Treatment for Condensation on Historic Glass and Storm Sashes

PART 1–GENERAL

1.01 SUMMARY

1. This specification provides guidance on cleaning and protection of glazing against condensation.

2. This specification should NOT be used on wood windows with a shellac finish, as the alcohol mixture recommended for treating condensation will destroy shellac.

3. Safety Precautions:

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

   2. DO NOT store any chemicals in unmarked containers.

   3. The proper Personal Protective Equipment (PPE) must be used when utilizing the chemicals involved. The proper eye and skin protection, and respirators fitted with appropriate solvent filters must be used. See the manufacturer’s MSDS for guidance.

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

   5. NOTE: EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY SOLVENT IS USED.

      1. No use of organic solvents indoors should be allowed without substantial air movement.

      2. Use only spark-proof fans near operations involving flammable liquids.

   6. Before work is commenced, you must have available any antidote and accident treatment chemicals that are noted in the MSDS.

4. Read “General Project Guidelines” along with this specification. 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). The 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)

1.02 DEFINITIONS

1. 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.
   1. Within a building, the amount of water vapor depends upon the amount of vapor generated by the users. Air can hold more water vapor in higher temperatures.
   2. 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.
2. 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.
   1. Just as each raindrop forms around a speck of dust, a dirty glazing surface will condense more readily than a clean one.
   2. The intent of this specification is to provide guidance for carrying out a regular maintenance regimen for removing a wide variety of surface contaminants from glazed surfaces.

PART 2–PRODUCTS

2.01 MATERIALS

NOTE: Not all the following chemicals will be needed for every application. Read the entire specification before moving forward.

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 (*).

1. Xylol:

   1. Any one of three specific, isomeric, aromatic hydrocarbons which are obtained from tar or petroleum distillates.

   2. It can also be a mixture of xylenes and ethyl-benzene that is used chiefly as a solvent.

   3. Other chemical or common names include Xylene; 1,4-dimethyl benzene.

   4. Potential Hazards: TOXIC AND FLAMMABLE.

   5. Available from chemical supply house, hardware store, paint store or printer’s supply distributor.

-OR-

2. Toluol:

   1. A liquid, aromatic hydrocarbon that resembles benzene but is less volatile, flammable and toxic.

   2. It is produced commercially from coke- oven gas, coal tar, and from petroleum, and is used as a solvent, in organic synthesis and as an antiknock agent for gasoline.

   3. Other chemical or common names include Toluene.

   4. Potential Hazards: TOXIC AND FLAMMABLE.

   5. Available from chemical supply house, hardware store, paint store or printer’s supply distributor.

3. Glycerin (or Glycerine):

   1. A sweet syrupy alcohol usually obtained from animal 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.

4. Methyl Alcohol:

   1. Other chemical or common names include Carbinol; Methanol; Methyl hydrate; Methyl hydroxide; Methylic alcohol; Colonial spirits*; Columbian 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 a retail camera shop).

5. Caulk such as DAP “Seal ‘N Peel Removable Caulk 18324” (not for glazing, see 3.03 D. 3. below for specific usage) or approved equal.

   1. Type to match application:

      1. Natural caulks are used for glazing most wood window members.

      2. Synthetic caulks are often used for glazing steel, aluminum or vinyl coated window members.

   2. For guidance on caulking, see also:

      1. “Replacing Broken Glass in Wood and Metal Windows”

      2. “Rehabilitating Wood Windows”

      3. “Cleaning and Painting Steel Windows”

2.02 EQUIPMENT

1. Clean cloths for drying

2. Caulking gun

PART 3–EXECUTION

3.01 EXAMINATION

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? (Embedded dust increases condensation)

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

5. Verify the putty is sound and complete.

3.02 PREPARATION

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

2. 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, IN ALL SEASONS. DO NOT USE THIS PROCEDURE ON WINDOWS WITH A SHELLAC FINISH, AS THE ALCOHOL MIXTURE WILL DESTROY THE FINISH.

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

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

3. Clean adjacent surfaces immediately if spills have occurred.

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

   1. Sweating on the inner face of the 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.

   3. If storm windows are to be removed and replaced each year, a removable sealant product, such as DAP “Seal ‘N Peel Removable Caulk 18324” or approved equal, should be used instead of a more permanent caulk. Silicone-based caulk should be avoided as it may damage the finish, and its superior adhesion could cause loss of wood when the pieces are separated. If plausible for your situation, a better solution is to utilize a natural wool or felt weatherstrip, to be installed on the storm window once and reused year after year.