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Historic Preservation - Technical Procedures

Spectitle:
Treatment For Condensation On Historic Glass And Storm Sash

Procedure code:
0880001P

Source:
Hspg Prepared For Nps - Sero

Division:
Doors And Windows

Section:
Glass & Glazing

Last Modified:
02/24/2012

Details:
Treatment For Condensation On Historic Glass And Storm Sash



TREATMENT FOR CONDENSATION ON HISTORIC GLASS AND STORM SASH


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on cleaning and
         protecting glazing against condensation.

    B.   This procedure should NOT be used on wood windows with a
         shellac finish.  The alcohol mixture recommended for
         treating condensation will destroy the finish.

    C.   Safety Precautions:

         1.   DO NOT save unused portions of stain-removal
              materials.

         2.   DO NOT store any chemicals in unmarked containers.

         3.   EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
              SOLVENT IS USED.  USE RESPIRATORS WITH SOLVENT
              FILTERS.

              NOTE:  SOME OF THE SOLVENTS LISTED ARE KNOWN
              CARCINOGENS AND MAY BE BANNED IN SOME STATES.

         4.   No use of organic solvents indoors should be
              allowed without substantial air movement.  Use only
              spark-proof fans near operations involving
              flammable liquids.

         5.   Provide adequate clothing and protective gear where
              the chemicals are indicated to be dangerous.

         6.   Have available antidote and accident treatment
              chemicals where noted.

    D.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   General Protection (Surface and Surrounding)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).

1.02 DEFINITIONS

    A.   Condensation in building terms is the process by which
         water vapor, a gas, changes to a liquid.  There is always
         water vapor in the air, the amount depending upon the
         local climatic conditions.  Within a building, the amount
         of water vapor depends upon the amount of vapor generated
         by the users.  Air has the ability to hold water vapor in
         accordance with the temperature of the air.  The higher
         the air temperature the more water vapor the air can hold
         and vice versa.  When the air is saturated it has reached
         the dew point.  If the temperature drops, the air can no
         longer hold all the water, so the excess is changed back
         into liquid form.

    B.   Surface condensation occurs on any building material
         whose temperature is lower than the dew point, but it is
         only visible on surfaces which are nonabsorbent, such as
         window glass in winter and exposed cold water pipes in
         basements in summer (surfaces which are nonabsorbent.)


PART 2---PRODUCTS

2.01 MATERIALS

    NOTE:  Chemical products are sometimes sold under a common
    name.  This usually means that the substance is not as pure as
    the same chemical sold under its chemical name.  The grade of
    purity of common name substances, however, is usually adequate
    for stain removal work, and these products should be purchased
    when available, as they tend to be less expensive.  Common
    names are indicated below by an asterisk (*).

    A.   Xylol:

         1.   Any of three toxic, flammable, oily, isomeric,
              aromatic hydrocarbons that are di-methyl momologues
              of benzene and are obtained from wood tar, coal
              tar, or petroleum distillates;  Also a mixture of
              xylenes and ethyl-benzene used chiefly as a
              solvent.

         2.   Other chemical or common names include Xylene; P-
              xylene; 1,4-dimethyl benzene.

         3.    Potential Hazards:  TOXIC AND FLAMMABLE.

         4.   Available from chemical supply house, hardware
              store, paint store or printer's supply distributor.

         -OR-

         Toluol:

         1.   A liquid, aromatic hydrocarbon that resembles
              benzene but is less volatile, flammable and toxic;
              Is produced commercially from light oils from coke-
              oven gas and coal tar and from petroleum, and is
              used as a solvent, in organic synthesis and an
              antiknock agent for gasoline.

         2.   Other chemical or common names include Toluene.

         3.    Potential Hazards:  TOXIC AND FLAMMABLE.

         4.   Available from chemical supply house, hardware
              store, paint store or printer's supply distributor.

    B.   Glycerin (or Glycerine):

         1.   A sweet syrupy hygroscopic trihydroxy alcohol
              usually obtained by the saponification of fats and
              used especially as a solvent and plasticizer.

         2.   Other chemical or common names include Glycerol;
              Glyceryl hydroxide; Glycyl alcohol; 1,2,3-
              propanetriol; Propenyl alcohol.

         3.   Potential Hazards:  FLAMMABLE.

         4.   Available from chemical supply house, drug store or
              hardware store.

    C.   Methyl Alcohol:

         1.   Other chemical or common names include Carbinol;
              Methanol; Methyl hydrate; Methyl hydroxide;
              Methyllic alcohol; Colonial spirits*; Columnian
              spirits*; Green wood spirits*; Manhattan spirits*;
              Pyroligneous spirit*; Pyroxylic spirit*; Standard
              wood spirits*; Wood alcohol*; Wood naphtha*; Wood
              spirit*.

         2.   Potential Hazards:  TOXIC AND FLAMMABLE.

         3.   Available from automotive supply distributor,
              chemical supply house, dry cleaning supply
              distributor, drugstore or pharmaceutical supply
              distributor, hardware store, paint store, or
              photographic supply distributor (not camera shop).

    D.   Caulk

2.02 EQUIPMENT

    A.   Clean cloths for drying

    B.   Caulking gun


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Before proceeding with steps to clean and protect glazing
         against condensation, first determine the cause and
         extent of the problem:

         1.   Determine the age of the structure and of the
              glazing.

         2.   Examine the condition of the window components.

         3.   Is glass free of embedded dust?

         4.   Check for cracked, broken, chipped, or otherwise
              damaged glass.

3.02 PREPARATION

    A.   Protection:  Provide adequate wash solutions (i.e. water,
         soap and towels) before starting the job.

    B.   Surface Preparation:  Remove all oil, dirt, and other
         materials from the glass and any metal framing members by
         means of proper solvents (xylol or toluol).

3.03 ERECTION, INSTALLATION, APPLICATION

    NOTE:  APPLY TREATMENT EVERY TIME THE GLASS IS WASHED (WINTER,
    SPRING, SUMMER, FALL)

    CAUTION:  DO NOT USE THIS PROCEDURE ON WINDOWS WITH A SHELLAC
    FINISH.  THE ALCOHOL MIXTURE WILL DESTROY THE WOOD FINISH.

    A.   Apply mixture of equal parts of glycerin and methyl
         alcohol to the inside of the glass with a clean cloth.

    B.   Clean excess solution from glass, frames and sash
         promptly.

    C.   Clean adjacent surfaces if spills have occurred.

    D.   If storm windows are in place, identify location of
         condensation (interior sash or exterior sash) and make
         necessary adjustments to reduce condensation.

         1.   Sweating on inside of interior sash is the result
              of cold air infiltration around the exterior sash.
              Caulk around exterior sash to eliminate
              infiltration.

         2.   Sweating on the inner face of the exterior sash
              indicates warm air infiltration around the interior
              sash.  Caulk around interior sash to eliminate
              infiltration.

                             END OF SECTION