VAPOR BARRIERSVAPOR BARRIERSMOISTURE CONTROLMOISTURE CONTROL

ININBUILDINGSBUILDINGS

ASHRAETECH SESSIONAPRIL 8, 2004

PRESENTED BY GARY PETERSGREENTECH

VAPOR BARRIERS versus AIR BARRIERS

Air Barriers prevent air movement while allowing moisture to pass through. Air barriers must be carefully sealed at all penetrations.

Vapor Barriers are used to control the flow of moisture through the building envelope’

.

Classes of Vapor Barriers and Vapor RetardersThe unit of measurement for water vapor permeability is the “perm”.Three general classes of materials, based on permeability.

Vapor Impermeable – “Vapor Barriers”0.1 perms or less: Class I

1.0 perms or less: Class IITypical Materials: Rubber membranes; polyethylene film; glass; aluminum foil; sheet metal; some vinyl wall covering; foil- faced insulating sheathings

Vapor Semi-permeable – “Vapor Retarders”10 perms or less: Class IIITypical Materials: Plywood; unfaced expanded polystyrene (EPS); asphalt impregnated building paper; many latex based paints; paper and bitumen facing on

fiberglass batt insulationVapor Permeable – “Breathable”

More than 10 permsTypical Materials: Unpainted gypsum board; unfaced fiberglass insulation; lightweight asphaltimpregnated building paper; exterior gypsum sheathing; “housewraps”

Permeability0.000Water vapor transmission of Zero Perm in a flat condition is 0.000 grams per hour per square meter. After sharp creasing under 25-lb. pressure at 3/4'' intervals with creases at right angles forming crease intersections at 3/4'' intervals permeance is only 0.0134 grams per 100 sq. in. per 24 hrs. Joints sealed with 1 1/2'' Zero Perm Pressure Sensitive Tape and joints overlapped 1 1/2'' and sealed with Alumiseal Zero Perm Adhesives also exhibit a permeance of 0.000 grams per lineal inch per 24 hrs. Test sources available on request.

UL ListingAn important feature of Zero Perm is its performance in Underwriters Laboratories (UL) Surface Burning Characteristics Test (UL 723). Zero Perm is UL listed as follows: Flame spread 5 Fuel contributed 0 Smoke developed 5Note: The numerical flame spread ratings are not intended to reflect hazards presented by this or any other material under actual fire conditions.

Flex LifeZero Perm's outer mylar layer can endure over 20,000 cycles of flexing without failure.

 Thermal StabilityZero Perm remains flexible and stable over a temperature range from -100° F to +300° F

 Tensile StrengthHas a tensile strength of over 25,000 psi, a bursting strength of 96.6 psi. It requires a 23,500 psi stress at 130% strain to cause an elongation break in the mylar outer laminate

InertnessZero Perm exhibits excellent inertness to water, salt spray, wet mortar, caustics plus chemical solvents, oils, greases and can be safely applied to masonry walls.

 Resistance to AbrasionZero Perm has extremely high resistance to abrasion.

Vapor Transportation Mechanisms

Capillary Action: Wetted surfaces

Air transported moisture – Air transported moisture can be more significant than vapor diffusion.

Vapor Diffusion: Second law of thermodynamics. Moisture will flow by diffusion because of a concentration gradient as well as a temperature gradient. “More to less” “Warm to cold”

Moisture control generally requires both an air barrier and a vapor barrier.

Uncontrolled air infiltration into walls because of inadequate air barriers can cause catastrophic problems

LOCATION of VAPOR BARRIERS and AIR BARRIERS

COLD CLIMATESGoal is to make it as difficult as possible for the building assemblies to get wet from the

interior.Install air barriers and vapor barriers on the interior building assemblies. Let the building

assemblies dry to the exterior by installing the vapor permeable materials toward the exterior.

HOT and HUMID CLIMATESGoal is to make it as difficult as possible for the building assemblies to get wet from the

exterior.Install air barriers and vapor barriers on the exterior of the building assemblies. Let the

building assemblies dry to the interior. Impermeable interior wall coverings must be avoided. The interior space must be maintained at a slight positive pressure with conditioned/dehumidified air to limit infiltration

MIXED CLIMATES COMPLICATED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

1. Flow through approach: Use permeable materials on both interior and exterior. This requires both air pressure control and interior moisture control.

2. Install the vapor barrier in the approximate thermal “middle” of the wall with insulating sheathing on the exterior. The air barrier can be toward the interior or the exterior. Air pressure control and interior moisture control must be utilized.

TRANSMISSION RATESTRANSMISSION RATESFORFOR

TYPICAL BUILDING MATERIALSTYPICAL BUILDING MATERIALS

MATERIALMATERIAL TRANSMISSION RATE TRANSMISSION RATE ( grams/hr./sq. meter) ( grams/hr./sq. meter)

PermsPermsConcrete BlockConcrete Block 2.40 2.40Gypsum BoardGypsum Board 50.00 50.00PlywoodPlywood 1.90 1.90PlasterPlaster 15.00 15.00Glazed TileGlazed Tile 0.12 0.12Vapor Retarder PaintVapor Retarder Paint 0.45 0.45Semi-Gloss AcrylicSemi-Gloss Acrylic 6.61 6.61Polyethylene, 6milPolyethylene, 6mil 0.06 0.06Polyethylene, 10 milPolyethylene, 10 mil 0.03 0.03Mylar/AluminumMylar/Aluminum 0.00 0.00 (Zero-Perm)(Zero-Perm)

VAPOR BARRIERS and MOLD

Moisture accumulates in the building envelope when the rate of moisture entry exceeds the rate of moisture removal.

When moisture accumulation exceeds the ability of the materials to store the moisture, moisture problems result.

Moisture storage capacity of materials depends on

Time – Dwell time, or drying time

Temperature

Material Properties

EXAMPLES:In a house the average 2000 square foot house, the wood based sheathing and wood framing have an equilibrium moisture content of 5% to 6%. The walls have a hygric buffer capacity of 10% which equals approximately 50 gallons of water for the 4,000 to 5,000 pounds of wood product in the exterior walls. When the moisture content exceeds 16% by weight, mold will develop.

That same house with steel framing and gypsum sheathing has a hygric buffer capacity of 5 gallons of water. A highly insulated wall has a high dwell time and poor drying characteristics. Very small amounts of water will cause problems because of the low hygric buffer capacity and the slow drying times.

A house with masonry exterior walls and masonry cladding has a hygric buffer capacity of 500 gallons.

Approx. 500 gallons (1892L)Masonry Wall

Approx. 50 gallons (189L)

Wood Frame with Wood Sheathing

Approx. 5 gallons (19L)Steel Frame with

Gypsum Sheathing

HYDRIC BUFFER CAPACITY FOR 2000 SQ. FT HOUSE

MOISTURE CONTROL IN BUILDINGS

TO MINIMIZE THE RISK OF

MOISTURE DAMAGE

I. Control Moisture Entry Repair roof leaks, flashing, floors, foundations

Prevent wind driven rain fro entering the wall assembly

Direct rain and ground water away from building

Airflow retarder must resist pressure from wind, stack effect, and mechanical ventilation

II. Control Water Vapor Migration

Limit water entry into building envelope with proper airflow retarders and vapor retarders

6 to 22% of air leakage at windows and doors

18 to 50% of air leakage occurs through walls

3 to 30% of air leakage occurs through ceilings

III.Control Moisture Accumulation

Control dominate direction of air flow

In climates requiring cooling, maintain the building at light positive pressure to prevent unconditioned, humid air from entering the envelope.

In climates requiring heating, maintain a neutral building pressure.

IV.Control the Removal of Moisture

Provide envelope system that allows assembly to dry to either the exterior or the interior, depending on climate.

Provide dedicated, conditioned low moisture content make up air systems

Maintain slight positive pressure

Leakage of saturated air from building AC system can migrate into building envelope assemblies.

Classic Example of a Connecticut Wall System

Building: Upper range hotel

Walls: Vinyl Wall Covering, Gypboard, Vapor Barrier,Fiberglass Insulation, Sheathing,EIFESand Brick

Flashing: Poorly installed

Guest Room AC: PTAC Thru the wall, exhaust fan in Bathroom

Corridor AC: Standard split system air conditioning unitsdelivering conditioned outside at saturatedconditions

Complaint: Employee complaints, very high rate of sickdays, some customers complained odors

Findings: Rooms were some times positively pressured,sometimes negative. Air leakage into buildingenvelope around PTACS. The gyp board andsheathing facing the interior of the wall cavitywere 100% covered with black and green mold

The Brick Veneer Wall Problem

Rain wetted followed by solar radiationThe sun drives the moisture inward. Ideally, the vapor barrier would

be behind the brick veneer to stop the inward flow. That does not work in a cold climate.

In a cold climate, the vapor barrier is typically on the “warm” side. Moisture can get trapped in the wall cavity for extended periods of time.

Possible Solutions1. Vapor Barrier behind the bricks and a vapor retarder on the inside2. Semi-vapor permeable insulating sheathing on the outside wall,

insulation to provide sufficient thermal resistance to elevate the temperature of the condensing surface during the heating season and a vapor permeable interior finish to allow drying to the interior

There are no easy answers!There is no one correct solution!

Class I•Temperature Moderated•Vapor Pressure Uncontrolled•Air Pressure Uncontrolled

Class II•Temperature Controlled•Vapor Pressure Moderated•Air Pressure Moderated

Class III•Temperature Controlled•Vapor Pressure Controlled•Air Pressure Controlled

Interior Climate Classes

ENVIRONMENTALLY CONTROLLED SPACES

VAPOR BARRIER IMPACT

ONEQUIPMENT SIZING

AND OPERATING

COST

ASHRAETECHNICAL SESSION PRESENTATION

“VAPOR BARRIERS”DEHUMIDIFICATION

Select and size a dehumidification system for a site constructed with and without a vapor barrier.Project the equipment (first) cost and the operating cost for the dehumidification system with each construction method.ASSUMPTIONS:Hours/per year of dehumidification: 4,000Electric Utility Rate: $0.11/Kwhr.Space Dimensions: 50’ x 50’ x 9’ high, all interior surrounded by conditioned space, 24” ceiling plenum and roof above.Room conditions to be maintained: 64 degrees db/35% RHRoom Load – Constant:

375,000 Btu/hr Sensible225,000 Btu/hr Latent600,000 Btu/hr Total

Room surrounding conditioned space: 80 degrees db / 50% RHCONDITION “A”Walls constructed with 5/8” sheetrock on both sides, no insulation and no vapor barrierCeiling, standard acoustical tilesRoof, insulated with no vapor barrierCONDITION “B” Walls constructed with 5/8” sheetrock on both sides, no insulation, and with a vapor barrier with a transmission rate of 0.000 grams/hr/sq. meter. The vapor barrier is installed under the sheetrock on the conditioned space side of the wall.Ceiling, acoustical tiles with a vapor barrier with a transmission rate of 0.04 grams/hr/sq. meterRoof, insulated with no vapor barrier

04/07/04 ###

CUSTOMER : EFFECT OF VAPOR BARRIER ON DEHUMIDIFICATION PROP.# : 0APPLICATON : NO VAPOR BARRIER BRY-AIR REP: VIVEK PAHWA

FDB FWB GR %RH 50 L80 0 77 50% 50 W = 22,50064 0 31 35% 9 H CUBIC FEET16 T 46 GR

375

GR/HR ( 22500 ÷ 14.0 ) x 46 x 1.26 x 0.58 x 1 x 0.9 = 48,566

(vol) ( gr) (f1) (f2) (f3) (f4)

5 x ( 21.0 ÷ 7 ) x 46 x 1.00 = 690(area) ( gr) (f1)

0 x ( 0.0 ÷ 7 ) x 0 x 1.00 = 0

( 0.0 x 300 ) ÷ ( 14.0 x 1.0 ) x 0 x 1.00 = 0(dep) ( gr) (f1)

5 x 1650 = 8,250(no.) (f5)

GR/HR REMOVED = 0

GR/HR ADDED = 0

= 57,506

( 14 x ÷ 60 )) ÷ ( 31.0 - 8.0 ) =

DEFAULT

5% 0 ÷ 14 x 46 x 60 = 0

#DIV/0!= 57,506

SYSTEM AIR#DIV/0! AIR CHANGES PER HOUR

0 CFM 600 CFM RETURN AIR @ 64 FDB 31 GRAINS

0 CFM MAKE-UP AIR @ 80 FDB 77 GRAINS

DEHUMIDIFIER INLET CONDITON: CFM 600( f4 ) factor= 0.9 DB TEMP. 64

GR/LB 31

( 14 x ÷ 60 )) ÷ ( 31 - 8.0 ) = 583

PROOF÷ 14 ) x ( 31 - 8 ) x 60 = 59,143

OVER SIZED BY 3%

DEHUMIDIFIER REQUIRED VFB- DEH. NOT LARGE ENOUGHPROCESS OUTLET COND. = 102 DEG. F

8 GR/LB

\\bry1\Sales\BRYAIR\Quote Development Project\vapor barrier study\[BRYCALB2.xls]DEH CAL

BRY-AIR DEHUMIDIFIER CALCULATION SHEET

583

( ACTUAL, IF CFM ENTERED MANUALLY ABOVE, OR IF PEOPLE WORKING IN SPACE )

( 57,506 SUGGESTEDCFM

(op/hr)

CONDITIONS ROOM SIZE

AMBIENT

DESIGN

22,500 ÷ 60 =

PERMEATION

DOOR LOAD

FIXED OPENING

(area)

PEOPLE LOAD

PRODUCT LOAD0

PROCESS LOAD0

TOTAL ROOM LOAD

CFM REQUIRED

MAKE-UP AIR

TOTAL GR/HR

( 57,506

( 600

SYSTEM CAPABILITY

DEHUMIDIFIER SIZING

CFM REQUIRED

PUSH TO SIZE /

SELECT MVB

PUSH TO SIZE /

SELECT MVB

DX AFTER-COOLING29.2 MBH 3 TR

RETURN AIR600 CFM64°FDB31 GR/LB

200 CFM

284°FDB

REACT

EXHAUST

600 CFM

97°FDB

7.9 GR/LB

600 CFM

56°FDB 7.9 GR/LB

30%

FILTER

DEH

600 CFM

64°FDB

31 GR/LB30%

FILTER

200 CFM

84°FDB

PROCESS

REACT

REACTFAN

CONDITIONED SPACE 22,500 FT.3

64°FDB35% RH 31 GR/LB

BRY-AIR, INC.ROUTE 37-WSUNBURY, OH 43074TEL (740) 965-2974FAX (740) 965-5470

The choice fordesiccant dehumidification

Approximate Full Connected Load: 22.6kW

FLOW DIAGRAM

(No Vapor Barrier)

Electric

Re-activation

12.7 kw

DEHUMIDIFIER

04/07/04 ###

CUSTOMER : EFFECT OF VAPOR BARRIER ON DEHUMIDIFICATION PROP.# : APPLICATON : WITH VAPOR BARRIER BRY-AIR REP:

FDB FWB GR %RH 50 L80 0 77 50% 50 W = 22,50064 0 31 35% 9 H CUBIC FEET16 T 46 GR

375

GR/HR ( 22500 ÷ 14.0 ) x 46 x 1.26 x 0.58 x 1 x 0.35 = 18,887

(vol) ( gr) (f1) (f2) (f3)

5 x ( 21.0 ÷ 7 ) x 46 x 1.00 = 690(area) ( gr) (f1)

0 x ( 0.0 ÷ 7 ) x 0 x 1.00 = 0

( 0.0 x 300 ) ÷ ( 14.0 x 1.0 ) x 0 x 1.00 = 0(dep) ( gr) (f1)

5 x 1630 = 8,150(no.) (f5)

GR/HR REMOVED = 0

GR/HR ADDED = 0

= 27,727

( 14 x ÷ 60 )) ÷ ( 31.0 - 5.0 ) =

DEFAULT

5% 0 ÷ 14 x 46 x 60 = 0

0.0%= 27,727

SYSTEM AIR0.8 AIR CHANGES PER HOUR

0 CFM 300 CFM RETURN AIR @ 64 FDB 31 GRAINS

0 CFM MAKE-UP AIR @ 80 FDB 77 GRAINS

DEHUMIDIFIER INLET CONDITON: CFM 300( f4 ) factor= 0.35 DB TEMP. 64

GR/LB 31

( 14 x ÷ 60 )) ÷ ( 31 - 5.0 ) = 249

PROOF÷ 14 ) x ( 31 - 5 ) x 60 = 33,429

OVER SIZED BY 21%

DEHUMIDIFIER REQUIRED MVB- 5PROCESS OUTLET COND. = 95 DEG. F

5 GR/LB

\\bry1\Sales\BRYAIR\Quote Development Project\vapor barrier study\[BRYCALB2.xls]DEH CAL

( 27,727

( 300

SYSTEM CAPABILITY

DEHUMIDIFIER SIZING

CFM REQUIRED

TOTAL ROOM LOAD

CFM REQUIRED

MAKE-UP AIR

TOTAL GR/HR

PRODUCT LOAD0

PROCESS LOAD0

DOOR LOAD

FIXED OPENING

(area)

PEOPLE LOAD

DESIGN

22,500 ÷ 60 =

PERMEATION

BRY-AIR DEHUMIDIFIER CALCULATION SHEET

249

( ACTUAL, IF CFM ENTERED MANUALLY ABOVE, OR IF PEOPLE WORKING IN SPACE )

( 27,727 SUGGESTEDCFM

(op/hr)

CONDITIONS ROOM SIZE

SURROUNDING

PUSH TO SIZE /

SELECT MVB

PUSH TO SIZE /

SELECT MVB

DX AFTER-COOLING29.2 MBH 3 TR

RETURN AIR300 CFM64°FDB31 GR/LB

100 CFM

284°FDB

REACT

EXHAUST

300 CFM

97°FDB

7.9 GR/LB

300 CFM

49°FDB 7.9 GR/LB

30%

FILTER

DEH

300 CFM

64°FDB

31 GR/LB30%

FILTER

100 CFM

84°FDB

PROCESS

REACT

REACTFAN

CONDITIONED SPACE 22,500 FT.3

64°FDB35% RH 31 GR/LB

BRY-AIR, INC.ROUTE 37-WSUNBURY, OH 43074TEL (740) 965-2974FAX (740) 965-5470

The choice fordesiccant dehumidification

Approximate Full Connected Load: 12.2kW

FLOW DIAGRAM

With Vapor Barrier

Electric

Re-activation

6.3 kw

DEHUMIDIFIER

EFFECT OF VAPOR BARRIER ON DEHUMIDFICATION COSTS

 

Room size: 50’ x 50’ x 9’

Room design: 64°F DB / 35% RH

Surrounding conditions: 80°F DB / 50% RH

Hours/per year of operation: 4,000

Electric Utility Rate: $0.11/Kwhr

 

Assuming a constant latent load in the space of 8,840 gr/hr from the 5 door openings/hour of a 7’x3’ door and moderate work done by 5 occupants in the space. This equates to a total internal latent load of 1330 BTUH (excluding infiltration).

 

Assuming a constant sensible load in the space of 2 BTUH per square foot, over 2500 sq ft of the space the total internal sensible load will be 5000 BTUH.

CONDITION “A” (NO VAPOR BARRIER)

Using 0.9 as the F4 factor in the dehumidification calculation sheet for no vapor barrier, the infiltration load is 48,566 gr/hr.

 

The total latent load is 57,406 gr/hr and the required airflow is 600 scfm.

 

Reactivation energy required is 43,200 BTUH or 12.7 KW.

 

Cooling (3 TR condensing unit) energy required is 5.9 KW.

 

Total energy required (including motors) is 22.6 KW.

 

First cost of equipment is approximately $20,000 USD.

 

Operating cost of equipment is $9,944 USD yearly.

CONDITION “B” (WITH VAPOR BARRIER)

Using 0.35 as the F4 factor in the dehumidification calculation sheet for room with vapor barrier, the infiltration load is 18,887 gr/hr.

 

The total latent load is 27,727 gr/hr and the required airflow is 300 scfm.

 

Reactivation energy required is 21,600 BTUH or 6.3 KW.

 

Cooling (2 TR condensing unit) energy required is 2.9 KW.

 

Total energy required (including motors) is 12.2 KW.

 

First cost of equipment is approximately $13,000 USD.

 

Operating cost of equipment is $5,368 USD yearly.

CONTROLLED ENVIRONMENTAL SPACE

VAPOR BARRIER PAYBACK

NO CORRECT

ITEM VAPOR BARRIER VAPOR BARRIER SAVINGS

Equipment Costs $20,000 $13,000 $7,000

Operating Costs $ 9,944 $ 5,368 $4,576

Cost to properly vapor treat the space……………..$1,200

ASHRAE TECHNICAL SESSION PRESENTATION

“VAPOR BARRIERS”HUMIDIFICATION

Select and size a humidifier system for a site constructed with and without a vapor barrier.Project the equipment (first) cost and the operating cost for the humidification system with each construction method.ASSUMPTIONS:Hours / year for humidification: 4,000Electric Utility Rate: $0.11/KwhrSpace Dimensions: 50’ x 50’ x 9’ high, all interior surrounded by conditioned space, 24” ceiling plenum and roof above.Room Conditions to be maintained: 72 degrees db/ 50% R.H.Room Load - Constant:

672,000 Btu/hr Sensible 50,000 Btu/hr Latent722,000 Btu/hr Total

Room surrounding conditioned space: 76 degrees db / 30% RHCONDITION “A”:Walls constructed with 5/8” sheetrock on both sides, no insulation and no vapor barrierCeiling, standard acoustical tilesRoof, insulated with no Vapor BarrierCONDITION B:Walls constructed with 5/8” sheetrock on both sides, no insulation, and with a vapor barrier with a transmission rate of 0.000 grams/hr/sq. meter. The vapor barrier is installed under the sheetrock on the conditioned space side of the wall.Ceiling, acoustical tiles with a vapor barrier with a transmission rate of: 0.04 grams/hr/sq. meter Roof, insulated with no vapor barrier

HUMIDIFIER SELECTION and OPERATING COST

Calculated humidifier load with “perfect” vapor barrier………9# / hr; 3.0 kW

Load with no vapor barrier – many variable – Probably…… 22# / hr; 7.3kW

Rule of thumb: 3# / hr / kw

Savings with vapor barrier………………………………………….4.0kW / hr

4.0kW / hr x 3500 hrs x $0.11 / kwhr = $1,540.00

Cost to vapor treat the space………………………………………$1,200.00

Use available manufacturer’s software to calculate the load

Neptronic Humidisoft Humidification Software is an indispensable tool for anyone who is involved in the design, selection or installation of humidification systems.

Consulting Engineers are able to quickly calculate humidification loads, select humidifiers, select steam dispersion systems, generate calculation reports, produce exportable product schedules and wiring diagrams.

Contractors can quickly obtain dimensional data, installation information and much more.

Humidisoft Humidification Design Software Features:

General:

English or French language Metric (SI) or English (US) units Easy to use, visual help Auto-update feature to ensure latest version is easily available All reports are exportable to rich text and PDF formats for easy transfer of information

Technical:

Design criteria (temperature, humidity and altitude) for most major cities already in the software

Load calculations can be done based on infiltration, mechanical or economizer fresh air exchange

Best-cost humidifier selection based on calculated load Dispersion distance calculation Dispersion manifold selection Calculation report Detailed option selection chart Integrated product schedule Complete submittal drawings including PROJECT AND PRODUCT SPECIFIC information, installation, dimensions

and wiring information

RESOURCES

Alumiseal Corporation

ASHRAE FUNDAMENTALS HANDBOOK

Bry-Air Corporation

Building Science Corporation, Joseph Lstiburek, PhD

Lincoln Electric System

Louisiana State University, Dept of Natural Resources

University of Wisconsin – Cooperative Education