High Performance Exterior Masonry Wall Design and J.B. SPEED SCHOOL - PowerPoint PPT Presentation

High Performance Exterior Masonry Wall Design and J.B. SPEED SCHOOL Detailing for Water OF ENGINEERING Resistance, Thermal Control and Crack Control W. Mark McGinley, Ph. D., PE FASTM MASONRY SEMINAR Masonry Institute of Iowa Thursday, March 2, 2017 1

Introduc tion The presentation will address the following learning objectives: • Describe the functions of exterior wall systems and discuss their behavior as it relates to their function as a building envelope. Address moisture, air, vapor and vapor and thermal barriers. • Present fault tolerant masonry detailing for moisture penetration, vapor transmission, etc 2

Introduc tion • Present an overview of masonry crack control and detailing for differential movements. • Discuss thermal resistance, U and R values and thermal mass effects on energy use in walls systems. • Present a number of “high” performance exterior masonry wall configurations and costs. 3

Exterior Wall Systems Functions • Resist loads • Control movement of air • Control movement of moisture (and vapor) • Control thermal movements • Control sound • Control fire – Masonry does so inherently • Others Must do so in a aesthetically pleasing, durable, cost effective manner 4

Drainage Walls – Moisture Resistance Single wythes of masonry can leak Drainage Walls OTHER TYPE BARRIER WALL All Single wythe 5

To be effective moisture barrier must detail for Fault Tolerance at Critical Locations Positively Extend Anchor Sill flashing on sill up behind window Make Cavity at least 2 in – Free to allow for tolerance and mortar fins- code – 1” Consider Extending flashing to shelf angle instead under sill brick – short heights – BIA.org - 6

Show Design for and Fault Tolerance detail end at Critical dams where Locations needed Step flashing down 7 7

Design for Fault Tolerance at Critical Locations Detail and show how to attached flashing to backing system Extend flashing or you likely have brick staining If you don’t like drip edge look Alternative way to provide this Perma Barrier more later Stainless steel edge 8

Be Careful Using Standard Details Poor Wet Bat. insulation 9

This is what can be built if you are not careful with details 10 10

Back to Envelope Function: Thermal/Air Movements Three major mechanisms of thermal energy loss/gain through exterior wall systems : - Conduction – Radiation - Convection Lump these into an overall heat transfer coefficient U - See earlier talk - more later Note R= 1/U 11

Thermal Resistance For conductive Thermal movements -Do one of: a) Meet prescriptive R , U values in Energy code b) Do a detailed energy analysis (LEED) c) Comply with ASHREA 90.1 – Prescriptive & Detailed analysis See my earlier Talk 12

Thermal/Air Movements Also a significant amount of heat energy can move through wall systems via air movement in the wall systems. – up to 30%? So ASHREA 90.1- IBC– Bldgs. must have an air barrier and it must be continuous – JOINTS & PENETRATIONS ARE VERY IMPORTANT – Must be flexible & strong enough to resist pressures. 13

ASHREA 90.1 Walls – (Not windows or doors) can be air barriers if they: (a)Have materials that have an air permeance not exceeding 0.004 cfm/ft 2 under a pressure differential of 0.3” w.g. (1.57psf) OR (b) Assemblies that have average air leakage not to exceed 0.04 cfm/ft 2 under a pressure differential of 0.3” w.g. (1.57psf). OR (c) Building demonstrates air leakage rates of ≤ 0.40 cfm/ft 2 at a pressure differential of 0.3” w.g. (1.57 psf) (2.0 L/s.m2 @ 75 Pa) Exception: Buildings in Zones 1, 2, and 3 constructed with mass walls are exempt. 14

Vapor Control Water vapor moves from high to low vapor pressure: Temp and RH related a) Put vapor barrier on warm side of insulation when cooling degree days are greater than heating degree days and have a vapor permeable Air/moisture barrier. b) In mixed climates and some wall systems its hard to find warm side- Do not have two vapor retarders! c) Some times better to have no vapor barrier. Know condensation point! 15

Movements in Clay Masonry Movements are produced by: • Thermal differences • Shrinkage • Moisture Expansion • Elastic- deformation both of the masonry and any supporting structural systems • Creep • Foundation Settlements See BIA Tech Notes 18 and 18A and NCMA TEK Notes 10-1A , 10-2A, 10-3

Movements of Clay Masonry Assemblies Irreversible Moisture Expansion Brick are the smallest when cooled from the kiln. Expansion ranges from 0.0002 to 0.0009 in/in Codes gives k e = 0.0003 in/in. 17

Control of Movements of Clay Masonry Assemblies (WALLS) Clay masonry wall panels generally expand if unrestrained. There is usually no problem in these walls if they are allowed to move freely. However, rarely are these walls unrestrained unless properly detailed. 18

Control of Movements of Clay Masonry Assemblies (WALLS) Clay masonry can expand significantly Benson Conv. Sealant forced out 19

Control of Movements of Clay Masonry Walls There is two ways in which the designer can deal with this expansion: 1. Design the masonry and surrounding elements to resist the stress induced by the restrained masonry. TECH Note 18 2. Design the systems so that masonry can move freely. See TECH Note 18A 20

Expansion Joints in Clay Masonry The primary function of this joint is allow free expansion of the masonry but must also resists water penetration and air movement Note that expansion joints and control joints not the same BIA Tech note 18A Vertical ExpansionJoints 21

Expansion Joints Clay Masonry Note that most sealants require a backer rod and the sealant depth should be about ½ the width of the joint (min ¼”) – Types include urethanes, silicones, polysulfides. 22

Vertical Expansion Joints in Clay Masonry A conservative estimate of vertical expansion joint spacing, S e , can be made using we j S  ( k e  k f  k t  t )100 e w = is the width of the joint (in) e j = the extensibility of the sealant (%) Tech note 18 and 18 A suggest equation above can be reduced to we S  j e 0.09 23

Vertical Expansion Joints in Clay Masonry For Example: for a 50% sealant, 3/8” joint, and 3/8” joint with the simplified equation: S e = 17’-4” ½” joint would have a spacing of 23’- 2”

Placement - Vertical Expansion Joints- Clay Masonry Consideration should be given for vertical expansion joints at: Corners Offsets Openings Wall intersections Changes in wall heights Parapets 25

Placement of Vertical Expansion Joints in Clay Masonry Corners Place joints near corner or cracks will develop BIATech Note 18A 26

Placement of Vertical Expansion Joints in Clay Masonry Walls do move Foundation was bonded to wall and went with movement Flashing can stop this 27

Placement of Vertical Expansion Joints in Clay Masonry Corner opening cracks

Placement of Vertical Expansion Joints in Clay Masonry Not an expansion joint just caulk You even get this with opening near the corner Shalimar 29

Placement of Vertical Expansion Joints in Clay Masonry Be careful with support at corners Backing wall Must have at least two ties on each Leg of column cover 30

Placement of Vertical Expansion Joints in Clay Masonry Offsets This is sort of a corner and an offset movement Benton Cov. 31

Placement of Vertical Expansion Joints in Clay Masonry Openings No expansion joint creates crack as shown (TMS) These are not due to settlement (up) Sections with openings move less and provide restraint to upper portions 32

Placement of Vertical Expansion Joints in Clay Masonry 33

Placement of Vertical Expansion Joints in Clay Masonry Openings There are openings above and below and a solid section between the edge column section is connected to both and creates distress due to differential movement 34

Placement of Vertical Expansion Joints in Clay Masonry Openings You should place a vertical expansion joint at opening edges - note if a loose angle is used it must be allowed to expand independent of brick - note min 4” bearing length of angle Need to put on both sides if large opening or lintel supported on backing 35

Placement of Vertical Expansion Joints in Clay Masonry Intersections and junctions You should place a vertical expansion joint at changes in heights, thickness an types of walls and on walls that undergo differential warming 36

Placement of Vertical Expansion Joints in Clay Masonry The parapet wall is exposed on three sides and usually moves more than other walls. Also a parapet has much less dead load restraint. The usual rule of thumb is reduce the spacing of vertical expansion joints in parapet to ½ elsewhere. 7 3

Placement of Vertical Expansion Joints in Clay Masonry Hidden joints can improve Aesthetics 38

Horizontal Expansion Joints in Clay Masonry Frame Brick moves shortens up Horizontal expansion joints typically placed below shelf angles They should be sized for the masonry and frame movements Ensures Masonry Non loadbearing 39