Public Works & Services - GNWT

5009 49 St.,  SMH 3,

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