Masonry Magazine June 1978 Page. 15
BIA Technical Notes on Brick Construction
Brick Institute of America 1750 Old Meadow Road, McLean, Virginia 22101
21A
Revised
May/June
1977
BRICK MASONRY CAVITY WALLS INSULATED
MINIMUM 1 (25 mm) CLEARANCE
GRANULAR FILL OR RIGID
BOARD INSULATION
METAL TIES
0000000
0000
WEEP HOLES
24 (610 mm) 0.C.
FLASHING
MINIMUM 2 (51 mm) CAVITY
Typical Insulated Brick Cavity Wall
FIG. 1
INTRODUCTION
The past two decades have seen an increased use of brick masonry cavity walls in the United States, especially in skeleton-frame construction. They are used because of their superior rain penetration resistance, excellent thermal capabilities, good sound transmission resistance, and high fire resistance.
In a cavity wall, the air space acts as an insulating layer. Because of this, heat transfer is substantially lowered, resulting in more economical heating and air-conditioning. As excellent as this system is, the thermal performance can be improved even more by placing insulation materials such as water repellent vermiculite or perlite granular fills, or expanded polystyrene or polyurethane boards in the cavity (see Fig. 1).
This Technical Notes is the second of a series dealing with brick masonry cavity walls. This issue considers insulated brick masonry cavity walls. It discusses their advantages, the selection of insulation, and installation. For general information concerning brick masonry cavity walls as to properties and design, see Technical Notes 21 Revised. For information on proper detailing and construction, see Technical Notes 21B and 21C.
SELECTION OF INSULATION MATERIALS
# General
Suitable types of insulation materials for cavity walls are granular fills and rigid boards. Each of these, if properly used, will produce a more thermally efficient wall.
The benefits of placing insulation material in the cavity have been extensively investigated since 1951. The Structural Clay Products Research Foundation, now a part of BIA, sponsored and conducted extensive testing in the early 1950s on the performance of granular fill insulation materials placed in the air space of brick masonry cavity walls. These tests provided substantial information about water permeability, effect of moisture on thermal transmission, vapor transmission, fire resistance, sound transmission, etc. As a result of these tests and others, the following criteria have been established for selection of suitable masonry cavity wall insulation materials:
1. The insulation must permit the cavity to perform its natural function as a barrier to moisture penetration by allowing moisture to drain, without transmission to the interior wythe.
2. Thermal insulating efficiency must not be impaired by retained quantities of moisture from any source; e.g., wind-driven rain or vapor condensation.
3. Granular fill insulating materials must be capable of supporting their own weight without settlement, to assure that no portion of the wall is without insulation.
4. Insulating materials must be inorganic, or have comparable resistance to rot, fire, and vermin.
5. Granular insulating materials must be "pourable" in lifts of at least 4 ft (1.2 m) for practical installation.
# Granular Fills
To date, two types of granular fill insulation have been tested by BIA and found to meet the above criteria. These are: water repellent vermiculite masonry fill, produced and marketed by members of the Vermiculite Association; and silicone-treated perlite loose fill insulation, produced and marketed by members of the Perlite Institute. Inc.