Framing, Sheathing and Insulation - Couverture rigide

Jones, Raymond; Ball, John E.

Couverture rigide

ISBN 10 : 0442241836 ISBN 13 : 9780442241834

Editeur : Van Nostrand Reinhold Company, 1977

Synopsis

Book by Jones Raymond Ball John E

A propos du livre

Présentation de l'éditeur

Excerpt from Framing, Sheathing, and Insulation

While a tree is living, both the cells and cell walls are filled with water. As soon as the tree is cut, the water within the cells begins to evaporate. This process continues until practically all of the "free water" has left the wood. When this stage is reached, the wood is said to be at the fiber-saturation point; that is, what water is contained is mainly in the fiber walls.

There is no change in size during this preliminary drying process and, therefore, no shrinkage during the evaporation of the "free water." Shrinkage begins when water begins to leave the cell walls themselves. These contract, becoming harder and denser, causing a general reduction in size of the piece of wood.

If a specimen is placed in an oven (kiln) which is maintained at 212˚ F, the temperature of boiling water, the water will evaporate and the specimen will continue to lose weight for a time. Finally, a point is reached at which the weight remains constant. This is a way of saying that all of the water in the cells and cell walls has been driven off. The piece is then said to be "kiln dry" (K.D.).

If it is now taken out of the oven and allowed to remain in the open air, it will gradually take on weight because of the absorption of moisture from the air. As in oven drying a point is reached at which the weight of the wood in contact with the air remains more or less constant. Tests show that it does not remain exactly constant, for the wood will take on and give off water as the moisture in the atmosphere increases or decreases. When the piece is in this condition, it is said to be "air dry" (A.D.).

The amount of water contained by wood in the green condition varies greatly. As a general average, at the fiber-saturation point, most woods contain from 23% to 30% water as compared with the oven-dry weight of the wood. When air-dry most woods contain from 12% to 15% moisture.

Kiln drying in great ov…

Détails de l'édition

• Éditeur: Van Nostrand Reinhold Company
• Date d'édition: 1977
• Langue: anglais
• ISBN 10: 0442241836
• ISBN 13: 9780442241834
• Reliure: Relié
• Nombre de pages: 227
• Coordonnées du fabricant: non disponible
• Personne responsable: non disponible